9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

The following sections describe in detail proper device implementation, depending on the final application

requirements.

9.1.1 Output Assert Delay

The TPS3435 features two options for setting the output assert delay (tWDO): using a fixed timing and

programming the timing through an external capacitor.

9.1.1.1 Factory-Programmed Output Assert Delay Timing

Fixed output assert delay timings are available using pinout C and J. Using these timings enables a high-

precision, 10% accurate output assert delay timing.

9.1.1.2 Adjustable Capacitor Timing

The TPS3435 also utilizes a programmable output assert delay, using a precision current source to charge

an external capacitor upon device startup. By monitoring the voltage on the CRST pin, the TPS3435 can be

programmed to have a desired output assert delay. The typical delay time resulting from a given external

capacitance on the CRST pin can be calculated by Equation 3, where tWDO is the output assert delay time in

seconds and CCRST is the capacitance in microfarads.

tWDO (sec) = 4.95 × 106 × CCRST (F)

(3)

Note that in order to minimize the difference between the calculated output assert delay time and the actual

output assert delay time, use a high-quality ceramic dielectric COG, X5R, or X7R capacitor and minimize

parasitic board capacitance around this pin. Table 9-1 lists the output assert delay time ideal capacitor values for

CCRST.

Table 9-1. Output Assert Delay Time for Common Ideal Capacitor Values

CCRST

OUTPUT ASSERT

DELAY TIME (tWDO)

UNIT

MIN(1)

TYP

MAX(1)

10 nF

39.6

49.5

59.4

ms

100 nF

396

495

594

ms

1 μF

3960

4950

5940

ms

(1)

Minimum and maximum values are calculated using ideal capacitors.

9.1.2 Watchdog Timer Functionality

The TPS3435 features two options for setting the watchdog timer (tWD): using a fixed timing and programming

the timing through an external capacitor.

9.1.2.1 Factory-Programmed Timing Options

Fixed watchdog timeout options are available using pinout C and J. Using these timings enables a high-

precision, 10% accurate watchdog timer tWD.

TPS3435

SNVSCF7 – DECEMBER 2022

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