MIC809/810
Micrel
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
ensure the /RESET output remains low with V
CC
down 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
VCC
VCC
µP
RESET
100K
Applications Information
Microprocessor Reset
The /RESET (or RESET) pin is asserted whenever V
CC
falls
below the reset threshold voltage. The /RESET pin remains
asserted for a period of 140ms after V
CC
has risen above
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
V
CC
as low as 1.4V (1V for SC-70 package).
V
CC
Transients
The MIC809/810 are relatively immune to negative-going V
CC
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.
MIC809
RESET
Reset Valid to V
CC
= 0V
April 2005
5
M0450-041405
MICREL [ MICREL SEMICONDUCTOR ]
