AD9246-125EB datasheet(29/45 Pages) AD

29 / 45 page

AD9246

Rev. A | Page 28 of 44

EVALUATION BOARD

The AD9246 evaluation board provides all of the support

circuitry required to operate the ADC in its various modes and

configurations. The converter can be driven differentially through

a double balun configuration (default) or through the AD8352

differential driver. The ADC can also be driven in a single-ended

fashion. Separate power pins are provided to isolate the DUT

from the AD8352 drive circuitry. Each input configuration can

be selected by proper connection of various components (see

Figure 60 to Figure 70). Figure 59 shows the typical bench

characterization setup used to evaluate the ac performance of

the AD9246.

It is critical that the signal sources used for the analog input and

clock have very low phase noise (<1 ps rms jitter) to realize the

optimum performance of the converter. Proper filtering of the

analog input signal to remove harmonics and lower the integrated

or broadband noise at the input is also necessary to achieve the

specified noise performance.

See Figure 60 to Figure 64 for the complete schematics and

layout diagrams that demonstrate the routing and grounding

techniques that should be applied at the system level.

POWER SUPPLIES

This evaluation board comes with a wall-mountable switching

power supply that provides a 6 V, 2 A maximum output. Connect

the supply to the rated 100 V ac to 240 V ac wall outlet at 47 Hz

to 63 Hz. The other end is a 2.1 mm inner diameter jack that

connects to the PCB at P500. Once on the PC board, the 6 V

supply is fused and conditioned before connecting to five low

dropout linear regulators that supply the proper bias to each of

the various sections on the board.

When operating the evaluation board in a nondefault condition,

L501, L503, L504, L508, and L509 can be removed to disconnect

the switching power supply. This enables the user to individually

bias each section of the board. Use P501 to connect a different

supply for each section. At least one 1.8 V supply is needed with

a 1 A current capability for AVDD_DUT and DRVDD_DUT;

however, it is recommended that separate supplies be used for

analog and digital. To operate the evaluation board using the

AD8352 option, a separate 5.0 V supply (AMP_VDD) with a

1 A current capability is needed. To operate the evaluation board

using the alternate SPI options, a separate 3.3 V analog supply

is needed, in addition to the other supplies. The 3.3 V supply

(AVDD_3.3V) should have a 1 A current capability, as well.

Solder Jumpers J501, J502, and J505 allow the user to combine

these supplies (see Figure 64 for more details).

INPUT SIGNALS

When connecting the clock and analog source, use clean signal

generators with low phase noise, such as Rohde & Schwarz SMHU

or Agilent HP8644 signal generators or the equivalent. Use

1-meter long, shielded, RG-58, 50 Ω coaxial cable for making

connections to the evaluation board. Enter the desired frequency

and amplitude for the ADC. Typically, most evaluation boards

from Analog Devices, Inc. can accept a ~2.8 V p-p or 13 dBm

sine wave input for the clock. When connecting the analog

input source, it is recommended to use a multipole, narrow-

band, band-pass filter with 50 Ω terminations. Analog Devices

uses TTE®, Allen Avionics, and K&L® types of band-pass filters.

Connect the filter directly to the evaluation board, if possible.

OUTPUT SIGNALS

The parallel CMOS outputs interface directly with the Analog

Devices standard single-channel FIFO data capture board

(HSC-ADC-EVALB-SC). For more information on the FIFO

boards and their optional settings, visit www.analog.com/FIFO.

ROHDE & SCHWARZ,

SMHU,

2V p-p SIGNAL

SYNTHESIZER

ROHDE & SCHWARZ,

SMHU,

2V p-p SIGNAL

SYNTHESIZER

BAND-PASS

FILTER

AIN

CLK

14-BIT

PARALLEL

CMOS

USB

CONNECTION

AD9246

EVALUATION BOARD

HSC-ADC-EVALB-SC

FIFO DATA

CAPTURE

BOARD

RUNNING

ADC

ANALYZER

AND SPI

USER

SOFTWARE

1.8V

–+

5.0V

2.5V

6V DC

2A MAX

WALL OUTLET

100V TO 240V AC

47Hz TO 63Hz

SWITCHING

POWER

SUPPLY

–+

3.3V

–+

3.3V

–+

3.3V

SPI

Figure 59. Evaluation Board Connection

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