Download CN-0037 利用电流输出DAC AD5426/AD5432/AD5443进行交流信号处理

CIRCUIT FUNCTION AND BENEFITS
1.8pF
VREF
±3.5V
VREF
VDD = +5V
RFB
VDD
AD5426/
AD5432/
AD5443
SYNC SCLK SDIN
IOUT1
A1
AD8038
VOUT = 0V TO –VREF
IOUT2
VDD
GND
VSS = –5V
10µF
0.1µF
MICROCONTROLLER
AGND
VSS
10µF
CIRCUIT DESCRIPTION
VOUT = − VREF × (D/2N)
where D is the digital word loaded to the DAC and N is the
number of bits: D = 0 to 255 (8-bit AD5426); D = 0 to 1023
(10-bit AD5432); and D = 0 to 4095 (12-bit AD5443). VREF can
be an ac input signal. Figure 2 shows the ac multiplying
bandwidth, which is essentially the frequency response of the
DAC when an ac reference is applied to the VREF input pin. The
plot shows that the circuit can handle a ±3.5 V ac waveform up
to approximately 10 MHz.
0.1µF
Figure 1. AC Signal Processing Configuration Using a Multiplying
Current Output DAC (Simplified Schematic)
6
LOADING
0
ZS TO FS
–6
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–72
–78
–84
–90
–96
–102
1
10
ALL ON
DB11
DB10
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
ALL OFF
100
1k
10k
100k
FREQUENCY (Hz)
TA = 25°C
VDD = 5V
VREF = ±3.5V
CCOMP = 1.8pF
AD8038 AMPLIFIER
1M
10M
Figure 2. AC Multiplying Bandwidth Performance
www.BDTIC.com/ADI
100M
08271-001
VDD1
10µF
GAIN (dB)
The AD5426, AD5432, and AD5443 are CMOS 8-bit/10-bit/
12-bit current output digital-to-analog converters, respectively.
These devices operate from a 2.5 V to 5.5 V power supply,
making them suitable for battery powered applications, signal
attenuation, channel equalization, and waveform generation.
The maximum signal range can be up to ±12 V, but the output
swing is limited by the supply voltage of the amplifier. Figure 1
shows a typical application circuit for a current output DAC for
ac signal processing. Using a single op amp, these devices can
easily be configured to provide either a 2-quadrant multiplying
operation or a unipolar output voltage swing, as shown in
Figure 1. When an output amplifier is connected in the unipolar
mode, the output voltage is given by
0.1µF
08271-002
This circuit provides 2-quadrant signal multiplication using the
AD5426/AD5432/AD5443 current output DACs and an
operational amplifier. It provides multiplying bandwidth up to
10 MHz, which allows accurate conditioning of ac signals with
bandwidths up to this frequency. The circuit is well suited for ac
signal conditioning applications in communications, industrial,
and medical applications.
VDD1 = +5V
LEARN MORE
Data Sheets
ADIsimPower Design Tool. Analog Devices
AD5426 Data Sheet.
Kester, Walt. 2005.The Data Conversion Handbook. Analog
Devices. Chapters 3 and 7.
AD5432 Data Sheet.
MT-015 Tutorial, Basic DAC Architectures II: Binary DACs.
Analog Devices.
AD8038 Data Sheet.
MT-031 Tutorial, Grounding Data Converters and Solving the
Mystery of AGND and DGND. Analog Devices.
REVISION HISTORY
MT-033 Tutorial, Voltage Feedback Op Amp Gain and
Bandwidth. Analog Devices.
Updated Format .................................................................. Universal
AD5443 Data Sheet.
7/09—Rev. 0 to Rev. A
MT-035 Tutorial, Op Amp Inputs, Outputs, Single-Supply, and
Rail-to-Rail Issues. Analog Devices.
MT-101 Tutorial, Decoupling Techniques. Analog Devices.
Voltage Reference Wizard Design Tool. Analog Devices.
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CN08271-0-7/09(A)
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