Dual-Voltage µP Supervisory Circuits

with Sequenced Reset Outputs

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5

Pin Description

PIN

MAX6391

MAX6392

NAME

FUNCTION

11

RESET IN2

Input Voltage for RESET2 Monitor. High-impedance input for internal reset

comparator. Connect this pin to an external resistive-divider network to set the reset

threshold voltage.

22

Supply Voltage and Input Voltage for Primary Supply Monitor

3

3

CSRT

minimum threshold.

4

4

GND

Ground

55

RESET2

Secondary Reset Output, Open-Drain, Active-Low. RESET2 changes from high to low

RESET IN2 meet their minimum thresholds.

66

R2

47k

Ω Internal Pullup Resistor for RESET2. Connect to external voltage for RESET2

high pullup.

77

RESET1

Primary Reset Output, Open-Drain (MAX6391) or Push-Pull (MAX6392), Active-Low.

the minimum threshold.

8—

R1

47k

Ω Internal Pullup Resistor for RESET1. Connect to external voltage for RESET1

high pullup.

—8

MR

Manual Reset, Active-Low, Internal 47k

RESET1 and RESET2 remain asserted as long as MR is LOW and for the RESET1 and

if unused.

Detailed Description

Each device includes a pair of voltage monitors with

only (RESET1 output is independent of the RESET IN2

is below the preset voltage threshold. RESET1 remains

reset threshold. RESET1 timing is internally set in each

device power supply.

asserts a reset signal (LOW) whenever RESET IN2 is

threshold. RESET2 remains asserted for a fixed 140ms

(min) or a user-adjustable time period after RESET IN2

rises above the 625mV reset threshold and RESET1 is

to 1V.

The timing diagram in Figure 2 shows the reset timing

characteristics of the MAX6391/MAX6392. As shown in

od) after RESET IN2 exceeds 625mV and RESET1 is

deasserted. When RESET IN2 drops below 625mV

within 10µs typ. RESET1 is unaffected when this hap-