TPS92641: TPS92641 : Cause of Overshoot at the rising edge of the current waveform

Hi SHUHEI

Can you please share the schematic?

Thanks and best regards.

Hi Gui

Thank you for your reply.

The schematic is shown below.

The laser diode is attached to the right side of this figure.

Best regards.

Hi SHUHEI,

Our expert will give you feedback later.

Hi Shuhei

Can you please also share the waveform of the iL , SDIM, IADJ ?

Thanks and best regards.

Hi, Gui

I share the waveforms of iL, SDIM, and IADJ in ppt file.
All were taken with the load current waveforms.

Best regards.Waveforms of TPS92641 circuit.pptx

Sorry I had all day meeting today, will take a look at this tomorrow. Thanks

Hi Shuhei

Sorry for late reply. Seems that the overshoot is related with the dynamic response, can you replace the Ccomp with a larger value like 0.47uF ? 

Thanks and best regards.

Thank you for your advice.
I tried Ccomp at 0.47uF, 1uF and 4.7uF with the same result.
The image shows the current waveform at 4.7uF.
Can you think of any other causes?

Hi Shuhei

I am thinking that during SHUNT FET ON period, the ton is small, and iL ripple is small, and since TPS92641 regulates the average current, then on the first cycle after SHUNT, the iL ramps up during the fixed TON set, so the current peak happens.

Can you please share the consideration/influence for the current spike? I will also find a TPS92641EVM and test the SHUNT performance.

Thanks and best regards.

Hi Gui,

Current spikes should be kept below the maximum value of current including ripple, since current spikes will worsen the life of the light source.
 Please test SHUNT performance and let us know if you find a way to reduce current spikes.
Thanks and best regards.

Hi Shuhei

I will check and feedback to you later todya.

Thanks and best regards.

Hi ShuHei

The EVM just arrived, I will fetch and measure tomorrow. THanks.

Hi Gui,

Thank you for confirming.
I understood that the current peaks are unavoidable.
Thank you very much for your kind response.