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1 ds04-27402-2e fujitsu semiconductor data sheet assp power-voltage monitoring ic with watchdog timer mb3793- 42/30 n description the mb3793 is an integrated circuit to monitor power voltage; it incorporates a watchdog timer. a reset signal is output when the power is cut or falls abruptly. when the power recovers normally after resetting, a power-on reset signal is output to microprocessor units (mpus). an internal watchdog timer with two inputs for system operation diagnosis can provide a fail-safe function for various application systems. two models with detection voltages of 4.2 and 3.0 v are available. there is also a mask option that can detect voltages of 4.9 to 3.0 v in 0.1-v steps. the model numbers are MB3793-42 or -30 corresponding to the detected voltage. the model number and package code are as shown below. n features precise detection of power voltage fall: 2.5% detection voltage with hysteresis low power dispersion: icc = 27 m a (reference) internal dual-input watchdog timer watchdog-timer halt function (by inhibition pin) independently-set watchdog and reset times mask option for detection voltage (4.9 to 3.0 v, 0.1-v steps) model no. package code detection voltage MB3793-42 3793-a 4.2 v mb3793-30 3793-n 3.0 v 8-pin plastic dip (dip-8p-m01) this device contains circuitry to protect the inputs against damage due to high static voltages or electric ?lds. however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum rated voltages to this high impedance circuit. 8-pin plastic sol (fpt-8p-m02)
2 mb3793 -42/30 n pin assignment n pin description pin no. symbol description pin no. symbol description 1 reset outputs reset 5 v cc power supply 2 ctw sets monitoring time 6 inh inhibits watchdog timer function 3 ctp sets power-on reset hold time 7 ck2 inputs clock 2 4 gnd ground 8 ck1 inputs clock 1 reset ctw ctp gnd 8 7 6 5 ck1 ck2 inh v cc 1 2 3 4 (top view) (dip-8p-m01) (fpt-8p-m02)
3 mb3793 -42/30 n block diagram q + - - + (3) (1) (6) (2) (8) (7) inh ctw ck2 (4) v s rsff2 qs r q rsff1 qs r v ref ? 1.24 v i 1 ? 3 m ai 2 ? 30 m a comp. s comp. o r1 ? 280 to 760 k w r1 ? 240 k w to gnd of all blocks to v cc of all blocks output buffer pulse generator 1 pulse generator 2 watchdog timer reference voltage generator gnd ctp reset (5) v cc ck1
4 mb3793 -42/30 n block functions 1. comp. s comp. s is a comparator with hysteresis to compare the reference voltage with a voltage (v s ) that is the result of dividing the power voltage (v cc ) by resistors 1 and 2. when v s falls below 1.24 v, a reset signal is output. this function enables the mb3793 to detect an abnormality within 1 m s when the power is cut or falls abruptly. 2. comp. o comp. o is a comparator to control the reset signal (reset ) output and compares the threshold voltage with the voltage at the ctp pin for setting the power-on reset hold time. when the voltage at the ctp pin exceeds the threshold voltage, resetting is canceled. 3. reset output buffer since the reset (reset ) output buffer has cmos organization, no pull-up resistor is needed. 4. pulse generator the pulse generator generates pulses when the voltage at the ck1 and ck2 clock pins changes to high from low level (positive-edge trigger) and exceeds the threshold voltage; it sends the clock signal to the watchdog timer. 5. watchdog timer the watchdog timer can monitor two clock pulses. short-circuit the ck1 and ck2 clock pins to monitor a single clock pulse. 6. inhibition pin the inhibition (inh) pin forces the watchdog timer on/off. when this pin is high level, the watchdog timer is stopped. 7. flip-?p circuit the ?p-?p circuit rsff1 controls charging and discharging of the power-on reset hold time setting capacity (c tp ). the ?p-?p circuit rsff2 switches the charging accelerator for charging c tp during resetting on/off. this circuit only functions during resetting and does not function at power-on reset.
5 mb3793 -42/30 n standard connection reset ctw ctp c tp c tw v cc mb3793 ck1 ck2 gnd inh microprocessor 1 reset ck v cc gnd reset ck v cc gnd v cc microprocessor 2 equation of time-setting capacitances (c tp and c tw ) and set time t pr (ms) ? a x c tp ( m f) t wd (ms) ? b x c tw ( m f) + c x c tp ( m f) however, when about 10, t wd (ms) ? b x c tw ( m f) t wr (ms) ? d x c tp ( m f) (example) when c tp = 0.1 m f and c tw = 0.01 m f, MB3793-42 mb3793-30 t pr ? 130 [ms] t pr ? 75 [ms] t wd ? 15 [ms] t wd ? 16 [ms] t wr ? 10 [ms] t wr ? 5.5 [ms] values of a, b, c, and d model no. abcd remark MB3793-42 1300 1500 3 100 mb3793-30 750 1600 4 55 c tp c tw
6 mb3793 -42/30 n timing chart 1. basic operation (positive clock pulse) reset t ckw t pr ctw inh ck2 ck1 v sl v sh v ccl t wd t pr t wr (1) (2) (3)(4) (5) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) v l v h v th v cc ctp
7 mb3793 -42/30 2. basic operation (negative clock pulse) reset t ckw t pr ctw ctp inh ck2 ck1 v cc v sl v sh v ccl t wd t pr t wr (1) (2) (3)(4) (5) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) v l v h v th
8 mb3793 -42/30 3. single-clock input monitoring (positive clock pulse) reset ctw ctp ck2 ck1 t wr v l v h v th
9 mb3793 -42/30 4. inhibition operation (positive clock pulse) reset t ckw t pr ctw ctp inh ck2 ck1 v cc v sl v sh v ccl t wd t pr t wr (1) (2) (3)(4) (5) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) v l v h v th
10 mb3793 -42/30 5. clock pulse input (positive clock pulse) n operation sequence the operation sequence is explained by using timing chart 1. the following item numbers correspond to the numbers in timing chart 1. (1) when the power voltage (v cc ) reaches about 0.8 v (v ccl ), a reset signal is output. (2) when v cc exceeds the rising-edge detection voltage (v sh ), charging of power-on reset hold time setting capacitance (c tp ) is started. v sh is about 4.3 v in the MB3793-42 and 3. 07 v in the mb3793-30. (3) when the voltage at the ctp pin setting the power-on reset hold time exceeds the threshold voltage (v th ), resetting is canceled and the voltage at the reset pin changes to high level to start charging of the watchdog-timer monitoring time setting capacitance (c tw ). vth is about 3.6 v in the MB3793-42 and 2.4 v in the mb3793-30. the power-on reset hold time (t pr ) can be calculated by the following equation. t pr (ms) ? a x c tp ( m f) where, a is about 1300 in the MB3793-42 and 750 in the mb3793-30. (4) when the voltage at the ctw pin setting the monitoring time reaches high level (v h ), c tw switches to discharging from charging. v h is about 1.24 v (reference value) in both the MB3793-42 and mb3793-30. (5) when clock pulses are input to the ck2 pin during c tw discharging after clock pulses are input to the ck1 pin?ositive-edge trigger, c tw switches to charging. (6) if clock pulse input does not occur at either the ck1 or ck2 clock pins during the watchdog-timer monitoring time (t wd ), the ctw voltage falls below low level (v l ), a reset signal is output, and the voltage at the reset pin changes to low level. v l is about 0.24 v in both the MB3793-42 and mb3793-30. t wd can be calculated from the following equation. t wd (ms) ? b x c tw ( m f) + c x c tp ( m f) where, b is about 1500 in the MB3793-42 and 1600 in the mb3793-30. c is about 3 in the MB3793-42 and 4 in the mb3793-30; it is much smaller than b. hence, when 10, the calculation can be simpli?d as follows: t wd (ms) ? b x c tw ( m f) ctw v l v h ck1 ck2 b the mb3793 watchdog timer monitors clock 1 (ck1) and clock 2 (ck2) pulses alternately. when a ck2 pulse is detected after detecting a ck1 pulse, the monitoring time setting capacity (c tw ) switches to charging from discharging. when two consecutive pulses occur on one side of this alternation before switching, the second pulse is ignored. in the above ?ure, pulses a and b are ignored. a ctp ctw
11 mb3793 -42/30 (7) when the voltage of the ctp pin exceeds v th again as a result of recharging c tp , resetting is canceled and the watchdog timer restarts monitoring. the watchdog timer reset time (t wr ) can be calculated by the following equation. t wr (ms) ? d x c tp ( m f) where, d is about 100 in the MB3793-42 and 55 in the mb3793-30. (8) when v cc falls below the rising-edge detection voltage (v sl ), the voltage of the ctp pin falls and a reset signal is output, and the voltage at the reset pin changes to low level. v sl is about 4.2 v in the MB3793-42 and 3.0 v in the mb3793-30. (9) when v cc exceeds v sh , c tp begins charging. (10) when the voltage of the ctp pin exceeds v th , resetting is canceled and the watchdog timer restarts. (11) when an inhibition signal is input (inh pin is high level), the watchdog timer is halted forcibly. in this case, v cc monitoring is continued ((8) - (9)) without the watchdog timer. the watchdog timer does not function unless this inhibition input is canceled. (12) when the inhibition input is canceled (inh pin is low level), the watchdog timer restarts. (13) when the v cc voltage falls below v sl after power-off, a reset signal is output. similar operation is also performed for negative clock-pulse input (timing chart 2). short-circuit the clock pins ck1 and ck2 to monitor a single clock. the basic operation is the same but the clock pulses are monitored at every other pulse (timing chart 3). n absolute maximum ratings *the power voltage is based on the ground voltage (0 v). note: permanent device damage may occur if the above absolute maximum ratings are exceeded. functional operation should be restricted to the conditions as detailed in the operational sections of this data sheet. exposure to absolute maximum rating conditions for extended periods may affect device reliability. n recommended operating conditions note: these recommended operation conditions guarantee normal logic operation of an lsi circuit. the limits of the ac and dc electrical characteristics are guaranteed within these recommended conditions. (ta = +25 c) parameter symbol limits symbo power voltage* v cc -0.3 to +7 v input voltage ck1 v ck1 -0.3 to +7 v ck2 v ck2 inh v inh reset output voltage (direct current) reset i ol i oh -10 to +10 ma allowable loss (ta +85 c) p d 200 mw storage temperature tstg -55 to +125 c parameter symbol limits unit min. typical max. reset (reset ) output current i ol i oh -5 - +5 ma power-on reset hold time setting capacity c tp 0.001 - 10 m f watchdog-timer monitoring time setting capacity c tw 0.001 - 1 m f watchdog timer monitoring time t wd 0.1 - 1500 ms operating ambient temperature ta -40 - +85 c
12 mb3793 -42/30 n electrical characteristics 1. dc characteristics *at clock input pins ck1 and ck2, the pulse input frequency is 1 khz and the pulse amplitude is 0 v to v cc . **inhibition input is at high level. (v cc = +5 v (MB3793-42), v cc = +3.3 v (mb3793-30), ta = +25 c) parameter symbol test conditions limits unit min. typical max. power current MB3793-42 i cc1 watchdog timer operation* - 27 50 m a i cc2 watchdog timer halt** - 25 45 mb3793-30 i cc1 watchdog timer operation* - 25 45 m a i cc2 watchdog timer halt** - 24 45 detection voltage MB3793-42 v sl v cc falling ta = +25 c 4.10 4.20 4.30 v ta = -40 to +85 c 4.05 4.20 4.35 v sh v cc rising ta = +25 c 4.20 4.30 4.40 v ta = -40 to +85 c 4.15 4.30 4.45 mb3793-30 v sl v cc falling ta = +25 c 2.90 3.00 3.10 v ta = -40 to +85 c 2.85 3.00 3.15 v sh v cc rising ta = +25 c 2.97 3.07 3.17 v ta = -40 to +85 c 2.92 3.07 3.22 detection voltage hysteresis difference MB3793-42 v shys v sh - v sl 50 100 150 mv mb3793-30 30 70 110 mv clock-input threshold voltage v thch - (1.4) 1.9 (2.5) v v thcl - (0.8) 1.3 (1.8) v clock-input hysteresis v chys - (0.4) 0.6 (0.8) v inhibition-input threshold voltage v thin - 0.8 1.5 2.0 v input current ck1 ck2 inh i ih v ck = v cc - 0 1.0 m a i il v ck = 0 v -1.0 0 - m a reset output voltage MB3793-42 v oh i reset = -5 ma 4.5 4.75 - v v ol i reset = +5 ma - 0.12 0.4 v mb3793-30 v oh i reset = -3 ma 2.8 3.10 - v v ol i reset = +3 ma - 0.12 0.4 v reset-output minimum power voltage v ccl i reset = +50 m a - 0.8 1.2 v
13 mb3793 -42/30 2. ac characteristics *the voltage range is 10% to 90% at testing the reset output transition time. n watchdog timer use example 1. monitoring two clocks (v cc = +5 v (MB3793-42), v cc = +3.3 v (mb3793-30), ta = +25 c) parameter symbol test conditions limits unit min. typical max. power-on reset hold time MB3793-42 t pr c tp = 0.1 m f 80 130 180 ms mb3793-30 30 75 120 ms watchdog timer monitoring time MB3793-42 t wd c tw = 0.01 m f c tp = 0.1 m f 7.5 15 22.5 ms mb3793-30 8 16 24 ms watchdog timer reset time MB3793-42 t wr c tp = 0.1 m f 51015ms MB3793-42 2.0 5.5 9 ms clock (ck1, ck2) input pulse duration t ckw - 500 - - ns reset (reset ) output transition time* rising t tlh c l = 50pf - - 500 ns falling t thl c l = 50pf - - 500 ns ctw ctp c tp c tw v cc mb3793 ck1 gnd inh microprocessor 1 reset ck v cc gnd reset ck v cc gnd v cc (2) (3) (5) (6) (4) (1) reset (8) (7) microprocessor 2 ck2
14 mb3793 -42/30 2. monitoring single clock 3. watchdog timer stopping ctw ctp c tp c tw v cc mb3793 gnd inh reset ck v cc gnd v cc (2) (3) (5) (6) (4) (1) reset (8) (7) microprocessor ck2 ck1 reset ctw ctp c tp c tw v cc mb3793 gnd reset ck v cc gnd reset ck v cc gnd v cc inh (6) (2) (3) (5) (1) (8) (7) (4) halt halt microprocessor 1 microprocessor 2 ck2 ck1
15 mb3793 -42/30 n reference characteristic curves (for MB3793-42) typ 500 400 300 200 100 0 ta -40 c +25 c +85 c vreset 98 mv 135 mv 167 mv ron 19.6 w 33.4 w 27 w 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 MB3793-42 f = 1 khz duty ? 10% v l = 0 v v h = v cc v inh v cc ctw 0.01 m f ctp 0.1 m f 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 40 35 30 25 20 15 10 -40 -20 0 20 40 60 80 100 4.5 4.4 4.3 4.2 4.1 4.0 ta = -40 to +85 c v sh v sl v sh (ta = +25 c) max typ min max min v sl (ta = +25 c) ta = -40 to +85 c 0-1-2-3-4-5-6-7-8-9-10 ta = -40 c ta = +25 c ta = +85 c ta -40 c +25 c +85 c vreset 4,800 v 4,750 v 4,707 v ron 40 w 58.6 w 50 w ireset -5 ma 012345678910 ta = -40 c ta = +25 c ta = +85 c power current - power voltage detection voltage - ambient temperature power current: i cc ( m a) detection voltage: v sh and v sl (v) power voltage: v cc (v) ambient temperature: ta ( c) ireset 5 ma reset output voltage - reset output current (p-mos side) reset output voltage - reset output current (n-mos side) reset output voltage: v reset (v) reset output voltage: v reset (mv) reset output current: i reset (ma) reset output current: i reset (ma) watchdog timer monitoring (v inh = 0 v) watchdog timer stopping (v inh = v cc ) reset (v cc < v sh ) inhibited
16 mb3793 -42/30 260 240 220 200 180 160 140 120 100 80 60 40 20 0 -40 -20 0 20 40 60 80 100 ta = +25 c ta = +85 c ta = -40 c 0 1234567 7 6 5 4 3 2 1 0 ta = +25 c max typ min -40 -20 0 20 40 60 80 100 ta = -40 to +85 c 26 24 22 20 18 16 14 12 10 8 6 4 2 0 max typ min ta = +25 c -40 -20 0 20 40 60 80 100 ta = -40 to +85 c 26 24 22 20 18 16 14 12 10 8 6 4 2 0 max typ min ta = +25 c reset output voltage - power voltage power voltage: v cc (v) reset output voltage: v reset (v) reset-on reset time - ambient temperature (when v cc rising) ambient temperature: ta ( c) power-on reset time: t pr (ms) watchdog timer reset time: t wr (ms) watchdog timer monitoring time: t wd (ms) ambient temperature: ta ( c) ambient temperature: ta ( c) watchdog timer reset time - ambient temperature (when monitoring) watchdog timer monitoring time - ambient temperature pull-up resistance: 100 k w ta = -40 to +85 c
17 mb3793 -42/30 10 -5 10 -4 10 -3 10 -2 10 -1 110 1 10 3 10 2 10 1 1 10 -1 10 -4 10 -3 10 -2 10 -1 110 1 10 2 10 4 10 3 10 2 10 1 1 10 -1 10 -4 10 -3 10 -2 10 -1 110 1 10 2 10 3 10 2 10 1 1 10 -1 10 -2 10 -5 10 -4 10 -3 10 -2 10 -1 110 1 10 4 10 3 10 2 10 1 1 10 -1 power-on reset time - c tp capacitance power-on reset time setting capacitance: c tp ( m f) power-on reset time: t pr (ms) power-on reset time setting capacitance: c tp ( m f) reset time - c tp capacitance reset time: t wr (ms) watchdog-timer monitoring time - c tw capacitance (under ta condition) watchdog-timer monitoring time setting capacitance: c tw ( m f) watchdog-timer monitoring time: t wd (ms) watchdog-timer monitoring time - c tw capacitance (under ctp condition) watchdog-timer monitoring time setting capacitance: c tw ( m f) watchdog-timer monitoring time: t wd (ms) ta = +25 c ta = +85 c ta = -40 c ta = +25 c ta = -40 c ta = +85 c ta = +25 c ta = -40 c ta = +85 c c tp = 0.1 m f c tp = 1 m f c tp = 0.01 m f
18 mb3793 -42/30 n package dimensions +0.30 C0 +.012 +.012 C0 +.016 C.012 C.012 +.014 C0 +0.30 C0 +0.40 C0.30 C0.30 +0.35 (.244.010) 6.200.25 1 pin index 15max typ 7.62(.300) 0.51(.020)min (.010.002) 0.250.05 (.018.003) 0.460.08 typ 2.54(.100) 3.00(.118)min 4.36(.172)max .039 .060 .370 .035 1.52 0.99 9.40 0.89 1994 fujitsu limited d08006s-2c-3 c 8 pin, plastic dip (dip-8p-m01) dimensions in mm(inches).
19 mb3793 -42/30 +0.25 ?.20 +.010 ?008 45 (stand off) (.020?.008) details of "a" part 0.20(.008) 0.40(.016) 0.18(.007)max 0.65(.026)max "a" (.006?.004) (.197?.012) (.236?.016) (.154?.012) (.008?.002) (.017?.004) m ?0.13(.005) 0.10(.004) 5.05 .199 3.81(.150)ref 0.40(.016) 5.00?0.30 0.50?.020 6.00?0.40 3.90?0.30 0.15?0.10 1.55?0.20(.061?.008) 0.20?0.05 0.42?0.10 1.27(.050)typ 1994 fujitsu limited f08004s-2c-4 c 8 pin, plastic sop (fpt-8p-m02) dimensions in mm(inches).
24 fujitsu limited for further information please contact: japan fujitsu limited corporate global business support division electronic devices kawasaki plant, 4-1-1, kamikodanaka nakahara-ku, kawasaki-shi kanagawa 211-88, japan tel: (044) 754-3763 fax: (044) 754-3329 north and south america fujitsu microelectronics, inc. semiconductor division 3545 north first street san jose, ca 95134-1804, u.s.a. tel: (408) 922-9000 fax: (408) 432-9044/9045 europe fujitsu mikroelektronik gmbh am siebenstein 6-10 63303 dreieich-buchschlag germany tel: (06103) 690-0 fax: (06103) 690-122 asia paci? fujitsu microelectronics asia pte. limited #05-08, 151 lorong chuan new tech park singapore 556741 tel: (65) 281-0770 fax: (65) 281-0220 f9703 ? fujitsu limited printed in japan all rights reserved. the contents of this document are subject to change without notice. customers are advised to consult with fujitsu sales representatives before ordering. the information and circuit diagrams in this document presented as examples of semiconductor device applications, and are not intended to be incorporated in devices for actual use. also, fujitsu is unable to assume responsibility for infringement of any patent rights or other rights of third parties arising from the use of this information or circuit diagrams. fujitsu semiconductor devices are intended for use in standard applications (computers, office automation and other office equipment, industrial, communications, and measurement equipment, personal or household devices, etc.). caution: customers considering the use of our products in special applications where failure or abnormal operation may directly affect human lives or cause physical injury or property damage, or where extremely high levels of reliability are demanded (such as aerospace systems, atomic energy controls, sea floor repeaters, vehicle operating controls, medical devices for life support, etc.) are requested to consult with fujitsu sales representatives before such use. the company will not be responsible for damages arising from such use without prior approval. any semiconductor devices have inherently a certain rate of failure. you must protect against injury, damage or loss from such failures by incorporating safety design measures into your facility and equipment such as redundancy, fire protection, and prevention of over-current levels and other abnormal operating conditions. if any products described in this document represent goods or technologies subject to certain restrictions on export under the foreign exchange and foreign trade control law of japan, the prior authorization by japanese government should be required for export of those products from japan.

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