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ADS1115 - Can it be damaged by over range inputs?

Dennis Fox
Prodigy 20 points
Other Parts Discussed in Thread: ADS1115

Can the ADS1115 be damaged by an input voltage on A0-A3 that over ranges the current programmable gain setting?

The voltages on the inputs will never exceed VCC +.3v or GND - .3v. This of course would damage the part per the data sheet.

An example  would be a differential input of 4.200 volts while the gain is set to 16. None of the input voltages will ever exceed 5.00 V (Vcc) or go below 0 V (Gnd).

Differential inputs A0-A1 - Signal 4.200 V Gain 2/3

Differential inputs A2-A3 - Signal 0.25 V Gain 16

I am thinking about an application that would change the gain setting on the fly for the two measurements. When the converter would be at gain = 16 to read the A2-A3 inputs, the A0-A1 inputs would be over ranged. It would be reasonable to not have a valid digital output on the A0-A1 channel until the gain was set to 2/3. If this is acceptable  usage of the ADS1115, how long will it take to recover from the over range condition and return an accurate digital conversion of the 4.200 V input on A0-A1?

  • 0
    TI__Guru* 94005 points

    Dennis,


    The ADS1115 should not be damaged by an input voltage on one of the analog inputs if it only over ranges the PGA. As you had mentioned, if the inputs go beyond the VDD+0.3V or GND-0.3V, then damage may occur.

    The ADS1115 should give a full scale reading when over ranged. It should give a correct reading in the first complete data period where the input is not over ranged. The PGA is not implemented as an amplifier, but as a sampled scale, so there is no saturation to overcome. Also, the modulator is reset after each data sample sample is completed. Regarless, your example shows a reasonable application.

    If you have any further questions, please don't hesitate to post.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 20 points

    Joseph,

    Thanks very much for your complete answer! I'm glad to hear that the ADS1115 recovers quickly from an over ranged input.

    Denny