8 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.

8.1 Application Information

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

requirements.

8.1.1 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.

8.1.1.1 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.

8.1.1.2 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. 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 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 8-1 lists the output assert delay time for ideal capacitor values.

Table 8-1. Output Assert Delay Time for Common Ideal Capacitor Values

CCRST

OUTPUT ASSERT

DELAY TIME ( tWDO )

UNIT

MIN(1)

TYP

MAX(1)

10nF

39.6

49.5

59.4

ms

100nF

396

495

594

ms

1μF

3960

4950

5940

ms

(1)

Minimum and maximum values are calculated using ideal capacitors.

8.1.2 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.

8.1.2.1 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 .

8.1.2.2 Adjustable Capacitor Timing

Adjustable tWD timing is achievable by connecting a capacitor to the CWD pin. If this method is used, please

consult Equation 1 for calculating typical tWD values using ideal capacitors. Capacitor tolerances cause the

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TPS3435

SNVSCF7A – DECEMBER 2022 – REVISED AUGUST 2024

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