TMUX2889YBHEVM: PWM signal pass though issue

Hi Kevin,

At first glance this does not seem like normal operation. Some things to check here: what is the frequency of the signal? We also want to make sure that no more than Idc + 10% of current is flowing through the switch. Can you confirm these two items? If you have a quick schematic you can provide as well then that should be helpful, too. 

Thanks!

Alex

Hi Alex,

Thanks for your quick reponse.

Alex Vish said:

what is the frequency of the signal

About 766KHz for the PWM signal.

Alex Vish said:

We also want to make sure that no more than Idc + 10% of current is flowing through the switch

The peak Idc is around 70mA

It worked after I inserted a LC filter to reduce the high frequency of the PWM singal. The purpose of TUMX2889 is to isolate AUX line in signal and codec's output when power down. So I was wondering if the frequency of PWM signal was too high to pass TUMX2889??

Brs,

Kevin

Hi Kevin, 

It does appear to be a matter of frequency that is causing your issue here. For converting PWM frequency to bandwidth of the device, we like to use a 5x conversion factor. So at ~4 MHz we start to see just a little bit of signal attenuation. I'm not sure how much you're seeing exactly without seeing some waveforms, but the addition of an LC filter further emphasizes this is an issue of bandwidth limitation. Is an LC filter practical for your application? If not, I would suggest going with a higher bandwidth device like the TS5A5223.

Regards,

Alex

Hi Alex,

It seems 4MHz is high enough for the PWM signal. Weird~~

Is TS5A5223(TS3A5223) support Powered Off Protection? When our device power off, VDD will be droped to 0V. I am not sure if it will be affected by the AUX signal voltage which present on the Normal Close channels . I could also add the LC filter on our application if TS5A5223(TS3A5223) is not suitable.

Brs,

Kevin

Hi Alex,

Thanks a lot for your help.

Brs,

Kevin