Power supply dependancy in analog cuircuits | Cypress Semiconductor
Power supply dependancy in analog cuircuits
I'm designing a low cost conductivity sensor device based on the Cy8C3446-LTI073, according to the schematics in attachment. The method of measurment in the temperature over pins labeled Ex1/Ex2 is a ratiometric method, is highly power supply independant and works perfectly in previous designs with the same chip layed out on the same pins.
We now added the circuitry for EC measurements (using the IDAC, comparators, PGA,...), causing the analog routing to be changed in such a matter that all analog properties in the device suffer from severe inaccuracy due to fluctations in the power supply. Even the ratiometric temperature measurement shows a severe power supply dependancy.
My question are mainly what is causing the problem and how can be dealt with them?
(BTW this is a high volume product)