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ADS8344: Lockup after esd spike

Part Number: ADS8344

Hi, a customer has reported a strange issue with the ADS8344 after the product has been subjected to an ESD spike.

he's what happens

1: Initially, ADC working normally

2: ESD spike applied to products external analogue lines .

3: SPI interface to ADC working correctly, but data output of selected channel does not alter with change of analogue input

4: Data output IS different between different channels, BUT for the selected channel, the channel data output never changes

5: after a power cycle, the ADC is working normally again.

How/why does an ESD spike effect the ADC in this way?

The ESD spike stops the conversion from working, but why when selecting a different channel would you get a different (but non-zero static) output value. Looking at the data sheet, the converted value is not latched per channel. So if the conversion had failed I would have expected the same static value on all channels.

Is there anyway to reset the device other than power cycle?

And most importantly, how to protected against ESD spikes. The ADC inputs are driven from opamp/voltage followers.  There is an RC low pass filter before the voltage follower input. (16K/100nF) The output is fed directly into the ADC with a 2k2 load resistor to gnd.  The ADC is configured for single ended operation.

My though would be to replace the load resistor with a clamp diode in existing units and future units mod the PCB to fit the clamp diode and series resistor on the ADC input. Is this the correct way to go?

Regards Stephen

  • Hi Stephen,

    If the customer knows their circuit will be exposed to ESD surges, it is best practice to use TVS diodes on the exposed lines; these diodes protect from ESD/voltage surges. ESD issues are tricky and unpredictable and can make products behave unexpedtectedly. If you send over the schematic, I can take a look at where best to add them.