DAC8512FP Analog Devices Inc, DAC8512FP Datasheet - Page 11

• 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

To maintain monotonicity and accuracy, R1, R2, and R4 should
be selected to match within 0.01% and must all be of the same
(preferably metal foil) type to assure temperature coefficient
matching. Mismatching between R1 and R2 causes offset and gain
errors while an R4 to R1 and R2 mismatch yields gain errors.
For applications that do not require high accuracy, the circuit
illustrated in Figure 29 can also be used to generate a bipolar
output voltage. In this circuit, only one op amp is used and no
potentiometers are used for offset and gain trim. The output
voltage is coded in offset binary and is given by:
For the 2.5 V output range and the circuit values shown in the
table, the transfer equation becomes:
Similarly, for the 5 V output range, the transfer equation
becomes:
REV. A
Hexadecimal Number
in DAC Register
F
801
800
7FF
000
FF
V
–2.5
Figure 29. Bipolar Output Operation without Trim
O
SCLK
CLR
= 1 mV
SDI
CS
LD
R2
R1
REF03
V
2
6
5
3
4
V
O
+5V
O
Table III. Bipolar Code Table
2
4
DAC8512
= 1.22 mV
Digital Code
= 2.44 mV
GND
0.1µF
7
+5V
V
6
1
DD
+2.5V
0.1µF
Decimal Number
in DAC Register
4095
2049
2048
2047
0
8
V
R1
OUT
R3
Digital Code – 2.5 V
Digital Code – 5 V
RANGE
2.5V
5V
R3 R4
R4
R4
2
3
R2
A1 = 1/2 OP295
10k
10k
R1
A1
+5V
–5V
10k
20k
8
R2
4
10k
10k
R3
1
Analog Output
Voltage (V)
–4.9976
–2.44E–3
0
+2.44E–3
+5
1
15.4k + 274
43.2k + 499
R2
R1
R4
V
O
–11–
Generating a Negative Supply Voltage
Some applications may require bipolar output configuration but
only have a single power supply rail available. This is very com-
mon in data acquisition systems using microprocessor-based
systems. In these systems, +12 V, +15 V, and/or +5 V are only
available. Shown in Figure 30 is a method of generating a nega-
tive supply voltage using one CD4049, a CMOS hex inverter,
operating on +12 V or +15 V. The circuit is essentially a charge
pump where two of the six are used as an oscillator. For the val-
ues shown, the frequency of oscillation is approximately 3.5 kHz
and is fairly insensitive to supply voltage because R1 > 2 R2.
The remaining four inverters are wired in parallel for higher out-
put current. The square wave output is level translated by C2 to
a negative-going signal, rectified using a pair of 1N4001s, and
then filtered by C3. With the values shown, the charge pump
will provide an output voltage of –5 V for current loadings in the
range 0.5 mA I
A High-Compliance, Digitally Controlled Precision Current
Source
The circuit in Figure 31 shows the DAC8512 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, R
so the transfer function is given by the following equation:
If R
with a 1 V input. Therefore, each DAC LSB corresponds to
2.4 A. If a bipolar output current is required, then the circuit
in Figure 28 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.
I
OUT
Figure 30. Generating a –5 V Supply When Only +12 V
or +15 V Is Available
CS
INVERTERS = CD4049
3
R1
510k
equals 100 , the output current is limited to +10 mA
7 mA with a +12 V supply.
2
5
R2
5.1k
0.02 F
C1
OUT
4
10 mA with a +15 V supply and 0.5 mA
14
11
9
7
I
OUT
6
10
12
15
=
CS
C2
47 F
V
R
. Voltage gain is set to unity,
IN
CS
D1
1N4001
1N4001
D2
DAC8512
C3
47 F
470
R3
1N5231
5.1V
ZENER
–5V