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MUX damage, o/p short to +Ve supply

Question asked by Jatin on Apr 23, 2015
Latest reply on May 6, 2015 by paul.osullivan



Using 8-channel MUX for 4-20mA current measurement analog module. It is differential input so two MUX one for +Ve lines and 2nd for -Ve lines. O/P of MUX interfaced with INA AD620. There are two models one having ADG508 and 2nd having ADG1408 MUX IC in design but rest is same.


One common observation with both these Analog input module (using ADG1408 or MUX508A) is that, sometimes +Ve line MUX IC get damaged. Damage is such that MUX IC's o/p becomes short with +Ve supply of MUX IC. It is +12V / -12V supply to MUX IC. Also in some case the damage extends up to INA AD620. MUX IC sometimes physically looks intact and sometimes burnt. No any other section damage observed so far.


4-20mA coming from isolated field Transducer having AC voltage and AC current at Transducer's input. Transducer is 2.2KV isolated for i/p to o/p. 4-20mA drop across 250 ohm resistor to convert to 1-5V range and through low pass R-C filter (10K , 0.1uF) in both +Ve and -Ve line of this signal pass through MUX IC. Total 8-such input channels there.


Need some help to understand failure condition.