TC1301A datasheet(15/28 Pages) MICROCHIP

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DS21798C-page 15

TC1301A/B

5.10

TC1301A SHDN2 Timing

VOUT1 will rise independent of the level of SHDN2 for

the TC1301A. Figure 5-1 is used to define the wake-up

time from shutdown (tWK) and the settling time (tS). The

wake-up time is dependant upon the frequency of

operation. The faster the SHDN pin is pulsed, the

shorter the wake-up time will be.

FIGURE 5-1:

TC1301A Timing.

5.11

TC1301B SHDN1 / SHDN2 Timing

For the TC1301B, the SHDN1 input pin is used to

control VOUT1. The SHDN2 input pin is used to control

VOUT2, independent of the logic input on SHDN1.

FIGURE 5-2:

TC1301B Timing.

5.12

VDET and RESET Operation

The TC1301A/B integrates an independent voltage

reset monitor that can be used for low-battery input

voltage detection or a microprocessor Power-On Reset

(POR) function. The input voltage for the detector is

different for the TC1301A than it is for the TC1301B.

For the TC1301A, the input voltage to the detector is

pin 8 (VDET). For the TC1301B, the input voltage to the

detector is internally connected to the output of LDO #1

(VOUT1). The detected voltage is sensed and com-

pared to an internal threshold. When the voltage on the

VDET pin is below the threshold voltage, the RESET

output pin is low. When the voltage on the VDET pin

rises above the voltage threshold, the RESET output

will remain low for typically 300 ms (RESET time-out

period). After the RESET time-out period, the RESET

output voltage will transition from the low output state

to the high output state if the detected voltage pin

remains above the threshold voltage.

The RESET output will be driven low within 180 µs of

VDET going below the RESET voltage threshold. The

RESET output will remain valid for detected voltages

greater than 1.2V overtemperature.

5.13

TC1301A RESET Timing

Figure 5-3 shows the RESET timing waveforms for the

TC1301A. This diagram is also used to define the

RESET active time-out period (tRPU) and the VDET

RESET delay time (tRPD).

FIGURE 5-3:

TC1301A RESET Timing.

VIN

SHDN2

VOUT1

VOUT2

twk

SHDN2

SHDN1

VIN

VOUT1

twk

VOUT2

RESET Time

TRPD

VTH

VDET

RESET

VOL

VOH

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