ADA4937-1YCPZ-R7 Analog Devices Inc, ADA4937-1YCPZ-R7 Datasheet - Page 23

• Manufacturer Part Number: ADA4937-1YCPZ-R7
• Description: IC ADC DRIVER DIFF 16-LFCSP
• Manufacturer: Analog Devices Inc
• Type: ADC Driverr

Specifications of ADA4937-1YCPZ-R7

• Design Resources: Driving AD9233/46/54 ADCs in AC-Coupled Baseband Appls (CN0051)
• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 16-LFCSP
• No. Of Amplifiers: 1
• Input Offset Voltage: 2.5mV
• Bandwidth: 1.9GHz
• Slew Rate: 6000V/µs
• Supply Voltage Range: 3V To 5.25V
• Supply Current: 39.5mA
• Amplifier Case Style: LFCSP
• No. Of Pins: 16
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ADA4937-1YCPZ-R7TR

HIGH PERFORMANCE ADC DRIVING
The ADA4937-x is ideally suited for broadband IF applications.
The circuit in Figure 64 shows a front-end connection for an
ADA4937-1 driving an AD9445, 14-bit, 105 MSPS ADC. The
AD9445 achieves its optimum performance when driven dif-
ferentially. The ADA4937-x eliminates the need for a transformer
to drive the ADC and performs a single-ended-to-differential
conversion and buffering of the driving signal.
The ADA4937-x is configured with a single 5 V supply and unity
gain for a single-ended input to differential output. The 61.9 Ω
termination resistor, in parallel with the single-ended input imped-
ance of 267 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
driving the noninverting input.
SIGNAL
GENERATOR
50Ω
61.9Ω
200Ω
226Ω
V
Figure 64. Driving an AD9445, 14-Bit, 105 MSPS ADC
OCM
ADA4937-1
200Ω
+
200Ω
5V
Rev. C | Page 23 of 28
0.1µF
0.1µF
24.3Ω
24.3Ω
The signal generator has a symmetric, ground-referenced bipolar
output. The V
allowing the internal divider to set the output common-mode
voltage at midsupply; one half of the common-mode voltage is
fed back to the summing nodes, biasing −IN and +IN at 1.25 V. For
a common-mode voltage of 2.5 V, each ADA4937-x output swings
between 2.0 V and 3.0 V, providing a 2 V p-p differential output.
The output of the amplifier is ac-coupled to the ADC through a
second-order, low-pass filter with a cutoff frequency of 100 MHz.
This reduces the noise bandwidth of the amplifier and isolates
the driver outputs from the ADC inputs.
The AD9445 is configured for a 2 V p-p full-scale input by
connecting the SENSE pin to AGND, as shown in Figure 64.
30nH
30nH
VIN–
47pF
VIN+
AVDD2
OCM
5V (A)
BUFFER T/H
CLOCK/
TIMING
pin of the ADA4937-x remains unconnected
3.3V (A)
AVDD1
AGND
3.3V (D)
DRVDD
ADA4937-1/ADA4937-2
REF
ADC
SENSE
AD9445
14