19-1615; Rev 4; 1/11 SOT3, Low-Power µp Supervisory Circuits General Description The supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery control functions in microprocessor (µp) systems. The circuits significantly improve system reliability and accuracy compared to that obtainable with separate ICs or discrete components. Their functions include µp reset, backup battery switchover, and power failure warning. The operate from supply voltages as low as +1.. The factory-preset reset threshold voltage ranges from.3 to 4.63 (see Ordering Information). These devices provide a manual reset input (MAX6361), watchdog timer input (MAX636), battery-on output (MAX6363), and an auxiliary adjustable reset input (MAX6364). In addition, each part type is offered in three reset output versions: an active-low open-drain reset, an active-low open-drain reset, and an active-high opendrain reset (see Selector Guide at end of data sheet). Computers Controllers Intelligent Instruments Critical µp/µc Power Monitoring TOP IEW, MR Applications Pin Configurations 1 6 BATT MAX6361 3 4 SOT3-6 Fax Machines Industrial Control POS Equipment Portable/Battery-Powered Equipment 5 OUT CC Pin Configurations continued at end of data sheet. Selector Guide appears at end of data sheet. Typical Operating Circuit appears at end of data sheet. Features Low +1. Operating Supply oltage ( CC or BATT ) Precision Monitoring of +5., +3.3, +3., and +.5 Power-Supply oltages Debounced Manual Reset Input (MAX6361) Watchdog Timer with 1.6s Timeout Period (MAX636) Battery-On Output Indicator (MAX6363) Auxiliary User-Adjustable IN (MAX6364) Three Available Output Structures Push-Pull, Open-Drain, Open-Drain / alid Down to 1. Guaranteed ( CC or BATT ) Power-Supply Transient Immunity 15ms (min) Reset Timeout Period Small 6-Pin SOT3 Package MAX6361LUT -T MAX6361PUT -T MAX6361HUT -T MAX636LUT -T MAX636PUT -T MAX636HUT -T MAX6363LUT -T MAX6363PUT -T MAX6363HUT -T MAX6364LUT -T MAX6364PUT -T MAX6364HUT -T Ordering Information TEMP RANGE PIN-PACKAGE Note: These parts offer a choice of reset threshold voltages. From the table below, select the suffix corresponding to the desired threshold voltage and insert it into the part number to complete it. When ordering from the factory, there is a 5- piece minimum on the SOT package (tape-and-reel only). Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing "-T" with "+T" when ordering. SUFFIX MIN TYP 46 4.5 4.63 44 4.5 4.38 31 3. 3.8 3.5 THRESHOLD RANGES () 9.85.93 6.55.63.3 MAX 4.75 4.5 3.15 3..7.38 Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-69-464, or visit Maxim s website at www.maxim-ic.com.
ABSOLUTE MAXIMUM RATINGS Terminal oltages (with respect to ) CC, BATT, OUT...-.3 to +6 (open drain), (open drain)...-.3 to +6 BATT ON, (push-pull), IN, WDI...-.3 to ( OUT +.3) MR...-.3 to ( CC +.3) Input Current CC Peak...1A CC Continuous...5mA BATT Peak...5mA BATT Continuous...4mA...75mA 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 Output Current OUT...Short-Circuit Protection for up to 1s,, BATT ON...mA Continuous Power Dissipation (T A = +7 C) 6-Pin SOT3 (derate 8.7mW/ C above +7 C)...696mW Operating Temperature Range... Junction Temperature...+15 C Storage Temperature Range...-65 C to +15 C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow) Lead(Pb)-free...+6 C Packages containing lead(pb)...+4 C ( CC = +.4 to +5.5, BATT = 3, T A =, reset not asserted. Typical values are at T A = +5 C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating oltage Range, CC or BATT Supply Current (Excluding I OUT ) I SUPPLY in Battery-Backup Mode (Excluding I OUT ) CC, BATT No load (Note ) CC =.8 CC = 3.6 CC = 5.5 BATT =.8, T A = +5 C CC = T A = T A = +5 C T A = CC = 4.75, I OUT 15mA No load, CC > TH, I CC WDI = CC or (MAX636) I SUPPLY BATT Standby Current I BATT 5.5 > CC > ( BATT +.) CC to OUT On-Resistance OUT in Battery-Backup Mode Battery-Switchover Threshold ( CC - BATT ) Reset Threshold CC Falling Reset Delay Reset-Active Timeout Period R ON TH t RP CC = 3.15, I OUT 65mA CC =.38, I OUT 5mA BATT = 4.5, I OUT ma BATT = 3., I OUT 1mA BATT =.5, I OUT 5mA CC < TH MAX636_UT46 MAX636_UT44 MAX636_UT31 MAX636_UT9 MAX636_UT6 MAX636_UT3 CC falling at 1/ms Power-up Power-down 5.5 1 3 11 35 15 5 1 3 -.1. -1..5.75 3. 4.6 BATT -. BATT -.15 BATT -.15-4.5 4.63 4.75 4.5 4.38 4.5 3. 3.8 3.15.85.93 3..55.63.7.5.3.38 35 µa µa µa Ω m µs 15 8 ms
ELECTRICAL CHARACTERISTICS (continued) ( CC = +.4 to +5.5, BATT = 3, T A =, reset not asserted. Typical values are at T A = +5 C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Output oltage I Output oltage OL Reset not asserted SINK = 1.6mA,.3 CC TH(MAX), Output Leakage Current MANUAL (MAX6361 only) MR Input oltage I SINK = 1.6mA,.3 Reset asserted, CC.1 OL BATT = I SINK = 1µA,.4 CC 1. OH IL IH Reset not asserted (MAX636_L only) I SOURCE = 5µA, CC TH(MAX).8 CC I LK MAX636_P, MAX636_H only 1 µa.3 CC.7 CC Pull-Up Resistance kω Minimum Pulse Width 1 µs Glitch Immunity CC = 3.3 1 ns MR to Reset Delay CC = 3.3 1 ns WATCHDOG INPUT (MAX636 only) Watchdog Timeout Period t WD 1. 1.6.5 s Minimum WDI Input Pulse Width t WDI 1 ns IL.3 CC Input oltage IH.7 CC BATT ON (MAX6363 only) Output oltage OL I SINK = 3.mA, BATT =.1.4 Output Short-Circuit Current Sink current, CC = 5 6 ma Source current, BATT 1 3 1 µa IN (MAX6364 only) Input Threshold 1.185 1.35 1.85 IN Leakage Current ±.1 ±5 na IN to Reset Delay Overdrive voltage = 5m, IN falling 1.5 µs Note 1: All devices are 1% production tested at T A = +5 C. Limits over temperature are guaranteed by design. Note : BATT can be anytime or CC can go down to if BATT is active (except at startup). 3
(T A = +5 C, unless otherwise noted.) SUPPLY CURRENT (µa) 18 16 14 SUPPLY CURRENT (NO LOAD) BATT = CC = 5. 1 MAX6361 toc1 BATTERY SUPPLY CURRENT (µa) 1. 1..8.6.4. BATTERY SUPPLY CURRENT (BACKUP MODE) BATT =.8 BATT =. Typical Operating Characteristics CC = MAX6361 toc BATT TO OUT ON-RESISTANCE (Ω) 7 6 5 4 3 BATTERY TO OUT ON-RESISTANCE BATT =. BATT =.8 BATT = 5. 1 I OUT = 5mA CC = MAX6361 toc3 OUT TO OUT ON-RESISTANCE (Ω) 1..9.6.3 CC TO OUT ON-RESISTANCE CC =.3 I OUT = 5mA CC = 4.5 I OUT = 15mA CC = 3. I OUT = 65mA MAX6361 toc4 TIMEOUT PERIOD (ms) 1 5 195 TIMEOUT PERIOD MAX6361 toc5 PROPAGATION DELAY (µs) 135 1 15 9 75 6 45 3 CC TO PROPAGATION DELAY CC FALLING.5/ms 1/ms MAX6361 toc6 15 1/ms 19 WATCHDOG TIMEOUT PERIOD (s). 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1. MAX636 WATCHDOG TIMEOUT PERIOD MAX6361toc6a THRESHOLD () 5. 4.5 4. 3.5 3..5 THRESHOLD MAX636_46 MAX636_6. MAX6361 toc7 MAXIMUM TRANSIENT DURATION (µs) 4 35 3 5 15 1 5 MAXIMUM TRANSIENT DURATION vs. THRESHOLD OERDRIE MAX636_46 MAX636_6 OCCURS ABOE CURE 1 1 1 1k 1k THRESHOLD OERDRIE TH - CC (m) MAX6361 toc8 4
(T A = +5 C, unless otherwise noted.) BATTERY SUPPLY CURRENT (µa) 1 9 8 7 6 5 4 3 1 BATTERY SUPPLY CURRENT vs. SUPPLY OLTAGE BATT =.8 BATT =.5 BATT =.3 TH =.93 1 3 4 CC () MAX6361 toc9 THRESHOLD () Typical Operating Characteristics (continued) 1.36 1.35 MAX6364 IN THRESHOLD 1.34 MAX6361 toc1 PROPAGATION DELAY (µs).8.5. 1.9 1.6 1.3 MAX6364 IN TO PROPAGATION DELAY OD = 5m 1. Pin Description MAX6361 toc11 PIN 1 3 4 5 6 NAME MR WDI BATT ON IN CC OUT BATT FUNCTION Active-High Reset Output. is continuously high when CC is below the reset threshold ( TH ), MR is low, or IN is low. It asserts in pulses when the internal watchdog times out. remains high for the reset timeout period (t RP ) after CC rises above the reset threshold, after the manual reset input goes from low to high, after IN goes high, or after the watchdog triggers a reset event. The MAX636_H is an active-high open-drain output. Active-Low Reset Output. is continuously low when CC is below the reset threshold ( TH ), MR is low, or IN is low. It asserts in pulses when the internal watchdog times out. remains low for the reset timeout period (t RP ) after CC rises above the reset threshold, after the manual reset input goes from low to high, after IN goes high, or after the watchdog triggers a reset event. The MAX636_L is an active-low push-pull output while the MAX636_P is an active-low open-drain output. Ground MAX6361 Manual-Reset Input. Maintaining logic low on MR asserts a reset. Reset output remains asserted for at least 15ms (t RP ) after MR transitions from low to high. Leave unconnected or connected to CC if not used. MAX636 Watchdog Input. If WDI remains high or low for longer than the watchdog timeout period (t WD ), the internal watchdog timer runs out and a reset pulse is triggered for the reset timeout period (t RP ) (Figure 1). The internal watchdog clears whenever reset asserts or whenever WDI sees a rising or falling edge. MAX6363 Battery-On Output. BATT ON goes high in battery backup mode. MAX6364 Reset Input. When IN falls below 1.35, reset is asserted. Reset output remains asserted as long as IN is low and for at least 15ms (t RP ) after IN goes high. Supply oltage, to 5.5. Reset is asserted when CC drops below the reset threshold voltage ( TH ). Reset remains asserted until CC rises above TH and for at least 15ms after CC rises above TH. Output. OUT sources from CC when it is above the reset threshold ( TH ), and from the greater of CC or BATT when CC is below TH. Backup-Battery Input. When CC falls below the reset threshold, BATT switches to OUT if BATT is m greater than CC. When CC rises m above BATT, CC switches to OUT. The 4m hysteresis prevents repeated switching if CC falls slowly. 5
Detailed Description The Typical Operating Circuit shows a typical connection for the family. OUT powers the static random-access memory (SRAM). OUT is internally connected to CC if CC is greater than the reset threshold, or to the greater of CC or BATT when CC is less than the reset threshold. OUT can supply up to 15mA from CC. When CC is higher than BATT, the BATT ON (MAX6363) output is low. When CC is lower than BATT, an internal MOSFET connects the backup battery to OUT. The on-resistance of the MOSFET is a function of backup-battery voltage and is shown in the Battery to Out On-Resistance vs. Temperature graph in the Typical Operating Characteristics section. Backup-Battery Switchover In a brownout or power failure, it may be necessary to preserve the contents of the RAM. With a backup battery installed at BATT, the automatically switch the RAM to backup power when CC falls. The MAX6363 has a BATT ON output that goes high when in battery-backup mode. These devices require two conditions before switching to batterybackup mode: 1) CC must be below the reset threshold. ) CC must be below BATT. Table 1 lists the status of the inputs and outputs in battery-backup mode. The device will not power up if the only voltage source is on BATT. OUT will only power up from CC at startup. Manual Reset Input (MAX6361 Only) Many µp-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. For the MAX6361, a logic low on MR asserts reset. Reset remains asserted while MR is low, and for a minimum of 15ms (t RP ) after it returns high. MR has an internal kω pull-up resistor to CC. This input can be driven with TTL/CMOS logic levels or with open-drain/collector outputs. Connect a normally open momentary switch from MR to to create a manual reset function; external debounce circuitry is not required. If MR is driven from long cables or the device is used in a noisy environment, connect a.1µf capacitor from MR to to provide additional noise immunity. Watchdog Input (MAX636 Only) The watchdog monitors µp activity through the input WDI. If the µp becomes inactive, the reset output is asserted in pulses. To use the watchdog function, connect WDI to a bus line or µp I/O line. A change of state (high to low or low to high) within the watchdog timeout period (t WD ) with a 1ns minimum pulse width clears the watchdog timer. If WDI remains high or low for longer than the watchdog timeout period, the internal watchdog timer runs out and a reset pulse is triggered for the reset timeout period (t RP ). The internal watchdog timer clears whenever reset asserts or the WDI sees a rising or falling edge within the watchdog timeout period. If WDI remains in a high or low state for an extended period of time, a reset pulse asserts after every watchdog timeout period (t WD ) (Figure 1). Reset In (MAX6364 Only) IN is compared to an internal 1.35 reference. If the voltage at IN is less than 1.35, reset is asserted. The IN comparator may be used as an undervoltage detector to signal a failing power supply. It can also be used as a secondary power-supply reset monitor. To program the reset threshold ( RTH ) of the secondary power supply, use the following equation (see Typical Operating Circuit): where REF = 1.35. To simplify the resistor selection, choose a value for R and calculate R1: Since the input current at IN is 5nA (max), large values (up to 1MΩ) can be used for R with no significant loss in accuracy. For example, in the Typical Table 1. Input and Output Status in Battery-Backup Mode PIN CC OUT BATT / BATT ON MR, IN, WDI R1 RTH = REF + 1 R [ ] R1 = R ( RTH / REF) 1 STATUS Disconnected from OUT Connected to BATT Connected to OUT. Current drawn from the battery is less than 1µA (at BATT =.8, excluding I OUT ) when CC =. Asserted High state Inputs ignored 6
Operating Circuit, the MAX636 monitors two supply voltages. To monitor the secondary 5 logic or analog supply with a 4.6 nominal programmed reset threshold, choose R = 1kΩ, and calculate R1 = 73kΩ. Reset Output A µp s reset input starts the µp in a known state. The µp supervisory circuits assert a reset to prevent code-execution errors during powerup, power-down, and brownout conditions. is guaranteed to be a logic low or high depending on the device chosen (see Ordering Information). or asserts when CC is below the reset threshold and for at least 15ms (t RP ) after CC rises above the reset threshold. or also asserts when MR is low (MAX6361) and when IN is less than 1.35 (MAX6364). The MAX636 watchdog function will cause (or ) to assert in pulses following a watchdog timeout (Figure 1). Applications Information Operation Without a Backup Power Source The were designed for batterybacked applications. If a backup battery is not used, connect CC to OUT and connect BATT to. Replacing the Backup Battery If BATT is decoupled with a.1µf capacitor to ground, the backup power source can be removed while CC remains valid without danger of triggering a reset pulse. The device does not enter battery-backup mode when CC stays above the reset threshold voltage. Negative-Going CC Transients These supervisors are relatively immune to short-duration, negative-going CC transients. Resetting the µp when CC experiences only small glitches is usually not desirable. The Typical Operating Characteristics section shows a graph of Maximum Transient Duration vs. Reset Threshold Overdrive for which reset is not asserted. The graph was produced using negative-going CC pulses, starting at CC and ending below the reset threshold by the magnitude indicated (reset threshold overdrive). The graph shows the maximum pulse width that a negative-going CC transient can typically have without triggering a reset pulse. As the amplitude of the transient increases (i.e., goes further below the reset threshold), the maximum allowable pulse width decreases. Typically, a CC transient that goes 1m below the reset threshold and lasts for 3µs will not trigger a reset pulse. A.1µF bypass capacitor mounted close to the CC pin provides additional transient immunity. WDI t WD t RP t WD t RP t WD = WATCHDOG TIMEOUT PERIOD t RP = TIMEOUT PERIOD Figure 1. MAX636 Watchdog Timeout Period and Reset Active Time 7
Watchdog Software Considerations (MAX636 Only) To help the watchdog timer monitor software execution more closely, set and reset the watchdog input at different points in the program, rather than pulsing the watchdog input low-high-low. This technique avoids a stuck loop, in which the watchdog timer would continue to be reset within the loop, keeping the watchdog from timing out. Figure shows an example of a flow diagram where the I/O driving the WDI is set low at the beginning of the program, set high at the beginning of every subroutine or loop, then set low again when the program returns to the beginning. If the program should hang in any subroutine, the problem would quickly be corrected, since the I/O is continually set low and the watchdog timer is allowed to time out, triggering a reset. START SET WDI LOW SUBROUTINE OR PROGRAM LOOP SET WDI HIGH RETURN END Figure. Watchdog Flow Diagram 8
MAX6361LUT MAX6361PUT MAX6361HUT MAX636LUT MAX636PUT MAX636HUT MAX6363LUT MAX6363PUT MAX6363HUT MAX6364LUT MAX6364PUT MAX6364HUT MANUAL INPUT MR WATCHDOG INPUT WDI BATT ON IN PUSH- PULL Selector Guide OPEN DRAIN OPEN DRAIN Device Marking Codes TOP MARK TOP MARK TOP MARK TOP MARK MAX6361LUT3 MAX6361LUT6 MAX6361LUT9* MAX6361LUT31 MAX6361LUT44 MAX6361LUT46* MAX6361PUT3 MAX6361PUT6 MAX6361PUT9* MAX6361PUT31 MAX6361PUT44 MAX6361PUT46* MAX6361HUT3 MAX6361HUT6 MAX6361HUT9 MAX6361HUT31 MAX6361HUT44 MAX6361HUT46* AAEI AAEH AAEG AAEF AAEE AAED AAEO AAEN AAEM AAEL AAEK AAEJ AAEU AAET AAES AAER AAEQ AAEP MAX636LUT3 MAX636LUT6 MAX636LUT9* MAX636LUT31 MAX636LUT44 MAX636LUT46* MAX636PUT3 MAX636PUT6 MAX636PUT9* MAX636PUT31 MAX636PUT44 MAX636PUT46* MAX636HUT3 MAX636HUT6 MAX636HUT9 MAX636HUT31 MAX636HUT44 MAX636HUT46* AAFA AAEZ AAEY AAEX AAEW AAE AAFG AAFF AAFE AAFD AAFC AAFB AAFM AAFL AAFK AAFJ AAFI AAFH MAX6363LUT3 MAX6363LUT6 MAX6363LUT9* MAX6363LUT31 MAX6363LUT44 MAX6363LUT46* MAX6363PUT3 MAX6363PUT6 MAX6363PUT9* MAX6363PUT31 MAX6363PUT44 MAX6363PUT46* MAX6363HUT3 MAX6363HUT6 MAX6363HUT9 MAX6363HUT31 MAX6363HUT44 MAX6363HUT46* AAFS AAFR AAFQ AAFP AAFO AAFN AAFY AAFX AAFW AAF AAFU AAFT AAGE AAGD AAGC AAGB AAGA AAFZ MAX6364LUT3 MAX6364LUT6 MAX6364LUT9* MAX6364LUT31 MAX6364LUT44 MAX6364LUT46* MAX6364PUT3 MAX6364PUT6 MAX6364PUT9* MAX6364PUT31 MAX6364PUT44 MAX6364PUT46* MAX6364HUT3 MAX6364HUT6 MAX6364HUT9 MAX6364HUT31 MAX6364HUT44 MAX6364HUT46* AAGK AAGJ AAGI AAGH AAGG AAGF AAGQ AAGP AAGO AAGN AAGM AAGL AAGW AAG AAGU AAGT AAGS AAGR *Sample stock generally held on standard versions only. Contact factory for availability of nonstandard versions. 9
TOP IEW, WDI 1 6 BATT MAX636 5 OUT 3 4 CC SOT3-6, BATT ON Pin Configurations (continued) 1 6 BATT, 1 6 BATT MAX6363 MAX6364 5 OUT 5 OUT 3 4 CC IN 3 4 CC SOT3-6 SOT3-6 Typical Operating Circuit Chip Information PROCESS: BiCMOS UNREGULATED DC OLTAGE.4 TO 5.5 R1 R.1µF 3.6 Li+ BATTERY CC IN MAX6364 BATT OUT.1µF CC µp BUS CC SRAM Package Information For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a +, #, or - in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. U6-1 1-58 9-175 1
REISION NUMBER REISION DATE DESCRIPTION Revision History PAGES CHANGED 1/ Initial release 3 11/5 Added lead-free information. 1 4 1/11 Updated Electrical Characteristics. 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. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. 11 Maxim Integrated Products, 1 San Gabriel Drive, Sunnyvale, CA 9486 48-737-76 11 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.