ADG467 as protection for ADC input (output clamping voltage accuracy)

Hello,

I use an ADG467 to protect input ADC channel (ADS1247). I need to read low current ~30uA with an accurate ADS1247 ADC through shunt resistance. It is important that the leackage current is very low to don't impact the accuracy. That the reason I use ADG467 protector in place of diode againt overvoltage. Unfortunately the typical value don't limit the output at the good level (Vss+1.5V Vdd-1.5 Vtyp for Output open circuit conditions). ADC input current is about 1nA.

My question is: Have you any experience about the ADG467 repeatability. Do I have to expect no negligeable output limitation varation between ADG467 series ?

My result with VDD = 4,16V VSS= -4.10V => ADG467 output range =  -2.89V to  3.22V  (in place of-2.6V to  2.66V)

Thanks for your help

  • 0
    •  Analog Employees 
    on Aug 19, 2014 6:55 PM over 6 years ago

    Hello Marc,

    To confirm, you are asking if the signal range will differ between parts even if they are all provided with the same supply voltage?

    The specification for the signal range is VDD-1.5V to VSS+1.5V for ±15V supplies. The saturation voltage changes slightly with supply voltage; please see figures 4 and 6 on page 6 of the data sheet. This accounts for the difference between the specification and your measurement.

    There will not be a significant difference between devices if they are all supplied with the same voltage.

    Regards,

    Sean

  • Yes it was my question.

    It was imposible (with datasheet only)  without tests to determine ADG467  power supply to use to limit the output at +/- 2.8V. With graph 6 I'm confident that between parts, I will not have significative output voltage if I use the same voltage power supply (accuracy = 2%).

    Thanks