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Rev.1.9 Mar. 21, 2011

AX6901/2/3/4



APPLICATION CIRCUIT

AX690X

GND

RESET

(RESET)

VCC

Microprocessor

VCC

GND

RESET

INPUT

VCC



FUNCTION DESCRIPTIONS

A microprocessor’s (µP’s) reset input starts the µP in a known state. The

AX6901/2/3/4 asserts reset to prevent code-execution errors during power-up, power-down,

or brownout conditions. They assert a reset signal whenever the VCC supply voltage

declines below a preset threshold, keeping it asserted for at least 200ms after VCC has

risen above the reset threshold. The AX6901/2/3/4 has a push-pull output stage.



APPLICATION INFORMATION

Negative-Going VCC Transients

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

conditions, the AX6901/2/3/4 is relatively immune to short-duration negative-going VCC

transients (glitches).

The AX6901/2/3/4 does not generate a reset pulse. The graph was generated using a

negative going pulse applied to VCC, starting 0.5V above the actual reset threshold and

ending below it by the magnitude indicated (reset comparator overdrive). The graph

indicates the maximum pulse width a negative going VCC transient can have without

causing a reset pulse. As the magnitude of the transient increases (goes farther below the

reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient

that goes 50mV below the reset threshold A 0.1µF bypass capacitor mounted as close as

possible to the VCC pin provides additional transient immunity.