The AD7476A is 12-bit, high speed, low power, successive-approximation analog-to-digital converter (ADC). The part operates from a single 2.35V to 5.25V power supply and feature throughput rates up to 1 MSPS. The part contains a low noise, wide bandwidth track-and-hold amplifier that can handle input frequencies in excess of 13 MHz.

Two reference designs are available for this part:

• A design which shows how to program the AD7476A ADC and acquire data from it.
  • HW Platform(s):
    • Spartan-6 LX9 Microboard (Avnet)
    • Nexys™3 Spartan-6 FPGA Board (Digilent)
    • PmodAD1 (Digilent)
      
  • System: Microblaze, AXI, UART
    

• A design which demonstrates how to acquire a signal and reproduce it using Digilent PmodAD1 and PmodDA1. Four types of waveforms (Square, Sine, Sawtooth and Triangle) are generated using the AD7303 DAC present on the PmodDA1 board. Each waveform has a period of 25 ms, and lasts for 25 s (1000 periods). A loopback cable is connected between the output of the AD7303 DAC (A1 Output) and the input of the AD7476 ADC (A0 input) present on the PmodAD1 board. The Xilinx ChipScope Analyzer tool is used to verify the digitized waveforms.
  • HW Platform(s): Nexys™3 Spartan-6 FPGA Board (Digilent) PmodAD1 (Digilent) PmodDA1 (Digilent)
    
  • System: Microblaze, AXI, UART
    

The bit file provided in the project *.zip file combines the FPGA bit file and the SDK elf files. It may be used for a quick check on the system. All you need is the hardware and a PC running a UART terminal and the programmer (IMPACT).

• Spartan-6 LX9 Microboard (Avnet)
• Nexys™3 Spartan-6 FPGA Board (Digilent)
• PmodAD1 (Digilent)

• Xilinx ISE 14.4 (Programmer (IMPACT) is sufficient for the demo and is available on Webpack).
• A UART terminal (Tera Term/Hyperterminal), Baud rate 115200 for the Avnet LX-9 Microboard or 9600 for the Digilent Nexys™3 Board.

Extract the project from the archive file (AD7476A_<board_name>.zip) to the location you desire.

To begin, connect the PmodAD1 to J5 connector of LX9 board, pins 1 to 6 (see image below). You can use an extension cable for ease of use. Connect the USB cable from the PC to the USB-UART female connector of the board for the UART terminal. The board will be programmed through its USB male connector.

To begin, connect the PmodAD1 to JA connector of Nexys™3 board, pins JA1 to JA6 (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board, one for programming (Digilent USB device) and one for the UART terminal (FT232R USB UART).

Start IMPACT, and double click “Boundary Scan”. Right click and select Initialize Chain. The program should recognize the Spartan 6 device (see screenshot below). Start a UART terminal (set to appropiate baud rate) and then program the device using the bit file provided in the project *.zip archive, located in the “sw” folder (../ad7476a/sw/AD7476A.bit).

If programming was successful, you should be seeing messages appear on the terminal window as shown in the figure below. After programming the AD7476A device, the program will automatically read the values of the analog voltage inputs, Vin1 and Vin2, and print them via UART. Pressing any key will initialize another conversion.

The reference design is a simple SPI interface with multiplexed MISO pins for the AD7476A. The software programs the device and prints the values of the analog input voltages Vin1 and Vin2. The information is displayed on UART.

The hardware SPI access allows reading the data sent by the AD7476A, using a single CS and SCLK pins, and a multiplexed MISO pin (PmodAD1 contains two AD7476A Integrated Circuits, which share the same CS and SCLK pins, but have separate MISO pins, which need to be multiplexed).

• ask questions about the FPGA reference design
• Example questions:

  • inconsistent base address of axi_hdmi_tx_16b_0 by z-trf
  • FMCOMMS TX DAC sample size hangup by AnalogDiode
  • Failed to build Linux with HDMI video output on the ZED board by z-trf
  • failed to boot kernel on zedboard with adv7511 by z-trf
  • FMCOMMS: ADC timing inconsistent if number of samples > 10,000 by AnalogDiode