V

=3V

(R +R )/R

REGF

1

2

2

·

3V

REGF

REGS

5V

Signal

Source

(Sensoror

DAC,for

example)

V

=24VSupply

VSP

I-Mirror

VSP

1

9

8

2

IS

(PullLowforNormalOperation)

OD

EF

C

1

R

2

8.2kW

VIN

6

4

5

R

SET

SET

7

10

GND

R

1

5.6kW

I

=10

OUT

()

V

VIN

R

SET

VG

Q

2

(1)

Q

1

15W

15W

S

D

G

10nF

0mAto20mA

4mAto20mA

Load

(±LoadGround)

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

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

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

compliance.

The output of the voltage regulator can be set over

An error detection circuit activates a logic output

(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