TPS5430: TPS5430 Vin range for negative outputs

Kevin Krasinski

Intellectual 265 points

Part Number: TPS5430

Hello,

Referencing slva257a and slvu243

If I configure a TPS5430 for negative output (between -3.3V and -15V), does that change the Vin range for the TPS5430.

Typically Vin is 5.5 to 36V (referenced to GND)

Does that change as GND is now the -Vout?

so if I have a -3.3Vout, can I run that from a Vin of 5V?

Thanks for your insight.

-Kevin

over 1 year ago

0 Hongjia-Wu over 1 year ago

TI__Expert 5250 points

Hi Kevin,

Suggest you can also take a look at this application note for the basic operation of IBB:

https://www.ti.com/lit/an/snva856b/snva856b.pdf?ts=1692699874679&ref_url=https%253A%252F%252Fwww.google.com%252F

Basically as IBB, the voltage across the VIN and GND pins of the regulator IC is equal to the input voltage plus the negative output voltage. So if you needed to convert from an input of +36 V to an output of –15 V, you would need a regulator with a voltage rating of at least 51V. So a device rated for 60V and higher is suggested.

Regards,

Hongjia

0 Kevin Krasinski over 1 year ago in reply to Hongjia-Wu

Intellectual 265 points

Hi Hongjia,

Thanks for your response, I'm aware of the max voltage spec, I'm asking about the min voltage. The spec says min 5.5v from Vin to GND, now that GND is -15, I'm trying to confirm if I can use a 5V nominal input to create -3.3 out-15v.

Kind regards,Kevin

+1 Hongjia-Wu over 1 year ago in reply to Kevin Krasinski

TI__Expert 5250 points

Hi Kevin,

The device is not able to start up with Vin=5V. Think that before the circuit can work, -Vo is also at GND level, and the Vin that the IC can see is still Vin-GND. i.e.5V.

Regards,

Hongjia

+1 Kevin Krasinski over 1 year ago in reply to Hongjia-Wu

Intellectual 265 points

Thanks Hongjia, I didn't realize it wouldn't even start up. I was hoping it would at least function, just not to spec until the 5.5V was met. This will not work for me then.

Kind Regards, Kevin

0 Hongjia-Wu over 1 year ago in reply to Kevin Krasinski

TI__Expert 5250 points

Hi Kevin,

No problem. If you want to make the circuit work with Vin=5V, you can try another device LMR33630. The min input of this device is 3.8V.

Regards,

Hongjia

0 Kevin Krasinski over 1 year ago in reply to Hongjia-Wu

Intellectual 265 points

Would it be fine to use the TPS62933DRLR? That is a smaller package and has plenty of stock

0 Hongjia-Wu over 1 year ago in reply to Kevin Krasinski

TI__Expert 5250 points

Hi Kevin,

Yes from the min Vin it looks good. But please make sure Vin_max + |Vo| is below 30V.

Regards,

Hongjia

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TPS5430: TPS5430 Vin range for negative outputs