8.2.2.2 Current Output Mode

The XTR305 does not require a shunt resistor for current control because it uses a precise current mirror arrangement.

In current output mode (M1 connected low, or left unconnected and M2 connected high), a precise copy of 1/10th of the output is internally routed back to the summing junction of the OPA through a multiplexer, closing the control loop for the output current.

The OPA driver can deliver more than ±24 mA within a wide output voltage range. An open-output condition or high-impedance load that prevents the flow of the required current activates the EF_LD flag and the IA can become overloaded and draw greater than 7-mA saturation current.

While in current output mode, a current (I_IA) that is proportional to the voltage at the IA input is routed to IA_OUT and can be used to monitor the load voltage. A resistor converts this current into voltage. This arrangement makes level shifting easy.

Alternatively, the IA can be used as an independent monitoring channel. If this output is not used, connect it to GND to maintain proper function of the monitor stage, as shown in Figure 42.

Figure 42. Simplified Current Output Mode Configuration

The transconductance (gain) can be set by the resistor, R_SET, according to Equation 3:

Equation 3.

or when adding an offset V_REF to get bidirectional output with a single-ended input shown in Equation 4:

Equation 4.