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june 2001 1 MIC280 MIC280 micrel MIC280 precision ittybitty thermal supervisor final information general description the MIC280 is a digital thermal supervisor capable of mea- suring its own internal temperature and that of a remote pn junction. the remote junction may be an inexpensive com- modity transistor, e.g., 2n3906, or an embedded thermal diode such as found in intel pentium* ii/iii/iv cpus, amd athlon* cpus, and xilinx virtex* fpga's. a 2-wire smbus* 2.0 compatible serial interface is provided for host communi- cation. remote temperature is measured with 1 c accuracy and 9-bit to 12-bit resolution (programmable). independent high, low, and over-temperature thresholds are provided for each zone. the advanced integrating a/d converter and analog front- end reduce errors due to noise for maximum accuracy and minimum guardbanding. the interrupt output signals tem- perature events to the host, including data-ready and diode faults. critical device settings can be locked to prevent changes and insure failsafe operation. the clock, data, and interrupt pins are 5v-tolerant regardless of the value of v dd . they will not clamp the bus lines low even if the device is powered down. superior accuracy, failsafe operation, and small size make the MIC280 an excellent choice for the most demanding thermal management applications. typical application data 5 4 62 3 1 to serial bus host 2n3906/ cpu diode 1800pf MIC280 clk /int 3v to 3.6v 3 10k vdd t1 gnd 0.1 f ceramic MIC280 typical application features measures local and remote temperature highly accurate remote sensing 1 c max., 60 c to 100 c superior noise immunity for reduced temperature guardbands 9-bit to 12-bit temperature resolution for remote zone fault queues to further reduce nuisance tripping programmable high, low, and over-temperature thresh- olds for each zone smbus 2 compatible serial interface including device timeout to prevent bus lockup voltage tolerant i/o? open-drain interrupt output pin - supports smbus alert response address protocol low power shutdown mode locking of critical functions to insure failsafe operation failsafe response to diode faults enables acpi compliant thermal management 3.0v to 3.6v power supply range ittybitty sot23-6 package applications desktop, server and notebook computers printers and copiers test and measurement equipment thermal supervision of xilinx virtex fpga's wireless/rf systems intelligent power supplies datacom/telecom cards micrel, inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com ittybiity is a trademark of micrel, inc. *all trademarks are the property of their respective owners.
MIC280 micrel MIC280 2 june 2001 pin configuration 1 vdd gnd t1 6 5 /int data clk 4 2 3 sot23-6 ordering information part number marking slave address ambient temp. range package MIC280-0bm6 ta00 100 1000 b 55 c to +125 c sot23-6 MIC280-1bm6 ta01 100 1001 b 55 c to +125 c sot23-6 MIC280-2bm6 ta02 100 1010 b 55 c to +125 c sot23-6 MIC280-3bm6 ta03 100 1011 b 55 c to +125 c sot23-6 MIC280-4bm6 ta04 100 1100 b 55 c to +125 c sot23-6 MIC280-5bm6 ta05 100 1101 b 55 c to +125 c sot23-6 MIC280-6bm6 ta06 100 1110 b 55 c to +125 c sot23-6 MIC280-7bm6 ta07 100 1111 b 55 c to +125 c sot23-6 pin description pin number pin name pin function 1 vdd power supply input. 2 gnd ground. 3 t1 analog input. connection to remote diode junction. 4 clk digital input. serial bit clock input. 5 data digital input/output. open-drain. serial data input/output. 6 /int digital output. open-drain. interrupt output.
june 2001 3 MIC280 MIC280 micrel absolute maximum ratings (note 1) power supply voltage, v dd ................................................... 3.8v voltage on t1 ........................................ 0.3v to v dd +0.3v voltage on clk, data, /int ............................ 0.3v to 6v current into any pin ................................................. 10ma power dissipation, t a = 125 c ............................... 109mw storage temperature ............................... 65 c to +150 c esd ratings, note 3 human body model ................................................ 1.5kv machine model ........................................................ 200v soldering (sot23-6 package) vapor phase (60s) .................................... 220 c +5 / -0 c infrared (15s) ............................................. 235 c +5 / -0 c operating ratings (note 2) power supply voltage, v dd .................................. +3v to +3.6v ambient temperature range (t a ) ........... 55 c to +125 c junction temperature ............................................... 150 c package thermal resistance ( ja ) sot23-6 ............................................................ 230 c/w electrical characteristics for typical values t a = 25 c, v dd = 3.3v, unless otherwise noted. bold values indicate 55 c t a 125 c, 3.0v v dd 3.6v, unless otherwise noted. note 2 symbol parameter conditions min. typ max units power supply i dd supply current /int, t1 open; clk = data = high; 0.23 0.4 ma normal mode shutdown mode; /int, t1 open; note 5 9 a clk = 100khz, data = high shutdown mode; /int, t1 open; 6 [tbd] a clk = data = high t por power-on reset time, note 5 v dd > v por 200 s v por power-on reset voltage all registers reset to default values; 2.65 2.95 v a/d conversions initiated v hyst power-on reset hysteresis voltage 300 mv note 5 temperature-to-digital converter characteristics accuracy, remote temperature 60 c t d 100 c, 0.25 1 c notes 2, 7, 10, 11 3.15v < v dd < 3.45v, 25 c < t a < 85 c 0 c t d 100 c, 1 2 c 3.15v < v dd < 3.45v, 25 c < t a < 85 c 55 c t d 125 c, 2 4 c 3.15v < v dd < 3.45v, 25 c < t a < 85 c accuracy, local temperature 0 c t a 100 c, 3.15v < v dd < 3.45v 1 2 c note 2, 10 55 c t a 125 c, 3.15v < v dd < 3.45v 1.5 2.5 c t conv conversion time, notes 2, 8 res[1:0]=00 (9 bits) 200 240 ms res[1:0]=01 (10 bits) 330 390 ms res[1:0]=10 (11 bits) 570 670 ms res[1:0]=11 (12 bits) 1000 1250 ms remote temperature input, t1 i f current into external diode t1 forced to 1.0v, high level 192 400 a note 5 low level 7 12 a
MIC280 micrel MIC280 4 june 2001 symbol parameter condition min typ max units serial data i/o pin, data v ol low output voltage, note 4 i ol = 3ma 0.3 v i ol = 6ma 0.5 v v il low input voltage 3v v dd 3.6v 0.8 v v ih high input voltage 3v v dd 3.6v 2.1 5.5 v c in input capacitance note 5 10 pf i leak input current 1 a serial clock input, clk v il low input voltage 3v v dd 3.6v 0.8 v v ih high input voltage 3v v dd 3.6v 2.1 5.5 v c in input capacitance note 5 10 pf i leak input current 1 a interrupt output, /int v ol low output voltage, note 4 i ol = 3ma 0.3 v i ol = 6ma 0.5 v t int interrupt propagation delay from tempx < tlowx or [t conv ] ms notes 5, 6 tempx > thighx or tempx > critx to /int < v ol ; r pullup = 10k ? t nint interrupt reset propagation delay from read of status or a.r.a. to 1 s note 5, 9 /int > v oh ; r pullup = 10k ? i leak 1 a serial interface timing t 1 clk (clock) period 2.5 s t 2 data in setup time to clk high 100 ns t 3 data out stable after clk low 300 ns t 4 data low setup time to clk low start condition 100 ns t 5 data high hold time after clk stop condition 100 ns high t to bus timeout 25 30 35 ms note 1 . exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating range. final test on outgoing product is performed at t a = 25 c. note 3. devices are esd sensitive. handling precautions recommended. note 4. current into the /int or data pins will result in self heating of the device. sink current should be minimized for best accurac y. note 5. guaranteed by design over the operating temperature range. not 100% production tested. note 6. t int and t crit are equal to t conv . note 7. t d is the temperature of the remote diode junction. testing is performed using a single unit of one of the transistors listed in table 8. note 8. t conv = t conv (local) + t conv (remote). following the acquisition of either remote or local temperature data, the limit comparisons for that zone are performed and the device status updated; status bits will be set and /int driven active, if applicable. note 9. the interrupt reset propogation delay is dominated by the capacitance on the bus. note 10. accuracy specification does not include quantization noise, which may be up to 1 / 2 lsb. note 11. tested at 10-bit resolution.
june 2001 5 MIC280 MIC280 micrel timing diagrams t 1 t 2 t 5 t 4 t 3 clk data input data output serial interface timing
MIC280 micrel MIC280 6 june 2001 typical characteristics v dd = 3.3v; t a = 25 c, unless otherwise noted. -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 -55 -35 -15 5 25 45 65 85 105125 measurment error ( c) junction temperature ( c) accuracy vs. temperature, internal sensor 0 20 40 60 80 100 120 140 012345678910 measured local temperature ( c) time (sec) response to immersion in 125 c fluid bath -20 -15 -10 -5 0 5 0 1000 2000 3000 4000 5000 6000 7000 8000 temperature error ( c) capacitance (pf) remote temperature error vs. capacitance on t1 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 0 20406080100 measurement error ( c) remote diode temperature ( c) remote temperature measurement error 0 50 100 150 200 250 300 350 400 -55 -35 -15 5 25 45 65 85 105125 supply current ( a) temperature ( c) supply current vs. temperature for v dd = 3.3v 0 5 10 15 20 25 30 -55 -35 -15 5 25 45 65 85 105125 quiescent current ( a) temperature ( c) quiescent current vs. temperature in shutdown mode /int, t1 open clk = data = high 0 1 2 3 4 5 6 7 8 9 10 2.6 2.8 3.0 3.2 3.4 3.6 quiescent current ( a) supply voltage (v) quiescent current vs. supply voltage in shutdown mode /int, t1 open clk = data = high 0 5 10 15 20 0 100 200 300 400 quiescent current ( a) frequency (khz) quiescent current vs. clock frequency in shutdown mode /int, t1 open data = high -8 -6 -4 -2 0 2 4 6 8 1x10 6 1x10 7 1x10 8 1x10 9 measurement error ( c) resistance from t1 ( ? ) measurement error vs. pcb leaka g e to +3.3v/gnd gnd 3.3v 0 1 2 3 4 5 6 7 remote temp. error ( c) noise injected into the base of remote transistor frequency (hz) 110 100 1k 10k100k 1m 10m 100m 3mv p-p 25mv p-p 10mv p-p 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 temperture error ( c) noise injected into the collector of remote transistor frequency (hz) 110 100 1k 10k100k 1m 10m 100m 50mv p-p 25mv p-p 100mv p-p
june 2001 7 MIC280 MIC280 micrel functional description serial port operation the MIC280 uses standard smbus write_byte, read_byte, and read_word operations for communication with its host. the smbus write_byte operation involves sending the device s slave address (with the r/w bit low to signal a write operation), followed by a command byte and the data byte. the smbus read_byte operation is a composite write and read operation: the host first sends the device s slave ad- dress followed by the command byte, as in a write operation. a new start bit must then be sent to the MIC280, followed by a repeat of the slave address with the r/w bit (lsb) set to the high (read) state. the data to be read from the part may then be clocked out. a read_word is similar, but two successive data bytes are clocked out rather than one. these protocols are shown in figure 1, figure 2, and figure 3. the command byte is eight bits (one byte) wide. this byte carries the address of the MIC280 register to be operated upon. the command byte values corresponding to the various MIC280 registers are shown in table 1. other command byte values are reserved, and should not be used. slave address the MIC280 will only respond to its own unique slave ad- dress. a match between the MIC280 s address and the address specified in the serial bit stream must be made to initiate communication. the MIC280 s slave address is fixed at the time of manufacture. eight different slave addresses are available as determined by the part number. see table 2 below and the ordering information table above. part number slave address MIC280-0bm6 100 1000 b = 48 h MIC280-1bm6 100 1001 b = 49 h MIC280-2bm6 100 1010 b = 4a h MIC280-3bm6 100 1011 b = 4b h MIC280-4bm6 100 1100 b = 4c h MIC280-5bm6 100 1101 b = 4d h MIC280-6bm6 100 1110 b = 4e h MIC280-7bm6 100 1111 b = 4f h table 2: MIC280 slave addresses alert response address in addition to the read_byte, write_byte, and read_word protocols, the MIC280 adheres to the smbus protocol for response to the alert response address (ara). the MIC280 expects to be interrogated using the ara when it has as- serted its /int output. command byte power-on target register value default label description read write temp0 local temperature result 00 h n/a 00 h (0 c) temp1h remote temperature result, high byte 01 h n/a 00 h (0 c) status status 02 h n/a 00 h config configuration 03 h 03 h 80 h imask interrupt mask register 04 h 04 h 07 h thigh0 local temperature high limit 05 h 05 h 3c h (60 c) tlow0 local temperature low limit 06 h 06 h 00 h (0 c) thigh1h remote temperature high limit, high byte 07 h 07 h 50 h (80 c) tlow1h remote temperature low limit, high byte 08 h 08 h 00 h (0 c) lock security register 09 h 09 h 00 h temp1l remote temperature result, low byte 10 h n/a 00 h thigh1l remote temperature high limit, low byte 13 h 13 h 00 h tlow1l remote temperature low limit, low byte 14 h 14 h 00 h crit1 remote over-temperature limit 19 h 19 h 64 h (100 c) crit0 local over-temperature limit 20 h 20 h 46 h (70 c) mfg_id manufacturer identification fe h n/a 2a h dev_id device and revision identification ff h n/a 0x h * * the lower nibble contains the die revision level, e.g., rev 0 = 00h. table 1: MIC280 register addresses
MIC280 micrel MIC280 8 june 2001 temperature data format the least-significant bit of each temperature register (high bytes) represents one degree centigrade. the values are in a two s complement format, wherein the most significant bit (d7) represents the sign: zero for positive temperatures and one for negative temperatures. table 3 shows examples of the data format used by the MIC280 for temperatures: temperature binary hex +127 c 0111 1111 7f +125 c 0111 1101 7d +25 c 0001 1001 19 +1 c 0000 0001 01 0 c 0000 0000 00 1 c 1111 1111 ff 25 c 1110 0111 e7 125 c 1000 0011 83 128 c 1000 0000 80 table 3: digital temperature format, high bytes extended temperature resolution is provided for the external zone. the high and low temperature limits and the measured temperature for zone one are reported as 12-bit values stored in a pair of 8-bit registers. the measured temperature, for example, is reported in registers temp1h, the high-order byte, and temp1l, the low-order byte. the values in the low- order bytes are left-justified four-bit binary values represent- ing one-sixteenth degree increments. the a-d converter resolution for zone 1 is selectable from nine to twelve bits via the configuration register. low-order bits beyond the resolu- tion selected will be reported as zeroes. examples of this format are shown below in table 4. fault queue a set of fault queues (programmable digital filters) are pro- vided in the MIC280 to prevent false tripping due to thermal or electrical noise. two bits, config[5:4], set the depth of the fault queues. the fault queue setting then determines the number of consecutive temperature events (tempx > thighx or tempx < tlowx) which must occur in order for the condition to be considered valid. as an example, assume config[5:4] is programmed with 10b. the measured tem- perature for a given zone would have to exceed thighx for four consecutive a/d conversions before /int would be asserted or the status bit set. like any filter, the fault queue function also has the effect of delaying the detection of temperature events. in this ex- ample, it would take 4 x t conv to detect a temperature event. the fault queue depth vs. config[5:4] of the configuration register is shown in table 5. note: there is no fault queue for over-temperature events (crit0 and crit1) or diode faults. the fault queue applies only to high-temperature and low- temperature events as determined by the thighx and tlowx registers. any write to config will result in the fault queues being purged and reset. writes to any of the limit registers, tlowx or thighx, will result in the fault queue for the corresponding zone being purged and reset. config[5:4] fault queue depth 00 1 (default) 01 2 10 4 11 6 table 5: fault queue depth settings interrupt generation there are eight different conditions that will cause the MIC280 to set one of the bits in status and assert its /int output, if so enabled. these conditions are listed in table 6. unlike previous generations of thermal supervisor ic s, there are no interdependencies between any of these conditions. that is, if condition is true, the MIC280 will respond accordingly, regardless of any previous or currently pending events. normally when a temperature event occurs, the correspond- ing status bit will be set in status, the corresponding interrupt mask bit will be cleared, and /int will be asserted. clearing the interrupt mask bit(s) prohibits continuous inter- rupt generation while the device is being serviced. (it is possible to prevent events from clearing interrupt mask bits by setting bits in the lock register. see table 7 for lockbit functionality.) a temperature event will only set bits in the status register if it is specifically enabled by the correspond- extended temperature, resolution low byte 9 bits 10 bits 11 bits 12 bits binary hex binary hex binary hex binary hex 0.0000 0000 0000 00 0000 0000 00 0000 0000 00 0000 0000 00 0.0625 0000 0000 00 0000 0000 00 0000 0000 00 0001 0000 10 0.1250 0000 0000 00 0000 0000 00 0010 0000 20 0010 0000 20 0.2500 0000 0000 00 0100 0000 40 0100 0000 40 0100 0000 40 0.5625 1000 0000 80 1000 0000 80 1000 0000 80 1001 0000 90 0.9375 1000 0000 80 1100 0000 c0 1110 0000 e0 1111 0000 f0 table 4: digital temperature format, low bytes
june 2001 9 MIC280 MIC280 micrel s1001 a2 a1 a0 0axxxxxxxxa d4 d5 d6 d3 d2 d1 d0 d7 ap MIC280slave address data clk command byte data byte to MIC280 start stop r/w = write acknowledge acknowledge acknowledge master-to-slave transmission slave-to-master response figure 1. write_byte protocol s1001 a2 a1 a0 a2 a1 a0 0axxxxxxxxas1 1 1 00 x x x xxxx a x /a p MIC280slave address data clk command byte MIC280slave address data read from MIC280 start start stop r/w = write r/w = read acknowledge acknowledge acknowledge not acknowledge master-to-slave transmission slave-to-master response figure 2. read_byte protocol s1001 a2 a1 a0 0a00000001a MIC280slave address data clk command byte start r/w = write acknowledge acknowledge s1001 a2 a1 a0 1a a d7 d8 d9 d6 d5 d4 d3 d10 d11 /a p d2 d1 d0 0000 MIC280slave address high-order byte (temp1h) from MIC280 low-order byte (temp1l) from MIC280 start stop r/w = read acknowledge acknowledge not acknowledge master-to-slave transmission slave-to-master response figure 3. read_word protocol for accessing temp1h : temp1l
MIC280 micrel MIC280 10 june 2001 s0001 100 1a /a a2 1 0a1a00p 0 1 alert response address data /int MIC280 respond with its slave address start t int event occurs stop r/w = read acknowledge not acknowledge t int master-to-slave transmission slave-to-master response figure 4. MIC280 alert response address protocol s1001 a2 a1 a0 0a a 0 0 0 011 1 0 0 xxxxxxxx/ap 0 0 1 a2 a1 a0 1 MIC280 slave address data /int command byte = 03h = config MIC280 slave address value in status** start t int event occurs ** all status bits are cleared to zero following this operation stop r/w = read acknowledge acknowledge not acknowledge master-to-slave transmission slave-to-master response t int figure 5. reading status in response to an interrupt
june 2001 11 MIC280 MIC280 micrel ing bit in the interrupt mask register. an interrupt signal will only be generated on /int if interrupts are also globally enabled (ie =1 in config). the MIC280 expects to be interrogated using the alert response address once it has asserted its interrupt output. following an interrupt, a successful response to the a.r.a. or a read operation on status will cause /int to be de- asserted. status will also be cleared by the read operation. reading status following an interrupt is an acceptable substitute for using the a.r.a. if the host system does not implement the a.r.a protocol. figure 4 and figure 5 illustrate these two methods of responding to MIC280 interrupts. since temperature-to-digital conversions continue while /int is asserted, the measured temperature could change be- tween the MIC280 s assertion of /int and the host s re- sponse. it is good practice for the interrupt service routine to read the value in tempx, to verify that the over-temperature or under-temperature condition still exists. in addition, more than one temperature event may have occurred simulta- neously or in rapid succession between the assertion of /int and servicing of the MIC280 by the host. the interrupt service routine should allow for this eventuality. at the end of the interrupt service routine, the interrupt enable bits should be reset to permit future interrupts. reading the result registers all MIC280 registers are eight bits wide and may be accessed using the standard read_byte protocol. the temperature result for the local zone, zone 0, is a single 8-bit value in register temp0. a single read_byte operation by the host is sufficient for retrieving this value. the temperature result for the remote zone is a twelve-bit value split across two eight- bit registers, temp1h and temp1l. a series of two read_byte operations are needed to obtain the entire twelve-bit tem- perature result for zone 1. it is possible under certain conditions that the temperature result for zone 1 could be updated between the time temp1l or temp1h is read and the companion register is read. in order to insure coherency, temp1h supports the use of the read_word protocol for accessing both temp1h and temp1l with a single operation. this insures that the values in both result registers are from the same adc cycle. this is illustrated in figure 3 above. read_word operations are only supported for temp1h:temp1l, i.e., only for command byte values of 01h. polling the MIC280 may either be polled by the host, or request the host s attention via the /int pin. in the case of polled operation, the host periodically reads the contents of sta- tus to check the state of the status bits. the act of reading status clears it. if more than one event that sets a given status bit occurs before the host polls status, only the fact that at least one such event has occurred will be apparent to the host. for polled systems, the global interrupt enable bit should be clear (ie = 0). this will disable interrupts from the MIC280 (prevents the /int pin from sinking current). for interrupt-driven systems, ie must be set to enable the /int output. shutdown mode putting the device into shutdown mode by setting the shut- down bit in the configuration register will unconditionally deassert /int, clear status, and purge the fault queues. therefore, this should not be done before completing the appropriate interrupt service routine(s). no other registers will be affected by entering shutdown mode. the last tem- perature readings will persist in the tempx registers. the MIC280 can be prevented from entering shutdown mode using the shutdown lockout bit in the lock register. if l3 in lock is set while the MIC280 is in shutdown mode, it will immediately exit shutdown mode and resume normal opera- tion. it will not be possible to subsequently re-enter shutdown mode. if the reset bit is set while the MIC280 is shut down, normal operation resumes from the reset state. (see below) warm resets the MIC280 can be reset to its power-on default state during operation by setting the rst bit in the configuration register. when this bit is set, /int will be deasserted, the fault queues will be purged, the limit registers will be restored to their normal power-on default values, and any a/d conversion in progress will be halted and the results discarded. this includes resetting bits l3 - l0 in the security register, lock. the state of the MIC280 following this operation is indistin- guishable from a power-on reset. if the reset bit is set while event condition MIC280 response* data ready a/d conversions complete for both zones; result set s7, clear im7, assert /int registers updated; state of /int updated over-temperature, remote ([temp1h:temp1l]) > crit1 set s1, assert /int over-temperature, local temp0 > crit0 set s0, assert /int high temperature, remote ([temp1h:temp1l]) > thigh1h:thigh1l]** set s4, clear im4, assert /int high temperature, local temp0 > thigh0** set s6, clear im6, assert /int low temperature, remote ( [temp1h:temp1l]) < tlow1h:tlow1l]** set s3, clear im3, assert /int low temperature, local temp0 < tlow0** set s5, clear im5, assert /int diode fault t1 open or t1 shorted to vdd or gnd set s2, clear im2, assert /int * assumes interrupts enabled. **condition must be true for fault_queue conversions to be recognized. table 6: MIC280 temperature events
MIC280 micrel MIC280 12 june 2001 the MIC280 is shut down, the shutdown bit is cleared and normal operation resumes from the reset state. if bit 4 of lock, the warm reset lockout bit, is set, warm resets cannot be initiated, and writes to the rst bit will be completely ignored. setting l4 while the MIC280 is shut down will result in the device exiting shutdown mode and resuming normal operation, just as if the shutdown bit had been cleared. configuration locking the security register, lock, provides the ability to disable configuration changes as they apply to the MIC280 s most critical functions: shutdown mode, and reporting diode faults and over-temperature events. lock provides a way to prevent malicious or accidental changes to the MIC280 registers that might prevent a system from responding prop- erly to critical events. once l0, l1, or l2 has been set, the global interrupt enable bit, ie, will be set and fixed. it cannot subsequently be cleared. its state will be reflected in the configuration register. the bits in lock can only be set once. that is, once a bit is set, it cannot be reset until the MIC280 is power-cycled or a warm reset is performed by setting rst in the configuration register. the warm reset function can be disabled by setting l4 in lock. if l4 is set, locked settings cannot be changed during operation and warm resets cannot be performed; only a power-cycle will reset the locked state(s). if l0 is set, the values of im0 and crit0 become fixed and unchangeable. that is, writes to crit0 and the correspond- ing interrupt enable bit are locked out. a local over-tempera- ture event will generate an interrupt regardless of the setting of ie or its interrupt mask bit. if l1 is set, the values of im1 and crit1 become fixed and unchangeable. a remote over-temperature event will gener- ate an interrupt regardless of the setting of ie or its interrupt mask bit. similarly, setting l2 will fix the state of im2, allowing the system to permanently enable or disable diode fault interrupts. a diode fault will generate an interrupt regardless of the setting of ie or its interrupt mask bit. l3 can be used to lock out shutdown mode. if l3 is set, the MIC280 will not shut down under any circumstances. at- tempts to set the shdn bit will be ignored and all chip functions will remain operational. if l3 is set while the MIC280 is in shutdown mode, it will immediately exit shutdown mode and resume normal operation. it will not be possible to subsequently re-enter shutdown mode. setting l4 disables the rst bit in the configuration register, preventing the host from initiating a warm reset. writes to rst will be completely ignored if l4 is set. lock bit function locked response when set l0 local over-temperature detection im0 fixed at 1, writes to crit0 locked-out; ie permanently set l1 remote over-temperature detection im1 fixed at 1; writes to crit1 locked-out; ie permanently set l2 diode fault interrupts locked on or off im2 fixed at current state; ie permanently set if im2=1 l3 shutdown mode shdn fixed at 0; exit shutdown if shdn=1 when l3 is set l4 warm resets rst bit disabled; cannot initiate warm resets table 7: lock bit functionality
june 2001 13 MIC280 MIC280 micrel local temperature result register (temp0) 8-bits, read-only local temperature result register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read-only read-only read-only read-only read-only read-only read-only read-only temperature data from adc bit function operation d[7:0] measured temperature data for the local zone. read only power-up default value: 0000 0000 b = 00 h (0 c)** read command byte: 0000 0000 b = 00 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000 b . see temperature data format (above) for more details. **temp0 will contain measured temperature data after the completion of one conversion. remote temperature result high-byte register (temp1h) 8-bits, read only remote temperature result high-byte register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read-only read-only read-only read-only read-only read-only read-only read-only temperature data from adc bit function operation d[7:0] measured temperature data for the remote zone, most significant byte. read only power-up default value: 0000 0000 b = 00 h (0 c)** read command byte: 0000 0001 b = 01 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000b. see temperature data format (above) for more details. temp1h can be read using either a read_byte operation or a read_word operation. using read_byte will yield the 8-bit value in temp1h. the complete remote temperature result in both temp1h and temp1l may be obtained by performing a read_word operation on temp1h. the MIC280 will respond to a read_word with a command byte of 01h (temp1h) by returning the value in temp1h followed by the value in temp1l. this guarantees that the data in both registers is from the same temperature-to-digital conversion cycle. the read_word operation is diagramed in figure 3. this is the only MIC280 register that supports read_word. **temp1h will contain measured temperature data after the completion of one conversion. detailed register descriptions
MIC280 micrel MIC280 14 june 2001 status register (status) 8-bits, read-only status register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read-only read-only read-only read-only read-only read-only read-only read-only s7 s6 s5 s4 s3 s2 s1 s0 bit(s) function operation* s7 data ready 1 = data available 0 = adc busy s6 local high temperature event 1 = event occurred, 0 = none s5 local low temperature event 1 = event occurred, 0 = none s4 remote high temperature event 1 = event occurred, 0 = none s3 remote low temperature event 1 = event occurred, 0 = none s2 diode fault 1 = fault, 0 = none s1 remote over-temperature event 1 = event occurred, 0 = none s0 local over-temperature event 1 = event occurred, 0 = none * all status bits are cleared after any read operation is performed on status. power-up default value: 0000 0000 b = 00 h (no events pending) read command byte: 0000 0010 b = 02 h the power-up default value is 00h. following the first conversion, however, any of the status bits may be set depending on the measured temperature results or the existence of a diode fault. configuration register (config) 8-bits, read/write configuration register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write reserved reserved reserved reserved reserved reserved interrupt shut-down fault queue resolution reserved reset enable (ie) (shdn) (fq[1:0]) (res[1:0]) (rst) bits(s) function operation* ie interrupt enable 1 = interrupts enabled, 0 = disabled shdn selects operating mode: normal/shutdown 1 = shutdown, 0 = normal fq[1:0] depth of fault queue* [00]=1, [01]=2, [10]=4, [11]=6 res[1:0] a/d converter resolution for external zone - affects conversion rate [00]=9-bits, [01]=10-bits, [10]=11-bits, [11]=12-bits d[1] reserved always write as zero! rst resets all MIC280 functions and restores the power-up default state write only; 1 = reset, 0 = normal operation; disabled by setting l4 power-up default value: 1000 0000 b = 80 h (not in shutdown mode; interrupts enabled; fault queue depth=1; resolution = 9 bits) read/write command byte: 0000 0011 b = 03 h * any write to config will result in the fault queues being purged and reset and any a/d conversion in progress being aborted a nd the result discarded. the a/d will begin a new conversion sequence once the write operation is complete.
june 2001 15 MIC280 MIC280 micrel interrupt mask register (imask) 8-bits, read/write interrupt mask register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write im7 im6 im 5 im 4 im 3 im 2 im 1 im0 bit(s) function operation* im7 data ready event mask 1 = enabled, 0 = disabled im6 local high temperature event mask 1 = enabled, 0 = disabled im5 local low temperature event mask 1 = enabled, 0 = disabled im4 remote high temperature event mask 1 = enabled, 0 = disabled im3 remote low temperature event mask 1 = enabled, 0 = disabled im2 diode fault mask 1 = enabled, 0 = disabled im1 remote over-temperature event mask 1 = enabled, 0 = disabled im0 local over-temperature event mask 1 = enabled, 0 = disabled power-up default value: 0000 0111 b = 07 h (over-temp. and diode faults enabled) read/write command byte: 0000 0100 b = 04 h local temperature high limit register (thigh0) 8-bits, read/write local temperature high limit register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write high temperature limit for local zone. bit function operation d[7:0] high temperature limit for the local zone. read/write power-up default value: 0011 1100 b = 3c h (60 c) read/write command byte: 0000 0101 b = 05 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
MIC280 micrel MIC280 16 june 2001 local temperature low limit register (tlow0) 8-bits, read/write local temperature low limit register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write low temperature limit for local zone bit function operation d[7:0] low temperature limit for the local zone read/write power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0000 0110 b = 06 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. remote temperature high limit high-byte register (thigh1h) 8-bits, read/write remote temperature high limit high-byte register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write high temperature limit for remote zone, most significant byte. bit function operation d[7:0] high temperature limit for the remote zone, most significant byte. read/write power-up default value: 0101 0000 b = 50 h (80 c) read/write command byte: 0000 0111 b = 07 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
june 2001 17 MIC280 MIC280 micrel remote temperature low limit high-byte register (tlow1h) 8-bits, read/write remote temperature low limit high-byte register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write low temperature limit for remote zone, most significant byte. bit function operation d[7:0] low temperature limit for the remote zone, most significant byte. read/write power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0000 1000 b = 08 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000b. see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. security register (lock) 8-bits, write once security register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] reserved reserved reserved read/ read/ read/ read/ read/ write-once write-once write-once write-once write-once reserved l4 l3 l2 l1 l0 bit function operation* d[7:5] reserved always write as zero l4 warm reset lockout bit 1 = rst bit disabled; 0 = unlocked l3 shutdown mode lockout bit* 1= shutdown disabled; 0 = unlocked l2 diode fault event lock bit 1 = locked, 0 = unlocked l1 remote over-temperature event lock bit 1 = locked, 0 = unlocked l0 local over-temperature event lock bit 1 = locked, 0 = unlocked power-up default value: 0000 0000 b = 00 h (all events unlocked) read/write command byte: 0000 1001 b = 09 h * if the chip is shutdown when l3 is set, the chip will exit shutdown mode and resume normal operation. it will not be possibl e to subsequently re-enter shutdown mode.
MIC280 micrel MIC280 18 june 2001 remote temperature result low-byte register (temp1l) 8-bits, read only remote temperature result low-byte register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read-only read-only read-only read-only reserved reserved reserved reserved temperature data from adc, least significant bits reserved - always reads zero bit function operation d[7:4] measured temperature data for the remote zone, least significant bits. read only d[3:0] reserved always reads as zeroes power-up default value: 0000 0000 b = 00 h (0 c)** read command byte: 0001 0000 b = 10 h each lsb represents one-sixteenth degree centigrade. the values are in a binary format such that 1/16th c (0.0625 c) is reported as 0001 0000 b . see temperature data format (above) for more details. temp1l can be accessed using a read_byte operation. however, the complete remote temperature result in both temp1h and temp1l may be obtained by performing a read_word operation on temp1h. the MIC280 will respond to a read_word with a command byte of 01h (temp1h) by returning the value in temp1h followed by the value in temp1l. this guarantees that the data in both registers is from the same temperature-to-digital conversion cycle. the read_word operation is diagramed in figure 3. temp1h is the only MIC280 register that supports read_word. **temp1l will contain measured temperature data after the completion of one conversion. remote temperature high limit low-byte register (thigh1l) 8-bits, read/write remote temperature high limit low-byte register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write reserved reserved reserved reserved high temperature limit for remote zone, least significant bits. reserved - always reads zero bit function operation d[7:4] high temperature limit for the remote zone, least significant bits. read/write d[3:0] reserved. always reads as zeros power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0001 0011 b = 13 h each lsb represents one-sixteenth degree centigrade. the values are in a binary format such that 1/16th c (0.0625 c) is reported as 0001 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
june 2001 19 MIC280 MIC280 micrel remote temperature low limit low-byte register (tlow1l) 8-bits, read/write remote temperature low limit low-byte register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write reserved reserved reserved reserved low temperature limit for remote zone, least significant bits. reserved - always reads zero. bit function operation d[7:4] low temperature limit for the remote zone, least significant bits. read/write d[3:0] reserved always reads as zeros. power-up default value: 0000 0000 b = 00 h (0 c) read/write command byte: 0001 0100 b = 14 h each lsb represents one-sixteenth degree centigrade. the values are in a binary format such that 1/16th c (0.0625 c) is reported as 0001 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. remote over-temperature limit register (crit1) 8-bit, read/write remote over-temperature limit register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write over-temperature limit for remote zone. bit function operation d[7:0] over-temperature limit for the remote zone. read/write power-up default value: 0110 0100 b = 64 h (100 c) read/write command byte: 0001 1001 b = 19 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
MIC280 micrel MIC280 20 june 2001 local over-temperature limit register (crit0) 8-bits, read/write local over-temperature limit register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read/write read/write read/write read/write read/write read/write read/write read/write over-temperature limit for local zone. bit function operation d[7:0] over-temperature limit for the local zone. read/write power-up default value: 0100 0110 b = 46 h (70 c) read/write command byte: 0010 0000 b = 20 h each lsb represents one degree centigrade. the values are in a two s complement binary format such that 0 c is reported as 0000 0000 b . see temperature data format (above) for more details. any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. manufacturer id register (mfg_id) 8-bits, read only manufacturer id register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read only read only read only read only read only read only read only read only 00101010 bit(s) function operation * d[7:0] identifies micrel as the manufacturer of the device. always returns 2a h . read only. always returns 2a h power-up default value: 0010 1010 b = 2a h read command byte: 1111 1110 b = fe h die revision register (die_rev) 8-bits, read only die revision register d[7] d[6] d[5] d[4] d[3] d[2] d[1] d[0] read-only read-only read-only read-only reserved reserved reserved reserved MIC280 die revision number bit(s) function operation* d[7:0] identifies the device revision number read only. power-up default value: [device revision number] h read command byte: 1111 1111 b = ff h
june 2001 21 MIC280 MIC280 micrel application information remote diode selection most small-signal pnp transistors with characteristics similar to the jedec 2n3906 will perform well as remote tempera- ture sensors. table 8 lists several examples of such parts that micrel has tested for use with the MIC280. other transistors equivalent to these should also work well. vendor part number package fairchild semiconductor mmbt3906 sot-23 on semiconductor mmbt3906l sot-23 philips semiconductor pmbt3906 sot-23 samsung semiconductor kst3906-tf sot-23 table 8: transistors suitable for use as remote diodes minimizing errors self-heating one concern when using a part with the temperature accu- racy and resolution of the MIC280 is to avoid errors induced by self-heating (v dd i dd ) + (v ol i ol ). in order to under- stand what level of error this might represent, and how to reduce that error, the dissipation in the MIC280 must be calculated and its effects reduced to a temperature offset. the worst-case operating condition for the MIC280 is when v dd = 3.6v. the maximum power dissipated in the part is given in the following equation: p d = [(i dd v dd )+(i ol(data) v ol(data) )+(i ol(/int) v ol(/int) ] p d = [(0.4ma 3.6v)+(6ma 0.5v)+(6ma 0.5v)] p d = 7.44mw r (j-a) of sot23-6 package is 230 c/w theoretical maximum ? t j due to self-heating is: 7.44mw 230 c/w = 1.7112 c worst-case self-heating in most applications, the /int output will be low for at most a few milliseconds before the host resets it back to the high state, making its duty cycle low enough that its contribution to self-heating of the MIC280 is negligible. similarly, the data pin will in all likelihood have a duty cycle of substantially below 25% in the low state. these considerations, combined with more typical device and application parameters, give a better system-level view of device self-heating in interrupt-mode usage given in the following equation: (0.23ma i dd(typ) 3.3v) + (25% 1.5ma i ol(data) 0.15v) + (1% 1.5ma i ol(/int) 0.15v) = 0.817mw ? t j = (0.8175mw 230 c/w) = 0.188 c real-world self-heating example in any application, the best test is to verify performance against calculation in the final application environment. this is especially true when dealing with systems for which tem- perature data may be poorly defined or unobtainable except by empirical means. series resistance the operation of the MIC280 depends upon sensing the v cb-e of a diode-connected pnp transistor ( diode ) at two different current levels. for remote temperature measure- ments, this is done using an external diode connected be- tween t1 and ground. since this technique relies upon measuring the relatively small voltage difference resulting from two levels of current through the external diode, any resistance in series with the external diode will cause an error in the temperature reading from the MIC280. a good rule of thumb is this: for each ohm in series with the external transistor, there will be a 0.8 c error in the MIC280 s tem- perature measurement. it is not difficult to keep the series resistance well below an ohm (typically < 0.1), so this will rarely be an issue. filter capacitor selection it is usually desirable to employ a filter capacitor between the t1 and gnd pins of the MIC280. the use of this capacitor is recommended in environments with a lot of high frequency noise (such as digital switching noise), or if long wires are used to conect to the remote diode. the maximum recom- mended total capacitance from the t1 pin to gnd is 2200pf. this typically suggests the use of a 1800pf np0 or c0g ceramic capacitor with a 10% tolerance. if the remote diode is to be at a distance of more than 6"-12" from the MIC280, using twisted pair wiring or shielded microphone cable for the connections to the diode can significantly reduce noise pickup. if using a long run of shielded cable, remember to subtract the cable's conductor-to-shield capacitance from the 2200pf maximum total capacitance. layout considerations the following guidelines should be kept in mind when design- ing and laying out circuits using the MIC280: 1. place the MIC280 as close to the remote diode as possible, while taking care to avoid severe noise sources such as high frequency power transformers, crts, memory and data busses, and the like. 2. since any conductance from the various volt- ages on the pc board and the t1 line can induce serious errors, it is good practice to guard the remote diode's emitter trace with a pair of ground traces. these ground traces should be returned to the MIC280's own ground pin. they should not be grounded at any other part of their run. however, it is highly desirable to use these guard traces to carry the diode's own ground return back to the ground pin of the MIC280, thereby providing a kelvin connection for the base of the diode. see figure 6. 3. when using the MIC280 to sense the tempera- ture of a processor or other device which has an integral thermal diode, e.g., intel's pentium ii, iii, iv, amd athlon cpu, xilinx virtex fpgas, connect the emitter and base of the remote sensor to the MIC280 using the guard traces
MIC280 micrel MIC280 22 june 2001 and kelvin return shown in figure 6. the collector of the remote diode is typically inacces- sible to the user on these devices. to allow for this, the MIC280 has superb rejection of noise appearing from collector to gnd. 4. due to the small currents involved in the mea- surement of the remote diode s ? v be , it is important to adequately clean the pc board after soldering to prevent current leakage. this is most likely to show up as an issue in situations where water-soluble soldering fluxes are used. 5. in general, wider traces for the ground and t1 lines will help reduce susceptibility to radiated noise (wider traces are less inductive). use trace widths and spacing of 10 mils wherever possible and provide a ground plane under the MIC280 and under the connections from the MIC280 to the remote diode. this will help guard against stray noise pickup. remote diode (t1) guard/return 1 2 vdd gnd t1 6 5 4 3 /int data clk guard/return MIC280 figure 6. guard traces/kelvin ground returns data 5 4 62 3 1 to serial bus host 2n3906/ cpu diode 1800pf MIC280 clk /int 3v to 3.6v 100 ? 3 10k vdd t1 gnd 0.1 f ceramic 4.7 f figure 7. v dd decoupling for very noisy supplies 6. always place a good quality power supply bypass capacitor directly adjacent to, or under- neath, the MIC280. this should be a 0.1 f ceramic capacitor. surface-mount parts provide the best bypassing because of their low induc- tance. 7. when the MIC280 is being powered from particularly noisy power supplies, or from supplies which may have sudden high-amplitude spikes appearing on them, it can be helpful to add additional power supply filtering. this should be implemented as a 100 ? resistor in series with the part s v dd pin, and a 4.7 f, 6.3v electrolytic capacitor from v dd to gnd. see figure 7.
june 2001 23 MIC280 MIC280 micrel package information 0.20 (0.008) 0.09 (0.004) 0.60 (0.024) 0.10 (0.004) 3.00 (0.118) 2.80 (0.110) 10 0 3.00 (0.118) 2.60 (0.102) 1.75 (0.069) 1.50 (0.059) 0.95 (0.037) ref 1.30 (0.051) 0.90 (0.035) 0.15 (0.006) 0.00 (0.000) dimensions: mm (inch) 0.50 (0.020) 0.35 (0.014) 1.90 (0.075) ref 6-lead sot23 (m6) micrel inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for an y infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or pat ent right of micrel inc. ? 2001 micrel incorporated

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