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MAX6412

Low-Power, Single/Dual-Voltage μP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay

Maxim Integrated 

MAX6412–MAX6420

Low-Power, Single/Dual-Voltage μP Reset Circuits

with Capacitor-Adjustable Reset Timeout Delay

Pin Description

PIN

MAX6412/

MAX6413/

MAX6414

MAX6415/

MAX6416/

MAX6417

1

1

2

2

—

3

3

—

4

4

5

5

MAX6418/

MAX6419/

MAX6420

1

2

3

—

4

5

NAME

RESET

RESET

GND

RESET

IN

MR

SRT

VCC

FUNCTION

RESET changes from high to low whenever VCC or RESET IN drops below the

selected reset threshold voltage (VTH or VRESET IN, respectively) or manual

reset is pulled low. RESET remains low for the reset timeout period after all

reset conditions are deasserted and then goes high.

RESET changes from low to high whenever the VCC or RESET IN drops below

the selected reset threshold voltage (VTH or VRESET IN) or manual reset is

pulled low. RESET remains high for the reset timeout period after all reset

conditions are deasserted and then goes low.

Ground

Reset Input. High-impedance input to the adjustable reset comparator. Connect

RESET IN to the center point of an external resistor-divider network to set the

threshold of the externally monitored voltage. See Reset Threshold section.

Manual Reset Input. Pull this pin low to manually reset the device. Reset

remains asserted for the reset timeout period after MR is released.

Set Reset Timeout Input. Connect a capacitor between SRT and ground to

set the timeout period. Determine the period as follows:

tRP = (2.71 x 106) x CSRT + 275µs with tRP in seconds and CSRT in Farads.

Supply Voltage and Input for Fixed-Threshold VCC Monitor

Detailed Description

The MAX6412–MAX6420 low-power microprocessor (μP)

supervisory circuits provide maximum adjustability for

supply-voltage monitoring and reset functionality. In addi-

tion, the MAX6412–MAX6420 reset timeout period is

adjustable using an external capacitor.

The MAX6412/MAX6413/MAX6414 have factory-trimmed

reset threshold voltages in approximately 100mV incre-

ments from 1.575V to 5.0V with a manual reset input. The

MAX6415/MAX6416/MAX6417 contain a reset threshold

that can be adjusted to any voltage above 1.26V using

external resistors. The MAX6418/MAX6419/MAX6420

offer both a factory-trimmed reset threshold and an adjust-

able reset threshold input for dual-voltage monitoring.

A reset signal is asserted when VCC and/or RESET IN

falls below the preset values or when MR is asserted.

The reset remains asserted for an externally programmed

interval after VCC and/or RESET IN has risen above the

reset threshold or MR is deasserted.

Reset Output

The reset output is typically connected to the reset input

of a μP. A μP’s reset input starts or restarts the μP in a

known state. The MAX6412–MAX6420 μP supervisory

circuits provide the reset logic to prevent code-execution

errors during power-up, power-down, and brownout con-

ditions (see Typical Operating Circuit).

For the MAX6413, MAX6416, and MAX6419, RESET

changes from low to high whenever VCC or RESET IN

drops below the reset threshold voltages. Once RESET

IN and VCC exceed their respective reset threshold

voltage(s), RESET remains high for the reset timeout

period, then goes low.

On power-up, once VCC reaches 1V, RESET is guaran-

teed to be a logic high. For applications requiring valid

reset logic when VCC is less than 1V, see the section

Ensuring a Valid RESET/RESET Output Down to VCC = 0V.

The active-low RESET output of the remaining super-

visors is the inverse of the MAX6413, MAX6416, and

MAX6419 active-high RESET output and is guaranteed

valid for VCC ≥ 1V.

Reset Threshold

The MAX6415–MAX6420 monitor the voltage on RESET

IN with an external resistor voltage-divider (Figure 1).

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