LM5168: High input current under no-load conditions

jan stappers

Part Number: LM5168

Best regards,

I am using this DCDC-converter in a prototype, but I am experiencing an input current of 10mA. See the schematic of our setup:

Input voltage = 84V, Output voltage 16,1V, switching frequency set at 866kHz.

Coil calculation:

If i look at the example in the datasheet they reference this:

When measuring I measure 10mA Iinput (this is not ok) and a Vout of 16,5V (this is ok). I am using this coil: ASPI-8040S-121M-T

Am I missing something? What is causing this high consumption?

Best regards,

Jan

+1 Marshall_Beck over 1 year ago

Hello Jan,

Looks like you are using the FPWM (F orderable) in your design. The frequency remains constant at light load for that device.

To get comparable no load supply current to figure 9-30, please design with highlighted orderable below

0 jan stappers over 1 year ago in reply to Marshall_Beck

Hello Marshall_Beck,

Indeed, but even the PFM version should be around 1mA, right?

I ordered a the PFM version to give it a go.

Best regards,

Jan

+1 Marshall_Beck over 1 year ago in reply to jan stappers

Hello Jan,

The figure 9-30 which you previously referenced would be the quiescent current for the PFM version. It is sub 1mA.

0 jan stappers over 1 year ago in reply to Marshall_Beck

Thank you,

I have tried with the P-version and now i am at a quiescent current of 0.5mA (and lower).

Best regards,

Jan

0 Marshall_Beck over 1 year ago in reply to jan stappers

You are welcome. That is good to hear, Jan.

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