Datasheet

ManualsBrandsANALOG DEVICES ManualsLinear ICsLinear IC - Op-amp Voltage feedback LFCSP 24 WQ (4x4)

Dual-Channel Ultralow Noise Amplifier with

Selectable Gain and Input Impedance

Data Sheet

AD8432

Rev. C

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FEATURES

Low noise

Input voltage noise: 0.85 nV/√Hz

Current noise: 2.0 pA/√Hz

High speed

200 MHz bandwidth (G = 12.04 dB)

295 V/µs slew rate

Selectable gain

G = 12.04 dB (×4)

G = 18.06 dB (×8)

G = 21.58 dB (×12)

G = 24.08 dB (×16)

Active input impedance matching

Integrated input clamp diodes

Single-ended input, differential output

Supply range: 4.5 V to 5.5 V

Low power: 60 mW/channel

APPLICATIONS

CW Doppler ultrasound front ends

Low noise preamplification

Predriver for I/Q demodulators and phase shifters

Wideband analog-to-digital drivers

FUNCTIONAL BLOCK DIAGRAM

BIAS

ENB COMM

INH1

IND1

INL1

INH2

IND2

INL2

VPS1 VPS2

OPH1

OPL1

GMH1

GOH1

GOL1

GML1

OPH2

OPL2

GMH2

GOH2

GOL2

GML2

LNA1

LNA2

AD8432

08341-001

Figure 1.

GENERAL DESCRIPTION

The AD8432 is a dual-channel, low power, ultralow noise

amplifier with selectable gain and active impedance matching.

Each channel has a single-ended input, differential output, and

integrated input clamps. By pin strapping the gain setting pins, four

accurate gains of G = 12.04 dB, 18.06 dB, 21.58 dB, and 24.08 dB

(×4, ×8, ×12, and ×16, respectively) are possible. A bandwidth of

200 MHz at G = 12.04 dB makes this amplifier well suited for many

high speed applications.

The exceptional noise performance of the AD8432 is made

possible by the active impedance matching. Using a feedback

network, the input impedance of the amplifiers can be adjusted

to match the signal source impedance without compromising

the noise performance. Impedance matching and low noise in

the AD8432 allow designers to create wider dynamic range

systems that are able to detect even very low level signals.

The AD8432 achieves 0.85 nV/√Hz input-referred voltage noise for

a gain of 12.04 dB. The AD8432’s ultralow noise, low distortion,

gain accuracy, and channel-to-channel matching are ideal for

high performance ultrasound systems and for processing I/Q

demodulator signals.

The AD8432 operates on a single supply of 5 V at 24 mA. It is

available in a 4 mm × 4 mm, 24-lead LFSCP. The LFCSP features

an exposed paddle that provides a low thermal resistance path to

the PCB, which enables more efficient heat transfer and increases

reliability. The operating temperature range is −40°C to +85°C.

Summary of content (32 pages)

PAGE 1
FEATURES Low noise Input voltage noise: 0.85 nV/√Hz Current noise: 2.0 pA/√Hz High speed 200 MHz bandwidth (G = 12.04 dB) 295 V/µs slew rate Selectable gain G = 12.04 dB (×4) G = 18.06 dB (×8) G = 21.58 dB (×12) G = 24.08 dB (×16) Active input impedance matching Integrated input clamp diodes Single-ended input, differential output Supply range: 4.5 V to 5.
PAGE 2
AD8432 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation ...................................................................... 18 Applications ....................................................................................... 1 Low Noise Amplifier (LNA) ..................................................... 18 Functional Block Diagram ...........................................................
PAGE 3
Data Sheet AD8432 SPECIFICATIONS VS = 5 V, TA = 25°C, RS = RIN = 50 Ω, RFB =150 Ω, CSH = 47 pF, RSH = 15 Ω, RL = 500 Ω (per SE output), CL = 5 pF (per SE output), G = 12.04 dB (single-ended input to differential output), f = 1 MHz, unless otherwise specified. Table 1.
PAGE 4
AD8432 Parameter Two-Tone IMD3 Distortion 10 MHz 1 MHz Input 1dB Compression Point Output Third-Order Intercept 1 MHz 10 MHz 1 MHz 10 MHz Crosstalk DC PERFORMANCE Input Offset Voltage Input Offset Voltage Drift INPUT CHARACTERISTICS Input Voltage Range Input Resistance Input Capacitance Input Common-Mode Voltage OUTPUT CHARACTERISTCS Output Common-Mode Voltage Output Offset Voltage Output Voltage Swing Output Resistance Output Resistance in Shutdown Mode Output Short-Circuit Current Enable Response Time PO
PAGE 5
Data Sheet AD8432 ABSOLUTE MAXIMUM RATINGS MAXIMUM POWER DISSIPATION Table 2. Parameter Voltage Supply Voltage Input Voltage Power Dissipation Temperature Operating Temperature Storage Temperature Package Glass Transition Temperature (TG) Lead Temperature (Soldering, 60 sec) Rating 5.5 V 0 V to VPS 120 mW –40°C to +85°C –65°C to +150°C 150°C 300°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device.
PAGE 6
AD8432 Data Sheet INH1 1 18 GOL1 INL1 2 17 OPL1 AD8432 IND1 3 16 COM1 TOP VIEW (Not to Scale) COMM 4 15 COM2 GML2 12 GMH2 11 9 OPH2 GOH2 10 IND2 7 14 OPL2 13 GOL2 VPS2 8 INL2 5 INH2 6 NOTES 1. EXPOSED PAD MUST BE CONNECTED TO GROUND. Figure 2. Pin Configuration Table 4. Pin Function Descriptions Pin No.
PAGE 7
Data Sheet AD8432 TYPICAL PERFORMANCE CHARACTERISTICS VS = 5 V, TA = 25°C, RS = RIN = 50 Ω, RFB =150 Ω, CSH = 47 pF, RSH = 15 Ω, RL =500 Ω (per SE output), CL = 5 pF (per SE output), G = 12.04 dB (single-ended input to differential output), f = 1 MHz, unless otherwise specified. 24 30 24 18 18 12 6 6 GAIN (dB) GAIN (dB) 12 0 –6 0 –6 –12 –12 –24 = 24.08dB = 21.58dB = 18.06dB = 12.
PAGE 8
AD8432 Data Sheet 30 240 24 230 18 INPUT IMPEDANCE (Ω) 220 6 0 –6 210 200 190 180 –12 –18 –24 = 24.08dB = 21.58dB = 18.06dB = 12.04dB 1 170 10 100 160 0.1 08341-011 G G G G 1k FREQUENCY (MHz) Figure 9. Differential Gain vs. Frequency, VOUT = 2 V p-p, RIN = 50 Ω G G G G = 24.08dB = 21.58dB = 18.06dB = 12.04dB 1 10 FREQUENCY (MHz) 08341-031 GAIN (dB) 12 Figure 12. Input Impedance RIN vs.
PAGE 9
Data Sheet AD8432 1.00 0.1 0.1 1 10 100 FREQUENCY (MHz) 0.90 0.85 0.80 0.75 0.70 –50 OUTPUT VOLTAGE NOISE (nV/√Hz) 1 RS THERMAL NOISE ALONE 10 100 1k 50 70 90 90 G = 24.08dB 14 12 G = 21.58dB 10 8 G = 18.06dB 6 4 G = 12.04dB 2 –50 08341-036 –30 –10 10 30 50 70 TEMPERATURE (°C) Figure 16. Input-Referred Voltage Noise vs. Source Resistance (RS) Figure 19. Output Voltage Noise vs. Temperature 1.6 100 f = 1MHz INPUT VOLTAGE NOISE (nV/√Hz) 1.4 G = 24.08dB G = 21.
PAGE 10
AD8432 Data Sheet –40 20 G G G G 16 HD2, 10MHz HD2, 1MHz HD3, 10MHz HD3, 1MHz MEASUREMENT LIMIT –50 –60 14 DISTORTION (dBc) OUTPUT VOLTAGE NOISE (nV/√Hz) 18 = 24.08dB = 21.58dB = 18.06dB = 12.04dB 12 10 8 6 –70 –80 –90 4 –100 0.1 1 10 100 FREQUENCY (MHz) Figure 21. Output Voltage Noise vs. Frequency 0 –110 08341-222 0 0.01 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 VOUT (V p-p) Figure 24. Harmonic Distortion vs. Differential Output Voltage, G = 12.
PAGE 11
Data Sheet AD8432 –50 –50 HD2, HD2, HD3, HD3, 2V p-p 1V p-p 2V p-p 1V p-p HD2, HD2, HD3, HD3, –55 DISTORTION (dBc) –70 –80 –90 10MHz, 10MHz, 10MHz, 10MHz, 2V p-p 1V p-p 2V p-p 1V p-p –60 –65 –70 –100 0 5 10 15 20 25 CL (pF) –75 08341-269 –110 0 200 400 600 800 1000 1200 1400 1600 1800 2000 RL (Ω) Figure 27. Harmonic Distortion at 1 MHz vs. Capacitive Load (CL), G = 12.04 dB 08341-229 DISTORTION (dBc) –60 1MHz, 1MHz, 1MHz, 1MHz, Figure 30.
PAGE 12
AD8432 Data Sheet –60 –70 HD2, HD2, HD3, HD3, –65 1MHz, 1MHz, 1MHz, 1MHz, 1V p-p 2V p-p 2V p-p 1V p-p –75 –80 –85 CROSSTALK (dB) DISTORTION (dBc) –70 –75 –80 –90 –95 –100 –105 –85 –110 –90 0 200 400 600 800 1000 1200 1400 1600 1800 2000 RL (Ω) –120 0.1 1 10 100 FREQUENCY (MHz) Figure 36. Channel Crosstalk vs. Frequency Figure 33. Harmonic Distortion at 1 MHz vs. Resistive Load (RL), G = 24.
PAGE 13
Data Sheet AD8432 CL = 5pF CL = 10pF CL = 15pF CL = 20pF CL = 30pF G = 24.08dB 50mV/DIV 200mV/DIV G = 21.58dB G = 18.06dB 10ns/DIV 08341-017 08341-014 G = 12.04dB 10ns/DIV Figure 39. Small Signal Transient Response vs. Gain, VIN = 100 mV p-p Figure 42. Small Signal Transient Response vs. Capacitive Load (CL), G = 24.08 dB 10ns/DIV 08341-018 08341-015 50mV/DIV 100mV/DIV RL = 499Ω RL = 249Ω RL = 24.9Ω RL = 15Ω RL = 10Ω 10ns/DIV Figure 40. Small Signal Transient Response, G = 12.
PAGE 14
AD8432 CL = 30pF CL = 20pF CL = 15pF CL = 10pF CL = 5pF G = 18.06dB 08341-020 50mV/DIV 500mV/DIV G = 21.58dB G = 24.08dB 10ns/DIV 08341-023 G = 12.04dB Data Sheet 10ns/DIV Figure 45. Small Signal Transient Response vs. Gain, VOUT = 200 mV p-p Figure 48. Large Signal Transient Response vs. Capacitive Load (CL), G = 24.08 dB RL = 499Ω RL = 249Ω RL = 24.9Ω RL = 15Ω G = 24.08dB 500mV/DIV 500mV/DIV G = 21.58dB G = 18.06dB 10ns/DIV 08341-024 08341-021 G = 12.04dB 10ns/DIV Figure 46.
PAGE 15
Data Sheet G = 12.04dB AD8432 140 G = 18.06dB G = 21.58dB G = 24.08dB 500mV/DIV SUPPLY CURRENT (µA) 120 100 80 60 40 10ns/DIV 0 –60 –40 –20 0 20 40 60 80 100 TEMPERATURE (°C) Figure 51. Large Signal Transient Response vs. Gain, VOUT = 2 V p-p Figure 54. Supply Current vs. Temperature in Disable Mode –20 ENB 5V/DIV –30 1 PSRR (dB) –40 –50 –60 OUTPUT 50mV/DIV –70 2 –80 0.1 1 10 100 FREQUENCY (MHz) TIME (100µs/DIV) 08341-252 –100 0.01 08341-248 G = 24.
PAGE 16
AD8432 Data Sheet TEST CIRCUITS 0.1µF RFB 1MHz (10MHz LPF) INH OPH AD8432 0.1µF INL 0.1µF 50Ω 1.7MHz (10.7MHz) G=1 RL 50Ω LP 56.2Ω AD8130 LNA1 CSH HP 475Ω RL 08341-046 0.1µF OPL INH INL RSH 1MHz (10MHz) SPECTRUM ANALZYER DUAL FILTER 0.1µF Figure 57. Harmonic Distortion vs. Resistive Load (RL) Measurements 0.1µF RFB DUAL FILTER SPECTRUM ANALYZER LP 50Ω 1MHz (10MHz LPF) RSH OPL INL OPH 0.1µF CL 26.1Ω 487Ω HP 1:1 IN LNA1 1.7MHz (10.7MHz) CL 26.1Ω RL Figure 58.
PAGE 17
Data Sheet AD8432 5pF 0.1µF RFB 10MHz X MULTIPLIER 0.1µF INH OPL 0.1µF 499Ω DIFF PROBE OSCILLOSCOPE CH1 RSH Y INL CSH OPH AD8432 1MHz LNA1 0.1µF 499Ω 5pF 08341-050 0.1µF Figure 61. Overdrive Recovery Measurements 499Ω 50Ω 0.1µF OUT RSH 0.1µF INH OPL INL OPH CSH 0.1µF 5pF 499Ω AD8432 0.1µF LNA1 08341-051 NETWORK ANALYZER 5pF 0.1µF RFB Figure 62. Input Impedance vs. Frequency Measurements 0.1µF RFB NETWORK ANALYZER 0.1µF 0.1µF INH RSH INL CSH OPH 0.
PAGE 18
AD8432 Data Sheet THEORY OF OPERATION LOW NOISE AMPLIFIER (LNA) differential gain of G = 12.04 dB, the maximum input voltage allowed is 1.2 V p-p. The AD8432 is a dual-channel, ultralow noise amplifier with integrated pin-strappable, gain-setting resistors. The resistors can be externally connected to achieve differential gains of 12.04 dB, 18.06 dB, 21.58 dB, and 24.08 dB (×4, ×8, ×12, and ×16, respectively). A simplified schematic of an LNA is shown in Figure 65.
PAGE 19
Data Sheet AD8432 Table 5. Gain Setting Using a Pin-Strapping Technique and −3 dB Bandwidth for Each Gain Configuration Differential Gain (dB) 12.04 Single Gain (dB) 6.02 −3 dB BW (MHz) 200 RG1 (Ω) 12 RG2 (Ω) 12 18.06 12.04 90 12 12 21.58 15.56 50 12 12 24.08 18.
PAGE 20
AD8432 Data Sheet The user must determine the level of matching accuracy desired and adjust RFB accordingly. The RFB and CFB network presents a load to OPL that OPH does not see. The user can add an identical load on OPH to improve slightly the distortion caused by this imbalance. 8 7 NOISE FIGURE (dB) 6 RESISTIVE TERMINATION (RS = RIN) 5 There is a feedback capacitor (CFB) in series with RFB (see Figure 65) because the dc levels of the positive output and the positive input are different.
PAGE 21
Data Sheet AD8432 APPLICATIONS INFORMATION The unterminated input impedance of the AD8432 is 6.2 kΩ. Any input resistance between 50 Ω and 6.2 kΩ can be synthesized using active impedance matching. The AD8432 LNA provides precision gain and ultralow noise performance with minimal external components. Because it is a high performance part, care must be taken to ensure that it is configured optimally to attain the best performance and dynamic range for the system. At the lowest gain (12.
PAGE 22
AD8432 Data Sheet Table 7. External Component Selections for Common Input Impedance RIN (Ω) 50 75 100 200 1k Unterminated, RS = 50 Ω Unterminated, RS = 0 Ω Gain (dB) 12 18 21 24 12 18 21 24 12 18 21 24 12 18 21 24 12 18 21 24 12 18 21 24 12 18 21 24 RFB1, 2 (Ω) 150 249 357 453 226 383 536 681 301 511 715 909 619 1.02 k 1.43 k 1.87 k 3.57 k 5.9 k 8.25 k 10.
PAGE 23
Data Sheet AD8432 I/Q DEMODULATION FRONT END 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 AD8432 low noise amplifiers can be used to drive the differential RF inputs of the dual AD8333 or the quad AD8339 I/Q demodulators. The primary application for the AD8339 is phased array beamforming in medical ultrasound, specifically in CW Doppler processing.
PAGE 24
AD8432 Data Sheet DIFFERENTIAL-TO-SINGLE-ENDED CONVERSION A transformer or balun can also be used to convert the differential output of the AD8432 to a single-ended output. Transformers have lower distortion; however, care must be taken to properly match the impedance of the transformer. The test circuit for distortion measurements in Figure 58 uses an ADTT1-1 transformer to perform differential-to-single-ended conversion.
PAGE 25
Data Sheet AD8432 EVALUATION BOARD Figure 73 is a photo of the AD8432 evaluation board. Completely assembled and pretested, the board provides convenient and fast verification of system design and to assess the performance of the AD8432 under user-specific operating conditions. The remainder of this section describes the operation and construction of the board. Figure 74 through Figure 79 are various artwork and assembly views and Figure 80 shows the schematic diagram.
PAGE 26
Data Sheet 08341-077 08341-074 AD8432 Figure 74. Evaluation Board Assembly 08341-075 08341-078 Figure 77. AD8432-EVALZ Power Plane Copper Figure 78. AD8432-EVALZ Ground Plane Copper 08341-076 Figure 75. AD8432 Primary Side Copper Figure 76. AD8432-EVALZ Secondary Side Copper Rev.
PAGE 27
Data Sheet AD8432 OSCILLOSCOPE SIGNAL GENERATOR 33250A OR EQUIV POWER SUPPLY 08341-079 DIFFERENTIAL PROBE P6247 OR EQUIV Figure 79. Bench Setup for Testing the AD8432-EVALZ Rev.
PAGE 28
AD8432 Data Sheet SCHEMATIC CFB1 0.1µF RFB1 357Ω GND +5V C11 10µF 10V VPOS OPH1 L3 120nH FB +VCH1 VPOS VPOS G0H1 GMH1 GML1 OFF IN1 24 ENB C5 0.1µF INH1 L1 120nH FB PR1 C3 0.1 µF TPENB ENB ON 1 RSH1 15Ω CSH1 47pF R1 0Ω DNI R2 0Ω R3 0Ω 23 22 21 VPS1 OPH1 GOH1 GMH1 20 19 PIN 1 IDENTIFIER INH1 PRB3 GML1 G0L1 INL1 2 C1 0.1µF INL1 OPL1 PIN 0 EXPOSED PADDLE CONNECTED TO GROUND IND1 COMM 4 COM1 COMM COM2 5 PR2 C6 0.
PAGE 29
Data Sheet AD8432 OUTLINE DIMENSIONS 0.30 0.25 0.18 0.50 BSC PIN 1 INDICATOR 24 19 18 1 EXPOSED PAD TOP VIEW 0.80 0.75 0.70 0.50 0.40 0.30 13 12 2.65 2.50 SQ 2.45 6 7 0.25 MIN BOTTOM VIEW 0.05 MAX 0.02 NOM FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. COPLANARITY 0.08 0.20 REF SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-220-WGGD. 04-12-2012-A PIN 1 INDICATOR 4.10 4.00 SQ 3.90 Figure 81.
PAGE 30
AD8432 Data Sheet NOTES Rev.
PAGE 31
Data Sheet AD8432 NOTES Rev.