AD5452 Analog Devices, AD5452 Datasheet - Page 17

• Manufacturer Part Number: AD5452
• Description: 12-Bit High Bandwidth Multiplying DACs with Serial Interface
• Manufacturer: Analog Devices

Specifications of AD5452

• Resolution (bits): 12bit
• Dac Update Rate: 2.7MSPS
• Dac Settling Time: 160ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Ser,SPI

Bipolar Mode
In some applications, it may be necessary to generate a full
4-quadrant multiplying operation or a bipolar output swing.
This can be easily accomplished by using another external
amplifier and some external resistors, as shown in Figure 45. In
this circuit, the second amplifier, A2, provides a gain of 2.
Biasing the external amplifier with an offset from the reference
voltage results in full 4-quadrant multiplying operation. The
transfer function of this circuit shows that both negative and
positive output voltages are created as the input data (D) is
incremented from Code 0 (V
(V
where:
D is the fractional representation of the digital word loaded to
the DAC.
D
n is the resolution of the DAC.
OUT
= 0 to 255 (8-bit AD5450).
= 0 to 1023 (10-bit AD5451).
= 0 to 4095 (12-bit AD5452).
V
− 0 V ) to full scale (V
OUT
=
⎛
⎜
⎝
V
REF
×
2
D
n
− 1
V
±10V
NOTES
1. R1 AND R2 USED ONLY IF GAIN ADJUSTMENT IS REQUIRED.
2. MATCHING AND TRACKING IS ESSENTIAL FOR RESISTOR PAIRS
3. C1 PHASE COMPENSATION (1pF TO 2pF) MAY BE REQUIRED
REF
⎞
⎟
⎠
ADJUST R1 FOR V
R3 AND R4.
IF A1/A2 IS A HIGH SPEED AMPLIFIER.
−
OUT
V
OUT
REF
= +V
R1
= − V
REF
V
SYNC
REF
REF
OUT
V
V
).
µCONTROLLER
DD
DD
) to midscale
= 0V WITH CODE 10000000 LOADED TO DAC.
Figure 45. Bipolar Mode Operation (4-Quadrant Multiplication)
SCLK SDIN
AD5450/
AD5451/
AD5452/
AD5453
R
FB
I
OUT
GND
20kΩ
R3
R2
Rev. E | Page 17 of 32
1
AGND
C1
A1
When V
multiplication. Table 6 shows the relationship between the
digital code and the expected output voltage for a bipolar
operation using the 8-bit AD5450.
Table 6. Bipolar Code Table for the AD5450
Digital Input
1111 1111
1000 0000
0000 0001
0000 0000
10kΩ
R4
IN
is an ac signal, the circuit performs 4-quadrant
AD5450/AD5451/AD5452/AD5453
20kΩ
A2
R5
V
OUT
= –V
Analog Output (V)
+V
0
−V
−V
REF
REF
REF
REF
TO +V
(127/128)
(127/128)
(128/128)
REF