TPS55288-Q1: output current limit behavior

Hi Ben,

Thanks for reaching out. May I know what is the customer and the application here?

1. Can you share the schematic and layout here?

2. Can you also add the SW1 waveform in the above test results? And zoom in the waveforms of 0.9A->1.0A, and 3.7A->3.8A?

3. As I know, PD3.1 spec shows currentt PPS doesn't need to support Vout smaller than 5V, why does the customer test this?

4. Please check the Vstart voltage of the e-load, when Vout is very small, the e-load may shutdown.

BRs,
Bryce

Hi Bryce,

Attachment is schematic and layout for your reference. For item4, we have check it not e-load issue. FYI

GE_METEOR LAKE_A1_20240205 TPS55288.pdfGEHC_Venue_MPB_Board-0A10-0129.zip

We found SW1 is switching during boost mode in below condition.

0.9 to 1A (ISN-ISP=10mV, Rsense=10mohm)

3.7 to 3.8A(ISN-ISP=40mV, Rsense=10mohm)

Regards,

Ben

Hi Bryce,

We also want to know why SW1 switching when device operate in buck mode and trigger to OCP.

Regards,

Ben

Hi Ben,

Thanks for the waveforms.

As I mentioned, PD3.1 spec shows current PPS doesn't need to support Vout smaller than 5V, why does the customer test this?

And from the waveforms, the Vout is very low close to zero, FYI, the minimum recommended output voltage by TPS55288 is 0.8V.

BRs,

Bryce

Hi Bryce,

Customer's application is 12Vin to 20Vout. And they want to know why output drop step by step (as picture in first post) even Iout not trigger to current limit.

They don't really care about PD3.1 spec or Vout close to 0V.

I found there are two different current limit, output current limit and average inductor current limit. Does this two both are cycle by cycle current limit? And the protection behavior is limited duty cycle and will cause output drop?

If yes, I think we need to focus on current limit accuracy.

If not, please show how this OC protection work.

Regards,

Ben