TPS54620 negative supply output

Anirudha Chougule

Prodigy 170 points

Other Parts Discussed in Thread: TPS54620

I am using TPS54620 IC's for generating +3 and -3V output from 12V input.

Below is the SCH implementation, can you please review and let me know for any issue.

Also how can I achieve the simultaneous output synchronization.

Thanks,

Anirudha

over 8 years ago

0 JohnTucker over 8 years ago

TI__Guru**** 191445 points

Your schematic did not post. Can you try again?

0 Anirudha Chougule over 8 years ago in reply to JohnTucker

Prodigy 170 points

0 JohnTucker over 8 years ago in reply to Anirudha Chougule

TI__Guru**** 191445 points

The compensation components look suspect. how did you calculate them? The EN and SS/TR functions for the negative supply must be referenced to - Vout, not GND. You may be able to level shift your SS/TR signal. See this:
www.ti.com/.../slva540

0 Anirudha Chougule over 8 years ago in reply to JohnTucker

Prodigy 170 points

Hi John,

Thanks for the information.
But with level shifting, how can I achieve synchronization between +3V and -3V as level shifting circuit will add delay in -3V start-up.

Also tps54620 has En threshold of 1.26V, so if I set EN threshold to 1.4V still will I require level shifting as my output is -3V and with this the Voltage on En pin will be 1.4+3= 4.4V which is within the limit of EN pin.

The SS/TR pin connection is for synchronization only of +3 and -3V, I will check for level shifting for it and let you know.

Thanks,
Anirudha

0 Anirudha Chougule over 8 years ago in reply to Anirudha Chougule

Prodigy 170 points

Hi John,

Any feedback on ground reference on EN pin if I set Ven=1.4V and Vout= -3V ?

Regards,
Anirudha

0 JohnTucker over 8 years ago in reply to Anirudha Chougule

TI__Guru**** 191445 points

I think in that configuration with Vin = 12 V, EN will be at 6.15 V relative the Vout. That is above the abs max for EN. I would follow the level shifting example.