April 2005

5

M0450-041405

MIC809/810

Micrel

Applications Information

Microprocessor Reset

below the reset threshold voltage. The /RESET pin remains

the reset threshold voltage. The reset function ensures the

microprocessor is properly reset and powers up in a known

condition after a power failure. /RESET will remain valid with

glitches below the reset threshold.Typically, a negative-going

transient 125mV below the reset threshold with a duration of

20µs or less (SC70 package) will not cause a reset.

Interfacing to Bidirectional Reset Pins

The MIC809/810 can interface with µPs with bidirectional

reset pins by connecting a 4.7kΩ resistor in series with the

MIC809/810 output and the µP reset pin.

/RESET Valid at Low Voltage

A resistor can be added from the /RESET pin to ground to

0V. A 100kΩ resistor connected from the /RESET to ground

is recommended. The resistor should be small enough to

pull-down any stray leakage currents and large enough not

to load the reset output. See Figure below.

VCC

RESET

µP

RESET

VCC

MIC809

VCC

100K