MIC811 データシートの表示（PDF） - Micrel

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MIC811

Micro-Power Comparator/ Battery Monitor

Micrel 

MIC811/MIC812 Microprocessor Reset Circuits

Circuit Description

Microprocessor Reset

The RESET pin is asserted whenever VCC falls below VCC

the reset threshold voltage or if MR (manual reset) is

forced low. The reset pin remains asserted for a period

of 240ms after VCC has risen above the reset threshold

MR

voltage or MR has returned high. The reset function

ensures the microprocessor is properly reset and powers

t1

up into a known condition after a power failure. RESET

will remain valid with VCC as low as 1.4V.

RESET

Vthr

t1

VCC Transients

The MIC811/MIC812 are relatively immune to negative-

going VCC glitches below the reset threshold. Typically,

a negative-going transient 125mV below the reset

threshold with a duration of 50µs (25µs for

MIC81_R/S/T) or less will not cause an unwanted reset.

Figure 2. Reset Timing Diagram

Interfacing to Bidirectional Reset Pins

The MIC811/MIC812 can interface with µPs with

bidirectional reset pins by connecting a 4.7KΩ resistor in

series with the MIC811/MIC812 output and the µP reset

pin.

VCC

VCC

MIC81 1

RESET

VCC

µP

RESET

100K

Figure 3. RESET Valid to VCC = 0V.

RESET Valid to 0V

A resistor can be added from the RESET pin to ground

to ensure the RESET output remains low with VCC

down to 0V. A 100KΩ resistor connected from RESET

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.

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