REV. A

ADR370

–7–

APPLICATIONS

Low Cost Negative Reference

A low cost negative reference can be obtained by leveraging the

pin of the device, a negative voltage reference can be obtained

remains between 1 mA to 5 mA.

ADR370

GND

–VREF

Figure 3. Low Cost Negative Reference

Precision Negative Reference

Without using any matching resistors, a precision negative reference

can be obtained using the configuration shown in Figure 4. The

forcing the GND pin to be the negative reference node. U2 should

be a low offset voltage precision op amp, such as the OP1177.

+15V

U2

U1

2.3V TO 12V

OP1177

–15V

ADR370

GND

–VREF

Figure 4. Precision Negative Reference

Low Cost Current Source

Figure 5 illustrates how a simple, low cost current source can be

I

V

R

SET

SET

=

2 048

.

(4)

ADR370

GND

2.048V

Figure 5. Low Cost Current Source

Precision Current Source with Adjustable Output

A precision current source can be implemented with the circuit

shown in Figure 6. By adding a mechanical or digital potenti-

ometer, this circuit becomes an adjustable current source. If a

digital potentiometer like the AD5201 is used, the load current

is simply the voltage across terminals B-to-W of the digital

I

VD

R

L

REF

SET

=

×

× 256

(5)

where D is the decimal equivalent of the digital potentiometer

input code.

+12V

A

B

W

12V

OP1177

AD5201

–12V

ADR370

GND

Figure 6. Programmable 0 mA to 5 mA Current Source

To optimize the resolution of this circuit, dual supply op amps

should be used because the ground potential of ADR370 can

potentiometer setting.