Hi TI Expert,
I need to design a optical detector with wide dynamitc range so the input voltage to the AIN_P may be very large, for instance 3.4V.
And I notice that when the AIN_P is large and clamped by the the ADC's internel diode (clamped to around 2.3V), there will be a signal around 3mV crosstalk detected by the channel B (read from ADC).
1) I tried adding external diode 1SS315TPH3F connected to the 1.8V power of ADC,now the it's clamped to around 2V, but still the crosstalk can be detected.
2) I tried limited the voltage to around 1.5V by connected the diode to a voltage devider.
Now the crosstalk seems disapeared.
I guess no one can guarantee the reliablity/crosstalk when the ADC gets overvoltage stress even if it only lasts 50~100us regularly, so the clamp is needed.
My concern is the diode's forward voltage is not constant and adds extra capacitor (Although my application is a low frequency one (<1MHz)), and I'm not sure if it distort the signal.
Is is OK or is there any other solution more reasonable?
Thanks!