V

=

VB

V

+ 0.6 V

STC

t

on

V

DDon

V

BUS

V

STC

V

VS

t

off

V

DDoff

V

VDD

V

PF

typical threshold voltage

for power fail PF

STC

VDDoff

off

STC

VDD

CI1

V

– V

t

= C

I

+ I

TSS521

SLAS980 – SEPTEMBER 2013

www.ti.com

Power On and Off

Figure 5. Power On/Off Timing

Power Fail Function

Because of the rectifier bridge BR at the input, BUSL1, and BUSL2, the TSS521 is polarity independent. The pin

level PF = 0 (power fail) provides a warning of a critical voltage drop to the microcontroller to save the data

immediately.

6

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