DAC8562

REV. A

–13–

To compensate for the SSM2018’s gain constant temperature

coefficient of –3300 ppm/

°C, a 1 kΩ, temperature-sensitive

resistor (R7) manufactured by the Precision Resistor Com-

pany with a temperature coefficient of +3500 ppm/

°C is used.

µF provides a control transition time of 1 ms which

yields a click-free change in the audio channel attenuation. Sym-

metry and offset trimming details of the VCA can be found in

the SSM2018 data sheet.

Information regarding the PT146 1 k

Ω “Compensator” can be

obtained by contacting:

Precision Resistor Company, Incorporated

10601 75th Street North

Largo, FL 34647

(813) 541-5771

A High-Compliance, Digitally Controlled Precision Current

Source

The circuit in Figure 38 shows the DAC8562 controlling a

high-compliance, precision current source using an AMP05 in-

strumentation amplifier. The AMP05’s reference pin becomes

the input, and the “old” inputs now monitor the voltage across a

so the transfer function is given by the following equation:

I

V

IN

R

CS

Ω, the output current is limited to +10 mA

with a 1 V input. Therefore, each DAC LSB corresponds to

2.4

µA. If a bipolar output current is required, then the circuit

in Figure 33 can be modified to drive the AMP05’s reference

pin with a

±1 V input signal.

Potentiometer P1 trims the output current to zero with the in-

put at 0 V. Fine gain adjustment can be accomplished by adjust-

ing R1 or R2.

A Digitally Programmable Window Detector

A digitally programmable, upper/lower limit detector using two

DAC8562s is shown in Figure 39. The required upper and

lower limits for the test are loaded into each DAC individually

by controlling HDAC/LDAC. If a signal at the test input is not

within the programmed limits, the output will indicate a logic

zero which will turn the red LED on.

9

18

1

2

17

R1

100k

7

6

R2

5k

Ω

P1

100k

Ω

5

4

11

0.1µF

–15V

AMP-05

10

100

Ω

0mA

2.4µA/ LSB

12

0.1µF

+15V

15

DGND

AGND

DATA

DAC-8562

13

+15V

10

16

CE

CLR

20

12

0.1µF

4

REF-02

6

2

0.1µF

R3

3k

R4

1k

8

Figure 38. A High-Compliance, Digitally Controlled

Precision Current Source

15

16

DGND AGND

DAC-8562

13

10

12

0.1µF

20

+5V

2

1

1/6

74HC05

HDAC/LDAC

CLR

+5V

1k

C1

C2

0.1µF

+5V

12

3

2

1

4

6

7

5

+5V

R1

604

Ω

RED LED

T1

3

4

+5V

R2

604

Ω

GREEN LED

T1

PASS/FAIL

C1, C2 = 1/4 CMP-404

15

16

DGND AGND

DAC-8562

13

10

12

0.1µF

20

+5V

DATA

1/6

74HC05

Ω

Figure 39. A Digitally Programmable Window Detector