JAJSNU4A May 2023 – June 2024 AFE78201 , AFE88201
PRODUCTION DATA
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Figure 8-3 shows a block diagram of an analog output module using the AFEx8201 and the XTR305.
The AFE88201 sets an output voltage from 0 V to 2.5 V using a 16-bit code. Use the AFE78201 in this same application if 14-bit performance is required. This DAC voltage is converted to an output voltage or an output current by the XTR305. The XTR305 provides two basic functional blocks: an instrumentation amplifier (IA) and an operational amplifier (OPA) for an output driver.
This application is a configurable current or voltage analog output. Figure 8-2 shows a schematic of the circuit. The AFE88201 DAC controls the XTR305, which is an industrial analog current or voltage output driver. The XTR305 takes an analog input control signal and drives a proportional analog output. The output is configured as a current output if M2 is high and M1 is low, and a voltage output if M2 and M1 are both low.
The input-to-output gain of the XTR305 is set by RSET and RGAIN. The gain components in this design are selected for ±11-V or 0-mA to 25-mA output.
During current-output mode, a precision current mirror generates an exact 1/10th copy of the output current, and this current is routed to the summing junction of the OPA to close the feedback loop. In voltage-output mode, the IA senses the output voltage and feeds back a current equal to 2 × VOUT / RGAIN to the summing junction of the OPA to close the feedback loop.
A basic design procedure using the XTR305 as an output stage is described in the following list.