Hi,
i am currently using the LM27762 to generate analog +5V and -5V on a PCBA.
The PCBA is beeing tested over a temperature range of -30 to 70°C.
Over this temperature range we noticed a certain voltage change over the temperature.
In the image above you are able to see the behavior of the -5V of 4 different PCBAs over time. In dark blue you can see the temperature over time (secondary axis). While most of the PCBAs have an expected temperature dependence which you are able to see in the curves light blue and purple, there are some that show a much larger temperature dependence.
In the following picture you can see the schematic i used. R3, R4, R17 and R18 are resistors with an accuracy of 0.1% and 25 ppm/°C.
The values are beeing measured with the internal 12 bit ADC of the TIVA TM4c123g via following schematic:
Again the resistors have an accuracy of 0.1% and 25ppm/°C.
The positive 5V does not have the same behavior, which makes me think that the ADC or reference voltage are not the cause of this voltage change.
Do you have an explanation why the voltage drops so much on some of the PCBs?
Thank you in advance,
Greetings,
Samuel
