FP6809-29CS3P datasheet(7/9 Pages) FITIPOWER

7 / 9 page

FP6809/6810-1.6-JUL-2014

FP6809/6810

fitipower integrated technology lnc.

Application Information

The

FP6809/FP6810

are

supervisory

circuits,

monitoring critical voltages and asserting reset

signal to the subsequent devices.

The reset signal

can start the microprocessor in a known state,

avoiding code- execution errors during power-up,

power-down,

brownout

conditions.

(RESET) is guaranteed to be a logic low

(high) for VTH>VCC>0.9V. Once VCC exceeds the

reset

threshold,

internal

timer

keeps

(RESET) low (high) for the reset timeout.

After this period,

(RESET) goes high (low).

VCC

falls

below

the

reset

threshold,

(RESET) goes low (high) immediately.

Whenever VCC drops below VTH, the internal timer

resets to zero and

(RESET) goes low

(high).

The internal timer keeps activated only

when VCC> VTH, and

(RESET) remains low

(high) for the reset timeout interval.

Negative-Going VCC Transients

In addition to issuing a reset to microprocessor

during

power-up,

power-down,

and

brownout

conditions, FP6809/FP6810 are relatively immune

to short-duration negative-going VCC transients

(glitches).

Figure 11 shows typical transient

duration vs. reset comparator overdrive, for which

the FP6809/ FP6810 do not generate a reset signal.

The graph was generated using a negative-going

pulse applied to VCC, as shown in Figure 12, starting

0.5V above the actual reset threshold and ending

below

the

magnitude

indicated

(reset

comparator overdrive).

The graph indicates the

maximum

pulse

width

negative-going

VCC

transient can have without causing a reset signal.

As the reset comparator overdrive increases, the

maximum allowable pulse width decreases.

typical 0.1

μF bypass capacitor mounted as close as

possible to the VCC pin provides additional transient

immunity.

Figure 11. Maximum Transient Durations Without Causing

a Reset Pulse vs. Reset Comparator Overdrive

VCC

VTH

Duration

Overdrive

Figure 12. The VCC with Negative Going Transients

100

200

300

400

500

100

120

Reset Comparator Overdrive(mV)

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