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参数资料
| 型号： | DAC8512FSZ-REEL7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 8/20页 |
| 文件大小： | 0K |
| 描述： | IC DAC 12BIT SRL LP 5V 8SOIC |
| 产品培训模块： | Data Converter Fundamentals DAC Architectures |
| 标准包装： | 1,000 |
| 设置时间： | 16µs |
| 位数： | 12 |
| 数据接口： | 串行 |
| 转换器数目： | 1 |
| 电压电源： | 单电源 |
| 功率耗散（最大）： | 2.5mW |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOIC |
| 包装： | 带卷 (TR) |
| 输出数目和类型： | 1 电压，单极；1 电压，双极 |
| 采样率（每秒）： | 62.5k |
DAC8512
–16–
REV. A
A Serial DAC, Audio Volume Control
The DAC8512 is well suited to control digitally the gain or at-
tenuation of a voltage controlled amplifier. In professional audio
mixing consoles, music synthesizers, and other audio processors,
VCAs, such as the SSM2018, adjust audio channel gain and at-
tenuation from front panel potentiometers. The VCA provides a
clean gain transition control of the audio level when the slew
rate of the analog input control voltage, VC, is properly chosen.
The circuit in Figure 40 illustrates a volume control application
using the DAC8512 to control the attenuation of the SSM2018.
6
2
DAC8512
8
+15V
7
CS
CLR
1
0.1
F
4
REF02
6
2
18k
10pF
470k
P1
100k
10M
OFFSET
TRIM
47pF
SYMMETRY
TRIM
P2
500k
V
OUT
+15V
–15V
30k
+15V
–15V
0.1
F
0.1
F
+15V
18k
V
IN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SSM2018
+5V
0.1
F
C
CON
1
F
R6
825
R7
1k
*
0V
≤ V
C ≤ +2.24V
* – PRECISION RESISTOR
PT146
1k
COMPENSATOR
5
LD
3
SCLK
4
SDI
Figure 40. A Serial DAC, Audio Volume Control
Since the supply voltage available in these systems is typically
±15 V or ±18 V, a REF02 is used to supply the +5 V required
to power the DAC. No trimming of the reference is required be-
cause of the reference’s tight initial tolerance and low supply
current consumption of the DAC8512. The SSM2018 is config-
ured as a unity-gain buffer when its control voltage equals 0
volt. This corresponds to a 000H code from the DAC8512.
Since the SSM2018 exhibits a gain constant of –28 mV/dB
(typical), the DAC’s full-scale output voltage has to be scaled
down by R6 and R7 to provide 80 dB of attenuation when the
Table IV. SSM-2018 VCA Attenuation vs.
DAC8512 Input Code
Hexadecimal Number
Control
VCA
in DAC Register
Voltage (V)
Attenuation (dB)
000
0
400
+0.56
20
800
+1.12
40
C00
+1.68
60
FFF
+2.24
80
digital code equals FFFH. Therefore, every DAC LSB corre-
sponds to 0.02 dB of attenuation. Table IV illustrates the at-
tenuation vs. digital code of the volume control circuit.
To compensate for the SSM2018’s gain constant temperature
coefficient of –3300 ppm/
°C, a 1 k, temperature-sensitive re-
sistor (R7) manufactured by the Precision Resistor Company
with a temperature coefficient of +3500 ppm/
°C is used. A
CCON of 1
F 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
“Compensator” can be
obtained by contacting:
Precision Resistor Company, Incorporated
10601 75th Street North
Largo, Fl 34647
(813) 541-5771
An Isolated, Programmable, 4-20 mA Process Controller
In many process control system, applications, two-wire current
transmitters are used to transmit analog signals through noisy
environments. These current transmitters use a “zero-scale” sig-
nal current of 4 mA that can be used to power the transmitter’s
signal conditioning circuitry. The “full-scale” output signal in
these transmitters is 20 mA. The converse approach to process
control can also be used; a low-power, programmable current
source can be used to control remotely located sensors or de-
vices in the loop.
A circuit that performs this function is illustrated in Figure 41.
Using the DAC8512 as the controller, the circuit provides a
programmable output current of 4 mA to 20 mA, proportional
to the DAC’s digital code. Biasing for the controller is provided
by the REF02 and requires no external trim for two reasons:
(1) the REF02’s tight initial output voltage tolerance and (2) the
low supply current consumption of both the OP90 and the
DAC8512. The entire circuit, including opto-couplers, con-
sumes less than 3 mA from the total budget of 4 mA. The OP90
regulates the output current to satisfy the current summation at
the noninverting node of the OP-90. The KCL equation at
Pin 3 is given by:
IOUT =
1
R7
×
1 mV
× Digital Code × R3
R1
+
VREF × R3
R2
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