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IC IVC102 not responding

SHREY BALUAPURI
Prodigy 20 points
Other Parts Discussed in Thread: IVC102

    

I am using IC IVC102 as a transimpedance amplifier. In the figure given on top is the switching signals given to S1 & S2 through microcontroller atmega 32.

First  two figures show the switching signals. Integration time is 200 ms.Switching signal are exactly as given in figure 3 given in datasheet. Supply voltage given is +/-

13V. Input given is 5V through a resistor of 1 giga ohms hence a current of 5 nA. Connections have been done as given for switched input measurement techique. Third

figure shows the output 

IC. Blue line is the output. The whole circuit is put into a box as shown in last figure above. 4th figure shows the pcb connections for IC IVC102.

As can be seen in 3rd figure the output of IC is not linearly rising but is constant at 2V.

Given below is pcb design for the IC IVC102. Why am I observing such behavior from the IC?


  • 0
    TI__Expert 3555 points

    Shrey,

    This is a very ambitious endevour. You are trying to convert your 5 V to 5nA and measure that with the IVC102. I asume that with your top figure the yellow line is connected to S2 and the bottom line (pink) is connected to S1. The most difficult issue to address when you measure things so small is to make sure that there are no current leakage paths to and from your input pins. The leakage paths can travel across your PCB or be emitted into your input pins. It seems that you have tried to reduce the chances of emitted signals into your measurement. Generally, I don't see any protection from leakages in your layout. You are using a PCB that by itself may have leakage across it. I would recommend an FR4 type of board. Also there are no trace guard rings as illustrated in figure 4 of the product data sheet. If you rprobelm is leakages across your board it iwll take a while to reduce these errors through the process of elimination.