Dear support:
how to use the convert the 0~3.3V signal to 4~20mA output ,below is my schematic design ,is there any problems?
Hi,
In order for the device to produce the 4-20mA output current with VIN = 0 V - 3.3 V, please change the following resistors:
- Change R16 from 40kOhm to 10.2kOhm.
- Change R17 from 10kOhm to 2.55kOhm.
Other changes:
- Add a 100nF Bypass capacitor to 12-V VSP supply in close proximity to VSP pin.
- Connect the regulator bypass capacitor (C15) directly to REGF (instead of REGS) and GND as shown on the schematic below.
Please see attached modified schematic, and a DC sweep simulation of the DACOUT 0V - 3.3V input voltage vs the XTR111 IOUT current below.
Many Thanks,
Kind Regards,
Luis
Hi,
The output current relation for the XTR111 is:
Iout = 10*VIN / RSET
For 4mA output current, and RSET=1.65kOhm, solve for VIN:
Vin = (Iout / 10) *RSET = (4mA / 10) * 1.65kOhm = 0.66V
Therefore, the XTR111 requires a 0.66V input voltage at VIN to generate 4mA output current.
Since we require DACOUT=0V to generate 4mA output, and VREGF is 3.3V, calculate the divider that will produce 0.66V at the voltage divider output (or XTR111 input):
Thank you and Best Regards,
Luis
