MIC811 Micrel Semiconductor, MIC811 Datasheet - Page 5

• Manufacturer Part Number: MIC811
• Description: Microprocessor Reset Circuits
• Manufacturer: Micrel Semiconductor

Circuit Description
Microprocessor Reset
The RESET pin is asserted whenever V CC falls below
the reset threshold voltage or if MR (manual reset) is
forced low. The reset pin remains asserted for a period
of 240ms after V CC has risen above the reset threshold
voltage or MR has returned high. The reset function
ensures the microprocessor is properly reset and powers
up into a known condition after a power failure. RESET
will remain valid with V CC as low as 1.4V.
V CC Transients
The MIC811/MIC812 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 50 s (25 s for
MIC81_R/S/T) or less will not cause an unwanted reset.
Interfacing to Bidirectional Reset Pins
The MIC811/MIC812 can interface with
bidirectional reset pins by connecting a 4.7K resistor in
series with the MIC811/MIC812 output and the P reset
pin.
Figure 3. RESET Valid to V CC = 0V.
MIC811/MIC812 Microprocessor Reset Circuits
Ps with
Figure 2. Reset Timing Diagram
RESET Valid to 0V
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 100K
to ground is recommended. The size of the resistor
should be large enough to not load the RESET output
and small enough to pull-down any stray leakage
currents.
resistor connected from RESET
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