TPS6122x : Vin>Vout

Nicolas DECROZE

Other Parts Discussed in Thread: TPS63000, TPS61200, TPS61220

Hello,

Here is a question about the design of TPS622x application, if the 3.3V Reg output what is th IC behavior if Vin became upper than Vout?

many thanks,

over 11 years ago

0 Chris Glaser over 11 years ago

TI__Guru**** 150900 points

TPS622x does not correspond to a proper part number. Please check which exact part you are asking about.

If you are asking about the TPS6122x boost converter, this wiki page has your answer: http://e2e.ti.com/support/power_management/non-isolated_dcdc/w/design_notes/1179.tps61220-performance-with-vin-near-vout.aspx

0 Nicolas DECROZE over 11 years ago in reply to Chris Glaser

Prodigy 40 points

Oh yes you are perfectly right, there is a mistake in my question.

The IC is TPS6122x.

Thank you for the link.

If i understand, if the Vin is upper than 4,2V, the output is no longer regulated and vin is directly on Vout.

Is that right?

The problem is that in my application, Vin is mostly under 3.3V but sometimes can go to 5V.

Do you have an ic who have special feature to avoid this problem (like LTC3105 form linear technology)?

best regards,

0 Juergen over 11 years ago in reply to Nicolas DECROZE

TI__Expert 5425 points

What is your minimum input votlage for this boost converter?

0 Nicolas DECROZE over 11 years ago in reply to Juergen

Prodigy 40 points

The application is "energy harvesting" so i need that the boost converter start as lower as possible (0,5V to 1V)

0 Chris Glaser over 11 years ago in reply to Nicolas DECROZE

TI__Guru**** 150900 points

A buck-boost converter would provide output regulation when Vin is above or below the setpoint. These are the TPS630xx devices (TPS63000, etc.).

But it sounds like you need a very low Vin boost IC. This would be the TPS61200. It has down mode, so Vout remains regulated when Vin goes above Vout. This is not the case with the TPS61220.

0 Nicolas DECROZE over 11 years ago in reply to Chris Glaser

Prodigy 40 points

Many thanks for your help !

TPS61200 seems to the good IC for my application.

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TPS6122x : Vin>Vout