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1300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com PmodAD5 Reference Manual Revised May 24, 2016 This manual applies to the PmodAD5 rev. A Overview The Digilent PmodAD5 is an analog-to-digital converter (ADC) that utilizes a fourth order - modulator, a programmable gain array, and on-chip digital filtering including a variety of sinc filters and zero latency features. Features include: High precision 24-bit Sigma-Delta analog-to-digital converter 4 differential or 8 pseudo differential input channels Ultra-low noise Programmable gain (1 to 128) Flexible digital filter with fast settling option Two SMA connectors Small PCB size for flexible designs 1.9 0.8 (4.8 cm 2.0 cm) The PmodAD5. 6-pin Pmod connector with SPI interface Follows Digilent Interface Specification Type 2 1 Functional Description The PmodAD5 utilizes Analog Devices AD7193 to provide 4 differential or 8 pseudo differential analog inputs. With 24-bit resolution and rms noise as low as 11 nV, highly accurate voltage measurements can be taken. 2 Interfacing with the Pmod The PmodAD5 communicates with the host board via the SPI protocol. By driving the Chip Select line low, users can transfer information to and from the device with the most significant bit (MSB) first. The default setting of the AD7193 upon power-up is that a single analog-to-digital conversion is made comparing the voltage difference between pins A1 (+) and A2 (-) on header J2. The input voltage that is allowed with the default settings is 19.53 mV with respect to the on-board reference voltage of 2.5V. Users are able to receive the Copyright Digilent, Inc. All rights reserved. DOC : 502-243 Page 1 of 4 Other product and company names mentioned may be trademarks of their respective owners. PmodAD5 Reference Manual 24 bits of data by first pulling the chip select line low and waiting the required conversion and settling time (100 ms by default). Users can then write to the communications register to indicate that they want to read the data and then clock in the 24 bits of data from the data register and finally pull the chip select line back to a high voltage state. An example of what the data stream might look like is given below: Communications Register ~Wen R/~W Data Register Address CREAD 0 0 0 1 0 1 1 0 0 0 Data Register Read Bits D23-D0 Table 1. Example data stream of the measured differential voltage. Some users may wish to have a wider voltage range than 2.5V 19.53 mV that they are able to analyze. This can be adjusted by changing specific values within the Configuration register namely, the Reference Select bit (D20) and the three gain bits (D2-D0). An example bit stream that changes the Reference Select bit from the default reference of 2.5V to the user supplied reference voltage between pins REFIN2+ and REFIN2- and changes the gain from the default of 128 to 1 is provided below: Communications Register ~Wen R/~W Configuration Register Address CREAD 0 0 0 0 0 1 0 0 0 0 Configuration Register (first 8 of 24 bits) Chop 0 0 REFSEL 0 Pseudo Short TEMP 0 0 0 1 0 0 0 0 Configuration Register (second 8 of 24 bits) Channel Enable bits for CH7 - CH0 0 0 0 0 0 0 0 1 Configuration Register (last 8 of 24 bits) Burn REFDET 0 BUF U/~B G2 G1 G0 0 0 0 1 0 0 0 0 Table 2. Example data stream of the measured differential voltage. Copyright Digilent, Inc. All rights reserved. Page 2 of 4 Other product and company names mentioned may be trademarks of their respective owners.