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LM5145: Wrong Output Driver Signal

Jayce Luo
Prodigy 590 points
Part Number: LM5145

Hi TI expert,

LM5145 output wrong drive signal to outside MOSFET.

Basic info: Input 50V, Output 5V, Load 10~15A. 200kHz switching frequency.

The LO Signal:

Still LO signal:

The HO output:

The LIM waveform:

The SYNC OUT waveform:

After change the frequency to 150kHz, the drive signal is OK, as show below:

But the output ripple is a little big, 300mV in 5V:

Can you help analysis what's wrong with the circuit? Possible issues? And how to reduce the output ripple? Is such a 300mV ripple amplitude inside a 5V power signal suitable?

B R,

Jayce L

  • 0
    TI__Guru 73752 points

    Hi Jayce,

    Looks like the design was unstable. Please check your circuit values using the LM5145 quickstart calculator (the file is available by download from the LM5145 product folder). Just make sure to derate the ceramic output capacitance for applied voltage as this affects compensation.

    If you need further help, please send the schematic and completed quickstart for review.

    Regards,

    Tim