Introduction : In one of our applications, we are using AD5410 current source dac to deliver 0-20mA current output.On our test bench an load 500 Ohms is connected between Output pin & Ground of the dac and the current output is measured with a DMM. The 0-20mA current output is communicated using 3 wire connection which has 24 input, GND , Output.(The schematic is inserted below)
Failure reported: While connecting the current source dac on field test bench, the ad5410 has failed and started heating up.
Observations after failure:
1. After Failure the output of the current source dac remains at 0.24mA. It does not either increase nor decrease.
2.However in the software program when i write diiferent values of data in the data register and read it back from the data register they tall i.e. they are same.
3.The connections provided in the field test bench are similar to connections of my test bench which are 24Input, GND & Output.
4. when We have checked the resistance between ouput & gnd in the field test bench, it shows 24.2 Mohms.
5. There is no voltage on the output pin of the field test bench w.r.t ground.
Observations in Failed AD5410 after removing from the board:
1. The 1 & 11 pin which are Analog Ground, are shorted internally. It shows 41.Ohms. That is not the case in a NEW AD5410.
2. The 1 & 20 pin(Boost pin) shows shorted internally. It shows 159.00 Ohms.The is not the case in a NEW AD5410.
Questions :
1. Pl. point out where things could go wrong or what points i need to analyse to identify the root cause of this problem.
The schematic is as below
