AD9432/PCB Analog Devices, AD9432/PCB Datasheet - Page 10

• Manufacturer Part Number: AD9432/PCB
• Description: 12-Bit/ 80 MSPS/105 MSPS A/D Converter
• Manufacturer: Analog Devices

AD9432
The minimum guaranteed conversion rate of the AD9432 is
1 MSPS. At internal clock rates below 1 MSPS, dynamic
performance may degrade. Therefore, input clock rates below
1 MHz should be avoided.
Code
+2047
•
•
0
–1
•
•
–2048
Using the AD8138 to Drive the AD9432
A new differential output op amp from Analog Devices, Inc.,
the AD8138 can be used to drive the AD9432 in dc-coupled
applications. The AD8138 was specifically designed for ADC
driver applications. Superior SNR performance is maintained up
to analog frequencies of 30 MHz. The AD8138 op amp provides
single-ended-to-differential conversion, providing for a low cost
option to transformer coupling for ac applications as well.
The circuit in Figure 26 was breadboarded and the measured
performance is shown in Figures 27 and 28. The figures shown
are for 5 V supplies at the AD8138—performance dropped by
about 1 dB–2 dB with a single +5 V supply at the AD8138.
Figure 27 shows SNR and SINAD for a –1 dBFS analog input
frequency varied from 2 MHz to 40 MHz with an encode rate of
105 MSPS. The measurements are for nominal conditions at
room temperature. Figure 28 shows the second and third har-
monic distortion performance under the same conditions.
The dc common-mode voltage for the AD8138 outputs can be
adjusted via input V
the AD9432 inputs require.
Table I. Output Coding (VREF = +2.5 V) (Two’s Complement)
VIN
25
50
500
500
AIN–AIN (V)
1.000
•
•
0
–0.00049
•
•
–1.000
OCM
to provide the 3 V common-mode voltage
V
500
OCM
AD8138
10pF
10pF
500
1111 1111 1111
1000 0000 0000
Digital Output
0111 1111 1111
•
•
0000 0000 0000
•
•
50
50
22pF
3k
5V
2k
AIN
AIN
AD9432
0.1 F
EVALUATION BOARD
The AD9432 evaluation board offers an easy way to test the
AD9432. It requires an analog signal, encode clock, and power
supplies as inputs. The clock is buffered on the board to provide
the clocks for an on-board DAC and latches. The digital outputs
and output clock are available at a standard 37-pin connector P7.
Power Connector
Power is supplied to the board via two detachable 4-pin power
strips P30, P40.
P40
P1
P2
P3
P4
P30
P5
P6
P7
P8
VCC2 5 V/165 mA
GND
VCC
GND
VD
GND
–100
–70
–80
–90
66
65
64
63
62
61
60
0
0
5 V/200 mA
3.3 V /105 mA Latch, ADC Digital Output Supply
H2
20
20
SINAD
SNR
H3
AIN MHz
DAC Supply
ADC Analog Supply
No Connect
No Connect
AIN MHz
40
40
60
60