TC1303A_08 Datasheet, PDF(22/38 Page) Microchip Technology – 500 mA Synchronous Buck Regulator, + 300 mA LDO with Power-Good Output

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TC1303A_08 Datasheet, PDF (22/38 Pages) Microchip Technology – 500 mA Synchronous Buck Regulator, + 300 mA LDO with Power-Good Output

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TC1303A/TC1303B/TC1303C/TC1304

4.4 Power-Good

A Power-Good (PG) output signal is generated based

off of the buck regulator output voltage (VOUT1), the

LDO output voltage (VOUT2) or the combination of both

outputs. A fixed delay time of approximately 262 ms is

generated once the monitored output voltage is above

the power-good threshold (typically 94% of VOUTX). As

the monitored output voltage falls out of regulation, the

falling PG threshold is typically 92% of the output

voltage. The PG output signal is pulled up to the output

voltage, indicating that power is good and pulled low,

indicating that the output is out of regulation. The

typical quiescent current draw for power-good circuitry

is less than 10 ÂµA.

If the monitored output voltage falls below the power-

good threshold, the power-good output will transition to

the Low state. The power-good circuitry has a 165 Âµs

delay when detecting a falling output voltage. This

helps to increase the noise immunity of the power-good

output, avoiding false triggering of the PG signal during

line and load transients.

VTH_H

VOUT1

or VOUT2

tRPU

VOH

tRPD

VOL

FIGURE 4-1:

Power-Good Timing.

4.5 Power Good Output Options

There are three monitoring options for the TC1303

family.

For the TC1303A, only the buck regulator output

voltage (VOUT1) is monitored. The PG output signal

depends only on VOUT1.

For the TC1303B, only the LDO output voltage (VOUT2)

is monitored. The PG output signal depends only on

VOUT2.

For the TC1303C and TC1304, both the buck regulator

output voltage and LDO output voltage are monitored.

If either one of the outputs fall out of regulation, the PG

will be low. Only if both VOUT1 and VOUT2 are within the

PG voltage threshold limits will the PG output be high.

For the TC1303A,C and TC1304, the PG output pin is

open drain and can be pulled up to any level within the

given absolute maximum ratings (AGND - 0.3V) to (VIN

+ 0.3V).

TABLE 4-1: PG AVAILABLE OPTIONS

Part

Number

PG Output

Buck

(VOUT1)

TC1303A

Yes

TC1303B

Output

LDO

(VOUT2)

Yes

TC1303C

Yes

TC1304

Yes

PG Output

Type

Open-Drain

Push-Pull

(VOUT2)

Open-Drain

DS21949C-page 22

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