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How to prevent adc latch up

Mori Jenab
Prodigy 40 points

Hello every body 

first off all sorry for my bad english .

We are  using a 24 bit ADC (AD7190) for load cell transmitter .

it's working fine in our office .

but sometimes in factories it latched up .

This our schematic :

 

up to here maybe said this is not about TI .

but as i read TI  Application Report SLYA014A - May 2000 ans see this part :

and try to apply this to our board .

when i add D1 (SMBj5CA) it hasn't affected  the ADC result .

but when i add D2 and D3 the adc behave nonlinear and have some more offset .!

i guess it's may happen because of leakage current .

Is there any specific schottky diode and TVS that you can recommend

that hasn't got these problem ?

I will be very happy if you help on this .

 Best Regards

  • 0
    TI__Guru* 97655 points
    Mori,


    Generally, this forum is for Texas Instruments precision data converters. The AD7190 is an Analog Devices part. If you are having problems with it, I suggest that you contact them.

    However, one thing I noticed in your schematic is that you have an inductor going from the supply source to the digital supply pin. I would remove it and replace it with a short. Inductances in the power supply line can give you spikes in the voltage because of the digital currents. For each clock pulse, there is a high current, and this Ldi/dt can cause spikes. I've seen this disrupt operations in data converters, and I suspect this would be a problem with the AD7190 as well.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 40 points

    Hello joseph

    The problem is not about AD7190 .

    I'm looking for appropriate schottky diode and tvs as protect against ESD .

    and about  inductor  actually this is a ferrite bead  and i have seen in AD7799 Evaluation board :

    Best Regards

  • 0 in reply to Mori Jenab
    TI__Guru* 97655 points
    Mori,


    If you're looking for low leakage, I think the BAV199 has been suggested in the past as a low-leakage Schottky. For TVS devices, most are not low in leakage, and I don't really have any suggestions.


    Joseph Wu