LM5176: Static current increase

zhang ping

Part Number: LM5176

Problem: in the buck mode, the static current will increase synchronously with the increase of the input voltage. The phenomenon is that the MOSFET U4 will be very hot. See the attachment for the schematic diagram. The waveforms of the four MOS base stages are as follows:

Note: the ringing part of the MOS end is caused by the radiation interference of the oscilloscope probe. Take off the probe, and one measurement will be much smaller。

6332.LM5176.pdf

over 5 years ago

0 Garrett Roecker over 5 years ago

TI__Mastermind 21720 points

Hi Zhang Ping,

Thanks for reaching out with your question and for using the LM5176 in your design.

Which current are you measuring? Is it the input current? What is the difference in the current measurement.

Thanks,

Garrett

0 user6295702 over 5 years ago in reply to Garrett Roecker

Prodigy 20 points

We use a DC power supply to power the board, and the current value is the displayed value of the power supply. The current value will increase as the voltage increases.

0 Garrett Roecker over 5 years ago in reply to user6295702

TI__Mastermind 21720 points

Hi Zhang Ping,

Can you please probe the switch nodes to see what mode of operation the device is in? With the output voltage set to 15V and the input voltage at 17V the LM5176 will be operating in buck-boost mode. In buck-boost mode the efficiency can be higher than at 24V. This is probably causing the input current to have the difference between the two selected input voltages.

Thanks,

Garrett

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LM5176: Static current increase