AD9200LQFP-EVAL AD [Analog Devices], AD9200LQFP-EVAL Datasheet - Page 15

• Manufacturer Part Number: AD9200LQFP-EVAL
• Description: Complete 10-Bit, 20 MSPS, 80 mW CMOS A/D Converter
• Manufacturer: AD [Analog Devices]

DIFFERENTIAL INPUT OPERATION
The AD9200 will accept differential input signals. This function
may be used by shorting REFTS and REFBS and driving them
as one leg of the differential signal (the top leg is driven into
AIN). In the configuration below, the AD9200 is accepting a
1 V p-p signal. See Figure 29.
AD876 MODE OF OPERATION
The AD9200 may be dropped into the AD876 socket. This will
allow AD876 users to take advantage of the reduced power
consumption realized when running the AD9200 on a 3.0 V
analog supply.
Figure 30 shows the pin functions of the AD876 and AD9200.
The grounded REFSENSE pin and floating MODE pin effec-
tively put the AD9200 in the external reference mode. The
external reference input for the AD876 will now be placed on
the reference pins of the AD9200.
The clamp controls will be grounded by the AD876 socket. The
AD9200 has a 3 clock cycle delay compared to a 3.5 cycle delay
of the AD876.
CLOCK INPUT
The AD9200 clock input is buffered internally with an inverter
powered from the AVDD pin. This feature allows the AD9200
to accommodate either +5 V or +3.3 V CMOS logic input sig-
nal swings with the input threshold for the CLK pin nominally
at AVDD/2.
REV. E
2V
1V
1.0 F
4V
2V
4V
2V
Figure 29. Differential Input
0.1 F
0.1 F
Figure 30. AD876 Mode
AVDD/2
10 F
AVDD/2
AVDD
0.1 F
0.1 F
REFTS
REFBS
VREF
AIN
REFSENSE
MODE
NC
AD9200
AIN
REFTS
REFTF
REFBF
REFBS
REFSENSE
CLAMP
CLAMPIN
MODE
OTR
REFBF
REFTF
AD9200
VREF
0.1 F
0.1 F
10 F
0.1 F
0.1 F
–15–
The pipelined architecture of the AD9200 operates on both
rising and falling edges of the input clock. To minimize duty
cycle variations the recommended logic family to drive the clock
input is high speed or advanced CMOS (HC/HCT, AC/ACT)
logic. CMOS logic provides both symmetrical voltage threshold
levels and sufficient rise and fall times to support 20 MSPS
operation. The AD9200 is designed to support a conversion rate
of 20 MSPS; running the part at slightly faster clock rates may
be possible, although at reduced performance levels. Conversely,
some slight performance improvements might be realized by
clocking the AD9200 at slower clock rates.
The power dissipated by the output buffers is largely propor-
tional to the clock frequency; running at reduced clock rates
provides a reduction in power consumption.
DIGITAL INPUTS AND OUTPUTS
Each of the AD9200 digital control inputs, THREE-STATE
and STBY are reference to analog ground. The clock is also
referenced to analog ground.
The format of the digital output is straight binary (see Figure
32). A low power mode feature is provided such that for STBY
= HIGH and the clock disabled, the static power of the AD9200
will drop below 5 mW.
THREE-
(D0–D9)
STATE
DATA
ANALOG
OUTPUT
CLOCK
INPUT
INPUT
DATA
Figure 33. Three-State Timing Diagram
OTR
S1
Figure 32. Output Data Format
t
Figure 31. Timing Diagram
CH
–FS
t
C
–FS+1LSB
t
CL
t
DHZ
S2
IMPEDANCE
HIGH
S3
+FS–1LSB
t
DEN
+FS
AD9200
S4
DATA 1
25ns