PIN DESCRIPTION

PIN

NAME

FUNCTION

1

GND

Ground

(SS8037L/38L)

rises above the reset threshold.

2

RESET

(SS8037H)

rises above the reset threshold.

3

Supply Voltage (+5V, +3.3V, +3.0V)

APPLICATIONS INFORMATION

A microprocessor’s (µP’s) reset input starts the µP in a

known state. The SS8037L/H and 8038L assert reset

to prevent code-execution errors during power-up,

power-down, or brownout conditions. They assert a reset

preset threshold, keeping it asserted for at least 140ms

SS8038L

uses

an

open-drain

output,

and

the

SS8037L/37H have push-pull output stages. Connect a

pull-up resistor on the SS8308L’s RESET output to any

supply between 0 and 5.5V.

Figure 1. Maximum Transient Duration Without

Causing a Reset Pulse vs. Reset Compara-

tor Overdrive

In addition to issuing a reset to the µP during power-up,

power-down,

and

brownout

conditions,

the

SS8037L/H/8038L are relatively immune to short-

Figure 1 shows typical transient duration vs. reset com-

parator overdrive, for which the SS8037L/H/8038L

do not generate a reset pulse. The graph was generated

above the actual reset threshold and ending below it by

the magnitude indicated (reset comparator overdrive).

The graph indicates the maximum pulse width a nega-

pulse. As the magnitude of the transient increases (goes

farther below the reset threshold), the maximum allow-

able pulse width decreases. Typically, for the SS803xx

100mV below the reset threshold and lasts 7µs or less

will not cause a reset pulse. A 0.1µF bypass capacitor

additional transient immunity.

no longer sinks current—it becomes an open circuit.

Therefore, high-impedance CMOS logic inputs con-

nected to RESET can drift to undetermined voltages.

This presents no problem in most applications since most

However, in applications where RESET must be valid

down to 0V, adding a pull-down resistor to RESET

causes any stray leakage currents to flow to ground,

holding RESET low (Figure 2). R1’s value is not critical;

100k

Ω is large enough not to load RESET and small

enough to pull RESET to ground.

A 100k

the SS8038L if RESET is required to remain valid for

0

100

200

300

400

500

600

1

10

100

1000

803xx308/293/263

803xx 463/438/400

V

CC

RESET

GND

R1

100k

V

CC

RESET

GND

SS8037

R1

100k

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SS8037/8(G)

10/6/2004 Rev.2.20