TPS5450: -12V / 3.5A Output Schematic Review

Hi Syukri,

I would double-check this again given that you are want a 24Vin|-12Vout|3.5A IBB conversion.

Using Equation 6 from this app note (https://www.ti.com/lit/an/snva856a/snva856a.pdf#page=7) assuming 85% efficiency and 20% inductor ripple current, the calculated Ipeak is around 5.9A which is very close to the 6A minimum current limit of the device. 

You may want to pick a 6A rated device which will have a slightly higher minimum current limited and allow for a more robust design given your application power conversion.

Perhaps you can look into the LM61460?

Regards,

Jimmy 

Hi Syukri,

I don't see any issues operating with those conditions for conventional buck topology. 

The TPS5450 is able to handle 5A continuous current. 

Only when the convert is configured for IBB is when the peak current should be observed since the current in an IBB setup is different than the current in a normal conventional buck.

Regards,

Jimmy

Hi Syukri,

Yes that is correct, you would need to make sure that the calculated  Ipeak in IBB topology is below the minimum high side current limit with some margin. I think a 6A rated device will be appropriate for this conversion.

Unfortunately the Pspice model does not have IBB feature.

Regards,

Jimmy

Hi Syukri,

I think a good margin would be 10% from the minimum peak current limit would be a good start. 

There should not be any issue with voltage stress since the voltage seen on the IC is within the recommended operating conditions of 36Vin.

Regards,
Jimmy

Hi Syukri,

Perhaps you might also want to look into the LM76005 which is a 60V|5A device that would be suitable given the higher VIN rating.

Regards,

Jimmy