The EVAL-AD7768FMCZ evaluation kit features the AD7768, a 24-bit, 256 kSPS, analog-to-digital converter (ADC). This aim of this document is to create a quick start guide for the AD7768/AD7768-4 customer evaluation board and to provide a support forum for any FAQs relating to initial set up of the evaluation boards. This post can be used for both the AD7768 and AD7768-4 evaluation boards ( 8 channel and 4 channel devices respectively) as both boards are configured in the same way.
The EVAL-AD7768FMCZ can be used as a standalone board for development or in conjunction with the EVAL-SDP-CH1Z high speed controller board. This document assumes the EVAL-AD7768FMCZ is being used in conjunction with the EVAL-SDP-CH1Z.
- Ensure that the EVAL-SDP-CH1Z board is disconnected from the USB port of the PC. Install the evaluation board software from the CD included in the evaluation board kit, or alternatively from the evaluation board web page. Restart the PC after the software installation is complete. (For complete software installation instructions, see the Software Installation Procedures section in the User Guide.)
- Connect the EVAL-SDP-CH1Z board to the EVAL-AD7768FMCZ board (unpowered). The attached image illustrates this connection: J4 of the EVAL-SDP-CH1Z board adapts to the receiving socket (P1) on the EVAL-AD7768FMCZ printed circuit board (PCB).
- Apply power to the EVAL-AD7768FMCZ board via the supplied 9 V dc adapter at J1. LK1 must be in Position B.
- Connect the 12 V dc supply to the EVAL-SDP-CH1Z board, and then connect to the PC using the supplied USB cable.
- Launch the AD7768 evaluation software from the Analog Devices subfolder in the Programs menu.
- Configuration of the AD7768 can be carried out using the software, in both the configuration tab and the register tab. Pressing the sample button on the top right of the AD7768 software window will sample the input of the ADC and the software displays the respective waveform, FFT and histogram of the sampled data.
Alternative Power Options
If preferred, there are a number of options to supply power to the board.
- Connector J3 can be used to supply between 7V and 9V to the board, between V+ and GND. This is done by setting LK1 to Position A. (V- does not need to be connected). This power is then supplied to the on board regulators (ADP7118 from Analog Devices) which supply 5V to AVDD1 and AVDD2 and 3.3V to IOVDD.
- Connector J2 can be used in the case where supplies other than the default evaluation board supplies are to be used. Please see the Power Supplies section of the datasheet for the full range of operating voltages. This can be selected by changing solder links SLP1, SLP2 and SLP4 to power AVDD1, AVDD2 and IOVDD respectively. Please note that the on board reference, amplifiers and VCM buffer will still need to be powered up in this case from either J1 or J3.
The analog input signal can be applied using either the SMB connectors for an ac signal, or using the terminal blocks for a dc signal. By default the signal is buffered on each channel using the ADA4896-2. For evaluation, this can be bypassed by changing the solder links labelled SLX+ and SLX-, where X is the channel number of interest.
The VCM voltage is applied at the input of each of the driver amps from the output VCM (pin 59) of the AD7768/AD7768-4 by default. This is buffered using the OP2177 and supplied to each analog input. The option to bypass this buffer is provided for by solder link SL15. A resistor divider can also be utilised in order to get any fraction of AVDD1 for the VCM voltage by changing SL19 to position B and by adjusting R166 and R167 accordingly. Please see the schematic and user guide on the evaluation board web page for more details.
The input signal is driven with the ADA4896 and passed through a low pass anti-aliasing filter. The on-board ADA4896-2 input driver amps are powered using U1 on the board, the ADP7118. This supply can be changed using the solder link options SL_AMP+ and SL_AMP-. The amplifiers will then take their supply voltage from either J1 if LK1 is set to position B, or J3 if LK1 is set to position A. If a negative supply is needed it can be applied using J3 at the V- terminal.
Please note in order for a negative voltage to be applied at J3 the resistors present on pin 4 of all eight of the ADA4896-2's will need to be replaced with decoupling capacitors. These resistors are shorted to ground in the default configuration.
Remember: Full specifications on the AD7768 and AD7768-4 are available in the product data sheet, which should be consulted in conjunction with user guide, UG-917 when working with the evaluation board.
1. Ensure that the EVAL-SDP-CH1Z board is disconnected from the USB port of the PC. Install the evaluation board software from the CD included in the evaluation board kit. Restart the PC after the software installation is complete. (For complete software installation instructions, see the Software Installation Procedures section.)
2. Connect the EVAL-SDP-CH1Z board to the EVAL-AD7768FMCZ board (unpowered). Figure 1 illustrates the connection: J4 of the EVAL-SDP-CH1Z board adapts to the receiving socket on the EVAL-AD7768FMCZ printed circuit board (PCB).
3. Ensure that the boards are connected firmly together.
4. Apply power to the EVAL-AD7768FMCZ board via the supplied 9 V dc adapter at J1 (LK1 in Position B). Alternatively, supply an external voltage in the range of 7 V to 9 V from a bench top power supply using the J3 connector (LK1 in Position A).
5. Connect the 12 V dc supply to the EVAL-SDP-CH1Z board, and then connect to the PC using the supplied USB cable. For Windows XP, the PC may need to search for the EVAL-SDP-CH1Z drivers. Choose to automatically search for the drivers for the EVAL-SDP-CH1Z board if prompted by the operating system.
6. Launch the AD7768 evaluation software from the Analog Devices subfolder in the Programs menu.