TPS54J060: Vintref and VFB of TPS54J060

Fred Cheng

Part Number: TPS54J060

Hi team,

why does VINTREF and VFB share same voltage and fixed to 0.9V, what would happen if I force a 1.5V power supply to this VINTREF pin?

since the datasheet show the maximum absolute voltage is 1.5V.

Would share the concept of internal design regarding above question so that I could understand?

over 4 years ago

0 Miranda Gu over 4 years ago

TI__Genius 16632 points

Hi Fred,

Our US team will check it and reply you soon.

0 Yitzhak Bolurian over 4 years ago

TI__Mastermind 18370 points

Hi Fred,

There is no "VINTREF pin" in TPS54J060, this is only an internal voltage.

And VFB (FB pin) is not fixed at 0.9V internally, but VFB will stay very close to 0.9V due to the closed loop, and only when the device is regulating; that is the beauty of closed loop.

VFB is proportional to Vout due to a voltage divider that is used as feed back network to close the loop.

The feedback loop will regulate the Vout to such a voltage that after going through the voltage divider keeps VFB at VINTREF(0.9V).

In other words, TPS54J060 tries to keep VFB at 0.9V and the attempt to keep VFB at 0.9V is actually what makes the Vout to be regulating.

Hope this makes sense.

Regards,

Yitzhak Bolurian

0 Fred Cheng over 4 years ago in reply to Yitzhak Bolurian

TI__Expert 5950 points

Hi Yitzhak,

Could I imagine of some sort of negative feedback OP circuits inside the Vfb pin , which positive side is connected to Vintref =0.9V and negative is the VFB pin, so that VFB would always try to be close to Vintref due to the virtual short or close loop?

Can I explain it with above way?

Regards,

Fred

0 Yitzhak Bolurian over 4 years ago in reply to Fred Cheng

TI__Mastermind 18370 points

Yes, the principal concept is the same.
There is no op-amp involved, but the closed loop idea is very similar.

Regards,

Yitzhak Bolurian

0 Yitzhak Bolurian over 4 years ago in reply to Yitzhak Bolurian

TI__Mastermind 18370 points

Hi Fred,

If the above addressed your question, please set the status of this post to resolved.

Regards,

Yitzhak

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TPS54J060: Vintref and VFB of TPS54J060