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AD8214: Input protection

Question asked by los on Apr 10, 2017
Latest reply on Apr 16, 2017 by m-kun

AD8214 is used in an existing design of a motor drive board to sense high side current. The power supply to the motors and AD8214 is 48V. The design has problems with false trigging of the comparator due to noisy signals and supply voltage.

One solution would be to increase the resistance of the shunt resistor in order to get higher signal-noise ratio.

The backside of this is the headroom above expected detected levels up to the absolute max differential input voltage of 500mV is decreasing. Let´s say the tripping point current is selected to be as high as 250mV, this gives a ratio of only x2.

- Is it possible to add a serial reistor with the -input to protect the inputs for signals above 500mV?

- What is the allowed max currents above 500mV for different pulse lenghts?

- Do you have any proposal for an external protection circuit / components that will not impact levels up to 250mV but give needed protection at 500mV?