PRELIMINARY TECHNICAL DATA

REV. PrG 4/01/2002

-15-

AD9430

DAC Outputs

Each channel is reconstructed by an on-board dual-channel DAC,

an AD9753. This DAC is intended to assist in debug—it should

not be used to measure the performance of the ADC. It is a current

output DAC with on-board 50

Ω termination resistors. The

figure below is representative of the DAC output with a full-scale

analog input. The scope setting is low bandwidth.

CH1

CH1

M 25.0nS

1

C1 FREQ

10.33592MHz

C1 PK-PK

448mV

2.00mV

248mV

Figure 14. DAC Output

Encode Xtal

An optional xtal oscillator can be placed on the board to serve

as a clock source for the PCB. Power to the xtal is through the

VCLK/VXTAL pin at the power connector. If an oscillator is used,

ensure proper termination for best results. The board has been

tested with a Valpey Fisher VF561 and a Vectron JN00158-163.84.

Test results for the VF561 are shown below.

MHz

0

–30

080

20

40

60

–60

–80

–20

–10

–50

–40

–100

–90

–70

ENCODE 163.84MHz

ANALOG 65.02MHz

SNR 63.93dB

SINAD 63.87dB

FUND –0.45dBFS

2ND –85.62dBc

3RD –91.31dBc

4TH –90.54dBc

5TH –90.56dBc

6TH –91.12dBc

THD –82.21dBc

SFDR 83.93dBc

SAMPLES 8k

NOISEFLR –100.44dBFS

WORSTSP –83.93dBc

Figure 15. FFT—Using VF561 XTAL as Clock Source

Optional Amplifier

The footprint for transformer T2 can be modified to accept a

wideband differential amplifier (AD8350) for low frequency

applications where gain is required. Note that Pin 2 would need

to be lifted and left floating for operation. Input transformer T1

would need to be modified to a 4:1 for impedance matching and

ADC input filtering would enhance performance (see AD8350

data sheet). SNR/SINAD Performance of 61 dB/60 dB is pos-

sible and would start to degrade at about 30 MHz.

CUT TRACE

AD9430

1

CUT TRACE

Figure 16. Using the AD8350 on the AD9430 PCB