ADA4937-2YCPZ-R7 Analog Devices Inc, ADA4937-2YCPZ-R7 Datasheet - Page 25

• Manufacturer Part Number: ADA4937-2YCPZ-R7
• Description: IC,Differential Amplifier,DUAL,BIPOLAR,LLCC,24PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: ADC Driverr

Specifications of ADA4937-2YCPZ-R7

• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 24-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ADA4937-2YCPZ-R7TR

3.3 V OPERATION
The ADA4937-x provides excellent performance in 3.3 V
single-supply applications. Significant power savings can be
realized when the ADA4937-x is used in combination with
a low voltage ADC.
The circuit in Figure 67 is an example of the ADA4937-1
driving an AD9230, 12-bit, 250 MSPS ADC that is specified
to operate with a single 1.8 V supply. The performance of the
ADC is optimized when it is driven differentially, making the
best use of the signal swing available within the 1.8 V supply.
The ADA4937-x performs the single-ended-to-differential
conversion, common-mode level-shifting, and buffering of
the driving signal.
The ADA4937-x is configured with a single 3.3 V supply and a
gain of 2 V/V for a single-ended input to differential output. The
50Ω
V
IN
59Ω
200Ω
226Ω
V
OCM
Figure 67. Driving an AD9230, 12-Bit, 250 MSPS ADC
ADA4937-1
+
453Ω
453Ω
3.3V
Rev. C | Page 25 of 28
33Ω
33Ω
10pF
56nH
56nH
59 Ω termination resistor, in parallel with the single-ended input
impedance of 306 Ω, provides a 50 Ω termination for the source.
The additional 26 Ω (226 Ω total) at the inverting input balances
the parallel impedance of the 50 Ω source and the termination
resistor that drives the noninverting input. The signal generator
has a symmetric, ground-referenced bipolar output. The V
is connected to the CML output of the AD9230, and sets the out-
put common mode of the ADA4937-x at 1.4 V. One third of the
output common-mode voltage of the amplifier is fed back to the
summing nodes, biasing −IN and +IN at ~0.5 V. For a common-
mode voltage of 1.4 V, each ADA4937-x output swings between
1.09 V and 1.71 V, providing a 1.25 V p-p differential output.
A third-order, 125 MHz, low-pass filter between the ADA4937-x
and the AD9230 reduces the noise bandwidth of the amplifier
and isolates the driver outputs from the ADC inputs.
30pF
VIN–
VIN+
AGND
AVDD
AD9230
1.8V
DRVDD
CML
ADA4937-1/ADA4937-2
D11 TO
D0
OCM
pin