AD7304 Analog Devices, AD7304 Datasheet - Page 17

• Manufacturer Part Number: AD7304
• Description: +3V/+5V, Rail-to-Rail Quad, 8-Bit DAC Serial-IN
• Manufacturer: Analog Devices

Specifications of AD7304

• Resolution (bits): 8bit
• Dac Update Rate: 1MSPS
• Dac Settling Time: 1µs
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

APPLICATIONS
The AD7304/AD7305 are inherently 2-quadrant multiplying
DACs. That is, they can easily be set up for unipolar output
operation. The full-scale output polarity is the same as the
reference input voltage polarity.
In some applications, it may be necessary to generate the full
4-quadrant multiplying capability or a bipolar output swing.
This is easily accomplished using an external true rail-to-rail op
amp, such as the OP295. Connecting the external amplifier with
two equal value resistors, as shown in Figure 38, results in a full
4-quadrant multiplying circuit. In this circuit, the amplifier
provides a gain of two, which increases the output span
magnitude to 10 V. The transfer equation of this circuit shows
that both negative and positive output voltages are created as
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the input data (D) is incremented from code zero (V
to midscale (V
V
OUT
Figure 38. 4-Quadrant Multiplying Application Circuit
REF
=
+5V
128
OUT
AD7304
D
−
10kΩ
= 0 V) to full scale (V
1
×
V
REF
10kΩ
2.2pF
–5V < V
AD7304/AD7305
OUT
= +5 V).
OUT
< +5V
OUT
= –5 V)
(2)