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LMR23615: SW stops after load transition

Kai Nomiyama
Expert 5355 points
Part Number: LMR23615

Hi team,

I have a question about LMR23615 transient response.

When changing output current from 200mA to 50mA, no switching period was observed.

please see below figure.

ch1: output current(upper waveform)

ch2: SW node(lower waveforme)

based on EVM and changed L .7uH to 15uH and Fsw is 400kHz

could you let me know the reason why this no sw period occurs?

I will get more detail information tomorrow so if you need any information to support this, could you let me know.

thanks,

regards,

kai

  • 0
    TI__Genius 11085 points
    I think your upper curve is SW node and lower curve is load current.

    If you also probe Vout signal (may need AC coupled to view transient response), you should see during the time there's no SW action, Vout should be higher than regulation, due to reduced load current. The control loop stops switching action to avoid further charging the Cout when Vout is already above regulation. It is a normal behavior after step down load transient.

    -Yang