If supply power to the PGA280 if off (VSN = VSP = 0V) can voltage be present on the inputs without damage. For example, if the power to the part is off and a +- 2V sine wave is present on the inputs, how will this impact the PGA280? This has happened repeatedly in some testing and the part seems to continue to function well without issues but I would like to confirm that this situation is OK.
Thanks
Hello John,
As with most amplifiers, the absolute maximum input voltage ratings are given relative to the supply voltage. For the PGA280, the allowable range is VSN - 0.5V to VSP + 0.5V, so if the power supplies are both at 0V then the absolute maximum input range is only ±0.5V. If the input exceeds this range, the input protection diodes will become forward biased and conduct current through the part. If this current exceeds 10mA, fatal damage to the device can occur.
The PGA280 has 600-ohm resistors in series with each input (shown below), so if a 2Vpk sine wave is applied while the supplies are off the worst-case input current will be equal to I_in = 2V / 600Ω = 3.33 mA. This is below the limit of 10mA, so you should be fine in your case. However, I would not recommend leaving the part in this condition long term. As a general rule of thumb, no input should be applied to an op amp while it is powered off.
Please see our TI Precision Labs series on Electrical Overstress (EOS) for more information on this topic.
Best regards,
Ian Williams
Linear Applications Engineer
Precision Analog - Op Amps
