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MAX6361LUT29+T-MAX6361PUT31+T-MAX6362PUT29+-MAX6363LUT29+T-MAX6364PUT29+T
SOT23, Low-Power Microprocessor Supervisory Circuits with Battery Backup
General DescriptionThe MAX6361–MAX6364 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 MAX6361–MAX6364 operate from supply voltages as
low as +1.2V. The factory-preset reset threshold voltage
ranges from 2.32V to 4.63V (see Ordering Information).
These devices provide a manual reset input (MAX6361),
watchdog timer input (MAX6362), 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 open-
drain reset (see Selector Guide at end of data sheet).
Applications
FeaturesLow +1.2V Operating Supply Voltage
(VCCor VBATT)Precision Monitoring of +5.0V, +3.3V, +3.0V, and
+2.5V Power-Supply VoltagesDebounced Manual Reset Input (MAX6361)Watchdog Timer with 1.6s Timeout Period
(MAX6362)Battery-On Output Indicator (MAX6363)Auxiliary User-Adjustable RESET IN (MAX6364)Three Available Output Structures
Push-Pull RESET, Open-Drain RESET,
Open-Drain RESETRESET/RESET Valid Down to 1.2V Guaranteed
(VCCor VBATT)Power-Supply Transient Immunity150ms (min) Reset Timeout PeriodSmall 6-Pin SOT23 Package
MAX6361–MAX6364
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup19-1615; Rev 4; 10/11
Ordering Information
Pin Configurations
Note:These parts offer a choice of reset threshold voltages.
From the table below, select the suffix corresponding to the
desired thresholdvoltage and insert it into the part number to
complete it. When ordering from the factory, there is a 2500-
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.
GND
VCCMRBATTOUT
RESET, RESET
MAX6361
TOP VIEW
SOT23-6Computers
Controllers
Intelligent Instruments
Critical µP/µC
Power Monitoring
Fax Machines
Industrial Control
POS Equipment
Portable/Battery-Powered
Equipment
Selector Guide appears at end of data sheet.Pin Configurations continued at end of data sheet.
6 SOT23-40°C to +85°CMAX6364HUT_ _-T
6 SOT23-40°C to +85°CMAX6364PUT_ _-T
6 SOT23-40°C to +85°C
MAX6364LUT_ _-T6 SOT23-40°C to +85°C
6 SOT23-40°C to +85°CMAX6363HUT_ _-T
MAX6363PUT_ _-T
6 SOT23-40°C to +85°C
6 SOT23-40°C to +85°C
MAX6363LUT_ _-T6 SOT23
PIN-PACKAGETEMP RANGE-40°C to +85°C
MAX6361HUT_ _-T
6 SOT23-40°C to +85°CMAX6361PUT_ _-T
MAX6361LUT_ _-T
PART6 SOT23-40°C to +85°CMAX6362HUT_ _-T
6 SOT23-40°C to +85°CMAX6362PUT_ _-T
6 SOT23-40°C to +85°C
MAX6362LUT_ _-T
SUFFIXMIN4.504.63
MAXTYP4.254.383.003.08
RESET THRESHOLD RANGES (V)
MAX6361–MAX6364
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +2.4V to +5.5V, VBATT= 3V, TA= -40°C to +85°C, reset not asserted. Typical values are at TA= +25°C, unless otherwise
noted.) (Note 1)
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.
Terminal Voltages (with respect to GND)
VCC, BATT, OUT.......................................................-0.3V to +6V
RESET(open drain), RESET (open drain)................-0.3V to +6V
BATT ON, RESET (push-pull), RESET IN,
WDI.......................................................-0.3V to (VOUT+ 0.3V).............................................................-0.3V to (VCC+ 0.3V)
Input Current
VCCPeak ............................................................................1A
VCCContinuous............................................................250mA
BATT Peak....................................................................250mA
BATT Continuous............................................................40mA
GND................................................................................75mA
Output Current
OUT................................Short-Circuit Protection for up to 10s
RESET, RESET, BATT ON ..............................................20mA
Continuous Power Dissipation (TA= +70°C)
6-Pin SOT23 (derate 8.70mW/°C above +70°C) .........696mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow)
Lead(Pb)-free...............................................................+260°C
Packages containing lead(Pb).....................................+240°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS05.5No load (Note 2)VCC,
VBATT
Operating Voltage Range,
VCCor VBATT
Supply Current
(Excluding IOUT)ICC
No load, VCC> VTH,
WDI = VCCor GND
(MAX6362)
VCC= 2.8V
VCC= 3.6V
VCC= 5.5V3035501= +25°C= -40°C to +85°C
VBATT= 2.8V,
VCC= 0VISUPPLYISUPPLYin Battery-Backup
Mode (Excluding IOUT)
BATT Standby CurrentIBATT5.5V > VCC>
(VBATT+ 0.2V)= +25°C= -40°C to +85°C
-1.00.05µA
VCC= 4.75V, IOUT≤150mA
VCC= 3.15V, IOUT≤65mA
VCC= 2.38V, IOUT≤25mA
RONVCCto OUT On-Resistance
VOUTin Battery-Backup Mode
Battery-Switchover Threshold
(VCC- VBATT)
Reset Threshold
VCCFalling Reset Delay
Reset-Active Timeout PeriodtRP
VTH
VBATT= 4.5V, IOUT≤20mA
VBATT= 3.0V, IOUT≤10mA
VBATT= 2.25V, IOUT≤5mA
VCC < VTH
MAX636_UT46
VCCfalling at 10V/ms
VBATT- 0.2
VBATT- 0.15
VBATT- 0.15
150280ms
Power-up
Power-down
MAX636_UT23
MAX636_UT26
MAX636_UT29
MAX636_UT31
MAX636_UT44
MAX6361–MAX6364
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup
ELECTRICAL CHARACTERISTICS (continued)(VCC= +2.4V to +5.5V, VBATT= 3V, TA= -40°C to +85°C, reset not asserted. Typical values are at TA= +25°C, unless otherwise
noted.) (Note 1)
Note 1:All devices are 100% production tested at TA= +25°C. Limits over temperature are guaranteed by design.
Note 2:VBATTcan be 0V anytime or VCCcan go down to 0V if VBATTis active (except at startup).
PARAMETERSYMBOLMINTYPMAXUNITSCONDITIONSOutput VoltageVOL0.4V
Output Short-Circuit Current60mA
ISINK= 3.2mA, VBATT= 2.1V
Sink current, VCC= 5V
RESET Output VoltageVOL0.3VInput Voltage0.7 ✕VCCV
Pull-Up Resistance20kΩ
Minimum Pulse Width1µs
Glitch Immunity100nsto Reset Delay120ns
Reset not asserted
VCC= 3.3V
VCC= 3.3V
RESETOutput Voltage
VOL
Reset asserted,
VBATT= 0V
Input Threshold1.1851.2351.285V
RESET IN Leakage Current±0.01±25nA
1.5µsOverdrive voltage = 50mV, RESET IN fallingRESET IN to Reset Delay30100µASource current, VBATT≥2V
VIH
VIL0.3 ✕VCC
VOH0.8 ✕VCCReset not asserted
(MAX636_L only)
ISOURCE= 500µA,
VCC≥VTH(MAX)
0.4ISINK= 100µA,
VCC≥1.2V
ISINK= 1.6mA,
VCC≥2.1V
RESET, RESET Output Leakage
Current ILK1µAMAX636_P, MAX636_H only
ISINK= 1.6mA,
VCC≥VTH(MAX)
Minimum WDI Input Pulse WidthtWDI100ns
Input VoltageVIL0.3 ✕VCCV
Watchdog Timeout PeriodtWD1.001.602.25s
MANUAL RESET (MAX6361 only)
BATT ON(MAX6363 only)
RESET IN(MAX6364 only)
WATCHDOG INPUT(MAX6362 only)
VIH0.7 ✕VCC
MAX6361–MAX6364
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup
Typical Operating Characteristics(TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
(NO LOAD)MAX6361 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (
VBATT = 0V
VCC = 5.0V0
BATTERY SUPPLY CURRENT
(BACKUP MODE) vs. TEMPERATURE
MAX6361 toc02
TEMPERATURE (°C)
BATTERY SUPPLY CURRENT (
VBATT = 2.0V
VCC = 0
VBATT = 2.8V
BATTERY TO OUT ON-RESISTANCE
vs. TEMPERATUREMAX6361 toc03
TEMPERATURE (°C)
BATT TO OUT ON-RESISTANCE (
VBATT = 5.0V
IOUT = 25mA
VCC = 0V
VBATT = 2.8V
VBATT = 2.0V
VCC TO OUT ON-RESISTANCE
vs. TEMPERATURE
MAX6361 toc04
TEMPERATURE (°C)
OUT
TO OUT ON-RESISTANCE (
VCC = 3.0V
IOUT = 65mA
VCC = 4.5V
IOUT = 150mA
VCC = 2.3V
IOUT = 25mA
RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6361 toc05
TEMPERATURE (°C)
RESET TIMEOUT PERIOD (ms)
VCC TO RESET PROPAGATION DELAY
vs. TEMPERATURE
MAX6361 toc06
TEMPERATURE (°C)
PROPAGATION DELAY (
VCC FALLING
0.25V/ms
1V/ms
10V/ms
RESET THRESHOLD
vs. TEMPERATURE
MAX6361 toc07
THRESHOLD (V)
MAX636_46
MAX636_26
MAX6362
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAX6361toc06a
WATCHDOG TIMEOUT PERIOD (s)
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVEMAX6361 toc08
MAXIMUM TRANSIENT DURATION (
MAX636_46
MAX636_26
RESET OCCURS
ABOVE CURVE
MAX6361–MAX6364
SOT23, Low-Power µP Supervisory Circuits
with Battery BackupMAX6364
RESET IN THRESHOLD
vs. TEMPERATURE
MAX6361 toc10
TEMPERATURE (°C)
THRESHOLD (V)
Typical Operating Characteristics (continued)
(TA= +25°C, unless otherwise noted.)
MAX6364
RESET IN TO RESET PROPAGATION DELAY
vs. TEMPERATURE
TEMPERATURE (°C)
PROPAGATION DELAY (
VOD = 50mV
Pin DescriptionBackup-Battery Input. When VCCfalls below the reset threshold, BATT switches to OUT if VBATTis 20mV
greater than VCC. When VCCrises 20mV above VBATT, VCCswitches to OUT. The 40mV hysteresis
BATT6
Supply Voltage, 0 to 5.5V. Reset is asserted when VCCdrops below the reset threshold voltage (VTH).
Reset remains asserted until VCCrises above VTHand for at least 150ms after VCCrises above VTH.VCC4
Output. OUT sources from VCCwhen it is above the reset threshold (VTH), and from the greater of VCCor
BATT when VCCis below VTH.OUT5
GroundGND2
PINActive-Low Reset Output. RESETis continuously low when VCCis below the reset threshold (VTH), MRis
low, or RESET IN is low. It asserts in pulses when the internal watchdog times out. RESETremains low for
the reset timeout period (tRP) after VCCrises above the reset threshold, after the manual reset input goes
from low to high, after RESET 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.
RESET
Active-High Reset Output. RESET is continuously high when VCCis below the reset threshold (VTH), MRis
low, or RESET IN is low. It asserts in pulses when the internal watchdog times out. RESET remains high
for the reset timeout period (tRP) after VCCrises above the reset threshold, after the manual reset input
goes from low to high, after RESET IN goes high, or after the watchdog triggers a reset event. The
MAX636_H is an active-high open-drain output.
RESET
FUNCTIONNAMEBATTERY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6361 toc09
VCC (V)
BATTERY SUPPLY CURRENT (
VBATT = 2.8V
VBATT = 2.5V
VTH = 2.93V
VBATT = 2.3V
MAX6361Manual-Reset Input. Maintaining logic low on MRasserts a reset. Reset output remains assert-
ed for at least 150ms (tRP) after MRtransitions from low to high. Leave unconnected or connected to VCC
if not used.
MAX6364Reset Input. When RESET IN falls below 1.235V, reset is asserted. Reset output remains
asserted as long as RESET IN is low and for at least 150ms (tRP) after RESET IN goes high.
MAX6363Battery-On Output. BATT ON goes high in battery backup mode.
MAX6362Watchdog Input. If WDI remains high or low for longer than the watchdog timeout period (tWD), the
internal watchdog timer runs out and a reset pulse is triggered for the reset timeout period (tRP) (Figure 1). The
internal watchdog clears whenever reset asserts or whenever WDI sees a rising or falling edge.
RESET IN
BATT ON
WDI
MAX6361–MAX6364
Detailed DescriptionThe Typical Operating Circuitshows a typical connection
for the MAX6361–MAX6364 family. OUT powers the stat-
ic random-access memory (SRAM). OUT is internally
connected to VCCif VCCis greater than the reset thresh-
old, or to the greater of VCCor VBATTwhen VCCis less
than the reset threshold. OUT can supply up to 150mA
from VCC. When VCCis higher than VBATT, the BATT ON
(MAX6363) output is low. When VCCis lower than VBATT,
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 Characteristicssection.
Backup-Battery Switchover In a brownout or power failure, it may be necessary to
preserve the contents of the RAM. With a backup bat-
tery installed at BATT, the MAX6361–MAX6364 auto-
matically switch the RAM to backup power when VCC
falls. The MAX6363 has a BATT ON output that goes
high when in battery-backup mode. These devices
require two conditions before switching to battery-
backup mode: VCCmust be below the reset threshold.VCCmust be below VBATT.
Table 1 lists the status of the inputs and outputs in bat-
tery-backup mode. The device will not power up if the
only voltage source is on BATT. OUT will only power up
from VCCat startup.
Manual Reset Input (MAX6361 Only)Many µP-based products require manual reset capabili-
ty, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. For the MAX6361, a logic
low on MRasserts reset. Reset remains asserted whileis low, and for a minimum of 150ms (tRP) after it
returns high. MRhas an internal 20kΩpull-up resistor to
VCC. This input can be driven with TTL/CMOS logic lev-
els or with open-drain/collector outputs. Connect a nor-
mally open momentary switch from MRto GND to create
a manual reset function; external debounce circuitry is
not required. If MRis driven from long cables or the
device is used in a noisy environment, connect a 0.1µF
capacitor from MRto GND to provide additional noise
immunity.
Watchdog Input (MAX6362 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, con-
nect 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 (tWD) with a 100ns 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 (tRP). 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
(tWD) (Figure 1).
Reset In (MAX6364 Only)RESET IN is compared to an internal 1.235V reference.
If the voltage at RESET IN is less than 1.235V, reset is
asserted. The RESET IN comparator may be used as
an undervoltage detector to signal a failing power sup-
ply. It can also be used as a secondary power-supply
reset monitor.
To program the reset threshold (VRTH) of the secondary
power supply, use the following equation (see Typical
Operating Circuit):
where VREF= 1.235V. To simplify the resistor selection,
choose a value for R2 and calculate R1:
Since the input current at RESET IN is 25nA (max), large
values (up to 1MΩ) can be used for R2 with no signifi-
cant loss in accuracy. For example, in the Typical
SOT23, Low-Power µP Supervisory Circuits
with Battery Backup
Table 1. Input and Output Status in
Battery-Backup Mode
PINSTATUSVCCDisconnected from OUT
OUTConnected to BATT
BATT
Connected to OUT. Current drawn from
the battery is less than 1µA (at VBATT=
2.8V, excluding IOUT) when VCC= 0.
RESET/RESETAsserted
BATT ONHigh state
MR, RESET IN,
WDIInputs ignoredRRTHREF=+⎛⎜⎞⎟ 11VVRTHREF121 / =()−[]
