DAC8562
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.
A CCON of 1 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.
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.
R2
5kΩ
+15V
7
0.1µF
17
18
Information regarding the PT146 1 kΩ “Compensator” can be
obtained by contacting:
6
12
R
CS
100Ω
Precision Resistor Company, Incorporated
10601 75th Street North
Largo, FL 34647
R1
10
AMP-05
100k
0mA
2.4µA/ LSB
≤
I
≤ 10mA
8
OUT
9
1
2
(813) 541-5771
11
5
A High-Compliance, Digitally Controlled Precision Current
Source
4
P1
100kΩ
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
precision current sense resistor, RCS. Voltage gain is set to unity,
so the transfer function is given by the following equation:
0.1µF
–15V
+15V
2
0.1µF
VIN
IOUT
=
RCS
0.1µF
6
REF-02
If RCS equals 100 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.
4
20
16
15
CE
R3
3k
DAC-8562
CLR
13
R4
1k
DATA
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.
AGND
12
DGND
10
A Digitally Programmable Window Detector
A digitally programmable, upper/lower limit detector using two
DAC8562s is shown in Figure 39. The required upper and
Figure 38. A High-Compliance, Digitally Controlled
Precision Current Source
V
+5V
20
IN
+5V
+5V
+5V
0.1µF
1k
Ω
R1
604Ω
R2
604Ω
+5V
16
15
0.1µF
DAC-8562
13
3
RED LED
T1
GREEN LED
T1
DGND AGND
12
10
2
5
4
PASS/FAIL
2
1
1/6
74HC05
C1
1
+5V
20
0.1µF
7
6
3
4
C2
12
1/6
74HC05
HDAC/LDAC
CLR
16
15
DAC-8562
13
DATA
C1, C2 = 1/4 CMP-404
DGND AGND
10
12
Figure 39. A Digitally Programmable Window Detector
REV. A
–13–
ADI [ ADI ]
