MAX6367LKA23-T Maxim Integrated, MAX6367LKA23-T Datasheet - Page 10

• Manufacturer Part Number: MAX6367LKA23-T
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX6365, MAX6366, MAX6367, MAX6368r

Specifications of MAX6367LKA23-T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 2.5 V, 3 V, 3.3 V, 5 V
• Undervoltage Threshold: 2.25 V
• Overvoltage Threshold: 2.38 V
• Output Type: Active Low, Push-Pull
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: Backup
• Power-up Reset Delay (typ): 280 ms
• Supply Voltage - Max: 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOT-23
• Chip Enable Signals: Yes
• Maximum Power Dissipation: 700 mW
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Supply Current (typ): 15 uA
• Supply Voltage - Min: 0 V

SOT23, Low-Power µP Supervisory Circuits
with Battery Backup and Chip-Enable Gating
The watchdog monitors µP activity through the watch-
dog input (WDI). If the µP becomes inactive, reset
asserts. To use the watchdog function, connect WDI to
a bus line or µP I/O line. A change of state (high to low,
low to high, or a minimum 100ns pulse) resets the
watchdog timer. If WDI remains high or low for longer
than the watchdog timeout period (t
watchdog timer runs out and a reset pulse is triggered
for the reset timeout period (t
timer clears whenever reset asserts or whenever WDI
sees a rising or falling edge. If WDI remains in either a
high or low state, a reset pulse asserts periodically after
every t
BATT ON is a push-pull output that drives high when in
battery-backup mode. BATT ON typically sinks 3.2mA
at 0.1V saturation voltage. In battery-backup mode, this
terminal sources approximately 10µA from OUT. Use
BATT ON to indicate battery-switchover status or to
supply base drive to an external pass transistor for
higher current applications (Figure 3).
RESET IN is compared to an internal 1.235V reference.
If the voltage at RESET IN is less than 1.235V, reset
asserts. Use the RESET IN comparator as an undervolt-
age detector to signal a failing power supply or as a
secondary power-supply reset monitor.
To program the reset threshold (V
power supply, use the following (see Typical Operating
Circuit ):
10
Figure 2. MAX6366 Watchdog Timeout Period and Reset Active Time
______________________________________________________________________________________
RESET IN Comparator (MAX6368 Only)
WD
BATT ON Indicator (MAX6367 Only)
(Figure 2).
Watchdog Input (MAX6366 Only)
V
RTH
= V
RESET
REF
WDI
(R1 / R2 + 1)
t
t
RP
WD
RP
= RESET TIMEOUT PERIOD
= WATCHDOG TIMEOUT PERIOD
). The internal watchdog
RTH
) of the secondary
WD
), the internal
t
WD
t
RP
t
WD
where V
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
significant loss in accuracy. For example, in the Typical
Operating Circuit , the MAX6368 monitors two supply
voltages. To monitor the secondary 5V logic or analog
supply with a 4.60V nominal programmed reset thresh-
old, choose R2 = 100kΩ, and calculate R1 = 273kΩ.
A µP’s reset input starts the µP in a known state. The
MAX6365–MAX6368 µP supervisory circuits assert a
reset to prevent code-execution errors during power-
up, power-down, and brownout conditions. RESET is
guaranteed to be a logic low or logic high, depending
on the device chosen (see the Ordering Information ).
RESET or RESET asserts when V
threshold and for at least 150ms (t
above the reset threshold. RESET or RESET also
asserts when MR is low (MAX6365) and when RESET IN
is less than 1.235V (MAX6368). The MAX6366 watch-
dog function will cause RESET (or RESET) to assert in
pulses following a watchdog timeout (Figure 2).
The MAX6365–MAX6368 provide battery-backup func-
tions. If a backup power source is not used, connect
BATT to GND and OUT to V
t
RP
REF
= 1.235V. To simplify the resistor selection,
R1 = R2 [(V
Applications Information
a Backup Power Source
RTH
CC
/ V
.
Operation Without
REF
CC
RP
) - 1]
is below the reset
Reset Output
) after V
CC
rises