ADA4937-1 Analog Devices, ADA4937-1 Datasheet - Page 24

• Manufacturer Part Number: ADA4937-1
• Description: Ultra-Low Distortion Differential ADC Driver
• Manufacturer: Analog Devices

ADA4937-1
3.3 V OPERATION
The ADA4937-1 provides excellent performance in 3.3 V
single-supply applications. Significant power savings can be
realized when the ADA4937-1 is used in combination with a
low voltage ADC.
The circuit in Figure 54 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 ADA4937-1 performs the single-ended-to-differential
conversion, common-mode level-shifting, and buffering of the
driving signal.
50Ω
V
IN
59Ω
Figure 54. ADA4937-1 Driving an AD9230, a 12-Bit, 250 MSPS ADC
200Ω
226Ω
V
OCM
ADA4937-1
+
453Ω
453Ω
3.3V
Rev. 0 | Page 24 of 28
33Ω
33Ω
10pF
The ADA4937-1 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
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 termination
resistor driving the noninverting input.
The signal generator has a symmetric, ground-referenced bipolar
output. The V
AD9230, and sets the output common mode of the ADA4937-1 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 ADA4937-1
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 ADA4937-1
and the
and isolates the driver outputs from the ADC inputs.
56nH
56nH
30pF
AD9230
VIN–
VIN+
OCM
AVDD
AGND
reduces the noise bandwidth of the amplifier
pin is connected to the CML output of the
AD9230
1.8V
DRVDD
CML
D11 TO
D0