Hi Folks - my first post here.

I have been using eBay CP2102's for some time with various projects. I recently bought 4 of these micro-usb converter boards - http://www.ebay.com.au/itm/191736125396?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT. When I checked the '3.3V' output on these boards, they all measured voltages around 4 or 4.2 volts. I bought two from two different suppliers so I don't know if they were the same batch or not.

I've checked the circuit boards as best I can, and they do appear correct and set up for a bus power supply. I've also check that they have been programmed for a bus power supply in the CP2102 internal register - and again, all appears in order.

I'm at a loss now. If it were a bad batch of chips, I would have expected to see others with the same problem on the internet - but nothing. If anyone has had a similar experience or can throw some light on this, I would be very grateful!

Regards
Mike H

 

Hi Folks - my first post here.

I have been using eBay CP2102's for some time with various projects. I recently bought 4 of these micro-usb converter boards - http://www.ebay.com.au/itm/191736125396?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT. When I checked the '3.3V' output on these boards, they all measured voltages around 4 or 4.2 volts. I bought two from two different suppliers so I don't know if they were the same batch or not.

I've checked the circuit boards as best I can, and they do appear correct and set up for a bus power supply. I've also check that they have been programmed for a bus power supply in the CP2102 internal register - and again, all appears in order.

I'm at a loss now. If it were a bad batch of chips, I would have expected to see others with the same problem on the internet - but nothing. If anyone has had a similar experience or can throw some light on this, I would be very grateful!

Regards
Mike H

Many regulator schemes require a minimum load -- Have you observed the output EMF under nominal load?

Best regards and good luck!
HP

 

Many regulator schemes require a minimum load -- Have you observed the output EMF under nominal load?

Best regards and good luck!
HP

Thanks for for your reply HP. Yes I did check it with a 20 mA load but the voltage only came down to about 4.05V. Given the rated output of the reg is only 100mA, this should have pulled it down to 3.3V I think.

Mike H

 

Note that page #8 of the specification (linked below) shows a maximum Vdd figure of 3.6V at a minimum load of 1mA...
https://www.silabs.com/Support Documents/TechnicalDocs/CP2102-9.pdf

Best regards
HP

 

Thanks for for your reply HP. Yes I did check it with a 20 mA load but the voltage only came down to about 4.05V. Given the rated output of the reg is only 100mA, this should have pulled it down to 3.3V I think.

Mike H

I agree Can you get a look at Vdd on a TDO?

 

I've just probed all the pins on the chip directly. Everything appears to be in order except for Vdd which was ~ 4V with a 40 mA load.