Datasheet

IA
CurrentCopy
OPA
R
GAIN
RG
1
RG
2
I
COPY
I
DRV
I
IA
IA
IN+
IA
IN-
Load
GND2
DRV
IA
OUT
V
IN
SET
I
MON
V-
DGND
V+XTR300
Digital
Control
OD
M2
M1
H
L
Error
Flags
EF
CM
EF
LD
EF
OT
InputSignal
R
IA
R
SET
GND3
GND1
I =
OUT
10
R
SET
V
IN
I =10
OUT
V
R
IN
SET
V V
R
-
IN REF
OS
+
(
(
XTR300
SBOS336C –JUNE 2005– REVISED JUNE 2011 www.ti.com
CURRENT OUTPUT MODE
The XTR300 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 ±24mA 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 7mA 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 41.
Figure 41. Simplified Current Output Mode Configuration
The transconductance (gain) can be set by the resistor, R
SET
, according to the equation:
(3)
space
or when adding an offset V
REF
to get bidirectional output with a single-ended input:
(4)
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