REF5050: Voltage output to high

Dear Trailokya

I checked the output again with the scope and there is no oscillation.  I removed R29 and C37 and checked again with the scope and there is no oscillation.  The output is still 5.5vdc.  I've used this part before in the same configuration without issue.  I took this old board out (see schematic below) to check the output of the REF5050 and it's right on at 4.998vdc.  

Dear Trailokya

I performed another test thinking the charge pump could be the problem.  I removed R30 and attached a wire to L1 (see schematic below).  I attached a GND wire to system GND.  I then powered the REF5050 with an outside 12vdc.  REF5050 output was still 5.5vdc.  

Dennis 

Thanks for the information. Can you please let me know about further stages.Where is 5V_REF connected in the circuit? Can you please disconnect the ADC/buffer and check it. Also I want to know if you are using 5.5V supply for the further block?

Regards

Trailokya 

Dear Trailokya

Please find attached the full schematic of the PCA.  5V_REF connections are marked with red boxes.  I removed BR1 (the pressure sensor bridge).  The bridge is connected to the 5V_REF through the TMUX1111RSVR switch (U4).  The output is still 5.5vdc.  Because there are no passive components between the REF5050 output and the loads, there is no way to disconnect the loads save lifting pin 6 on the REF5050 devise itself.  If I do that, it will disconnect the output from the output filter.  Will this be a problem?  

10mm_Top-Hat_Constant_Voltage sch rev 1 6-14-2022.pdf

Hi Dennis 

• If you diconnet the output with from the capacitor , it won't work. 
• Can you please remove the REF50 pin 6 and and check what is the output you are getting across C35. I suspect it is getting shorted from some where else on the board. 
• The drop out of the device is 200mV in unloaded condition and 750mV in loaded condition. Can you please check the output volatge at VIN = 5.75 , Vin = 5.5 and Vin =5.25V .

Also can you please conifrm if you are seeing this issue at multiple parts. 

Regards

Trailokya 

Dear Trailokya

Trailokya Rai said:

If you diconnet the output with from the capacitor , it won't work. 

I think I'll try to connect a capacitor to the lifted pin 6 to see if this make any difference.  

Trailokya Rai said:

Can you please remove the REF50 pin 6 and and check what is the output you are getting across C35. I suspect it is getting shorted from some where else on the board. 

I'll do the experiment and let you know what I find.  

Trailokya Rai said:

Also can you please conifrm if you are seeing this issue at multiple parts.

The condition is on all PCAs that I've tested.

Thanks Denis. 

Please vary the supply also and check , you can do this experiment in last if you are sure that 5.5 is coming from REF only.  

Regards

Trailokya