I ordered a CP2102 USB-to-serial module from Ebay, but I found that the output labeled "3.3V" on the silkscreen actually measures at 4.25V. I thought it was just a bad part, but I found the same module on sale at Banggood, and the same problem is mentioned in reviews posted by three buyers. One of them had ordered three modules, and all of them were 4.25V. So it appears all of these modules output 4.25V instead of 3.3V. I can't use 4.25V because the microprocessor it will connect to has a maximum voltage of 3.6V.
On the back side it says "CJMCU" and "BQ09615H2 2025a"
The chip is labeled:
SILABS
CP2102
DCL00X
1612+
I don't see anything in the datasheet that indicates the output of the regulator is adjustable. Can anyone offer an explanation for the 4.25V output? Could all the chips, or a large number of them, be faulty? That seems unlikely. It seems much more likely that this was done deliberately.
I also ordered another CP2102 module of a different design, and its 3.3V output is correct:
But it is bigger than the first module, and less suitable for my project. So I would like to find a source for the first module with an on-spec 3.3V output, if that exists.
Any help or explanation would be appeciated.
Sherman
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Answered
It was strange, do you have a schematic for this board?
0
delu wrote:
It was strange, do you have a schematic for this board?
I do not have a schematic, but continuity testing with my meter confirms the 3.3V output pin of the module is directly connected to pin 6 of the CP2102. So the voltage regulator is generating the 4.25V. I have removed the LEDs and their resistors, so the only parts left on the module are three capacitors and the CP2102. The voltage is still high.
Is it possible that Silabs made a special run of CP2102s with the higher regulator output? Is it possible to change the regulator output by flashing new parameters to the CP2102?
If not, what would be the explanation for this? Is this a common failure mode?
0
Does the board still works fine?
according the datasheet the regulator should output a voltage in the range of [3.0 3.6]. refer table 6 on page 9 of the CP202-9 datasheet.
Since you don't have the schematic, it is hard to know what problem the issue come from.
Since you also have some device that seems normal, I suggest you try to measure the resistance between the VDD and VBus to see if there is some difference between the normal and problematic part.
My views are my own and do not necessarily represent the views of Silicon Labs
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My guess is that REGIN (pin7) is not connected to VBUS on the connector, but VBUS (pin8) is. This will probably leak power through the bulk diode of the silicon to VDD (pin6) which explains the 0.7V drop.
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vanmierlo wrote:
My guess is that REGIN (pin7) is not connected to VBUS on the connector, but VBUS (pin8) is. This will probably leak power through the bulk diode of the silicon to VDD (pin6) which explains the 0.7V drop.
So REGIN-pin7 should be connected to VBUS on the connector? What should pin8 be connected to?
Well if you are right about this, then all of them are that way. And somewhat difficult to repair in QFN land.
0
If you take look at the datasheet, for bus powered mode both PIN7 and PIN8 should be connected to VBUS.
0
I was able to check continuity, and both pin 7 and pin 8 are connected directly to the 5V pin on the USB connector. And I previously determined that the 3 3.3V output is connected properly.
Can you think of any other connection, or lack thereof, that would cause the regulator not to output 3.3V?
If not, then we either have a bad batch of CP2102s, or perhaps there was too much heat in reflow.
0
Is it possible that the flash memory of this device has been modified in a way that would cause this behavior? The ANs say there is a setting for Power Option where "Bus Powered" is the normal setting, as well as a setting for maximum milliamps. Would selecting some non-standard options cause the regulator to be bypassed in this way?
The driver does recognize this device, so I think that means the identifiers are correct. If I install the Silabs flashing software, will it tell me the current settings?
Just looking for an explanation that might have a solution. Anyway, I have three more of these coming in from other sources over the next couple weeks, and will see if they have the same problem. I just suspect they are all like this, but only those who bother to measure the voltage notice that it's wrong. But if all are like this, then there may be nothing wrong with the chip, just some circuit design or parameter setting that was done deliberately for some purpose.
Does anyone know who CJMCU is?
0
Ok, it's not just my imagination. Here is a Youtube video of a guy with a handful of modules exactly like mine, and they all measure 4.25V at the 3.3V output:
So this was done intentionally, and all modules of this design are like this. But how did they do it?
0
There is a major design flaw in the board, RST-pin (9) is connected to 5.0V (VBUS). This is reported deep into a forum on Banggood but not properly informed to buyers.
Quote: The problem with the 3.3V line at 4.2 is due to the RST input being tied not to 3.3 V out but to the Vbus in (5V) this back feeds into the 3.3V line pulling it up above spec, cut the trace you see coming from pin 9 before it reaches the capacitor, then optionally pull it to 3.3 via a 4k7 resistor to pin 6. This also seems to solve the variability with Win10 Posted 2017-02-22 09:12:56 by instoned @t aol dot com
I just noticed that the cutting of RST on these CJMCU CP2102-boards already was discussed in another thread, CP2102 - 4.24V output on pin 6 Vdd
0
Hi...i am a new user here. As per my knowledge it is true that there is a major design flaw in the board, RST-pin (9) is connected to 5.0V (VBUS) and this is reported deep into a forum on Banggood but not properly informed to buyers.
Just looking for an explanation that might have a solution. Anyway, I have three more of these coming in from other sources over the next couple weeks, and will see if they have the same problem. I just suspect they are all are ready like this, but only those who bother to write my paper and measure the voltage notice that it's wrong. But if all are like this, then there may be nothing wrong with the chip, just some circuit design or parameter setting that was done deliberately for some purpose.
Does anyone know who CJMCU is?
I've been also searching for their contact details. Their official cjmcu is not loading. And somehow I managed to find the solution on Electrondepot forums (In short: you can disconnect pin 9 from USB+ and then leave it floating). Hope this helps, if someone is also looking for the info.
0
Maybe you can look http://www.lhd-pcb.com
0
It doesn't help me, summer Liu. Maybe something else?
CP2102 3.3V output is 4.25V on CJMCU module
I ordered a CP2102 USB-to-serial module from Ebay, but I found that the output labeled "3.3V" on the silkscreen actually measures at 4.25V. I thought it was just a bad part, but I found the same module on sale at Banggood, and the same problem is mentioned in reviews posted by three buyers. One of them had ordered three modules, and all of them were 4.25V. So it appears all of these modules output 4.25V instead of 3.3V. I can't use 4.25V because the microprocessor it will connect to has a maximum voltage of 3.6V.
This is the module I bought:
http://www.ebay.com/itm/272469914995
On the back side it says "CJMCU" and "BQ09615H2 2025a"
The chip is labeled:
SILABS
CP2102
DCL00X
1612+
I don't see anything in the datasheet that indicates the output of the regulator is adjustable. Can anyone offer an explanation for the 4.25V output? Could all the chips, or a large number of them, be faulty? That seems unlikely. It seems much more likely that this was done deliberately.
I also ordered another CP2102 module of a different design, and its 3.3V output is correct:
http://www.ebay.com/itm/291874318571
But it is bigger than the first module, and less suitable for my project. So I would like to find a source for the first module with an on-spec 3.3V output, if that exists.
Any help or explanation would be appeciated.
Sherman
It was strange, do you have a schematic for this board?
I do not have a schematic, but continuity testing with my meter confirms the 3.3V output pin of the module is directly connected to pin 6 of the CP2102. So the voltage regulator is generating the 4.25V. I have removed the LEDs and their resistors, so the only parts left on the module are three capacitors and the CP2102. The voltage is still high.
Is it possible that Silabs made a special run of CP2102s with the higher regulator output? Is it possible to change the regulator output by flashing new parameters to the CP2102?
If not, what would be the explanation for this? Is this a common failure mode?
Does the board still works fine?
according the datasheet the regulator should output a voltage in the range of [3.0 3.6]. refer table 6 on page 9 of the CP202-9 datasheet.
Since you don't have the schematic, it is hard to know what problem the issue come from.
Since you also have some device that seems normal, I suggest you try to measure the resistance between the VDD and VBus to see if there is some difference between the normal and problematic part.
My views are my own and do not necessarily represent the views of Silicon Labs
My guess is that REGIN (pin7) is not connected to VBUS on the connector, but VBUS (pin8) is. This will probably leak power through the bulk diode of the silicon to VDD (pin6) which explains the 0.7V drop.
So REGIN-pin7 should be connected to VBUS on the connector? What should pin8 be connected to?
Well if you are right about this, then all of them are that way. And somewhat difficult to repair in QFN land.
If you take look at the datasheet, for bus powered mode both PIN7 and PIN8 should be connected to VBUS.
I was able to check continuity, and both pin 7 and pin 8 are connected directly to the 5V pin on the USB connector. And I previously determined that the 3 3.3V output is connected properly.
Can you think of any other connection, or lack thereof, that would cause the regulator not to output 3.3V?
If not, then we either have a bad batch of CP2102s, or perhaps there was too much heat in reflow.
Is it possible that the flash memory of this device has been modified in a way that would cause this behavior? The ANs say there is a setting for Power Option where "Bus Powered" is the normal setting, as well as a setting for maximum milliamps. Would selecting some non-standard options cause the regulator to be bypassed in this way?
The driver does recognize this device, so I think that means the identifiers are correct. If I install the Silabs flashing software, will it tell me the current settings?
Just looking for an explanation that might have a solution. Anyway, I have three more of these coming in from other sources over the next couple weeks, and will see if they have the same problem. I just suspect they are all like this, but only those who bother to measure the voltage notice that it's wrong. But if all are like this, then there may be nothing wrong with the chip, just some circuit design or parameter setting that was done deliberately for some purpose.
Does anyone know who CJMCU is?
Ok, it's not just my imagination. Here is a Youtube video of a guy with a handful of modules exactly like mine, and they all measure 4.25V at the 3.3V output:
https://www.youtube.com/watch?v=8qcGdB2yVd8
So this was done intentionally, and all modules of this design are like this. But how did they do it?
There is a major design flaw in the board, RST-pin (9) is connected to 5.0V (VBUS).
This is reported deep into a forum on Banggood but not properly informed to buyers.
Quote: The problem with the 3.3V line at 4.2 is due to the RST input being tied not to 3.3 V out but to the Vbus in (5V) this back feeds into the 3.3V line pulling it up above spec, cut the trace you see coming from pin 9 before it reaches the capacitor, then optionally pull it to 3.3 via a 4k7 resistor to pin 6. This also seems to solve the variability with Win10
Posted 2017-02-22 09:12:56 by instoned @t aol dot com
I just noticed that the cutting of RST on these CJMCU CP2102-boards already was discussed in another thread, CP2102 - 4.24V output on pin 6 Vdd
Hi...i am a new user here. As per my knowledge it is true that there is a major design flaw in the board, RST-pin (9) is connected to 5.0V (VBUS) and this is reported deep into a forum on Banggood but not properly informed to buyers.
pcb assembly
I've been also searching for their contact details. Their official cjmcu is not loading. And somehow I managed to find the solution on Electrondepot forums (In short: you can disconnect pin 9 from USB+ and then leave it floating). Hope this helps, if someone is also looking for the info.