AD8432-EVALZ Analog Devices Inc, AD8432-EVALZ Datasheet - Page 23

BOARD EVALUATION FOR AD8432

AD8432-EVALZ

Manufacturer Part Number
AD8432-EVALZ
Description
BOARD EVALUATION FOR AD8432
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD8432-EVALZ

Channels Per Ic
2 - Dual
Amplifier Type
Voltage Feedback
Output Type
Differential
Slew Rate
295 V/µs
-3db Bandwidth
200MHz
Current - Output / Channel
77mA
Operating Temperature
-40°C ~ 85°C
Current - Supply (main Ic)
24mA
Voltage - Supply, Single/dual (±)
4.5 V ~ 5.5 V
Board Type
Fully Populated
Utilized Ic / Part
AD8432
Silicon Manufacturer
Analog Devices
Application Sub Type
Noise Amplifier
Kit Application Type
Amplifier
Silicon Core Number
AD8432
Kit Contents
Board
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
I/Q DEMODULATION FRONT END
The AD8432 low noise amplifiers can be used to drive the
differential RF inputs of the dual
I/Q demodulators. The primary application for the AD8339 is
phased array beamforming in medical ultrasound, specifically
in CW Doppler processing. Other applications include phased
array radar and smart antennas for mobile communications.
Because of its low output noise and low distortion, the AD8432
ensures minimal degradation in dynamic range while amplifying
the RF input signal. At the lowest gain of 12.04 dB, the AD8432
contributes only 3.4 nV/√Hz output voltage noise.
Figure 70 shows a simplified block diagram of one channel of
the AD8432 driving the AD8339. The AD8432 outputs can be
connected directly to the AD8339 RF inputs through 20 Ω
resistors. A differential clock signal, 4LO, which is applied to the
0.1µF
IN1
IN2
0.1µF
Figure 70. Block Diagram of AD8432 and AD8339 Application for
R
15Ω
R
15Ω
C
47
C
47
SH2
SH1
SH2
AD8432
SH1
pF
pF
0.1µF
0.1µF
0.1µF
0.1µF
20Ω
20Ω
ENB
INH1
IND1
INL1
INH2
IND2
INL2
Ultrasound Beamforming
0.1µF
Figure 71. Schematic of the AD8432 (G = 12.04 dB) and AD8339 Application for Ultrasound Beamforming
VPS1
RF1P
RF1N
0.1µF
G = 12dB
AD8339
BIAS
AD8333
VPS2
LNA1
LNA2
4LO
Q1OP
I1OP
GMH1
GMH2
GOH1
GML1
GOH2
GML2
GOL1
GOL2
COMM
AD8432
0.1µF
or the quad
OPH1
OPH2
OPL1
OPL2
2.2nF
2.2nF
AD8021
787Ω
787Ω
AD8021
AD8339
Q1
20Ω
20Ω
20Ω
20Ω
I1
Rev. B | Page 23 of 28
RF1P
RF1N
RF2P
RF2N
0.1µF
VPOS
+5V
0.1µF
4LOP and 4LON pins of the AD8339, has a frequency 4× that of
the RF inputs. The AD8339 downconverts the RF signals,
generates quadrature, and phase-shifts the resultant I and Q
signals.
The I and Q outputs of the AD8339 are current outputs. A
transimpedance amplifier, such as the AD8021, processes the
outputs and performs several functions, including the following:
In beamforming applications, the I and Q outputs of a number
of receiver channels are summed, which increases the system
dynamic range by 10 log
channels being summed. The external RC feedback network of
the AD8021 is a 100 kHz low-pass filter as shown in Figure 70.
See the AD8333 and AD8339 datasheets for more details on
implementing I/Q demodulators.
Evaluation boards are available for the AD8432 and the AD8339
to facilitate system level design and testing. A detailed reference
schematic of the setup is shown in Figure 71. The AD8432 is
shown in this configuration with a gain of 12.04 dB, with
unterminated inputs. If active termination is preferred, use an
R
section. The IND1/IND2 clamping diodes can be connected to
IN1/IN2 to protect the LNA input from being overdriven.
G = –1.3dB
FB
and C
VNEG
−5V
AD8339
Current-to-voltage conversion
Summation amplifier for multiple channels
Active low-pass filter
FB
4LOP
network as discussed in the Theory of Operation
4LO
Q1OP
I1OP
Q2OP
I2OP
f
C
= 100kHz
10
LPF
AD8021
(N), where N is the number of
AD8021
0.1µF
0.1µF
2 7
3 4
2 7
3 4
−5V
−5V
+5V
+
+5V
+
0.1µF
0.1µF
6
6
2.2nF
787Ω
787Ω
2.2nF
0Ω
0Ω
AD8432
I1 + I2
Q1 + Q2

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