TPS54231 UVLO

Sachin Kurawatti

Prodigy 130 points

Other Parts Discussed in Thread: TPS54231

Hi,

Please can anybody help me with my below query.

I dont want to use external UVLO option by providing pullup and pull down resistor to enable pin.

Vin for the regulator is fixed 12V and Vout is 1.2V.

As per datasheet of TPS 54231 "It is recommended to use an external VIN UVLO to add Hysteresis unless VIN is greater than (VOUT + 2 V)".

In my design Vin > Vout+2V and for my design Internal under voltage lockout threshold of 3.5V is good enough(as per datasheet).

so do I really require to use external resistor for UVLO?

I want to enable the regulator by connecting the enable pin to open drain output signal.

Please help me to understand, if there will be any problem in enabling the regulator with open drain output signal without the external UVLO resistor?

over 14 years ago

0 Michael Green over 14 years ago

TI__Genius 16870 points

Hi Sachin,

I am not completely sure if this is what you wanted but, for 12V Vin and 1.2V Vout the TPS54231 will start up with Vin and turn off with Vin, even if the Ren1 and Ren2 resistors are not present. Refer to datasheet page 8 for more information. I tested this with an EVM in the lab and found that the IC did operate without the Ren resistors. You can order an EVM for your own testing at http://focus.ti.com/docs/toolsw/folders/print/tps54231evm-372.html.

Thank you for your question and interest,

Michael Green

0 SACHIN KURAWATTI81378 over 14 years ago in reply to Michael Green

Prodigy 100 points

Hi Michael,

Thank you for your reply.

Yes I dont want to use Ren1 and Ren2, which are external UVLO option resistors. I would like to use the default internal UVLO threshold i.e 3.5V.

I want to ON/OFF the regulator output by controlling enable pin of the regulator. I want to connect an open drain output signal to the enable pin of regulator.

(Without pullup resistor to the open drain signal i.e. if the open drain signal is not LOW it will be floating)

Please can you suggest if you see any problem in controlling the regulator output by this method?

Best Regards,

Sachin.M.Kurawatti

0 Michael Green over 14 years ago in reply to SACHIN KURAWATTI81378

TI__Genius 16870 points

Hi Sachin,

As long as you operate the TPS54231 with 12Vin and 1.2Vout, the external UVLO is not needed. If you float the EN pin the IC will be Enabled. If you ground the EN pin the IC will be disabled. So, yes you can control the EN pin with the open drain signal.

Thanks,

Michael Green

0 SACHIN KURAWATTI81378 over 14 years ago in reply to Michael Green

Prodigy 100 points

Thank You Michael

Power management

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TPS54231 UVLO