TPS60400 Startup Problem

asilva

Prodigy 40 points

Other Parts Discussed in Thread: TPS60400

Hi all,

I have the following circuit in order to get a negative voltage of -2v5 from 3v3.

When it start up ok, the circuit is fine, but the question is that it does not startup often.

When I have a failed startup I get 1V5 at C39.

Can anyone give me a tip?

thanks

over 12 years ago

0 Chris Glaser over 12 years ago

TI__Guru**** 150650 points

You'll need to get some waveforms to see what's going on but it's likely that your op amp is unable to drive the required startup current of the TPS60400. Does the circuit work when you just connect the 3.3V to the input?

0 asilva over 12 years ago in reply to Chris Glaser

Prodigy 40 points

Hi Chris,

When I set (just for a moment) 3v3 from main LDO on C39, I get the proper voltages +2v5 and-2v5.

It is possible to know the startup current requeired for TPS60400 (lets assume a corrent load of 7mA)? I would need to check if I will need to replace the op amp, and use an LDO 2v5.

thanks

antónio silva

0 Chris Glaser over 12 years ago in reply to asilva

TI__Guru**** 150650 points

There's figure 6 in the D/S.

0 asilva over 12 years ago in reply to Chris Glaser

Prodigy 40 points

Hi,

I will give up of voltage divider + op amp, a use and LDO 2v7, ir order to get the desired voltage.

thx

Power management

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TPS60400 Startup Problem