Datasheet

MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
7
Maxim Integrated
Pin Description
PIN
MAX6730
MAX6731
MAX6732
MAX6733
MAX6734
MAX6735
NAME FUNCTION
111RST
Active-Low Reset Output. The MAX6730/MAX6732/MAX6734 provide an open-drain
output. The MAX6731/MAX6733/MAX6735 provide a push-pull output. RST asserts
low when any of the following conditions occur: V
CC
1 or V
CC
2 drops below its
preset threshold, RSTIN drops below its reset threshold, or MR is driven low. Open-
drain versions require an external pullup resistor.
2 2 2 GND Ground
334WDO
Active-Low Watchdog Output. The MAX6730/MAX6732/MAX6734 provide an open-
drain WDO output. The MAX6731/MAX6733/MAX6735 provide a push-pull WDO
output. WDO asserts low when no low-to-high or high-to-low transition occurs on
WDI within the watchdog timeout period (t
WD
) or if an undervoltage lockout
condition exists for V
CC
1, V
CC
2, or RSTIN. WDO deasserts without a timeout period
when V
CC
1, V
CC
2, and RSTIN exceed their reset thresholds, or when the manual
reset input is asserted. Open-drain versions require an external pullup resistor.
4—5MR
Active-Low Manual Reset Input. Drive MR low to force a reset. RST remains
asserted as long as MR is low and for the reset timeout period after MR releases
high. MR has a 50kΩ pullup resistor to V
CC
1; leave MR open or connect to V
CC
1 if
unused.
5 5 3 WDI
Watchdog Input. If WDI remains high or low for longer than the watchdog timeout
period, the internal watchdog timer expires and the watchdog output asserts low.
The internal watchdog timer clears whenever RST asserts or a rising or falling edge
on WDI is detected. The watchdog has an initial watchdog timeout period (35s min)
after each reset event and a short timeout period (1.12s min) after the first valid
WDI transition. Leaving WDI unconnected does not disable the watchdog timer
function.
668V
CC
1
Primary Supply-Voltage Input. V
CC
1 provides power to the device when it is greater
than V
CC
2. V
CC
1 is the input to the primary reset threshold monitor.
—4 6V
CC
2
Secondary Supply-Voltage Input. V
CC
2 provides power to the device when it is
greater than V
CC
1. V
CC
2 is the input to the secondary reset threshold monitor.
— — 7 RSTIN
Undervoltage Reset Comparator Input. RSTIN provides a high-impedance
comparator input for the adjustable reset monitor. RST asserts low if the voltage at
RSTIN drops below the 626mV internal reference voltage. Connect a resistive
voltage-divider to RSTIN to monitor voltages higher than 626mV. Connect RSTIN to
V
CC
1 or V
CC
2 if unused.