Does the LTC2271 need input clamps

We're using the LTC2271. The analog inputs, could occasionally have voltages as high as 10 V. Under absolute maximum ratings on page 2 the datasheet says the range is -0.3V to VDD+0.2V (2.0V). But then note 3 on page 6 says:

Note 3: When these pin voltages are taken below GND or above VDD, they
will be clamped by internal diodes. This product can handle input currents
of greater than 100mA below GND or above VDD without latchup.

This seems to imply we can let the voltage go to 10 V so long as we use say a 100 ohm resistor to limit the current. But then the purpose of the absolute maximum rating on the voltage is unclear.

Or do we need to add clamps on Ain to limit the voltage to VDD + 0.2 V?

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  • That's the answer I was hoping for since we have a severely space constrained board. And it's hard to find diodes that don't distort the signal.

    I should note, I got a somewhat different answer from Analog support, but it made me wonder what the point of the internal diodes was:

    You should clamp the voltages externally using schottky 
    diodes. Note 3 could be clearer, but what they're trying
    to convey is the internal diodes will conduct if the
    inputs go beyond the rails, and that they can withstand
    100mA without the device latching up. It's best to
    clamp those signals externally, as repeated overvoltage
    can degrade the internal diodes.


    We will in fact be going over Vdd+0.2 fairly often.

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