Datasheet

V =3V (R +R )/R
REGF 1 2 2
·
3V
REGF
REGS
5V
Signal
Source
(Sensoror
DAC,for
example)
V =24VSupply
VSP
I-Mirror
VSP
1
9
8
2
IS
(PullLowforNormalOperation)
OD
EF
C
1
R
2
8.2kW
VIN
6
4
5
R
SET
SET
710
GND
R
1
5.6kW
I =10
OUT
()
V
VIN
R
SET
VG
Q
2
(1)
Q
1
15W
15W
S
D
G
10nF
0mAto20mA
4mAto20mA
Load
(±LoadGround)
3
XTR111
SBOS375C –NOVEMBER 2006– REVISED JUNE 2011 www.ti.com
APPLICATION INFORMATION
used during power-on, multiplexing and other
The XTR111 is a voltage-controlled current source
conditions where the output should present no
capable of delivering currents from 0mA to 36mA.
current. It has an internal pull-up that causes the
The primary intent of the device is to source the
XTR111 to come up in output disable mode unless
commonly-used industrial current ranges of
the OD pin is tied low.
0mA–20mA or 4mA–20mA. The performance is
specified for a supply voltage of up to 40V. The The onboard voltage regulator can be adjusted
maximum supply voltage is 44V. The between 3V to 15V and delivers up to 5mA load
voltage-to-current ratio is defined by an external current. It is intended to supply signal conditioning
resistor, R
SET
; therefore, the input voltage range can and sensor excitation in 3-wire sensor systems.
be freely set in accordance with the application Voltages above 3V can be set by a resistive divider.
requirement. The output current is cascoded by an
Figure 36 shows a basic connection for the XTR111.
external P-Channel MOSFET transistor for large
The input voltage V
VIN
reappears across R
SET
and
voltage compliance extending below ground, and for
controls 1/10 of the output current. The I-Mirror has a
easy power dissipation. This arrangement ensures
precise current gain of 10. This configuration leads to
excellent suppression of typical interference signals
the transfer function:
from the industrial environment because of the
extremely high output impedance and wide voltage
I
OUT
= 10 • (V
VIN
/R
SET
)
compliance.
The output of the voltage regulator can be set over
An error detection circuit activates a logic output
the range of 3V to 12V by selecting R
1
and R
2
using
(error flag) in case the output current cannot correctly
the following equation.
flow. It indicates a wire break, high load resistor, or
(1)
loss of headroom for the current output to the positive
supply. The output disable (OD) provided can be
Figure 36. Basic Connection for 0mA to 20mA Related to 0V to 5V Signal Input. The Voltage Regulator is
Set to 5V Output
12 Copyright © 2006–2011, Texas Instruments Incorporated