TPS552892: CDC showing wrong value, only 2*(ISP-ISN)

Andrew Xiang

Prodigy 210 points

Part Number: TPS552892

Tool/software:

I do not see any other issues except the CDC, it is only about 2X of the ISP-ISN instead of 20X .

I connect 10mohm between ISP-ISN, and connect the CDC directly to a 12bit ADC.

I measured the V(ISP-ISN) = 20mV, current = 20/10=2.

But CDC only show 30mV roughly.

What could be the cause?

2 months ago

0 Bryce Xun 2 months ago

TI__Mastermind 27910 points

Hi Andrew,

Can you share the schematic?

May I know how ISP-ISN is tested? And can you also test the output current or Vin, Vout, inductor current?

BRs,

Bryce

0 Andrew Xiang 2 months ago in reply to Bryce Xun

Prodigy 210 points

I found the problem, it is sinking current so I reversed the ISP and ISN and it is measuring.

However I have those Issues;

1. This part can only sink up to 3A? can you check?

2. If it is sinking, current going into the device, the CDC current measurement does not work anymore.

0 Andrew Xiang 2 months ago in reply to Andrew Xiang

Prodigy 210 points

when I say sinking, I have VIN = 5.5V, Vout=lower , VIn and Vout connected to 1ohm TEC cooler. I can only sink 3A, Need 4A. Vout in this case is 2.5V only.

What can I do to fix this? I remember you mentioned 2.5A only, but the spec says 8A . Anything I can do , or another similar part?

0 Shipeng Cheng 2 months ago in reply to Andrew Xiang

TI__Genius 17540 points

Hi Andrew,

Can you share the schematic?

And if your load is a resistor, the output current is decided by your setting output voltage.

0 Andrew Xiang 2 months ago in reply to Shipeng Cheng

Prodigy 210 points

same as the ref design. Vin----1ohm ------Vout.

0 Shipeng Cheng 2 months ago in reply to Andrew Xiang

TI__Genius 17540 points

I can't understand what you mean. Show me schematic.

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TPS552892: CDC showing wrong value, only 2*(ISP-ISN)