LM5177EVM-HP: fixed current output

Hello Brian,

Do they want to limit the current to 5A on average or do they want to regulate the current instead of the voltage?

Best regards,
Brigitte

Hi Brigitte,

They want to regulate the current.

And they have find one guide but didn't tell them the specific value of the R & C:

https://www.ti.com.cn/cn/lit/an/zhcad33/zhcad33.pdf?ts=1696843781178&ref_url=https%253A%252F%252Fwww.ti.com.cn%252Fproduct%252Fzh-cn%252FLM5177%253FkeyMatch%253DLM5177%2526tisearch%253Dsearch-everything%2526usecase%253DGPN

Could you please kindly give a specific value for them to test?

Thanks,

Brian

Hi Brigitte,

Could you please help tell me which components on the EVM need to be changed and give a specific R&C for 5A?

Thanks,

Brian

Hi Moritz,

 Customer is testing our EVM. And they saw we can regulate the current with LM5177.

So right now they want a guide or a reference design about which components on the EVM need to be changed can make them get a 5A current output.

If we can not give them such a guide, please help explain how to design the compensation circuit for Rimon and Cimon.

And please help explain how does this 3x 5x faster come?

Thanks,

Brian

Hi Moritz,

Thanks a lot for your reply.

Could you please also help explain how to calculate the RIMON and CIMON and how can we have the 3x 5x performance as datasheet say?

An example for this will be very helpful. 

And do we have a test case and related design for constant current output to share with customer?

Thanks,

Brian

Hi Brian,

3x- 5x faster in the datasheet means the crossoverfrequency compared to the output voltage loop.

You can use the quickstart calculator for this device and check what the crossover frequency is with the used compensation network on the EVM. Then you can adjust the values and see with which R and C values you will get a crossover frequency that is 3 times higher.

Fo LM5177 we dont have a reference design, but for LM5176 and LM5175, there are constant current examples for battery charging:

https://www.ti.com/tool/PMP20660

https://www.ti.com/tool/PMP22125

Best regards,

Moritz

Hi Moritz,

I have sent customer these two before, but LM5177 has a compensation current loop compared to LM5175&LM5176.

Have we ever tested constant current output before RTM this device?

Do we have some test report and design at that time?

Thanks,

Brian

Hello Brian,

The app note is based on tests. I will update next week which formulas from the datasheet need to be used for current regulation.

Best regards,
Brigitte

Hi Brigitte,

Looking forward to your reply.

Thanks a lot.

Brian

Hi Brigitte,

Any feedback?

Thanks,

Brian