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AD8236 Level-Shift Output (pin 7) offset

Question asked by JSaggio on Aug 6, 2018
Latest reply on Aug 9, 2018 by krisf

Our AD8236 level-shift output at p7 has an offset relative to a stable and accurate Vref at pin 6. What conditions or issues could cause the AD8236 to (pin 7) output level shift to not match the provide REF at pin6? Could capacitive loading on the AD8236(pin7) cause this? Our AD8236 has a low pass filter on the output with 100 Ohms feeding 22uF RC LPF.

 

I have provided the circuit in hopes of any recommendations. A rework was done on the circuit that set R23 to 0 Ohm and removed C15. The AD5160 sits at  ~100Ohms during production and this is where we have seen PCBs drop out due to a AD8236 p7 output level shift output...it should be 1.65V. Many PCBs pass, but 5 have dropped out (out of 100) due to pin 7 level shift starting as high as 2.5V instead of 1.65V...I have also noticed tha the starting level shift, when high or low will capacitively discharge or charge to the neighborhood of 1.65V...ie 1.8V, 1.73V etc

 

Could a hot-air re-work to pull C15 and change R23 have damaged the AD8236 on these particular PCBS? Since 95 have passed? R23 and C15 are right next to the AD8236 chip.

 

Also I thought 100 Ohms should be enough isolation from the 22uF capacitor C16...we never saw this issue until production :-)

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