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AN-1215 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 40 Channels of Programmable Industrial Level Output Span Using the AD5370 16-Bit Voltage Output DAC CIRCUIT FUNCTION AND BENEFITS The AD5370 is the industry’s only 40-channel DAC offering these industrial signal level outputs and the flexibility of multiple output spans with 16-bit resolution. Coupled with the XFET® series of low noise precision references, the total solution represents industry-leading DAC channel density, smallest footprint, flexibility, and performance. This circuit is a multichannel DAC configuration with different output spans on groups of channels. It utilizes the AD5370 to provide 40 DAC channels with 16 bits of resolution. The AD5370 is configured to have eight channels with an output span of ±10 V and 24 channels with an output span of −4 V to +8 V. 15V 5V 0.1µF 0.1µF 10µF 5V ADR435 DVCC VDD VREF0 VOUT0 0.1µF ±10V 3V VOUT7 ADR423 AD5370 VOUT8 VREF1 –4V TO +8V VOUT39 0.1µF VSS SIGGND AGND DGND 0.1µF –15V 08948-001 10µF Figure 1. 40 Channels of Programmable Output Voltage Span Using the AD5370 DAC (Simplified Schematic: Decoupling and All Connections Not Shown) Rev. A | Page 1 of 2 AN-1215 Application Note CIRCUIT DESCRIPTION COMMON VARIATIONS Table 1. Devices Connected/Referenced The AD5371 is a 40-channel, 14-bit version of the AD5370 with three reference input pins. The AD5372 and AD5373 are 16-bit and 14-bit, 32 channel versions of the AD5370. Product AD5370 Description 40-Channel, 16-Bit Voltage Output DAC ADR431/ ADR421 2.5 V Ultralow Noise Voltage Reference ADR423 3 V Ultralow Noise Voltage Reference ADR435 5 V Ultralow Noise Voltage Reference The circuit described here can be used with any of the AD537x devices mentioned. The references can also be changed to give different output ranges if required. The ADR421 and ADR431 are 2.5 V references, which can be used to create a ±5 V output. The AD5370 is a 40-channel, 16-bit DAC available both in 64-lead LFCSP and 64-lead LQFP packages. The AD5370 has two reference input pins. VREF0 is the reference pin for DAC channels VOUT0 to VOUT7. VREF1 is the reference pin for DAC channels VOUT8 to VOUT39. Figure 1 shows a typical configuration for the AD5370 using two external references. The nominal output span for the AD5370 is four times the reference voltage. The default offset DAC register values for the AD5370 allow for an output span of −4 V to +8 V using a 3 V reference. Programming the offset DAC register associated with VOUT0 to VOUT7 allows a span of ±10 V to be achieved using a 5 V reference. The ADR435 is a low noise precision 5 V reference. The ADR423 is a low noise precision 3 V reference. When connected as shown in Figure 1, the AD5370 will have an output span of ±10 V on VOUT0 to VOUT7 and an output span of −4 V to +8 V on VOUT8 to VOUT39. The AD5370 has two offset DAC registers, which allow the mid-scale point of the span to be adjusted within the limits of part functionality and headroom. The default value of the offset DAC registers is 5461 (0x1555) giving a mid-scale point of 2 V when using a 3 V reference. This gives an output span of −4 V to +8 V and is the default for VOUT8 to VOUT39. Programming the offset DAC 0 register with 8192 (0x2000) sets the mid-scale point to 0 V. This gives output spans of ±10 V on VOUT0 to VOUT7. The flexibility of the AD5370 allows systems to be designed with multiple different output ranges, with the same components on the bill of materials. LEARN MORE Kester, Walt. The Data Conversion Handbook. Chapters 3, 7. Analog Devices. 2005. MT-015 Tutorial, Basic DAC Architectures II: Binary DACs. Analog Devices. MT-031 Tutorial, Grounding Data Converters and Solving the Mystery of AGND and DGND. Analog Devices. MT-101 Tutorial, Decoupling Techniques. Analog Devices. Voltage Reference Wizard Design Tool. Analog Devices. Data Sheets and Evaluation Boards AD5370 Data Sheet AD5370 Evaluation Board AD5371 Data Sheet AD5372 Data Sheet AD5373 Data Sheet ADR421 Data Sheet ADR423 Data Sheet ADR431 Data Sheet ADR435 Data Sheet REVISION HISTORY 4/13—Rev. 0 to Rev. A The circuit must be constructed on a multilayer PC board with a large area ground plane. Proper layout, grounding, and decoupling techniques must be used to achieve optimum performance (see Tutorial MT-031 and Tutorial MT-101). Changed Document Title from CN-0149 to AN-1215 .............................................................................. Universal 4/10—Revision 0: Initial Version ©2010–2013 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. AN08948-0-4/13(A) Rev. A | Page 2 of 2