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ADS1298: input protection

Vincenzo Pizzolante
Mastermind 26106 points

Part Number: ADS1298

hi,

we are using ADS1298IPAG on an ECG and I have one question related to input protection. 

The ECG shall withstand defibrillator pulse, which will cause about 10V / 30ms on the input protection.

This voltage could appear on ADS1298 analog inputs, through 470Ohm resistor. 

The ADS1298 is powered by 3.0V, so the resulting current is about 14mA on each input.

How can I understand Absolute maximum rating for current, is it for each input or for all inputs together? How long is momentary? 

Is 14mA+tols x # of inputs supported?

thansk a lot in advance

KR

Vincenzo

  • 0
    TI__Guru 69076 points

    Hi Vincenzo,

    Thanks for your post.

    There is no strict definition of what "momentary" means in the Absolute Maximum Ratings table, but the safest assumption is that the inputs should never see an input current above 100 mA. Even the briefest of instances above this rating can result is permanent damage to the device.

    Internally, the ESD diodes will clamp to about AVDD + 0.3 V. So your basic calculation for the expected input current on each input sounds correct (14 V - 3.3 V) / 470 ohms = 14.3 mA. However, the internal ESD diodes should not be relied upon for input voltage protection. It's best to use external diodes to clamp the voltage on the pin to less than the absolute maximum voltage rating (5.5 V). 

    Best regards,