SN74LVC1G74: We need to convert momentary push button switch to toggle switch & Its application is Power On Off Switch

Shubham patil

Intellectual 520 points

Part Number: SN74LVC1G74
Other Parts Discussed in Thread: SN74HCS74-Q1

Hii Team ,

We are planing to attached image for power ON switch .

VSYS-------Battery Charger output-----3.3V to 4.2V'

The output of this circuit is given to Booster EN pin to control the power of HUB.

We required following requirement for Power On Off Switch:

By-default Board is ON

When First time Switch is Press then Board Power will Off.

Second time Switch Press then Board Power need to ON .

use attached image and review the circuit give your feedback.

over 4 years ago

0 Shubham patil over 4 years ago

Intellectual 520 points

Hi Team ,

If you have some better option for above requirement then please share your feedback on above circuit.

Thanks ,

Shubham.

0 Clemens Ladisch over 4 years ago

Guru 253780 points

This circuit looks correct. By default, the BAT_POWER_ON_OFF signal is open; the first button press will pull it low.

The time constant of the debouncing filter (C697/R1039) is 0.22 ms, which is rather short. The switch datasheet should specify the worst-case bouncing time, but I would not want to use less than about 20 ms.

0 Shubham patil over 4 years ago in reply to Clemens Ladisch

Intellectual 520 points

Thanks for the response,

Can please provide some other low cost options for above use case ..

BAT_POWER_ON_OFF is default pull high .

Thanks

Shubham

0 Clemens Ladisch over 4 years ago in reply to Shubham patil

Guru 253780 points

All components in this circuit have a meaningful function.

It would be possible to replace everything (except the ESD protection) with a microcontroller, but that is not necessarily a low-cost option.

0 Dylan Hubbard over 4 years ago in reply to Clemens Ladisch

TI__Mastermind 43230 points

Hi Shubham,

You can use the SN74HCS74-Q1 (non-automotive version coming soon) which has integrated schmitt-triggers eliminating the need for LVC2G14 device. This will most likely save some cost and board space. Since you won't have an inverting stage preceding the flip-flop, the POR circuit and button debounce circuit will have to be adjusted accordingly.

Logic

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SN74LVC1G74: We need to convert momentary push button switch to toggle switch & Its application is Power On Off Switch