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ADS1292R (momentary input current)

Denis Kreider
Prodigy 45 points
Other Parts Discussed in Thread: ADS1292R, ADS1292, ADS1291

Hello,

in the datasheet of ADS1292R under "ABSOLUTE MAXIMUM RAITINGS" the input current to any pin except supply pins is defined. The continuous current is 10 mA and the momentary one 100 mA. But there is no definition about the time limit for the momentary current. Could you give me this information, please?

Many thanks in advance!

 

  • TI__Guru**** 180831 points

    Hi Denis,

    The momentary 100mA is into any one pin - we'll talk with the process engineers for this device and see what details we can get you for the time limit.

  • Prodigy 45 points

    Hello,

    I have a very important concern, please help me. I use ADS1292R for measuring ecg and impedance in a defibrillator. So ít´s necessary to know what happens if the voltage on pins 3,4,5,6,31,32 gets higher than supply voltage for a short time (< 10ms)? In the datasheet under "ABSOLUTE MAXIMUM RATINGS, Analog input to AVSS" there is a definition of "AVSS - 0.3 to AVDD + 0.3". I use +2.5V (AVDD) and - 2.5V (AVSS), so the limits are +2.8V and -2.8V. During the shock I measured the voltage and current on pin 31, it was about 1.6V (to GND) and 16mA. On pin 6 the voltage was at 5.8V (to GND). After that the chip still works without any problems, but I´m not sure if it would get damaged after many shocks. Do you think it´s dangerous for the chip?

    Many thanks in advance!

  • in reply to Denis Kreider
    TI__Guru**** 180831 points

    Hi Dennis,

    The momentary current of 100mA  described in the Absolute Maximum Ratings table of the datasheet refers to the maximum current the ESD cell of the device can withstand during start up conditions, where the duration of the current  is less than <200 milliseconds.  Do you have any defib protection external to the ADS1292?  

  • in reply to Tom Hendrick
    Prodigy 45 points

    Hello Tom,

    thank you very much for the answer to my first question, it helps me a lot.

    On the output pins 31,32 I have 330 kOhms, that limits the current during the shock to 16 mA (<10 ms). The question is whether the higher voltage (1.6 V to GND) could be a problem.

    On the other 4 input pins I have 4.7 kOhms and clamping diodes. The current is about 100 mA for 200 microseconds, but the voltage is about 5.8 V to GND!

  • in reply to Denis Kreider
    Prodigy 210 points

    I have the same question regarding exceeding max specified input voltage - I would have thought that a large enough series resistor would keep the voltage at the pin clamped to AVDD+0.3, with the goal being to keep the transient input current <100mA. Is the 5.8V Denis is seeing going to damage the part?

    Also, did you ever get a response back from engineering on the 100mA transient limit?

     

    Thanks, Doug

  • in reply to Denis Kreider
    Intellectual 865 points

    Hi Denis

    I am using ADS1291 could share please how do you measure the impedance?

     

    Thank you