Microprocessor Supervisory Circuits
______________________________________________________________Pin Description
PIN
MAX690A/MAX692A
MAX802L/MAX802M
MAX805L
NAME
FUNCTION
MAX690A/MAX692A/MAX802L/MAX802M/MAX805L
1
1
V
OUT
Supply Output for CMOS RAM. When V
CC
is above the reset threshold,
V
OUT
connects to V
CC
through a P-channel MOSFET switch. When V
CC
is below the reset threshold, the higher of V
CC
or V
BATT
will be
connected to V
OUT
.
+5V Supply Input
Ground
Power-Fail Comparator Input. When PFI is less than 1.25V,
PFO
goes
low. Connect PFI to GND or V
CC
when not used.
Power-Fail Output. When PFI is less than 1.25V,
PFO
goes low;
otherwise
PFO
stays high.
Watchdog Input. If WDI remains high or low for 1.6sec, the internal
watchdog timer runs out and reset is triggered. If WDI is left floating or
connected to a high-impedance three-state buffer, the watchdog
feature is disabled. The internal watchdog timer clears whenever reset
is asserted, WDI is three-stated, or WDI sees a rising or falling edge.
Reset Output. Whenever
RESET
is triggered, it pulses low for 200ms. It
stays low when V
CC
is below the reset threshold (4.65V in the
MAX690A/MAX802L and 4.4V in the MAX692A/MAX802M) and remains
low for 200ms after V
CC
rises above the reset threshold. A watchdog
timeout also triggers
RESET.
2
3
4
2
3
4
V
CC
GND
PFI
5
5
PFO
6
6
WDI
7
RESET
–
7
RESET
Active-High Reset Output is the inverse of
RESET.
When RESET is
asserted, the RESET output voltage = V
CC
or V
BATT
, whichever is
higher.
8
8
V
BATT
Backup-Battery Input. When V
CC
falls below the reset threshold, V
BATT
will be switched to V
OUT
if V
BATT
is 20mV greater than V
CC
. When V
CC
rises to 20mV above V
BATT
, V
OUT
will be reconnected to V
CC
. The 40mV
hysteresis prevents repeated switching if V
CC
falls slowly.
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5
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
