AD9656EBZ

AD9656EBZ Datasheet


EVALUATING THE AD9656 ANALOG-TO-DIGITAL CONVERTER

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EVALUATING THE AD9656 ANALOG-TO-DIGITAL CONVERTER

This user guide describes the AD9656 evaluation board AD9656EBZ, which provides the support circuitry required to operate the ADC in its various modes and configurations. The application software used to interface with the device is also described. The AD9656 data sheet provides additional information and should be consulted when using the evaluation board. Documents and software tools are available at AD9656 and For additional information or questions, send an email to

Typical Measurement Setup

Figure Evaluation Board on Left and HSC-ADC-EVALEZ on Right
q SPI interface for setup and control q External, on-board oscillator q On-board LDO regulator, needing a single external 6V, 2A dc supply q ADC VREF configurable for ADC-internal reference, on-board reference, off-board reference q and SPIController software interfaces

Helpful Documents
q AD9656 data sheet q High speed ADC FIFO evaluation kit HSC-ADC-EVALEZ q HSC-ADC-EVALEZ Wiki Guide q AN-905 Application Note, VisualAnalog Converter Evaluation Tool Version User Manual q AN-878 Application Note, High Speed ADC SPI Control Software q AN-877 Application Note, Interfacing to High Speed ADCs via SPI q AN-835 Application Note, Understanding ADC Testing and Evaluation

Design and Integration Files
q Schematics, layout files, bill of materials <Coming Soon>

Equipment Needed
q Analog signal source s and antialiasing filter s q Sample clock source if not using the on-board crystal oscillator q Switching power supply 6.0V, 2.5A for AD9656EBZ q Switching power supply 12V, 3,3A for HSC-ADC-EVALEZ q PC running q USB port q AD9656EBZ board q HSC-ADC-EVALEZ FPGA-based data capture kit

Getting Started

This section provides quick start procedures for using the AD9656EBZ board. Both the default and optional ADC settings are described.

Configuring the Board

Before using the software for testing, configure the evaluation board as follows Connect the evaluation board to the data capture board, as shown in Figure On the ADC evaluation board, confirm that the jumpers are installed as shown in Figure The AD9656EBZ can be powered in one of three ways. The default is to have the AD9656EBZ
obtain its power from the HSC-ADC-EVALEZ through the FMC connector. For this configuration, jumper pin 1 to pin 2 on both P101 and P103 on the AD9656EBZ. The other power configurations will be described in the Power Supplies section below. Connect the 12V, 3.3A switching power supply to the HSC-ADC-EVALEZ board. Connect the HSC-ADC-EVALEZ board P702 to the PC using a USB cable. On the ADC evaluation board, use a clean signal generator with low phase noise to provide an input signal to the desired channel s . Use a shielded, RG-58, 50Ω coaxial cable optimally 1 m or shorter to connect the signal generator. For best results, use a narrow-band, band-pass filter with 50Ω terminations and an appropriate center frequency. Analog Devices, Inc. uses TTE, Allen Avionics, and K&L band-pass filters.

Evaluation Board Hardware

The evaluation board provides the support circuitry required to operate the AD9656 in its various modes and configurations. Figure 1 shows the typical bench characterization setup used to evaluate AC performance. It is critical that the signal sources used for the analog input and clock have very low phase noise ideally ~100 fs rms jitter to realize the optimum performance of the signal chain. Proper filtering of the analog input signal to remove harmonics and lower the integrated or broadband noise at the input is necessary to achieve the specified noise performance.

See AD9656 Design Support <Coming Soon> for schematics and layout diagrams. These diagrams demonstrate the routing and grounding techniques that should be applied at the system level when designing application boards using these converters.

Power Supplies

The AD9656EBZ can obtain its power from the HSC-ADC-EVALEZ through the FMC connector. P101 and P103 both need to have pin 1 tied to pin 2 for obtaining board power through the FMC connector from the HSC-ADC-EVALEZ capture board. If P101 and P103 have pin 1 jumpered to pin 2, do not connect the supplied 6V wall supply to the AD9656 evaluation board. When changing the configuration of P101 and P103, please remove both jumpers and then place them in their desired positions.

Alternatively, the AD9656EBZ can obtain its power from the wall-mountable 6V, 2A switching power supply. For this mode, P101 and P103 both need to have pin 2 tied to pin Connect the supply to a 100V ac to 240V ac, 47Hz to 63Hz wall outlet. The output from the supply is provided through a 2.1mm inner diameter jack that connects to the printed circuit board PCB at P102. The 6V supply is fused and conditioned on the PCB before connecting to the low dropout linear regulators that supply the proper bias to each of the various sections on the board.

Also, the evaluation board can be powered in a nondefault condition using external bench power supplies. To do this, remove the E104, E105, E106, and E108 ferrite beads to disconnect the on-board LDOs from the power planes. Note that in some board configurations some of these might already be uninstalled. P104 and P105 headers can be installed to facilitate connection of external bench supplies to the board. E110, E111, E112 and E113 need to be populated to connect P104 and P105 to the board power domains. A 1.8V , 0.5A supply is needed for 1.8V_DUT_AVDD, 1.8V_DRVDD and 1.8V_DVDD. Although the voltage requirements are the same for these three, it is recommended that separate supplies be used for each of these.

A 3.3V, 0.5A supply is needed for 3.3V_DIG, which is used to power additional on board circuitry.

Input Signals

The four channel inputs on the evaluation board are set up for a double balun-coupled analog input
with a 50Ω impedance. When connecting the ADC clock and analog source, use clean signal generators with low phase noise, such as the Rohde & Schwarz SMA, or an equivalent. Use a shielded, RG-58, 50Ω coaxial cable optimally 1 m or shorter for connecting to the evaluation board. Enter the desired frequency and amplitude see the Specifications section in the data sheet . When connecting the analog input source, use of a multipole, narrow-band-pass filter with 50Ω terminations is recommended. Analog Devices uses band-pass filters from TTE and K&L Microwave, Inc. Connect the filters as close to the evaluation board as possible.

Clock

The default clock input circuit is derived from an on-board 125MHz crystal oscillator feeding through a transformer-coupled circuit using a high bandwidth 1:1 impedance ratio transformer T302 that adds negligible jitter to the clock path. The external clock input J302 is 50 Ω terminated and ac-coupled to handle single-ended sinusoidal inputs. The transformer converts the single-ended input to a differential signal that is clipped by CR301 before entering the ADC clock inputs. The AD9656 ADC is equipped with an internal clock divider programmable divide ratios of 1 through 8 to facilitate usage with higher frequency clocks. When using the internal divider and a higher input clock frequency, remove CR301 to preserve the slew rate of the clock signal.

The AD9656EBZ board is set up to be clocked through the transformer-coupled input network from the 125MHz crystal oscillator, Y801. If an external clock source is desired, remove C302 optionally and Jumper J304 to disable the oscillator from running and connect the external clock source to the SMA connector, J302 labeled CLOCK+ . If an external clock source is used instead of the onboard crystal oscillator, it should also be supplied with a clean signal generator as previously specified for the analog input signals. Analog Devices evaluation boards typically can accept ~2.8V p-p or 13 dBm sine wave input for the clock at the board SMA clock connector.

Output Signals

The default setup uses the Analog Devices high speed converter evaluation platform HSC-ADC-EVALEZ for data capture. The JESD204B outputs from the ADC are routed to P2 using 100Ω differential traces. For more information on the data capture board and its optional settings, visit

Jumper Settings

Set the jumper settings/link options on the evaluation board for the required operating modes before powering on the board. The functions of the jumpers are described in Table Figure 2 shows the default jumper settings.

Table Jumper Settings

Jumper P101, P103 J304

J206

These jumpers determine the power source for the AD9656EBZ. Connect Pin 1 to Pin 2 on both P101 and P103 to power the ADC board from the HSC-ADC-EVALEZ through the FMC connector. Connect Pin 2 to Pin 3 on both P101 and P103 to power the ADC board from the wall supply connected to P102. Leave both P101 and P103 unjumpered if using headers P104 and P105.

This jumper enables the on-board crystal oscillator. Remove this jumper and optimally C302 if an external off-board clock source is used.

This jumper selects between internal VREF and external VREF. To choose the ADC's internal reference, connect Pin 3 DUT_SENSE to Pin 5 GND as shown in Figure The default value of the internal reference is 1 V. SPI Register 0x18 Bits[7:6] can be used to program the internal reference voltage to values from 1 V to V, in V increments. Register control is accomplished with SPIController software, which is discussed below in the Setting up the SPI Controller Software section.
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Datasheet ID: AD9656EBZ 517778