TPS54302: EN pin control using N.O. switch

Seth Johnson

Part Number: TPS54302

I'd like to turn on the device by closing a Normally Open switch. However, the datasheet specifies that the EN pin needs to be floated to enable (which calls for a Normally Closed switch to pull the EN pin to GND for off, and can then be opened for EN to float).

Can I instead use the UVLO resistor voltage divider circuit as shown on page 10 of the TPS54302 datasheet, but modified to insert the N.O. switch in series with R4? This way, when the switch is open (off), R4 is disconnected from the EN pin. R5 is always connected to EN and will pull down the EN pin to GND, disabling the device. When the switch is closed (on), R4 is connected as per the circuit on page 10 and acts as a divider pulling the EN pin up over the VENrising threshold and enabling the device.

Would this modification work correctly? Thanks.

over 8 years ago

0 Ryan Hu (BSR-MV) over 8 years ago

TI__Expert 4035 points

Hi Seth,

I think you could control the EN pin voltage like that. Swtich OFF, disable the device, Swtich ON, enable the device with UVLO.

Ryan

0 Luke Pan over 8 years ago

TI__Intellectual 2790 points

Hi,

What's the type of your switch? FET or transistor? FET won't be applicable to your circuit as the FET needs high side driver. Transistor should work in your application, however the transistor is only used as a buffer., so R4 and R5 won't work for precision UVLO. If you need both precision UVLO and EN control with right logic. Below circuit is recommended.

0 Ryan Hu (BSR-MV) over 8 years ago in reply to Luke Pan

TI__Expert 4035 points

Ｈi Luke,
Thanks, i thought the Normally Open switch was a mechanical swtich for a easy control way but doubt now. if not a mechanical swtich, the solution you showed is highly recommended.

0 Seth Johnson over 8 years ago in reply to Ryan Hu (BSR-MV)

Intellectual 380 points

My apologies for not specifying in my original post. I will be using a mechanical switch as Ryan assumed. Thanks for verifying that it should work as planned.

Also thanks to Luke for suggesting an alternate solution. I'm sure it could come in handy to for anyone referencing this thread and planning on using that control style.

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TPS54302: EN pin control using N.O. switch