Transcript
AN-1231 APPLICATION NOTE One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com
AC Signal Processing Using the AD5426/AD5432/AD5443 Current Output DACs CIRCUIT FUNCTION AND BENEFITS
VDD1 = +5V
This circuit provides two-quadrant signal multiplication using the AD5426/AD5432/AD5443 current output, digital-to-analog converters (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.
1.8pF
VREF
±3.5V VREF
VDD = +5V
RFB
VDD
AD5426/ AD5432/ AD5443
SYNC SCLK SDIN
IOUT1
A1 AD8038
VDD
GND VSS = –5V
10µF
0.1µF
MICROCONTROLLER AGND
VSS 10µF
CIRCUIT DESCRIPTION
0.1µF
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. Figure 2 shows that the circuit can handle a ±3.5 V ac waveform up to approximately 10 MHz.
VOUT = −VREF × (D/2N) where: D is the digital word loaded to the DAC. 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.
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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
100M
08271-002
The AD5426, AD5432, and AD5443 are CMOS 8-bit/10-bit/12-bit current output DACs, 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; however, the supply voltage of the amplifier limits the output swing. 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 two-quadrant multiplying operation or a unipolar output voltage swing, as shown in Figure 1. When an output amplifier is connected in unipolar mode, the output voltage is given by
0.1µF
Figure 1. AC Signal Processing Configuration Using a Multiplying Current Output DAC (Simplified Schematic)
GAIN (dB)
Description 8-bit/10-bit/12-bit multiplying DACs Low power, high performance amplifier
10µF
08271-001
VDD1
Table 1. Devices Connected/Referenced Product AD5426/AD5432/AD5443 AD8038
VOUT = 0V TO –VREF
IOUT2
AN-1231
Application Note
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. MT-033 Tutorial, Voltage Feedback Op Amp Gain and Bandwidth. Analog Devices. MT-035 Tutorial, Op Amp Inputs, Outputs, Single-Supply, and Rail-to-Rail Issues. Analog Devices.
AD5443 Data Sheet.
REVISION HISTORY 5/13—Rev. A to Rev. B Document Title Changed from CN-0037 to AN-1231 . Universal 7/09—Rev. 0 to Rev. A Updated Format .................................................................. Universal
MT-101 Tutorial, Decoupling Techniques. Analog Devices. Voltage Reference Wizard Design Tool. Analog Devices.
©2009–2013 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. AN08271-0-5/13(B)
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