MCP111 datasheet(12/22 Pages) MICROCHIP

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MCP111/112

DS21889B-page 12

 2004 Microchip Technology Inc.

4.2

Negative Going VDD Transients

The minimum pulse width (time) required to cause a

reset may be an important criteria in the implementa-

tion of a POR circuit. This time is referred to as

transient duration and is the amount of time needed for

these supervisory devices to respond to a drop in VDD.

The transient duration time is dependant on the magni-

tude of VTRIP – VDD. Generally speaking, the transient

duration decreases with increases in VTRIP – VDD.

Figure 4-3 shows a typical transient duration vs. reset

comparator overdrive for which the MCP111/112 will

not generate a reset pulse. It shows that the farther

below the trip point the transient pulse goes, the

duration of the pulse required to cause a reset gets

shorter. Figure 2-18 shows the transient response

characteristics for the MCP111/112.

A 0.1 µF bypass cap mounted as close as possible to

the VDD pin provides additional transient immunity

(refer to Figure 4-1).

FIGURE 4-3:

Example of Typical

Transient Duration Waveform.

4.3

Effect of Temperature on Time-out

Period (tRPU)

The time-out period (t

RPU) determines how long the

device remains in the reset condition. This is affected

by both V

DD and temperature. The graph shown in

Figures 2-22,

2-23 and

2-24 show the typical

response for different V

DD values and temperatures.

Time (µs)

VTRIP(MIN) - VDD

tTRANS

VTRIP(MAX)

VTRIP(MIN)

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