Datasheet

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CT CT DELAY

CT DELAY

DELAY

CT CT

DELA

V = 1.24V, I = 300 nA, T = 1.4 ms

C = T 0.5 ms

Example for EVM CT pins with a desired T = 1.4 ms

300 nA

C = (1.4 ms 0.5 ms) = 218 pF (choose C = 220 pF)

1.24 V

´ -

1.24 V

= 220 pF + 0.5 ms = 1.41 ms

300 nA

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Description

4.2.3 RESET Outputs

The TPS386000/40 RESET outputs are used on the EVM to enable the associated power supplies. The

TPS386000 has open drain outputs and are pulled up by R3-R6 pullup resistors by default on the

TPS386000EVM. The TPS386040 has push-pull outputs and R3-R6 are not installed on the

TPS386040EVM.

Jumpers allow the RESET pins to be connected to an external power supply enable for use with a user

system.

4.2.4 Timing Delay on CT Pins

Delay from SENSE input to output RESET can be adjusted with the value at the CT1-CT4 pins. Use the

following equations to adjust the delay from the nominal 1.3mS EVM value.

4.3 Watch Dog Timer Function

The TPS386000/40 contains a watch dog timer (WDT) and the EVM contains a local WDT (LWDT) as well

as a provision for an external WDT connection. LWDT provides a pulse approximately every 140ms to the

TPS386000/40 WDI pin when configured by J11. LED D2 indicates when the LWDT is active.

The TPS386000/40 WDT function can be tested in the LWDT mode by holding LWDT in reset by placing

a shunt on J12 (RST LWDT). When a shunt is installed on J12, the WDO output on J9 will go to logic low

after approximately 600ms. WDO can be reset to logic high by pressing the S1 push-button switch to reset

the TPS386000/40.

A system WDT can also be provided externally through J10 when J11 is set to the EXT WDT position.

SLVU341–October 2009 Evaluation Module for TPS386000 and TPS386040

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