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LM5123-Q1: SW point output undershoot

Part Number: LM5123-Q1

Tool/software:

Hi team,

My customer is using LM5123 and met SW point output undershoot issue.

They met the issue both in EVM and their own design board. Below is the figure from EVM testing.

Datasheet limits the voltage of SW within -1V. So -2V can not be accepted. LO and HO also have undershoot issue.

Customer tried below three methods but they have no help.

1. Add fast recovery diode

2. reduce the resistor before MOSFET Gate.

3. Slow down switching frequency

Do you have any other solutions?

  • Hi Gary,

    We are updating the datasheet. -5V 10ns on SW is acceptable.

    Please follow below items when performing the measurement:

    • Make sure you are measuring with a ground springing.

    • Use high sample rate (<1ns/pt) and >200MHz bandwidth
    • Use scope full Y-axis scale

    Best Regards,
    Feng