DAC8512FP Analog Devices Inc, DAC8512FP Datasheet - Page 15

• Manufacturer Part Number: DAC8512FP
• Description: IC DAC 12BIT 5V COMPLETE 8-DIP
• Manufacturer: Analog Devices Inc

Specifications of DAC8512FP

• Mounting Type: Through Hole
• Rohs Status: RoHS non-compliant
• Settling Time: 16µs
• Number Of Bits: 12
• Data Interface: Serial
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 2.5mW
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Resolution (bits): 12bit
• No. Of Pins: 8
• Peak Reflow Compatible (260 C): No
• Update Rate: 0.0625MSPS
• No. Of Bits: 12 Bit
• Leaded Process Compatible: No
• Interface Type: Serial
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

REV. A
A Digitally Controlled, Ultralow Noise VCA
The circuit in Figure 38 illustrates how the DAC8512 can be
used to control an ultralow noise VCA, using the AD600/
AD602. The AD600/AD602 is a dual, low noise, wideband,
variable gain amplifier based on the X-AMP topology.* Both
channels of the AD600 are wired in parallel to achieve a
wideband VCA which exhibits an RTI (Referred To Input)
noise voltage spectral density of approximately 1 nV/ Hz. The
output of the VCA requires an AD844 configured in a gain of 4
to account for signal loss due to input and output 50
tions. As configured, the total gain in the circuit is 40 dB.
Since the output of the DAC8512 is single quadrant, it was nec-
essary to offset the AD600’s gain control voltage so that the gain
of the circuit is 0 dB for zero scale and 40 dB at full scale. This
was achieved by setting C1LO and C2LO to +625 mV using R1
and R2. Next, the output of the DAC8512 was scaled so that
the gain of the AD600 equaled 20 dB when the digital input
code equaled 800
function of digital code is shown in Figure 39.
*For more details regarding the AD600 or AD602, please consult the AD600/
AD602 data sheet.
SCLK
CLR
SDI
CS
LD
V
I N
H
. The frequency response of the VCA as a
+625mV
4
619
2
6
5
3
R1
0.1 F
DAC8512FZ
4.32k
R2
V+
1
7
1
3
4
5
6
8
2
7
Figure 38. A Digitally Controlled, Ultralow Noise VCA
V+
AD600JN
REF
8
2.26k
12
10
16
15
14
13
11
9
R6
1 F
termina-
0.1 F
0.1 F
V+
V–
R7
1k
0
–15–
V G
402
402
R4
R3
1.25V
Figure 39. VCA Frequency Response vs. Digital Code
+70
+60
+50
+40
+30
+20
+10
–10
–20
–30
SUPPLY DECOUPLING NETWORK
0
10k
V+
V–
3
2
806
AD844
R5
4095
3072
2048
1024
V+
V–
–5V
0
+5V
0.1 F
0.1 F
FB = FAIR RITE
100k
#2743001111
6
10 F
10 F
FREQUENCY – Hz
49.9
R4
1M
V
0.01dB/BIT
10M
DAC8512
OUT
100M