Hi ,
I want to use XTR110 +/-200mA AO circuit, but it doesn't work.
It was designed as shown in the Datasheet Page 9.
I couldn't find IR9513, IR513, and IRFF9113, so I used RD3L01BATTL1 , FDD86381-F085, and RD3L140SPTL1 as substitutes.
Please check my circuit.
Hi ByungJin,
Unfortunately it appears the circuit in the data sheet is drawn incorrectly; the NMOS, T2, is the wrong orientation. The way it is drawn, the source is connected to the output, with the drain on resistor R2. As it is, this leads to the NMOS body diode connected from the output to R2. This is incorrect.
The image below shows the correct orientation. In the schematic below (set up with comparable voltages from the circuit), AM1 measures 200 mA, which is the correct current value. The NMOS T2 should always be sinking 200 mA, the PMOS T1 will supply current from 0 mA to 400 mA, which leads to an output current swing of -200 mA to +200 mA.
Can you reverse the drain and source connections, and try again?
Best Regards,
Mike
Hi ByungJin,
The first step is to lower the sinking current that flows through T2 and R2 from 200 mA to 10 mA. This can be done by increasing R2 to 100 Ohms.
The second step is to change the current that flows through T1 from 0 to 400 mA to 0 to 20 mA. You have a couple of options here. The first option is easiest, given that you already have figure 8 connected- that would be to change the resistance of R1 from 2 Ohms to 40.2 Ohms. (20x larger).
The second option would allow you to use the internal resistors on XTR110, but you would need to change the configuration. The XTR110 allows for a 0 to 20 mA setting without needing the additional sense resistor, as seen in figure 1:
In order to do this, you would need to change the sense connection from R1 (in figure 8) to pin 1; so, you would remove R1, and, connect the source of T1 to Pin 1. Then pins 9 and 10 would be connected to GND (same as Com, in the table). Also, pin 3 would need to be connected to pins 15 and 12.
The advantage to the second option would be improved accuracy, since the resistor used is internal to XTR110, and the ratio between this resistor and the other resistors internal to XTR110 will be matched.
Regards,
Mike
