Hi all
we are having isolated current transmitter circuitry in our design using XTR116 but minimum current we are able to achieve is from 12mA despite lowest duty cycle at 20Khz (we tried with differnt frequency also).we are unable to get 4mA output current. we removed opamp(shorted pin2 &3) and tried but we are getting 12mA as a minimum current.Please find our schematics below.
Hello,
We've tested a very similar system in our lab recently with good results. The schematic is shown at the bottom of this message. There are a few key differences between the two designs.
First, you should buffer the output of the RC filter with the op-amp instead of the output of the isolator. The op-amp won't be able to keep up with a digital signal applied to it's inputs and it doesn't serve much of a benefit there.
Second, remove the 750 Ohm resistor in series with the collector of your pass transistor. That component will reduce the compliance voltage of your system and it serves no benefit.
Third, you'll need to be sure that the current consumption of the components powered from the VREG output consume less than ~3.5mA as explained in this blog. So select a low current op-amp and reduce the capacitive loading and speed of the ISO7310 to reduce the current as shown in the datasheet.
