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19-1952; Rev 2; 8/03
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer
General Description
The MAX6701-MAX6708 microprocessor (P) supervisory circuits reduce the complexity and components required to monitor power-supply functions in P systems. These devices significantly improve system reliability and accuracy compared to separate ICs or discrete components. The MAX6701-MAX6708 family provides four functions: a reset output during power-up, power-down, and brownout conditions; an independent watchdog output that goes low if the watchdog input has not been toggled within 1.6s; a 0.62V threshold detector for power-fail warning; and an active-low manual reset input. The MAX6701-MAX6708 family offers several pinout options to accommodate a variety of multivoltage microprocessor supervision applications. The MAX6701(A)/MAX6702(A)/MAX6703(A) monitor three supply voltages (one fixed threshold and two adjustable) to drive a single reset output and include a manual reset input and a watchdog timer with an independent output. The MAX6704 monitors a single-supply voltage to drive complementary reset outputs and includes an independent adjustable power-fail-in/powerfail-out comparator, a manual reset input, and a resetbased watchdog timer. The MAX6705(A)/MAX6706(A)/ MAX6707(A) monitor a single-supply voltage to drive a single reset output and include an independent adjustable power-fail-in/power-fail-out comparator, a manual reset input, and a watchdog timer with an independent output. The MAX6708 is the same as the MAX6704 but without the watchdog timer function. See the Detailed Description for differences between non-A and A versions.
Features
o Small 8-Pin SOT23 Package o Precision Monitoring of +5.0V, +3.3V, +3.0V, +2.5V Supply Voltages o 140ms Reset Timeout Delay o Power-Fail Input with Independent Output; Monitor Inputs Down to 0.62V (MAX6704-MAX6708) o Dual Adjustable Reset Input for Triple-Voltage Monitoring (MAX6701(A)/MAX6702(A)/MAX6703(A)) o 1.6s Watchdog Timeout Period (MAX6701(A)-MAX6707(A)) o Independent Watchdog Output (MAX6701(A)/MAX6702(A)/MAX6703(A)/ MAX6705(A)/MAX6706(A)/MAX6707(A)) o Manual Reset Input o Four Reset Output Stage Options Active Low Push-Pull (MAX6701(A), MAX6705(A)) Active Low Open Drain (MAX6703(A), MAX6707(A)) Active High Push-Pull (MAX6702(A), MAX6706(A)) Dual Active Low/High Push-Pull (MAX6704, MAX6708) o Guaranteed Reset Valid to VCC = 1V o Immune to Short Falling VCC Transients o Low Cost, Few External Components
MAX6701-08/MAX6701A-03A/05A-07A
Ordering Information
PART MAX6701_KA-T MAX6701A_KA-T TEMP RANGE -40C to +125C -40C to +125C PIN-PACKAGE 8 SOT23-8 8 SOT23-8
Applications
Computers Controllers Intelligent Instruments Automotive Systems Critical P Power Monitoring White Goods Networking Telecommunications
Insert the desired suffix letter (from the Threshold Suffix Guide table) into the blank to complete the part number. All devices must be ordered in increments of 2500 pieces. Sample stock is typically held on standard versions only. Contact factory for availability. Ordering Information continued at end of data sheet.
Pin Configurations
TOP VIEW
MR VCC GND 1 2 3 8 7 WDO RESET (RESET) WDI RST_IN2
MAX6701(A) MAX6702(A) MAX6703(A)
6 5
RST_IN1 4
Typical Operating Circuit and Selector Guide appear at end of data sheet.
( ) ARE FOR MAX6702(A) ONLY.
SOT23
Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
ABSOLUTE MAXIMUM RATINGS
VCC ........................................................................-0.3V to +6.0V Open-Drain RESET, WDO, PFO ...........................-0.3V to +6.0V Push-Pull RESET, RESET, WDO, PFO ........-0.3V to (VCC + 0.3V) MR, WDI, PFI, RST_IN1, RST_IN2 ..............-0.3V to (VCC + 0.3V) Input Current (VCC) .............................................................20mA Output Current (RESET, RESET, PFO, WDO) .....................20mA Continuous Power Dissipation (TA = +70C) 8-Pin SOT23 (derate 8.9mW/C above +70C)............714mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +4.25V to +5.5V for L/M versions, VCC = +2.55V to +3.6V for the T/S/R versions, VCC = +2.1V to +2.75V for the Z/Y versions. TA = -40C to +125C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range Supply Current MR Unconnected SYMBOL VCC CONDITIONS TA = 0C to +125C TA = -40C to +125C VCC < 5.5V, no load ICC VCC < 3.6V, no load VCC < 3.6V, no load (MAX6708 only) MAX670_L/MAX670_AL MAX670_M/MAX670_AM MAX670_T/MAX670_AT VCC Reset Threshold (VCC falling) VTH MAX670_S/MAX670_AS MAX670_R/MAX670_AR MAX670_Z/MAX670_AZ MAX670_Y/MAX670_AY Reset Threshold Temperature Coefficient VCC to Reset Output Delay Reset Timeout Period VCC Falling to WDO Delay PFI, RST_IN1, RST_IN2 Threshold PFI Hysteresis tRP VTH VCC falling at 10mV/s TA = -40C to +85C TA = -40C to +125C MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/ MAX6706(A)/MAX6707(A) VCC = 1.8V to 5.5V TA = -40C to +85C TA = -40C to +125C 602 593 6 140 120 5 618 634 642 TA = -40C to +85C TA = -40C to +125C TA = -40C to +85C TA = -40C to +125C TA = -40C to +85C TA = -40C to +125C TA = -40C to +85C TA = -40C to +125C TA = -40C to +85C TA = -40C to +125C TA = -40C to +85C TA = -40C to +125C TA = -40C to +85C TA = -40C to +125C 4.50 4.47 4.25 4.22 3.00 2.97 2.85 2.83 2.55 2.53 2.25 2.24 2.12 2.11 60 12 200 280 300 2.19 2.32 2.63 2.93 3.08 4.38 MIN 1.0 1.2 12 9 6 4.63 TYP MAX 5.5 5.5 25 20 20 4.75 4.78 4.50 4.53 3.15 3.17 3.00 3.02 2.70 2.72 2.38 2.40 2.25 2.27 ppm/C s ms s mV mV V A UNITS V
2
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Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +4.25V to +5.5V for L/M versions, VCC = +2.55V to +3.6V for the T/S/R versions, VCC = +2.1V to +2.75V for the Z/Y versions. TA = -40C to +125C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER PFI, RST_IN1, RST_IN2 Leakage Current PFI to PFO Delay MR Input Voltage MR Minimum Input Pulse MR Glitch Rejection MR to Reset Delay VCC Rising to WDO Delay MR Pullup Resistance Watchdog Timeout Period WDI Pulse Width WDI Input Voltage WDI Input Current tWD tWDI VIL VIH IWDI WDI = 0V or VCC VCC 1.0V, ISINK = 50A, output asserted (TA = 0C to +125C) VOL VCC 1.2V, ISINK = 100A, output asserted VCC 2.55V, ISINK = 1.2mA, output asserted VCC 4.25V, ISINK = 3.2mA, output asserted PFO Output Low (Push-Pull or Open Drain) RESET, WDO, PFO Output High (Push-Pull Only) RESET, WDO, PFO Output Open-Drain Leakage Current VCC 1.80V, ISINK = 200A, output asserted VOL VCC 2.55V, ISINK = 1.2mA, output asserted VCC 4.25V, ISINK = 3.2mA, output asserted VOH VCC 2.7V, ISOURCE = 500A, output not asserted VCC 4.75V, ISOURCE = 800A, output not asserted VCC > VTH, output not asserted VCC 1.0V, ISOURCE = 1A, reset asserted (TA = 0C to +125C) RESET Output High (Push-Pull Only) VOH VCC 1.2V, ISOURCE = 50A, reset asserted VCC 2.55V, ISOURCE = 500A, reset asserted VCC 4.25V, ISOURCE = 800A, reset asserted RESET Output Low (Push-Pull Only) VOL VCC 2.7V, ISINK = 1.2mA, reset not asserted VCC 4.75V, ISINK = 3.2mA, reset not asserted 0.8 x VCC 0.8 x VCC 1.0 0.7 x VCC -1 +1 0.3 0.3 0.3 0.4 0.3 0.3 0.4 V V V TA = -40C to +85C TA = -40C to +125C (Note 2) tMD MAX6701(A)/MAX6702(A)/MAX6703(A)/ MAX6705(A)/MAX6706(A)/MAX6707(A) 25 1.12 0.96 50 0.3 x VCC tPF VIL VIH 0.7 x VCC 1 100 200 100 50 1.6 75 2.4 2.52 SYMBOL (Note 2) CONDITIONS TA = -40C to +85C TA = -40C to +125C MIN -50 -200 1 0.3 x VCC TYP MAX +50 +200 UNITS nA s V s ns ns ns k s ns V A
MAX6701-08/MAX6701A-03A/05A-07A
RESET, WDO Output Low (Push-Pull or Open Drain)
ILKG
A
0.8 x VCC 0.8 x VCC 0.8 x VCC 0.8 x VCC 0.3 0.4 V V
Note 1: Over-temperature limits are guaranteed by design and not production tested. Devices are tested at TA = +25C. Note 2: Guaranteed by design. Not production tested. _______________________________________________________________________________________ 3
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX6701 toc01
RESET TIMEOUT PERIOD vs. TEMPERATURE
MAX6701 toc02
VCC TO RESET OUTPUT DELAY vs. TEMPERATURE
MAX6701 toc03
20
210
20 VCC TO RESET OUTPUT DELAY (s)
16 SUPPLY CURRENT (A) VCC = 5V MAX6705(A)
RESET TIMEOUT PERIOD (ms)
205
15
12
200
10
8 VCC = 3.3V MAX6708
4
195
5
0 -40 -15 10 35 60 85 TEMPERATURE (C)
190 -40 -15 10 35 60 85 TEMPERATURE (C)
0 -40 -15 10 35 60 85 TEMPERATURE (C)
WATCHDOG TIMEOUT PERIOD vs. TEMPERATURE
MAX6701 toc04
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
MAX6701 toc05
MAXIMUM VCC TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE
MAXIMUM TRANSIENT DURATION (s) MAX670_Y 50 40 30 20 10 0 RESET OCCURS ABOVE LINE
MAX6701 toc06
1.70 WATCHDOG TIMEOUT PERIOD (s)
1.05 1.04 NORMALIZED RESET THRESOLD 1.03 1.02 1.01 1.00 0.99 0.98 0.97 0.96
60
1.65
1.60
1.55
1.50 -40 -15 10 35 60 85 TEMPERATURE (C)
0.95 -40 -15 10 35 60 85 TEMPERATURE (C)
0
40
80
120
160
RESET THRESHOLD OVERDRIVE (mV)
OUTPUT VOLTAGE LOW vs. SINK CURRENT
MAX6701 toc07
VCC - VOH vs. SOURCE CURRENT
VCC 4.25V
300 250 VCC - VOH (mV) 200 150 100 50
MAX6701 toc08
100
VCC 4.25V
75 VOL (mV)
350
50
25
0 0 400 800 1200 1600 2000 2400 2800 3200 SINK CURRENT (A)
0 0 400 800 1200 1600 2000 2400 2800 3200 SOURCE CURRENT (A)
4
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Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer
Pin Description
PIN MAX6701(A) MAX6702(A) MAX6704 MAX6703(A) MAX6705(A) MAX6706(A) MAX6708 MAX6707(A) NAME FUNCTION
MAX6701-08/MAX6701A-03A/05A-07A
1
1
1
1
MR
Active-Low, Manual Reset Input, Internal 50k Pullup to VCC. Pull low to force a reset. Reset remains active as long as MR is low and the reset timeout period after MR goes high. Leave unconnected or connect to VCC if unused. WDO deasserts when MR is low (MAX6701(A)/MAX6702(A)/MAX6703(A)/ MAX6705(A)/ MAX6706(A)/MAX6707(A) only). Supply Voltage for MAX6701-MAX6708 and Input for Primary Reset Threshold Monitor. Push-pull outputs are powered by VCC. Ground Power-Fail Voltage Monitor Input. High-impedance input for internal power-fail comparator. Connect this pin to an external resistive-divider network to set the reset threshold voltage; 0.62V (typ) threshold. Connect to GND or VCC when not used. Power-Fail Monitor Output. Open drain or push-pull active low. PFO goes low when PFI is less than 0.62V. Watchdog Input. If WDI remains high or low for longer than the watchdog timeout period, the internal watchdog timer runs out and WDO is asserted. WDO is asserted low after each watchdog overflow and remains low until the watchdog timer is cleared (the reset output is not affected). The internal watchdog timer clears whenever a VCC/RST_IN1/RST_IN2 reset is asserted, the manual reset is asserted, or WDI sees a rising or falling edge. The watchdog timer remains cleared until the reset output is deasserted. On the MAX6704, RESET pulse asserts for the reset timeout period after each watchdog timeout overflow. The watchdog timer cannot be disabled. No Connection. Not internally connected. Active-Low Reset Output (Open Drain or Push-Pull). RESET changes from high to low when the VCC input drops below the selected reset threshold (or RST_IN1/ RST_IN2 for the MAX6701(A)/MAX6702(A)/MAX6703(A), MR is pulled low, or the watchdog triggers a reset (MAX6704 only). RESET remains low for the reset timeout period after the reset conditions are terminated.
2 3
2 3
2 3
2 3
VCC GND
--
4
4
4
PFI
--
5
5
5
PFO
6
6
6
--
WDI
--
--
--
6
N.C.
7
7
7
7
RESET
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5
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
Pin Description (continued)
PIN MAX6701(A) MAX6702(A) MAX6704 MAX6703(A) MAX6705(A) MAX6706(A) MAX6708 MAX6707(A) NAME FUNCTION
8
--
8
--
WDO
Active-Low Watchdog Output (Open Drain or Push-Pull). WDO is asserted whenever the watchdog times out and VCC or the reset inputs are below their respective thresholds. WDO deasserts after a valid WDI transition without a reset timeout period. In the A versions, WDO deasserts without a timeout delay when VCC, RST_IN1, and RST_IN2 rises above its threshold. Pull MR low to assert WDO (MAX6701/MAX6702/ MAX6703/MAX6705/MAX6706/MAX6707 only). Pull MR low to deassert WDO (MAX6701(A)/MAX6702(A)/MAX6703(A)/ MAX6705(A)/MAX6706(A)MAX6707(A) only). Active-High Reset Output (Push-Pull). RESET changes from low to high when the VCC input drops below the selected reset threshold (or RST_IN1/RST_IN2 for MAX6701(A)/MAX6702(A)/ MAX6703(A), MR is pulled low, or the watchdog triggers a reset (MAX6704 only). RESET remains high for the reset timeout period after the reset conditions are terminated. Input for User-Adjustable VCC2 Monitor. High-impedance input for second internal reset comparator. Connect this pin to an external resistive-divider network to set the reset threshold voltage; 0.62V (typ) threshold. Connect to VCC when not used. Reset is asserted when either VCC, RST_IN1, or RST_IN2 are below threshold. Input for User-Adjustable VCC3 Monitor. High-impedance input for third internal reset comparator. Connect this pin to an external resistive-divider network to set the reset threshold voltage; 0.62V (typ) threshold. Connect to VCC when not used. Reset is asserted when either VCC, RST_IN1, or RST_IN2 are below threshold.
7*
8
7*
8
RESET
4
--
--
--
RST_IN1
5
--
--
--
RST_IN2
*RESET active-high for the MAX6702(A)/MAX6706(A).
Detailed Description
Figures 1, 2, and 3 are functional diagrams for the MAX6705(A)/MAX6706(A)/MAX6707(A), MAX6704/ MAX6708, and MAX6701(A)/ MAX6702(A)/MAX6703(A), respectively.
Reset Output
A microprocessor's (P's) reset input starts the P in a known state. The MAX6701-MAX6708 assert reset during power-up and prevent code execution errors during power-down or brownout conditions. On power-up, once VCC reaches 1V, RESET is a guaranteed logic low of 0.4V or less. As VCC rises, RESET
6
stays low. After VCC, RST_IN1, or RST_IN2 rise above the reset threshold, an internal timer holds RESET low for about 200ms. RESET pulses low whenever VCC dips below the reset threshold, including brownout conditions. If a brownout occurs in the middle of a previously initiated reset pulse, the pulse continues for at least another 140ms. On power-down, once VCC falls below the reset threshold, RESET stays low and is guaranteed to be 0.4V or less, until VCC drops below 1V. The MAX6702(A)/MAX6704/MAX6706(A)/MAX6708 active-high RESET output is the complement of the RESET output, and is guaranteed to be valid with VCC down to 1V.
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Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
6 VCC 50k MR 1 VCC 2 RESET GENERATOR 7 RESET (RESET)
VREF
WDI
WATCHDOG TIMER
8
VCC
WDO
50k
MR VCC
MAX6701(A) MAX6702(A) MAX6703(A)
RESET GENERATOR
RESET (RESET) WDO WATCHDOG TIMER WDI
VREF PFI 4
MAX6705(A) MAX6706(A) MAX6707(A)
5
RST_IN1
RST_IN2
PFO
0.62V 0.62V
0.62V
( ) ARE FOR MAX6706(A) ONLY.
3
GND
( ) ARE FOR MAX6702(A) ONLY.
Figure 1. MAX6705(A)/MAX6706(A)/MAX6707(A) Functional Diagram
Figure 3. MAX6701(A)/MAX6702(A)/MAX6703(A) Functional Diagram
VCC 50k
VTH VCC
VTH tRP tRP
MAX6704 MAX6708
8
MR VCC
1 2 RESET GENERATOR 7
RESET
VCC RESET 0V VCC MR 0V tMD
RESET
WATCHDOG TIMER
6
WDI (MAX6704 ONLY)
VREF
VCC WDO
5 PFO
PFI
4
0V MR EXTERNALLY DRIVEN LOW VCC WDI 0V
0.62V
3 GND
NOTE: THE MAX6706 RESET OUTPUT IS THE INVERSE OF THE RESET SHOWN.
Figure 2. MAX6704/MAX6708 Functional Diagram
Figure 4. MAX6705/MAX6706/MAX6707 RESET, MR, WDO, and WDI Timing 7
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Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
Standard- vs. A-Version Comparison
The MAX6701/MAX6702/MAX6703/MAX6705/MAX6706/ MAX6707s' WDO latches low when one of the following events occurs: * * * * The watchdog timer times out (1.6s, typ). VCC, RST_IN1, or RST_IN2 is below its reset threshold. MR is pulled low. WDO only deasserts with a valid WDI transition. threshold, WDO goes low whether or not the watchdog timer has timed out. Normally this would trigger an NMI, but RESET goes low simultaneously, and thus overrides the NMI. The MAX6704 watchdog circuit does not have an independent watchdog output (WDO). If the P does not toggle the watchdog input within 1.6s, the MAX6704 asserts a reset output pulse for the reset timeout period.
TheMAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/ MAX6706(A)/MAX6707(A)s' WDO asserts when either VCC, RST_IN1, or RST_IN2 is below its reset threshold. WDO deasserts without a timeout delay when the undervoltage situation has expired. WDO is latched low when the watchdog timer elapses without seeing a WDI transition. WDO deasserts with a valid WDI transition OR by pulling MR low. See Figures 4 and 5 for standard-version timing. See Figures 6 and 7 for A-version timing.
Manual Reset
The manual reset input (MR) allows reset to be triggered by a pushbutton switch. The switch is effectively debounced by the reset pulse width. MR is CMOS logic compatible, so it can be driven by an external logic line. MR can be used to force a watchdog timeout to generate a reset pulse in the MAX6701(A)/MAX6702(A)/ MAX6703(A)/MAX6705(A)/MAX6706(A)/MAX6707(A) by connecting WDO to MR.
Power-Fail Comparator
The uncommitted power-fail comparator can be used for various purposes because its noninverting input and output are externally available. The inverting input is internally connected to a 0.62V reference. To build an early warning circuit for power failure, connect the PFI pin to a voltage-divider (see Typical Operating Circuit). Choose the voltage-divider ratio so that the voltage at PFI falls below 0.62V just before the regulator drops out. Use PFO to interrupt the P so it can prepare for an orderly power-down. The low-input current at this pin allows for large resistor values in the divider.
Watchdog Timer
The MAX6701-MAX6707 watchdog circuit monitors the P's activity. If the P does not toggle the WDI within 1.6s, WDO goes low. When RESET is asserted, the watchdog timer stays cleared and does not count. As soon as reset is released, the timer starts counting. WDO deasserts after a valid transition is detected at WDI. Pulses as short as 50ns can be detected. Typically, WDO is connected to the NMI input of a P. When VCC, RST_IN1, or RST_IN2 drop below the reset
tWDI WDI +5V 0V
tWD
tWD
VTH VCC
VTH tRP tRP
+5V
+5V WDO 0V +5V RESET
+5V RESET 0V
0V RESET EXTERNALLY TRIGGERED BY MR +5V t RP
MR 0V tMD tMR
(RESET)
0V +5V
WDO
+5V
MR
0V
0V
( ) ARE FOR MAX6702/MAX6706 ONLY.
Figure 5. MAX6701/MAX6702/MAX6703/MAX6705/MAX6706/ MAX6707 Watchdog 8
Figure 6. MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/ MAX6706(A)/MAX6707(A) RESET, MR, and WDO Timing with WDI Three-Stated
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Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
tWDI WDI +5V 0V +5V WDO 0V +5V RESET 0V t RP +5V (RESET) 0V +5V MR 0V VEXT-TH = 1 + R1 x 0.62V R2
0.62V
tWD
tWD tWD VEXTERNAL R1
MAX6701(A)- MAX6708
PFI, RST_IN1, OR RST_IN2
R2
(
)
R1 = R2 x
EXT-TH (V0.62 - 1)
WHERE VEXT-TH IS THE EXTERNAL VOLTAGE TRIP LEVEL.
( ) ARE FOR MAX6702(A)/MAX6706(A) ONLY.
Figure 7. MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/ MAX6706(A)/MAX6707(A) Watchdog Timing
Figure 8. Calculating Adjustable Voltage Thresholds
Reset Input
The MAX6701(A)/MAX6702(A)/MAX6703(A) include two adjustable reset inputs for monitoring up to a total of three system voltages (including VCC). The thresholds for the monitored RST_IN supplies are externally set with resistor-divider networks (Figure 8). The reset output is asserted if any of the monitored supplies (VCC, RST_IN1, or RST_IN2) go below its specified threshold and remains asserted for the reset timeout period after all supplies are above their thresholds.
Monitoring Other System Voltages
Other systems can be monitored by connecting a voltage-divider to PFI and adjusting the ratio appropriately. In noisy systems, a capacitor between PFI and GND reduces the power-fail circuit's sensitivity to high-frequency noise on the line being monitored. Reset can be asserted on other voltages in addition to the VCC supply line. Connect PFO to MR to initiate a reset output pulse when PFI drops below 0.62V. Figure 10 shows the MAX6704-MAX6708 configured to assert a reset output when the secondary supply falls below the reset threshold.
Applications Information
Ensuring a Valid RESET Output Down to VCC = 0
When V CC falls below 1V, the MAX6701-MAX6708 RESET output no longer sinks current--it becomes an open circuit. High-impedance CMOS logic inputs can drift to undetermined voltages if left undriven. If a pulldown resistor is added to the RESET pin as shown in Figure 9, any stray charge or leakage currents are drained to ground, holding RESET low. A resistor value (R1) is not critical; 100k is large enough not to load RESET and small enough to pull RESET to ground. This application works for push-pull output only (not for open-drain resets).
Generating a Reset from Watchdog Overflow
Connect WDO to MR to force a watchdog timeout to generate a reset pulse for only the reset timeout period on the MAX6701(A)/MAX6702(A)/MAX6703(A)/MAX6705(A)/ MAX6706(A)/MAX6707(A). When the MAX6704 watchdog times out, reset outputs are automatically asserted (no external connections required). For the MAX6701/ MAX6702/MAX6703/MAX6705/MAX6706/MAX6707 non-A versions, do not connect WDO to MR; this creates a locked condition.
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9
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
0.9V 3.3V
MAX6701(A) MAX6704 MAX6705(A) MAX6708
RESET R1 (100k) VCC PFI RESET (RESET) MAX6704- MR MAX6708 PFO
I/O SUPPLY RESET P
CORE SUPPLY
() ARE FOR MAX6704/MAX6706(A)/MAX6708 ONLY.
Figure 9. RESET Valid to Ground Circuit
Figure 10. Monitoring Other System Voltages
Selector Guide
PART MAX6701 MAX6701A* MAX6702 MAX6702A* MAX6703 MAX6703A* MAX6704 MAX6705 MAX6705A* MAX6706 MAX6706A* MAX6707 MAX6707A* MAX6708 RESET PP LOW -- -- -- -- -- -- -- -- RESET PP HIGH -- -- -- -- -- -- -- -- RESET OD-LOW -- -- -- -- -- -- -- -- -- -- WDI -- WDO PP PP PP PP OD OD -- PP PP PP PP OD OD -- PFI, PFO -- -- -- -- -- -- PP PP PP PP PP OD OD PP RST_IN1, RST_IN2 -- -- -- -- -- -- -- --
PP = push-pull, OD = open drain. *WDO deasserts when MR is pulled low. See the Standard- vs. A-Version Comparison section for the differences on WDO.
Threshold Suffix Guide
SUFFIX L M T S R Z Y RESET THRESHOLD (V) 4.63 4.38 3.08 2.93 2.63 2.32 2.19
Bold indicates standard version. 10 ______________________________________________________________________________________
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
Pin Configurations (continued)
TOP VIEW
MR VCC GND 1 2 8 7 RESET RESET WDI PFO MR VCC GND 1 2 3 8 7 WDO RESET (RESET) WDI PFO MR VCC GND 1 2 8 7 RESET RESET N.C. PFO
MAX6704
3 6 5
MAX6705(A) MAX6706(A) MAX6707(A)
MAX6708
3 6 5
6 5
PFI 4
PFI 4
PFI 4
SOT23
SOT23
( ) ARE FOR MAX6706(A) ONLY.
SOT23
Typical Operating Circuit
UNREGULATED DC DC/DC REGULATOR P VCC PFI RESET WDI MAX6705(A) WDO MAX6706(A) MR MAX6707(A) PFO VCC RESET I/O NMI INTERRUPT
Ordering Information (continued)
PART MAX6702_ KA-T MAX6702A_ KA-T MAX6703_ KA-T MAX6703A_ KA-T MAX6704_KA-T MAX6705_KA-T MAX6705A_KA-T MAX6706_KA-T MAX6706A_KA-T MAX6707_KA-T MAX6707A_KA-T MAX6708_KA-T TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8 8 SOT23-8
PUSHBUTTON SWITCH
Insert the desired suffix letter (from the Threshold Suffix Guide table) into the blank to complete the part number. All devices must be ordered in increments of 2500 pieces. Sample stock is typically held on standard versions only. Contact factory for availability.
Chip Information
TRANSISTOR COUNT: 716 PROCESS: BiCMOS
______________________________________________________________________________________
11
Low-Voltage, SOT23 P Supervisors with PowerFail In/Out, Manual Reset, and Watchdog Timer MAX6701-08/MAX6701A-03A/05A-07A
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SOT23, 8L .EPS
REV.
SEE DETAIL "A" b
C L
e
SYMBOL A A1 A2 b C D E E1 L L2 e e1
MIN 0.90 0.00 0.90 0.28 0.09 2.80 2.60 1.50 0.30
MAX 1.45 0.15 1.30 0.45 0.20 3.00 3.00 1.75 0.60 0.25 BSC. 0.65 BSC. 1.95 REF.
C L
E
C L
E1
PIN 1 I.D. DOT (SEE NOTE 6) e1 D C
C L
0
0
8
L2 A A2 A1
SEATING PLANE C
GAUGE PLANE
L
0
NOTE:
1. ALL DIMENSIONS ARE IN MILLIMETERS. 2. FOOT LENGTH MEASURED FROM LEAD TIP TO UPPER RADIUS OF HEEL OF THE LEAD PARALLEL TO SEATING PLANE C. 3. PACKAGE OUTLINE EXCLUSIVE OF MOLD FLASH & METAL BURR. 4. PACKAGE OUTLINE INCLUSIVE OF SOLDER PLATING. 5. COPLANARITY 4 MILS. MAX. 6. PIN 1 I.D. DOT IS 0.3 MM MIN. LOCATED ABOVE PIN 1. 7. SOLDER THICKNESS MEASURED AT FLAT SECTION OF LEAD BETWEEN 0.08mm AND 0.15mm FROM LEAD TIP. 8. MEETS JEDEC MO178.
PROPRIETARY INFORMATION TITLE:
DETAIL "A"
PACKAGE OUTLINE, SOT-23, 8L BODY
APPROVAL DOCUMENT CONTROL NO.
21-0078
1 1
D
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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