TPS54232: Unstable Output

paresh valand

Prodigy 100 points

Part Number: TPS54232

Hi,

I have generated 3.8V using TPS54232 with taking reference of webench design.

I have attached image of schematic.

My input range is 4.5V to 5.5V and output is 3.8@2A.

But I am getting varying output from 2V to 3V.

Kindly suggest.

over 7 years ago

0 paresh valand over 7 years ago

Prodigy 100 points

I have not used under voltage protection resistor and made enable pin floating.

0 JohnTucker over 7 years ago in reply to paresh valand

TI__Guru**** 191445 points

I would have to see a waveform to be sure, but most likely you are operating in low headroom drop out condition. Does teh output regulate properly when you increase the load? See this link for more details. It is applicable to TPS54232 as well.

www.ti.com/.../slva547

0 paresh valand over 7 years ago in reply to JohnTucker

Prodigy 100 points

Hi John,

Thanks for your answer.

I want to know is there any method to find out proper load resistance value.

Because by trial and error I have placed 47ohm resistor and got stable output which required. As per your provided they use resistor value in kohm which is not working in my case.

Kindly suggest.

0 JohnTucker over 7 years ago in reply to paresh valand

TI__Guru**** 191445 points

The low headroom drop out only occurs when VIN is near VOUT and when the circuit is in eco mode. Eco-mode boundary is hard to predict. See this app note:

Generally, you can always avoid it when you operate in CCM. That is when the load current is greater than 1/2 the ac ripple current:

ILp-p = (Vout/Vin) * (Vin-Vout) / (Fsw*Lout)

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TPS54232: Unstable Output