AD8260ACPZ-WP [ADI]
High Current Driver Amplifier and Digital VGA/Preamplifier with 3 dB Steps; 大电流驱动器放大器和数字VGA /前置放大器为3 dB步
| 型号： | AD8260ACPZ-WP |
| 厂家： | 
ADI |
| 描述： | High Current Driver Amplifier and Digital VGA/Preamplifier with 3 dB Steps |
| 文件： | 总32页 (文件大小：1034K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
High Current Driver Amplifier and
Digital VGA/Preamplifier with 3 dB Steps
AD8260
FEATURES
FUNCTIONAL BLOCK DIAGRAM
VOCM INPP INRP INRN INPN TXFB VNEG VNEG
High current driver
32
31
30
29
28
27
26
25
Differential input—direct drive from DAC
Preset gain: 1.5×
1.5kΩ 1kΩ
1kΩ 1.5kΩ
−3 dB bandwidth: 195 MHz
Large output drive: > 300 mA
VGA/preamplifier
Low noise
Voltage noise: 2.4 nV/√Hz
1
2
VMDO
TXEN
VMDI
24
23
22
21
20
TXOP
+
–
GM
×1
TXOP
VPOS
HIGH CURRENT DRIVER
AD8260
3
4
5
VMID
Current noise: 5 pA/√Hz
VNCM
VPOS
VPSR
VMDO
BIAS
−3 dB bandwidth: 230 MHz
Gain range: 30 dB in 3 dB steps
−6 dB to +24 dB (for preamplifier gain of 6 dB)
Single-ended preamplifier input and differential VGA
output
Supplies: 3.3 V to 10 V (with VMID enabled)
3.3 V to 5 V (with VMID disabled)
Power: 93 mW with 3.3 V supplies
Power-down for VGA, driver amplifier, and system
VPSB
VGA/PREAMPLIFIER
ATTENUATOR
19
6
7
8
ENBL
VGAP
VGAN
18
17
PRAI
GM STAGES
LOGIC
FDBK
9
10
11
12
13
14
15
16
VNGR VPSR GNS3 GNS2 GNS1 GNS0 PRAO VNGR
APPLICATIONS
Figure 1. Functional Block Diagram
Digital AGC systems
Tx/Rx signal processing
Power line transceivers
GENERAL DESCRIPTION
The AD8260 includes a high current driver, usable as a
transmitter, and a low noise digitally programmable variable
gain amplifier (DGA), useable as a receiver.
dynamic range, it is essential that the part be ac-coupled when
operating on a single supply.
The AD8260 preamplifier (PrA) is configured with external
resistors for gains greater than 6 dB and can be inverting or
noninverting. The DGA is characterized with a noninverting
preamplifier gain of 2×. The attenuator has a range of 30 dB and
the output amplifier has a gain of 8× (18.06 dB). The lowest
noninverting gain range is −6 dB to +24 dB and shifts up with
increased preamplifier gain. The gain is controlled via a parallel
port (Pin GNS0 to Pin GNS3) with 10 gain steps of 3 dB per
code. The preamplifier and DGA are disabled for any code that
is not assigned a gain step.
The receiver section consists of a single-ended input preampli-
fier, and linear-in-dB, differential-output DGA. The receiver has
a small signal –3 dB bandwidth of 230 MHz; the driver small
signal bandwidth is 195 MHz. The driver delivers 300 mA,
well suited for driving low impedance loads, even when
connected to a 3.3 V supply.
The AD8260 DGA is ideal for trim applications and has a gain
span of 30 dB, in 3 dB steps. Excellent bandwidth uniformity is
maintained across the entire frequency range. The low output-
referred noise of the DGA is advantageous in driving high
speed ADCs. The differential output facilitates the interface to
modern low voltage high speed ADCs.
The AD8260 can operate with single or dual supplies from 3.3 V
to 5 V. An internal buffer normally provides a split supply
reference for single-supply operation; an external reference
can also be used when the VMID buffer is shut down.
Single-supply and dual-supply operation makes the part versatile
and enables gain control of negative-going pulses, such as those
generated by photodiodes or photo-multiplier tubes, as well as
processing band-pass signals on a single supply. For maximum
The operating temperature range is −40°C to +105°C. The
AD8260 is available in a 5 mm × 5 mm, 32-lead LFCSP.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2008 Analog Devices, Inc. All rights reserved.
AD8260
TABLE OF CONTENTS
Features .............................................................................................. 1
VMID Buffer............................................................................... 22
Preamplifier................................................................................. 22
Preamplifier Noise...................................................................... 22
DGA............................................................................................. 23
Gain Control ............................................................................... 23
Output Stage................................................................................ 23
Attenuator.................................................................................... 23
Single-Supply Operation and AC Coupling ........................... 24
Power-Up/Power-Down Sequence .......................................... 24
Logic Interfaces........................................................................... 24
Applications Information.............................................................. 25
Evaluation Board ............................................................................ 26
Connecting the Evaluation Board............................................ 27
Outline Dimensions....................................................................... 32
Ordering Guide .......................................................................... 32
Applications....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 6
ESD Caution.................................................................................. 6
Pin Configuration and Function Descriptions............................. 7
Typical Performance Characteristics ............................................. 8
Test Circuits..................................................................................... 16
Theory of Operation ...................................................................... 20
Overview...................................................................................... 20
High Current Driver Amplifier ................................................ 21
Precautions to Be Observed During Half-Duplex
Operation..................................................................................... 22
REVISION HISTORY
5/08—Revision 0: Initial Version
Rev. 0 | Page 2 of 32
AD8260
SPECIFICATIONS
VS (supply voltage) = 3.3 V, TA = 25°C, preamplifier gain = 2× (RFB1 = RFB2 = 100 Ω), VVMDO = VS/2, f = 10 MHz, CL = 5 pF, RLOAD = 500 Ω,
DGA differential output. All dBm values are referenced to 50 Ω, gain code 1011, unless otherwise specified.
Table 1.
Parameter
Conditions
Min
Typ
Max Unit
DRIVER AMPLIFIER—GENERAL PARAMETERS
–3 dB Small Signal Bandwidth
VOUT = 10 mV p-p, RLOAD = 500 Ω
VOUT = 10 mV p-p, RLOAD = 50 Ω
VOUT = 10 mV p-p, RLOAD = 10 Ω
VOUT = 1 V p-p
195
120
85
MHz
MHz
MHz
MHz
MHz
MHz
V/μs
V/μs
V/μs
dB
–3 dB Large Signal Bandwidth
Slew Rate
195
190
180
730
725
620
3.52
9.5
VOUT = 2 V p-p
VOUT = 2 V p-p, RLOAD = 50 Ω
VOUT = 1 V p-p
VOUT = 2 V p-p
VOUT = 2 V p-p, RLOAD = 50 Ω
Nominal gain with internal gain setting resistors
f = 10 MHz
Gain
3.0
Input Voltage Noise
Noise Figure
nV/√Hz
RS = 100 Ω (differential, 2 × 50 Ω that convert
17.6
dB
differential DAC output currents to differential voltage)
Output-Referred Noise
Gain = 3.52 dB (1.5×), includes internal gain setting
resistors
14.3
nV/√Hz
Output Impedance
Output Current
DC to 10 MHz, VS = 3.3 V
≤1.7
Ω
RLOAD = 1 Ω, VIN
RLOAD ≥ 500 Ω
VS = +5 V
=
0.5 V
310
mA
V
Output Signal Range
VMDO 1.5
VMDO 2.3
V
4.7
V
VS = 5 V
Input Signal Range
Differential input signal
2
5
V p-p
mV
Output Offset Voltage
Gain = 3.52 dB (1.5×), max and min limits are 3σ
−20
+20
DRIVER AMPLIFIER—DYNAMIC PERFORMANCE
Harmonic Distortion
VOUT = 1 V p-p
f = 1 MHz
HD2
−84
−85
−83
−70
dBc
dBc
dBc
dBc
HD3
HD2
f = 10 MHz
HD3
Harmonic Distortion
VOUT = 2 V p-p
f = 1 MHz
HD2
−78
−76
−70
−58
13
dBc
dBc
dBc
dBc
dBm
dBc
HD3
HD2
f = 10 MHz
HD3
Input 1 dB Compression Point
Multitone Power Ratio (MTPR, In-Band)
RLOAD = 50 Ω, VOUT = 1.4 V p-p max, 10 tones, 2 MHz to
22 MHz with missing tone at 12 MHz (spacing 2 MHz)
−49
RLOAD = 50 Ω, VOUT = 1.4 V p-p max, 16 tones, 2 MHz to
38 MHz with missing tones at 10 MHz, 20 MHz, 30 MHz,
and 40 MHz (spacing 2 MHz)
−43
dBc
Two-Tone Intermodulation Distortion (IMD3)
Output Third-Order Intercept
VOUT = 1 V p-p, f1 = 10 MHz, f2 = 11 MHz
VOUT = 2 V p-p, f1 = 10 MHz, f2 = 11 MHz
VOUT = 1 V p-p, f1 = 45 MHz, f2 = 46 MHz
VOUT = 2 V p-p, f1 = 45 MHz, f2 = 46 MHz
VOUT = 1 V p-p, f = 10 MHz
−90
−71
−60
−48
43
dBc
dBc
dBc
dBc
dBm
dBm
dBm
dBm
dBc
VOUT = 2 V p-p, f = 10 MHz
40
VOUT = 1 V p-p, f = 45 MHz
28
VOUT = 2 V p-p, f = 45 MHz
28
Two-Tone Intermodulation Distortion (IMD3),
VOUT = 1 V p-p, f1 = 10 MHz, f2 = 11 MHz
−69
R
LOAD = 50 Ω
VOUT = 2 V p-p, f1 = 10 MHz, f2 = 11 MHz
VOUT = 1 V p-p, f1 = 45 MHz, f2 = 46 MHz
VOUT = 2 V p-p, f1 = 45 MHz, f2 = 46 MHz
−72
−51
−48
dBc
dBc
dBc
Rev. 0 | Page 3 of 32
AD8260
Parameter
Conditions
Min
Typ
33
Max Unit
dBm
Output Third-Order Intercept, RLOAD = 50 Ω
VOUT = 1 V p-p, f = 10 MHz
VOUT = 2 V p-p, f = 10 MHz
VOUT = 1 V p-p, f = 45 MHz
VOUT = 2 V p-p, f = 45 MHz
40
dBm
23
dBm
28
dBm
PREAMPLFIER AND VGA—GENERAL PARAMETERS
−3 dB Small Signal Bandwidth
VOUT = 10 mV p-p, gain code = 0110
VOUT = 1 V p-p, gain code = 0110
VOUT = 2 V p-p, gain code = 0110
VOUT = 1 V p-p, gain code = 0110
VOUT = 1.6 V p-p, gain code = 0110
f = 10 MHz (shorted input)
230
165
135
330
335
2.4
MHz
MHz
MHz
V/μs
V/μs
−3 dB Large Signal Bandwidth
Slew Rate
Input Voltage Noise
Noise Figure
nV/√Hz
f = 10 MHz (input open)
6.2
nV/√Hz
dB
Max gain (gain code = 1011), RS = 50 Ω, unterminated
10.2
15.5
Max gain (gain code = 1011), RS = 50 Ω,
shunt terminated with 50 Ω
dB
Output-Referred Noise
Max gain (gain code = 1011), gain = 24 dB (input short)
38
nV/√Hz
Max gain (gain code = 1011), gain = 24 dB (input open)
98.1
nV/√Hz
Min gain (gain code = 0001), gain = −6 dB
25
nV/√Hz
Output Impedance
DC to 10 MHz
≤3
Ω
V
Output Signal Range (per Pin)
RLOAD ≥ 500 Ω
VMDO 0.7
VMDO 1.4
3.6
VS = +5 V
V
VS = 5 V
V
Input Signal Range
Preamplifier input
VMDO 0.3
20
V
Output Offset Voltage
Max gain (gain code = 1011), gain = 24 dB, 3 σ limits
−50
+50
mV
PREAMPLIFIER AND VGA—DYNAMIC PERFORMANCE
Harmonic Distortion
Gain code = 0110, gain = 9 dB, VOUT = 1 V p-p
f = 1 MHz
HD2
−90
−87
−75
−58
dBc
dBc
dBc
dBc
HD3
HD2
f = 10 MHz
HD3
Harmonic Distortion
Gain code = 1011, gain = 24 dB, VOUT = 2 V p-p
f = 1 MHz
HD2
−94
−90
−61
−84
1.9
dBc
dBc
dBc
dBc
dBm
HD3
HD2
f = 10 MHz
HD3
Input 1 dB Compression Point
Min gain (gain code = 0001), gain = −6 dB
(preamplifier limited)
Max gain (gain code = 1011), gain = 24 dB
(VGA limited)
−9.2
−68
dBm
dBc
MTPR (In-Band)
VOUT = 1.4 V p-p-max, 10 tones, 2 MHz to 22 MHz with
missing tone at 12 MHz (spacing 2 MHz),
gain code = 1011, gain = 24 dB
VOUT = 1.4 V p-p-max, 16 tones, 2 MHz to 38 MHz with
missing tones at 10 MHz, 20 MHz, 30 MHz, and 40 MHz
(spacing 2 MHz)
−61
dBc
Two-Tone Intermodulation Distortion (IMD3)
Output Third-Order Intercept
Gain code = 1011, gain = 24 dB
VOUT = 1 V p-p, f1 = 10 MHz, f2 = 11 MHz
VOUT = 2 V p-p, f1 = 10 MHz, f2 = 11 MHz
VOUT = 1 V p-p, f1 = 45 MHz, f2 = 46 MHz
VOUT = 2 V p-p, f1 = 45 MHz, f2 = 46 MHz
Gain code = 1011, gain = 24 dB
VOUT = 1 V p-p, f = 10 MHz
−92
−77
−50
−36
dBc
dBc
dBc
dBc
44
43
27
22
50
dBm
dBm
dBm
dBm
ns
VOUT = 2 V p-p, f = 10 MHz
VOUT = 1 V p-p, f = 45 MHz
VOUT = 2 V p-p, f = 45 MHz
Overload Recovery
Max gain (gain code = 1011), gain = 24 dB,
VIN = 50 mV p-p to 500 mV p-p
Group Delay Variation
1 MHz < f < 50 MHz, full gain range
2
ns
Rev. 0 | Page 4 of 32
AD8260
Parameter
Conditions
Min
Typ
Max Unit
ACCURACY
Absolute Gain Error
All gain codes, limits are 3σ
−0.5
−0.3
0.15
0.15
+0.5 dB
+0.3 dB
Gain Law Conformance (DNL)
GAIN CONTROL
Differential gain error code-to-code
Gain Step per Code
Gain Range
3.0
dB
dB
ns
Default = −6dB to +24 dB
30
50
Response Time
30 dB gain change (gain code stepped from 0001 to 1011)
LOGIC INTERFACES
High Level Input Voltage
Low Level Input Voltage
Logic Input Bias Current
1.4
0
VS
V
0.8
V
Logic high, VLOGIC = 3.3 V
Logic low
0.2
18
ꢀA
nA
POWER SUPPLY
Supply Voltage
Single supply
3.3
3.3
10
5
V
Dual supply
V
Quiescent Current
Full chip enabled (TXEN = 1, ENBL = 1, gain code = 0001)
TXEN = 0, ENBL = 1, gain code = 0001, driver off, DGA on
TXEN = 1, ENBL = 1, gain code = 0000, driver on, DGA off
Chip disabled (TXEN = 0, ENBL = 0, gain code = 0000)
VS = 5 V, no signal
28.3
19.1
10.8
35
mA
mA
mA
μA
mA
dB
34.2
−30
−48
93
PSRR
Max gain (gain code = 1011), gain = 24 dB, 1 MHz
Driver amplifier, 1 MHz
dB
Power Dissipation
No signal
mW
mW
No signal, VPOS − VNEG = 10 V
342
ENABLE TIMES
Chip Enable Time
Bias only, TXEN = 0, gain code = 0000, ENBL = 0 to 1
0.4
0.3
μs
μs
All at once, TXEN = 0 to 1, gain code = 0000 to 0001,
ENBL = 0 to 1
Preamplifier and DGA Enable Time
Driver Enable Time
ENBL = 1, TXEN = 0, gain code = 0000 to 0001
0.3
0.2
μs
μs
ENBL = 1, gain code = 0001, TXEN stepped from 0 to 1
DISABLE TIMES
Chip Disable Time
TXEN = 1 to 0, gain code = 0001 to 0000,
ENBL = 1 to 0, ISUPPLY = 100 ꢀA
20
50
μs
μs
All at once, TXEN = 1 to 0, gain code = 0001 to 0000,
ENBL = 1 to 0, ISUPPLY = 35 μA
Preamplifier and DGA Disable Time
Driver Disable Time
ENBL = 1, TXEN = 0, gain code = 0001 to 0000
ENBL = 1, gain code = 0000, TXEN = 1 to 0
0.4
2.2
μs
μs
Rev. 0 | Page 5 of 32
AD8260
ABSOLUTE MAXIMUM RATINGS
Table 2.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Parameter
Rating
Voltage
Supply Voltage (VPOS, VNEG)
Input Voltage (INxx, PRAI,
FDBK, VMDI, VOCM)
Logic Voltages
Temperature
Operating Temperature Range
Storage Temperature Range
6 V
VPOS, VNEG
VPOS, ground
–40°C to +105°C
–65°C to +150°C
300°C
ESD CAUTION
Lead Temperature (Soldering, 60 sec)
Thermal Data1
Maximum Junction Temperature
125°C
θJA
θJC
θJB
ΨJT
ΨJB
47.3°C/W
6.9°C/W
28.6°C/W
0.6°C/W
27.4°C/W
1 Thermal data at zero airflow with exposed pad soldered to four-layer JEDEC
board with vias per JESD51-5.
Rev. 0 | Page 6 of 32
AD8260
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
32 31 30 29 28 27 26 25
24 TXOP
23 TXOP
22 VPOS
21 VPOS
20 VPSR
19 VMDO
18 PRAI
17 FDBK
VMDO
TXEN
VMDI
1
2
3
4
5
6
7
8
PIN 1
INDICATOR
VNCM
VPSB
ENBL
VGAP
VGAN
AD8260
TOP VIEW
(Not to Scale)
9
10 11 12 13 14 15 16
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No. Mnemonic
Description
1, 191
VMDO
TXEN
VMDI
VMID Buffer Output. Requires robust ac decoupling with a capacitance of 0.1 μF capacitor or greater.
Driver Enable. Logic threshold = 1.1 V with 0.2 V hysteresis.
VMID Input Voltage. Normally decoupled with a 0.1 μF capacitor. When pulled to VNCM, the VMID buffer shuts
down. This can be useful when using the part with dual supplies or when an external midpoint generator is used.
2
3
4
5
6
VNCM
VPSB
ENBL
Negative Supply for Bias Cell, VMID Cell, and Logic Inputs. (Ground this pin in applications.)
Positive Supply for Bias Cell and VMID Cell.
Enable. Logic threshold = 1.1 V. When low, the AD8260 is disabled and the supply current is 35 μA when TXEN
and all GNSx pins are also low.
7
8
VGAP
VGAN
VNGR
VPSR
GNS3
GNS2
GNS1
GNS0
PRAO
FDBK
PRAI
Positive VGA Output (Needs to Be Ac-Coupled for Single Supply).
Negative VGA Output (Needs to Be Ac-Coupled for Single Supply).
Negative Supply for Preamplifier and DGA (Set to −VPOS for Dual Supply; GND for Single Supply).
Positive Supply for Preamplifier, DGA, and GNSx Logic Decoder.
MSB for Gain Control. Logic threshold = 1.1 V.
Gain Control Bit. Logic threshold = 1.1 V.
Gain Control Bit. Logic threshold = 1.1 V.
LSB for Gain Control. Logic threshold = 1.1 V.
Preamplifier Output.
9, 161
10, 201
11
12
13
14
15
17
18
Negative Input of Preamplifier.
Positive Input of Preamplifier.
21, 221
23, 241
25, 261
27
28
29
VPOS
TXOP
VNEG
TXFB
INPN
INRN
INRP
Positive Supply for Driver Amplifier.
Driver Output.
Negative Supply for Driver Amplifier (Set to −VPOS for Dual Supply; GND for Single Supply).
Feedback for Driver Amplifier.
Negative Driver Amplifier Input.
Negative Gain Resistor Input for Driver Amplifier.
Positive Gain Resistor Input for Driver Amplifier.
Positive Driver Amplifier Input.
30
31
INPP
32
VOCM
Output Common Mode Pin. Normally connected to Pin VMDO.
1 Pins with the same name are connected internally.
Rev. 0 | Page 7 of 32
AD8260
TYPICAL PERFORMANCE CHARACTERISTICS
VS (supply voltage) = 3.3 V, TA = 25°C, CL = 5 pF, f = 10 MHz, preamplifier gain = 2×, RFB1 and RFB2 of the preamplifier = 100 ꢀ,
RLOAD of the driver amplifier = 500 ꢀ, TX and RX enabled, unless otherwise specified.
20
15
10
5
5
4
3
2
1
V
= 200mV p-p
OUT
T = +25°C
T = –40°C
RTO
RTI
T = +105°C
0
100k
0
100k
1M
10M
200M
100M
1M
FREQUENCY (Hz)
10M
50M
FREQUENCY (Hz)
Figure 3. Small-Signal Frequency Response at Three Temperatures of the
High Current Driver—See Figure 51
Figure 6. Input-Referred and Output-Referred Noise of the High Current
Driver—See Figure 52
100
10
1
5
V
= 200mV p-p
OUT
V
= +3.3V
S
4
3
2
1
V
= +5V
S
V
= ±5V
S
0
100k
0.1
100k
1M
10M
FREQUENCY (Hz)
200M
100M
1M
10M
100M
FREQUENCY (Hz)
Figure 4. Small-Signal Frequency Response of the High Current Driver for
Three Supply Voltages—See Figure 51
Figure 7. Output Impedance of the High Current Driver
See Figure 53
5
–20
–30
–40
–50
–60
–70
–80
–90
–100
V
V
V
V
= 1V p-p; R
= 1V p-p; R
= 2V p-p; R
= 2V p-p; R
= 50Ω
= 500Ω
= 50Ω
= 500Ω
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
4
3
2
1
2V p-p
HD2
HD3
1V p-p
0
100k
10
100
1k
1M
10M
FREQUENCY (Hz)
200M
100M
LOAD RESISTANCE (ꢀ)
Figure 5. Large-Signal Frequency Response of the High Current Driver for Two
Values of Output Voltage and Two Values of Load Resistance—See Figure 51
Figure 8. Harmonic Distortion (HD2, HD3) vs. Load Resistance for the High
Current Driver—See Figure 54
Rev. 0 | Page 8 of 32
AD8260
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
–20
f = 10MHz
HD2, V
HD3, V
HD2, V
HD3, V
= 1V p-p
= 1V p-p
= 2V p-p
= 2V p-p
OUT
OUT
OUT
OUT
R
R
R
R
= 50ꢀ, V
= 50ꢀ, V
= 500ꢀ, V
= 500ꢀ, V
= 1V p-p
= 2V p-p
LOAD
LOAD
LOAD
LOAD
OUT
OUT
–40
= 1V p-p
= 2V p-p
OUT
OUT
–60
–80
–100
0
10
20
30
40
50
60
70
80
90
100
2M
10M
FREQUENCY (Hz)
100M
LOAD CAPACITANCE (pF)
Figure 9. Harmonic Distortion (HD2, HD3) vs. Load Capacitance at Two
Values of Output Voltage for the High Current Driver—See Figure 54
Figure 12. IMD3 vs. Frequency for Two Values of Output Voltage and Two
Values of Load Resistance for the High Current Driver—See Figure 55
0
50
40
30
f = 10MHz
–20
–40
–60
R
R
R
R
= 50ꢀ, V
= 50ꢀ, V
= 500ꢀ, V
= 500ꢀ, V
= 1V p-p
= 2V p-p
LOAD
LOAD
LOAD
LOAD
OUT
HD3
OUT
HD2
20
10
0
= 1V p-p
= 2V p-p
OUT
OUT
–80
–100
–120
0
0.5
1.0
1.5
2.0
2.5
3.0
2M
10M
FREQUENCY (Hz)
100M
OUTPUT VOLTAGE (V p-p)
Figure 13. Third-Order Intercept (OIP3) vs. Frequency for the High Current Driver
See Figure 55
Figure 10. Harmonic Distortion (HD2, HD3) vs. Output Voltage for the High
Current Driver—See Figure 54
–20
–30
–40
20
R
R
= 50ꢀ
= 500ꢀ
LOAD
LOAD
15
10
5
HD2
HD3
–50
2V p-p
–60
–70
–80
1V p-p
–90
0
1M
–100
10M
100M
10M
100M
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 11. Harmonic Distortion (HD2, HD3) vs. Frequency of the High Current
Driver at Two Values of Output Voltage—See Figure 54
Figure 14. Input-Referred 1 dB Compression (IP1dB) vs. Frequency for Two
Values of Load Resistance for the High Current Driver
Rev. 0 | Page 9 of 32
AD8260
0.20
0.15
0.10
0
–10
–20
–30
–40
–50
–60
–70
–80
C
C
C
= 5pF
= 10pF
= 47pF
LOAD
LOAD
LOAD
0.05
0
–0.05
–0.10
–0.15
–0.20
R
= 50ꢀ
LOAD
NONINVERTING
–90
0
–30 –20 –10
0
10
20
30
40
50
60
70
80
2
4
6
8
10 12 14 16 18 20 22 24
FREQUENCY (MHz)
TIME (ns)
Figure 15. Missing Tone Power Ratio for the High Current Driver
Figure 18. Small-Signal Pulse Response of the High Current Driver for Various
Values of Load Capacitance, CLOAD, and 50 Ω Load—See Figure 56
0.20
2.0
C
= 5pF
LOAD
NONINVERTING
C
= 5pF
LOAD
NONINVERTING
0.15
0.10
1.5
1.0
0.5
0 .05
0
0
–0.5
–1.0
–1.5
–2.0
–0.05
–0.10
R
R
R
R
= 10ꢀ
R
R
R
R
= 10ꢀ
= 50ꢀ
= 100ꢀ
= 500ꢀ
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
= 50ꢀ
= 100ꢀ
= 500ꢀ
–0.15
–0.20
–30 –20 –10
0
10
20
30
40
50
60
70
80
30
20
10
0
10
20
30
40
50
60
70
80
TIME (ns)
TIME (ns)
Figure 19. Large-Signal Pulse Response of the High Current Driver for Various
Values of Load Resistance, RLOAD—See Figure 56
Figure 16. Small-Signal Pulse Response of the High Current Driver for Various
Values of Load Resistance, RLOAD—See Figure 56
0.20
2.0
C
C
C
= 5pF
= 10pF
= 47pF
C
C
C
= 5pF
= 10pF
= 47pF
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
0.15
0.10
1.5
1.0
0.05
0
0.5
0
–0.05
–0.10
–0.15
–0.20
–0.5
–1.0
–1.5
–2.0
R
= 500ꢀ
LOAD
NONINVERTING
R
= 500ꢀ
LOAD
NONINVERTING
–30 –20 –10
0
10
20
30
40
50
60
70
80
–30 –20 –10
0
10
20
30
40
50
60
70
80
TIME (ns)
TIME (ns)
Figure 17. Small-Signal Pulse Response of the High Current Driver for Various
Values of Load Capacitance, CLOAD, and RLOAD = 500 Ω—See Figure 56
Figure 20. Large-Signal Pulse Response of the High Current Driver for Various
Values of Load Capacitance, CLOAD, and RLOAD = 500 Ω—See Figure 56
Rev. 0 | Page 10 of 32
AD8260
2.0
1.5
1.00
R
= 50ꢀ
LOAD
NONINVERTING
C
C
C
= 5pF
= 10pF
= 47pF
LOAD
LOAD
LOAD
0.75
0.50
0.25
0
AVERAGE OF 3 SAMPLES
f = 1MHz, 10MHz, AND 40MHz
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–0.25
–0.50
–0.75
–1.00
–30 –20 –10
0
10
20
30
40
50
60
70
80
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
GAIN SELECT CODE
TIME (ns)
Figure 21. Large-Signal Pulse Response of the High Current Driver for Various
Values of Load Capacitance, CLOAD, and 50 Ω Load—See Figure 56
Figure 24. Absolute Gain Error vs. Gain Select Code for Three Samples for the
VGA/Preamplifier at Three Frequencies Normalized to 1 MHz and Code 0110
See Figure 57
27
24
1.00
0.75
21
18
15
AVERAGE OF 3 SAMPLES
f = 1MHz, 10MHz, AND 40MHz
T = +105°C
T = +25°C
T = –40°C
0.50
0.25
12
9
0
–0.25
–0.50
6
3
0
–3
–6
–9
AVERAGE OF 3 SAMPLES AT
–0.75
EACH TEMPERATURE
–1.00
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
GAIN SELECT CODE
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
GAIN SELECT CODE
Figure 22. Gain vs. Gain Select Code for Three Samples for the
VGA/Preamplifier at Three Frequencies—See Figure 57
Figure 25. Gain Error vs. Gain Select Code at Three Temperatures for the
VGA/Preamplifier—See Figure 57
4.00
3.75
50
40
T = +105°C
30
20
T = +25°C
T = –40°C
3.50
AVERAGE OF 3 SAMPLES
f = 1MHz, 10MHz, AND 40MHz
3.25
10
3.00
2.75
2.50
2.25
0
–10
–20
–30
–40
–50
AVERAGE OF 3 SAMPLES AT
EACH TEMPERATURE
2.00
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
GAIN SELECT CODE
0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
GAIN SELECT CODE
Figure 23. Gain Step vs. Gain Select Code for Three Samples for the
VGA/Preamplifier at Three Frequencies—See Figure 57
Figure 26. Output Offset Voltage vs. Gain Select Code at Three Temperatures
for the VGA/Preamplifier—See Figure 58
Rev. 0 | Page 11 of 32
AD8260
27
24
21
18
15
12
9
10
1011
1010
1001
1000
0111
0110
0101
0100
0011
0010
0001
8
6
4
2
6
3
0
–3
–6
–9
–12
100k
0
1M
1M
10M
FREQUENCY (Hz)
100M 200M
10M
100M
FREQUENCY (Hz)
Figure 27. Frequency Response for a Supply Voltage (VS) of 3.3 V for all Codes
of the VGA/Preamplifier—See Figure 59
Figure 30. Group Delay vs. Frequency for the VGA/Preamplifier
See Figure 59
100
27
1011
1010
1001
1000
0111
0110
0101
0100
0011
0010
0001
24
21
18
15
12
9
6
3
0
–3
–6
10
VGAN
VGAP
1
–9
V
= 5V
S
–12
100k
0.1
100k
1M
10M
100M
1M
10M
100M 200M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 28. Frequency Response for a Supply Voltage (VS) of 5 V for All Codes
for the VGA/Preamplifier—See Figure 59
Figure 31. Output Resistance vs. Frequency for the VGA/Preamplifier
See Figure 60
27
50
40
30
20
1011
1010
1001
1000
0111
0110
0101
0100
0011
0010
0001
24
21
18
15
12
9
6
3
0
–3
–6
–9
V
= ±5V
S
–12
100k
10
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
1M
10M
100M 200M
GAIN SELECT CODE
FREQUENCY (Hz)
Figure 29. Frequency Response for a Dual Supply (VS) = 5 V for All Codes for
the VGA/Preamplifier—See Figure 59
Figure 32. Output-Referred Noise vs. Gain Select Code for the
VGA/Preamplifier—See Figure 61
Rev. 0 | Page 12 of 32
AD8260
30
40
50
60
70
80
100
V
= 1V p-p
OUT
GAIN CODE = 0110
GAIN CODE = 1011
HD2
HD3
10
100k
0
200 400 600 800 1000 1200 1400 1600 1800 2000
1M
10M
50M
FREQUENCY (Hz)
LOAD RESISTANCE (ꢀ)
Figure 33. Output-Referred Noise vs. Frequency for the VGA/Preamplifier at
Maximum Gain—See Figure 61
Figure 36. Harmonic Distortion (HD2, HD3) vs. Load Resistance for the
VGA/Preamplifier—See Figure 62
100
–30
V
= 1V p-p
OUT
GAIN CODE = 0110
–40
–50
–60
–70
–80
10
HD2
HD3
1
50
0
10
20
30
40
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
LOAD CAPACITANCE (pF)
GAIN SELECT CODE
Figure 34. Input-Referred Noise vs. Gain Select Code for the VGA/Preamplifier
See Figure 61
Figure 37. Harmonic Distortion (HD2, HD3) vs. Load Capacitance for the
VGA/Preamplifier—See Figure 62
10
0
HD2, fC = 1MHz
HD3, fC = 1MHz
HD2, fC = 10MHz
GAIN CODE = 1011
–20
V
= 1V p-p
HD3, fC = 10MHz
OUT
–40
–60
MEASUREMENT OF
DISTORTION IS
LIMITED BY THE
MAXIMUM DYNAMIC
INPUT RANGE OF
THE PREAMPLIFIER
–80
–100
–120
1
100k
0101 0110 0111 1000 1001 1010 1011
1M
10M
50M
FREQUENCY (Hz)
GAIN SELECT CODE
Figure 35. Short-Circuit Input Noise vs. Frequency for the VGA/Preamplifier
See Figure 61
Figure 38. Harmonic Distortion (HD2, HD3) vs. Gain Select Code at 1 MHz
and 10 MHz for the VGA/Preamplifier—See Figure 62
Rev. 0 | Page 13 of 32
AD8260
0
10
5
GAIN CODE = 1011
= 1V p-p
IP1dB LIMITED AT LOW GAIN BY THE
V
OUT
DYNAMIC RANGE OF THE PREAMPLIFIER
–20
–40
0
HD2
HD3
–5
–60
–10
–15
–20
–25
–30
–80
1MHz
10MHz
–100
–120
1M
10M
100M
0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011
GAIN SELECT CODE
FREQUENCY (Hz)
Figure 39. Harmonic Distortion (HD2, HD3) vs. Frequency for the
VGA/Preamplifier—See Figure 62
Figure 42. Input 1 dB Compression (IP1dB) vs. Gain Select Code at 1 MHz and
10 MHz for the VGA/Preamplifier
0
T
INPUT
–20
2mV/DIV
1
0V
V
= 1V p-p
OUT
TONES 1MHz APART
EACH TONE 0.5V p-p
GAIN CODE = 1011
–40
–60
LOWER
UPPER
–80
OUTPUT
50mV/DIV
0V
M
–100
–120
M10.0ns
A
CH4
180µV
1M
10M
FREQUENCY (Hz)
100M
CH1 2.00Vꢀ
MATH
5.00mV
10.0ns
T
27.2000ns
Figure 40. Third-Order Intermodulation Distortion (IMD3) vs. Frequency for
the VGA/Preamplifier
Figure 43. Small-Signal Pulse Response for the VGA/Preamplifier
60
50
40
30
20
T
INPUT
20mV/DIV
0V
3
OUTPUT
500mV/DIV
0V
M
LOWER
UPPER
GAIN CODE = 1011
10
TONES 1MHz APART
0
1M
M10.0ns
A
CH4
200µV
10M
100M
CH3 20.0mVꢀ
FREQUENCY (Hz)
MATH
50.0mV
10.0ns
T
27.2000ns
Figure 41. OIP3 vs. Frequency for the VGA/Preamplifier
Figure 44. Large-Signal Pulse Response for the VGA/Preamplifier
Rev. 0 | Page 14 of 32
AD8260
1.5
1.0
0.5
0
–10
–20
–30
–40
–50
–60
–70
+SUPPLY VGA/PREAMPLIFIER
+SUPPLY HIGH CURRENT DRIVER
–SUPPLY VGA PREAMPLIFIER
–SUPPLY HIGH CURRENT DRIVER
V
= +3V, +5V, AND ±5V
S
–0.5
–1.0
–1.5
V
= ±3.3V
GAIN CODE = 1011
S
100k
1M
5M
–3
–2
–1
0
1
2
3
4
5
6
7
8
FREQUENCY (Hz)
TIME (ns)
Figure 48. PSRR vs. Frequency for Dual Supplies for the High Current Driver
and the VGA/Preamplifier
Figure 45. Large-Signal Pulse Response for Various Values of Supply Voltage
for the VGA/Preamplifier
40
35
30
25
20
15
10
T
M
CH1 AMPL
3.28V
1
CH2 AMPL
1.20mV
MATH AMPL
117mV
4
FULLY ENABLED
5
VGA/PREAMPLIFIER ENABLED
HIGH CURRENT DRIVER ENABLED
0
CH1 1.00Vꢀ CH2 20.0mVꢀ
CH2 20.0mVꢀ
M200ns
A
CH1
760mV
–55
–35
–15
5
25
45
65
C)
85
105
125
TEMPERATURE (
°
T
595.200ns
MATH
100mV
200nV
Figure 46. Gain Response for the VGA/Preamplifier, Yellow: Gain Code Select,
Red: VGA Differential Output, Blue/Green: VGAP and VGAN
Figure 49. Quiescent Supply Current vs. Temperature for Three Operating States
2
80
70
60
50
40
30
20
10
0
1
0
–1
–2
–200 –100
0
100 200 300 400 500 600 700 800
TIME (ns)
–55
–35
–15
5
25
45
65
85
105
125
TEMPERATURE (°C)
Figure 47. Overdrive Recovery of the VGA/Preamplifier—Gain Code = 1011
Figure 50. Standby Quiescent Supply Current vs. Temperature
Rev. 0 | Page 15 of 32
AD8260
TEST CIRCUITS
NETWORK ANALYZER
OUT 50ꢀ
50ꢀ IN
AD8260—HIGH CURRENT DRIVER
0.1µF
INRN
TXFB
50ꢀ
–
+
0.1µF
453ꢀ
TXOP
INRP
5pF
0.1µF
VOCM
VMDO
Figure 51. Test Circuit for Frequency Response of the High Current Driver
SPECTRUM
ANALYZER
AD8260—HIGH CURRENT DRIVER
INRN
TXFB
0.1µF
0.1µF
–
0.1µF
TXOP
IN
INRP
50ꢀ
+
VOCM
VMDO
Figure 52. Test Circuit for Input-Referred and Output-Referred Noise of the High Current Driver
+3.3V
AD8260—HIGH
CURRENT DRIVER
NETWORK ANALYZER
WITH S-PARAMETER MODE
INRN
TXFB
TXOP
0.1µF
0.1µF
–
IN
INRP
+
VOCM
50ꢀ
–3.3V
Figure 53. Test Circuit for Output Impedance of the High Current Driver
LP
FILTER
SPECTRUM
ANALYZER
AD8260—HIGH CURRENT DRIVER
0.1µF
1:1
INRN
TXFB
SIGNAL
GENERATOR
50ꢀ
50ꢀ
R
–
LOAD
0.1µF
TXOP
IN
50ꢀ
INRP
50ꢀ
+
C
LOAD
0.1µF
VOCM
VMDO
Figure 54. Test Circuit for Harmonic Distortion of the High Current Driver
Rev. 0 | Page 16 of 32
AD8260
SIGNAL
GENERATORS
AD8260—HIGH CURRENT DRIVER
SPECTRUM
ANALYZER
50ꢀ
0.1µF
0.1µF
1kꢀ
1kꢀ
1:1
INRN
TXFB
–
0.1µF
453ꢀ
TXOP
IN
INRP
50ꢀ
+
50ꢀ
VOCM
VMDO
Figure 55. Test Circuit for IMD3 and OIP3 of the High Current Driver
AD8260—HIGH CURRENT DRIVER
0.1µF
0.1µF
OSCILLOSCOPE
INRN
INRP
TXFB
50ꢀ
R
LOAD
0.1µF
TXOP
IN
50ꢀ
C
LOAD
VOCM
12.5ꢀ
50ꢀ
VMDO
Figure 56. Test Circuit for Pulse Response of the High Current Driver
OSCILLOSCOPE
AD8260—VGA/PREAMPLIFIER
0.1µF
0.1µF
SIGNAL
GENERATOR
453ꢀ
453ꢀ
0.1µF
+
PREAMP
–
50ꢀ
50ꢀ
IN
50ꢀ
100ꢀ
100ꢀ
VMDO
Figure 57. Test Circuit for Gain Step Size and Error of the VGA/Preamplifier
AD8260—VGA/PREAMPLIFIER
DMM
0.1µF
+
PREAMP
–
100ꢀ
100ꢀ
VMDO
Figure 58. Test Circuit for Output-Referred Offset Voltage of the VGA/Preamplifier
Rev. 0 | Page 17 of 32
AD8260
NETWORK ANALYZER
50ꢀ
IN
AD8260—VGA/PREAMPLIFIER
0.1µF
453ꢀ
453ꢀ
0.1µF
+
PREAMP
–
50ꢀ
0.1µF
100ꢀ
100ꢀ
VMDO
Figure 59. Test Circuit for Frequency Response and Group Delay of the VGA/Preamplifier
NETWORK ANALYZER
WITH S-PARAMETER
CAPABILITY
50ꢀ
IN
+3.3V
AD8260—VGA/
PREAMPLIFIER
0.1µF
+
PREAMP
–
100ꢀ
–3.3V
100ꢀ
Figure 60. Test Circuit for Output Resistance of the VGA/Preamplifier
SPECTRUM
ANALYZER
AD8260—VGA/PREAMPLIFIER
+
0.1µF
0.1µF
AD8129
×10
0.1µF
0.1µF
1kꢀ
1kꢀ
VGA
PREAMP
–
VMDO
50ꢀ
100ꢀ
100ꢀ
VMDO
Figure 61. Test Circuit for Input-Referred and Output-Referred Noise Measurements of the VGA/Preamplifier
Rev. 0 | Page 18 of 32
AD8260
SPECTRUM
ANALYZER
AD8260—VGA/PREAMPLIFIER
+
LP
FILTER
0.1µF
0.1µF
475ꢀ
475ꢀ
0.1µF
50ꢀ
1:1
IN
50ꢀ
PREAMP
–
50ꢀ
SIGNAL
GENERATOR
100ꢀ
100ꢀ
VMDO
Figure 62. Test Circuit for Harmonic Distortion Measurements of the VGA/Preamplifier
AD8260—VGA/PREAMPLIFIER
OSCILLOSCOPE
0.1µF
+
PREAMP
–
50ꢀ
50ꢀ
IN
50ꢀ
100ꢀ
100ꢀ
VMDO
Figure 63. Test Circuit for IP1dB, Pulse Response, Overdrive Recovery, and Gain Response of the VGA/Preamplifier
Rev. 0 | Page 19 of 32
AD8260
THEORY OF OPERATION
4-bit parallel interface. Figure 64 shows the circuit block
diagram and basic application connections, and illustrates the
envisioned external DAC, ADC, and power-line bus interface
connections. The diagram shows the connections for single 3.3 V
supply operation; if a dual supply is available, the VMID
generator can be shut down and Pin VMDI, Pin VMDO, and
Pin VOCM need to be grounded. Note that Pin VNCM
functions as the negative supply for the bias and VMID cells,
plus the logic interfaces, and should always be tied to ground.
OVERVIEW
The AD8260 is a self-contained transceiver intended for analog
communications using a power line as the media. Operating on
supplies as low as 3.3 V, it includes a high current driver usable
as a transmitter and a low noise digitally programmable variable
gain amplifier (DGA), usable as a receiver (see Figure 64). An
uncommitted current-feedback high frequency op amp acts as a
preamplifier and interface to the DGA and is user configured
for gains greater than 6 dB. Combined, the VGA and preamplifier
are usable at high signal levels from dc to 100 MHz, with a
small-signal −3 dB bandwidth of 230 MHz. To implement a
high current-output VGA, the VGA output can be connected
to the driver-amplifier differential input.
For optimal dynamic range, it is important that the inputs and
outputs to both the driver amplifier and the preamplifier and
the DGA output amplifier be ac-coupled in a single-supply
application. In Figure 64, the DAC and ADC are presumed to
operate on a 1.8 V or 3.3 V supply with a corresponding limited
output and input swing. The DAC outputs are currents that
point down and generate a voltage in the 50 ꢀ resistors that are
connected to ground. The maximum voltage with a peak DAC
output current of 15 mA is 0.75 V; if a DAC with a 20 mA peak
current is used, then the maximum voltage is 1 V per side for a
differential input signal of 2 V p-p.
The small-signal −3 dB bandwidth of the driver amplifier is
195 MHz and the large-signal bandwidth is >115 MHz, even
when driving a 50 ꢀ load.
The device is fabricated on the Analog Devices, Inc., high speed
(eXtra Fast Complementary Bipolar) XFCB process. The pream-
plifier and DGA feature low dc offset voltage, and a nominal
gain range of −6 dB to +24 dB, a 30 dB gain span, and a differential
output for ADC driving. The power consumption is 93 mW
with a single 3.3 V supply. The supply current is typically about
28 mA when all circuits in the device are active. During normal
usage, either the driver amplifier is on or the preamplifier and
DGA are on and, therefore, the supply current in general is less
than 28 mA. The gain of the AD8260 VGA is programmed via a
The driver amplifier supports a 3 V p-p output swing on a
3.3 V supply. Because of its gain of 1.5, the maximum input
swing is 2 V p-p. The corresponding maximum output swing for
the DGA is 2.4 V p-p differential; the input to the preamplifier
can be a maximum of 0.6 V p-p.
Rev. 0 | Page 20 of 32
AD8260
1V MAX WITH
200mA pk
1.8V OR 3.3V
20mA DAC
50ꢀ
OPTIONAL USER SELECTED
REDUCES HF PEAKING
C
FB
WITH CAPACITIVE LOADING
50ꢀ
0.1µF
0.1µF
C
FB
VOCM INPP
32 31
30
29
28
27
26
25
1.5kꢀ 1kꢀ
1kꢀ 1.5kꢀ
OPTIONAL CLAMP DIODES
AND SNUBBING RESISTORS
TXOP
VMDO
TXEN
VMDI
1
2
24
23
22
21
20
19
18
17
+
–
0.1µF
GM
×1
TXOP
VPOS
0.1µF
0.1µF
0V, 1.8V/3.3V
AD8260
3
4
5
6
7
8
0.1µF
VMID
VNCM
VPOS
VPSR
VMDO
PRAI
POWERLINE
CABLE, ETC.
BIAS
VPSB
ENBL
VGAP
VGAN
3.3V
0V, 1.8V/3.3V
3.3V
1.8V OR 3.3V
LOW-PASS
AA FILTER
ATTENUATOR
0.1µF
0.1µF
0.1µF
INP
ADC
FS INPUT
2V p-p
RFB1
100ꢀ
GM STAGES
LOGIC
FDBK
INN
RFB2
100ꢀ
9
10
11
12
13
14
15
16
3.3V
Figure 64. Block Diagram and Basic Application Connections
For optimum distortion, the input drive must be controlled
such that the output swing is well within saturation levels
established by the supply rail. The output swing can be reduced
by using load resistors with values less than 50 ꢀ or by reducing
the amplifier gain by connecting external resistors in parallel
with the internal 1 kΩ and 1.5 kΩ resistors between Pin 27,
Pin 28, and Pin 29, and between Pin 30, Pin 31, and Pin 32.
Coincidently, noise is reduced because the gain setting resistors
are the primary noise sources of the high current driver amplifier.
HIGH CURRENT DRIVER AMPLIFIER
The high current driver amplifier can deliver very large output
currents suitable for driving complex impedances, such as a
power line, a 50 ꢀ line, or a coaxial cable. The input of the
amplifier is fully differential and intended to be driven by a
differential current-output DAC, as shown in Figure 64. The
differential input signal is amplified by 1.5× and produces a
2.25 V p-p single-ended output signal from a 1.5 V p-p input
signal. A DAC with 15 mA maximum output current into a
50 Ω load provides 1.5 V p-p of input voltage and results in
2.25 V p-p at the output. A DAC whose output is 20 mA produces
an output swing of 3 V p-p (neglecting a small gain error when
driving the parallel combination of the 50 Ω load-resistor and the
internal 1 kΩ gain resistor of the AD8260).
The output-referred noise is 14 nV/√Hz, of which 11 nV/√Hz is
due to the gain setting resistors. Matching of the gain setting
resistors is important for good common-mode rejection and the
accuracy of the differential gain. If external resistors are used,
their accuracy should be at least 1ꢁ. How low the resistor
values can be is primarily determined by the quality of the ac
ground at Pin VOCM; as the gain setting resistors decrease in
value, the dynamic current increases, and the quality of the
decoupling capacitors needs to increase correspondingly.
For a 3.3 V supply rail, the maximum limit of the output voltage
is 3 V p-p and distorts severely if exceeded. The recommended
output for optimum distortion is 2 V p-p for a 3.3 V supply.
Correspondingly, larger output swings are accommodated for
higher supply voltages such as +5 V or 5 V.
Rev. 0 | Page 21 of 32
AD8260
determine the −3 dB bandwidth of the amplifier. Smaller
resistor values may compromise preamplifier stability.
PRECAUTIONS TO BE OBSERVED DURING HALF-
DUPLEX OPERATION
Because the AD8260 is internally dc-coupled, larger preamplifier
gains increase its offset voltage. The circuit contains an internal
bias resistor and some offset compensation; however, if a lower
value of offset voltage is required, it can be compensated by
connecting a resistor between the FDBK pin and the supply
voltage. If the offset is negative, the resistor value connects to
the negative supply; otherwise, it connects to the positive supply.
During receive, when the high current driver-amplifier is
disabled, its gain setting resistors provide a signal path from
input to output. To prevent inadvertent DAC signals from being
transmitted while receiving via the preamplifier and DGA, the
DAC in Figure 64 must have no output signal.
During transmit, the preamplifier and VGA should be disabled
through any of the nongain-setting codes (see Table 4).
For larger gains, the overall noise is reduced if a low value of
VMID BUFFER
R
FB1 is selected. For values of RFB1 = 20 Ω and RFB2 = 301 Ω, the
The VMID buffer is a dc bias source that generates the voltage
on Pin 1 and Pin 19, VMDO. Node VMDO cannot accommodate
large dynamic currents and requires excellent ac decoupling to
ground. A high quality 0.1μF capacitor located as close as
possible to Pin 1 and Pin 19 (see Figure 64) is normally sufficient
to decouple the high values of current from Node VMDO.
preamplifier gain is 16× (24.1 dB) and the input-referred noise
is about 1.5 nV/√Hz. For this value of gain, the overall gain range
increases by 18 dB so that the absolute gain range is 12 dB to 42 dB.
PREAMPLIFIER NOISE
The total input-referred voltage and current noise of the positive
input of the preamplifier is about 2.4 nV/√Hz and 5 pA/√Hz,
respectively. The DGA output referred noise is about 25 nV/√Hz
at low gains and 39 nV/√Hz at the highest gain. The 25 nV/√Hz
divided by the DGA fixed gain of 8× results in 3.12 nV/√Hz
referred to the DGA input. Note that this value includes the
noise of the DGA gain setting resistors as well. If this voltage is
divided by the preamplifier gain of 2×, the DGA noise referred
all the way to the preamplifier input is about 1.56 nV/√Hz. From
this, it can be determined that the preamplifier, including the
100 Ω gain setting resistors, contributes about 1.8 nV/√Hz. The
two 100 Ω resistors each contribute 1.29 nV/√Hz at the output
of the preamplifier and 0.9 nV/√Hz referred to the input. With
the gain resistor noise subtracted, the preamplifier noise alone
is about 1.6 nV/√Hz.
When operating with dual power supplies, the buffer is disabled
by connecting Pin VMDI, Pin VOCM, and Pin VMDO to ground.
Because the logic decoder in the DGA (GNSx inputs) requires
3.3 V of headroom, the positive supply rails must be 3.3 V or
greater whether single-ended or dual. If a dual supply is used,
the negative rails are the same magnitude (opposite polarity)
as the positive, that is, −3.3 V when VPOS, VPSB, and VPSR
are +3.3 V.
PREAMPLIFIER
The AD8260 includes an uncommitted current feedback op
amp to buffer the resistive attenuator of the DGA. External
resistors are used to adjust the gain. The preamplifier is
characterized with a noninverting gain of 6 dB (2×) and both
gain resistor values of 100 Ω. The preamplifier gain can be
increased using different gain ratios of RFB1 and RFB2, trading off
bandwidth and offset voltage. The sum of the values of RFB1 and
Equation 1 shows the calculation that determines the output-
referred noise at maximum gain (24 dB or 16×).
RFB2 should be ≥200 Ω to maintain low distortion. RFB2 should
be ≥100 Ω because it and an internal compensation capacitor
RFB2
RFB1
2
en−out
where:
=
(
en,RS × At
)
2 +(en,PrA × At )2 +(in,PrA ×RS )2 +(en,RFB1
×
× AVGA )2 +(en,RFB2 × AVGA )2 +(en,VGA × AVGA
)
(1)
At is the total gain from preamplifier input to the VGA output.
en,RS is the noise of the source resistance.
e
i
n,PrA is the input-referred voltage noise of the preamplifier.
n,PrA is the current noise of the preamplifier at the PRAI pin.
RS is the source resistance.
VGA is the VGA gain.
A
e
e
e
n,RFB1 is the voltage noise of RFB1
.
n,RFB2 is the voltage noise of RFB2
.
n,VGA is the input-referred voltage noise of DGA (low gain output-referred noise divided by a fixed gain of 8×).
Rev. 0 | Page 22 of 32
AD8260
Assuming RS = 0, RFB1 = RFB2 = 100 ꢀ, At = 16, and AVGA = 8, the
noise simplifies to
Table 4. Gain Control Logic Table
D3 D2 D1 D0 Function Comments
en−out = (1.6×16)2 + 2 (1.29×8)2 +(3.12×8)2
=
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Disable
PrA and DGA powered down
(2)
−6
−3
0
3
6
9
12
15
The numbers in the function
column are composite gain
values in dB for the correspond-
ing code, when the preamplifier
gain is 6 dB. For other values of
preamplifier gain, the gain is
amended accordingly; for
example, if the preamplifier
gain is 12 dB, the gain values
increase by 6 dB. When using
the DGA single ended, the
composite gain decreases
by 6 dB.
39 nV / Hz
Taking this result and dividing by 16 gives the total input-referred
noise with a short-circuited input as 2.4 nV/√Hz. When the
preamplifier is used in the inverting configuration with the
same RFB1 = RFB2 = 100 ꢀ as in the previous example, then en-out
does not change; however, because the gain decreases by 6 dB,
the input-referred noise increases by a factor of 2 to about
4.8 nV/√Hz. The reason for this is that the noise gain to the DGA
output of all the noise generators stays the same, but the preamp
inverting gain is (−1×) compared to the (+2×) in the noninverting
configuration. This doubles the input-referred noise.
18
21
24
Disable
Disable
Disable
Disable
PrA and DGA powered down
PrA and DGA powered down
PrA and DGA powered down
PrA and DGA powered down
DGA
Referring to Figure 64, the signal path consists of a 30 dB
programmable attenuator followed by a fixed gain amplifier of
18 dB for a total DGA gain range of −12 dB to +18 dB. With the
preamplifier configured for a gain of 6 dB, the composite gain
range is −6 dB to +24 dB from single-ended preamplifier input
to differential DGA output.
OUTPUT STAGE
The gain of the voltage feedback output stage is fixed at 18 dB and
inaccessible to the user. Otherwise, it is similar to the preamplifier
in speed and bandwidth. The overall −3 dB bandwidth of the
preamplifier and DGA combination is 230 MHz.
ATTENUATOR
The DGA plus preamplifier with 6 dB of gain implements the
following gain law:
The input resistance of the VGA attenuator is nominally 265 ꢀ.
Assuming that the default preamplifier feedback network of RFB1
and RFB2 is 200 ꢀ, the effective preamplifier load is about 114 ꢀ.
The attenuator is composed of ten 3.01 dB sections for a total
attenuation span of −30.10 dB. Following the attenuator is a
fixed gain amplifier with 18 dB (8×) gain. Because of this relatively
low gain, the output offset is less than 20 mV over the operating
temperature range; the offset is largest at maximum gain because
the preamplifier offset is amplified. The VMDO pin defines the
common-mode reference for the input and output. The voltage
at VMID is half the supply voltage for single-supply operation
and 0 V when dual supplies are used.
dB
Code
⎡
⎤
Gain(dB) = 3.01
×Code + ICPT(dB)
⎢
⎣
⎥
⎦
where:
ICPT is the nominal intercept, −9 dB.
Code values are decimal from 1 to 11.
The ICPT increases as the gain of the preamplifier is increased.
For example, if the gain of the preamplifier is increased by 6 dB,
then ICPT increases to −3 dB.
GAIN CONTROL
To change the gain, the desired four bits are programmed on
Pin GNS0 to Pin GNS3, where GNS0 is the LSB (D0) and GNS3
is the MSB (D3). The states of Decimal 0 and Decimal 12 through
Decimal 15 disable the preamplifier (PrA) and DGA (see Table 4).
Rev. 0 | Page 23 of 32
AD8260
active first to listen to any signals, and the driver needs to
be off. Therefore, the gain code should be set to 0001 (−6 dB
of gain) first and then the gain adjusted as needed. Note
that any code besides 1 to 11 (binary) disables the receive
section (see Table 4). During receive, it is also important
that the DAC that provides the signal for the high current
driver be disabled to avoid interfering with the received signal.
3. After receive, presumably data needs to be transmitted via
the high current driver amplifier. At this point, the DAC
should still be off. Pull Pin TXEN high and allow the high
current driver to settle. Enable the DAC. Although the
preamplifier and DGA can remain enabled during the
previous sequence, there may be significant preamplifier
overdrive, and it is best that the receiver be disabled while
transmitting.
SINGLE-SUPPLY OPERATION AND AC COUPLING
When operating the AD8260 from a single supply, there are two
bias options for VMDO.
•
Use an external low impedance midpoint reference at
Pin VMDO and pull VMDI to VNCM to shut down the
VMID buffer.
•
Use the internal VMID buffer as shown in Figure 64.
In both cases, decoupling capacitors are needed on Pin VMDO
to absorb the dynamic currents.
During single-supply operation, the preamplifier input is normally
ac-coupled. An internal bias resistor (nominally 1 k Ω) connected
between PRAI and VMDO provides bias to the preamplifier
input pin. A 50 Ω resistor connected between Pin PRAI and
Pin VMDO, in parallel with the internal 1 kΩ, serves as a termina-
tion resistor and at the same time reduces the offset; the result
is a composite value of about 48 Ω. The VGA input is biased
through the attenuator network and the voltage at Pin VMDO.
When active, the VMID buffer provides the needed bias currents.
When the buffer is disabled, an external voltage is required at
Pin VMDO to provide the bias currents. For example, for a single
5 V application, a reference such as the ADR43 and a stable op
amp provide an adequate 2.5 V VMDO source.
4. Pull Pin ENBL low to disable the chip. To achieve the
specified sleep current of 35 μA, all logic pins must be
pulled low as well.
LOGIC INTERFACES
All logic pins use the same interfaces and, therefore, have the
same behavior and thresholds. The interface contains a Schmitt
trigger type input with a threshold at about 1.1 V and a hystere-
sis of 0.2 V.
POWER-UP/POWER-DOWN SEQUENCE
Therefore, the logic low is between ground and 0.8 V, and logic
high is from 1.4 V to VPOS. Because the threshold is so low, the
logic interfaces can be driven directly from 1.8 V or 3.3 V CMOS.
For glitch-free power-up operation, the following power-up and
power-down sequence is recommended:
The input bias current is nominally 0.2 μA when the applied
voltage is 3.3 V and 18 nA when grounded.
1. Enable the bias by pulling the ENBL pin high. Maintain
GNS0 to GNS3 and TXEN at ground.
2. It is assumed that after the part wakes up from sleep mode,
the receive section (preamplifier and DGA) needs to be
Rev. 0 | Page 24 of 32
AD8260
APPLICATIONS INFORMATION
CONTROLLER
The AD8260 is ideally suited for compact applications requiring
high frequency and large current drive of complex modulation
products. Because the driver is capable of providing up to 300 mA
(using a 3.3 V supply rail) to very low impedance loads, undefined
network impedances are of little consequence. Such applications
can include, but are not limited to, local power line wiring
found in homes or in automobiles, or low impedance complex
filters used in communications. Pulse response performance
with loading effects are illustrated by various curves in the
Typical Performance Characteristics section.
MICROPROCESSOR +
MODULATOR
DAC ADC
AD8260
COUPLING
Figure 65 is an application block diagram showing AD8260
devices configured as transceivers in a small local network.
In this figure, consider a small security system consisting of a
master controller and four satellite cameras. For example, the
master can be a processor-controlled switch that routes data to
and from local satellite cameras. The cameras video signals are
modulated for transmission over an existing power system such
as the wiring found in homes or small businesses. Using the
existing power network in this way eliminates the need to install
additional cabling, thereby saving cost. Portability is also
achieved because the system can be moved to other locations
should the need arise, simply by unplugging a satellite and
moving it elsewhere. The AD8260 transceivers perform the
same function at the master and slave locations; a high frequency
current-output DAC converts digital-to-analog data for the
high current driver for transmission over a low impedance load.
The input of the VGA/preamplifier connects to the same load,
functioning as the receiver. In such a system, multiple AD8260
devices are connected to form a network, much like a LAN,
except using the power-line wiring in a home or automobile in
lieu of a CAT-5 cable, for example.
LOCAL POWER WIRING
COUPLING
COUPLING
AD8260
AD8260
SATELLITE
CAMERAS
DAC ADC
DAC ADC
MICROPROCESSOR +
MODULATOR
MICROPROCESSOR +
MODULATOR
CAMERA
CAMERA
Figure 65. AD8260 Transceiver Application
Figure 66 shows the AD8260 as a low distortion, high power
driver. The VGA and high current driver are combined by
simply connecting the differential output of the VGA directly to
the input of the driver.
AD8260
VGA/
HIGH CURRENT
DRIVER
COMPLEX LOW
Z FILTER ≥10Ω
PREAMPLIFIER
DAC
Figure 66. AD8260 Used as a VGA Driving a Low Impedance Load
Rev. 0 | Page 25 of 32
AD8260
EVALUATION BOARD
Analog Devices provides evaluation boards to customers as a
support service so that the circuit designer can become familiar
with the device in the most efficient way possible. The AD8260
evaluation board provides a fast, easy, and convenient means to
assess the performance of the AD8260 before going through the
inconvenience and expense of design and layout of a custom
board. The board is shipped fully assembled and tested and
provides basic functionality as shipped. Connectors enable the
user to connect standard types of lab test equipment without
having to wait for the rest of the design to be completed. Figure 67
shows a digital image of the top view and Figure 70 shows the
schematic.
PCB artwork for all conductor and silkscreen layers is shown in
Figure 71 through Figure 76. A description of a typical test setup is
explained in the Connecting the Evaluation Board section. The
artwork can be used as a guide in circuit layout and parts
placement. This is particularly useful for multiple function
circuits with many pins, requiring multiple passive components.
The board is shipped with the device fully enabled. Moving the
ENABLE jumper to its upper position on the board disables the
device. When the TX_EN jumper is in its upper position, the
high current driver is disabled.
Figure 67. Top View of the AD8260-EVALZ
Rev. 0 | Page 26 of 32
AD8260
DEFAULT GAIN SETTING
COMPONENTS ARE SHOWN IN BLACK,
OPTIONAL COMPONENTS
CONNECTING THE EVALUATION BOARD
Figure 69 shows an evaluation board with typical test connec-
tions. The various pieces of test equipment are representative,
and equivalent equipment may be substituted.
ARE SHOWN IN GRAY.
VMDO
1
VOCM
1.5kꢀ
32
31
30
The AD8260 includes two amplifier channels: a high current
driver and a digitally controlled VGA that is independently
enabled. The slide switch labeled ENABLE functions as the chip
enable, the GNSx switches permit the preamplifier/VGA to
operate, and the TX_EN switch enables the high current driver.
These independent enable functions permit the device to
operate in a send or listen mode when used as a transceiver.
INPP
INRP
1kꢀ
TXOP
+
–
24
TXOP
TXFB
23
27
1.5kꢀ
1kꢀ
INRN
INPN
29
28
The high current driver features differential inputs and is
optimally driven by a differential signal source. The input signal
is monitored at the 2-pin header labeled INP, using a differential
probe such as the Tektronix P6247 (not shown). Two 49.9 ꢀ
resistors are provided (R12 and R13), either for terminating
coaxial cables from a signal generator or to be used as load
resistors for a DAC with a current source output. An optional
external load resistor is connected at the SMA connector TXOP
and the output signal monitored at the 2-pin header labeled
TXOP_1.
C
COMP
Figure 68. Gain-Setting Resistors of the High Current Driver
The VGA/preamplifier is completely independent of the high
current driver and features a single-ended input at the SMA
connector PRAI. The input signal is monitored at the header
VPRE_IN. The output is monitored at the 2-pin header
VGA_OUT.
As shipped, the gain of the high current driver is 1.5×, its default
value. The internal differential network with resistor values of
1 kꢀ and 1.5 kꢀ establishes this value. Other values of gain are
realized by connecting external resistors to the device at Pin 23,
Pin 24, Pin 27, Pin 28, and Pin 31, as shown in Figure 68, which
shows the internal structure for the default gain and how the
gain can be modified.
The gain bits, GNS0 through GNS3, must be set before the
VGA/preamplifier can operate. Table 4 lists the binary gain
codes. The board is shipped with both enables (ENBL and
TXEN) engaged and the gain-code switches adjusted for
maximum DGA gain (1011). Resistor R5 and Resistor R6
establish the preamplifier gain and are 100 ꢀ as shipped for a
noninverting preamplifier gain of 2×.
Rev. 0 | Page 27 of 32
AD8260
PULSE GENERATOR WITH
DIFFERENTIAL OUTPUT
HIGH
CURRENT
DRIVER
INPUTS
VGA
OUTPUT
HIGH
(TO SCOPE)
CURRENT
DRIVER
OUTPUT
R
LOAD
SINGLE-
ENDED
VGA INPUT
POWER SUPPLY
FUNCTION
GENERATOR FOR VGA
INPUT
Figure 69. Typical Evaluation Board Connections
Rev. 0 | Page 28 of 32
AD8260
+VS GND
–VS
–VS
INRP
INRN
+
R12
49.9ꢀ
R13
49.9ꢀ
C8
0.1µF
C9
C3
10µF
C4
0.1µF
10µF
+
+VS
C19
0.1µF
C18
0.1µF
GND1 GND2 GND3 GND4 GND5 GND6
INR
INP
L7
120nH
FB
R18
–VS
C1
C2
R17
R15
0.1µF
0.1µF
R14
OR
C
COMP
C17
0.1µF
R7
0ꢀ
R9
0ꢀ
TXOP
C14
0.1µF
R21
0ꢀ
VMDO
R16
TX_OP
32 31 30 29
VOCM
28 27 26 25
VNEG
VPSB
TXEN
1
2
3
4
5
24
23
22
21
20
19
18
17
L6
120nH
FB
VMDO
TXOP
TXOP
VPOS
VPOS
VPSR
VMDO
PRAI
EN
TX_EN
DIS
+VS
TXEN
VMDI
VNCM
VPSB
VMDI
C6
0.1µF
C5
0.1µF
L5
120nH
FB
C13
0.1µF
L1
VPSB
120 nH
FB
U1
AD8260
VPS
C7
0.1µF
C15
0.1µF
ENBL
6
7
8
C11
0.1µF
EN
ENABLE
DIS
ENBL
VGAP
PRAI
PREAMP_IN
R10
49.9ꢀ
C10
0.1µF
C23
0.1µF
FDBK
VGAN
R6
100ꢀ
R1
453ꢀ
VGAP
VNGR
9
VNGR
C12
0.1µF
10 11 12 13 14 15 16
R5
100ꢀ
R11
453ꢀ
PRAO
C10
0.1µF
VGA _OUT
R2
453ꢀ
PRAO
VGAN
–VS
GNS0
H
C20
0.1µF
L2
120nH
FB
L
R19
0ꢀ
R20
0ꢀ
R4
GNS1
C16
0.1µF
L3
120nH
FB
R3
L4
GNS2
GNS3
120nH
FB
+VS
–VS
C22
0.1µF
Figure 70. AD8260 Evaluation Board—Schematic Diagram
Rev. 0 | Page 29 of 32
AD8260
Figure 71. AD8260-EVALZ Component Side Assembly
Figure 73. AD8260-EVALZ Secondary Side Copper
Figure 72. AD8260-EVALZ Component Side Copper
Figure 74. AD8260-EVALZ Power Plane
Rev. 0 | Page 30 of 32
AD8260
Figure 75. AD8260-EVALZ Ground Plane
Figure 76. Component Side Silkscreen
Rev. 0 | Page 31 of 32
AD8260
OUTLINE DIMENSIONS
5.00
BSC SQ
0.60 MAX
0.60 MAX
PIN 1
INDICATOR
25
32
1
24
0.50
BSC
PIN 1
INDICATOR
TOP
VIEW
2.85
2.70 SQ
2.55
4.75
BSC SQ
EXPOSED
PAD
(BOT TOM VIEW)
0.50
0.40
0.30
17
16
8
9
0.20 MIN
3.50 REF
0.80 MAX
0.65 TYP
THE EXPOSED PAD IS NOT CONNECTED
INTERNALLY. FOR INCREASED RELIABILITY
OF THE SOLDER JOINTS AND MAXIMUM
THERMAL CAPABILITY IT IS RECOMMENDED
THAT THE PAD BE SOLDERED TO THE
GROUND PLANE. THE GROUND PLANE
PATTERN SHOULD INCLUDE A PATTERN OF
VIAS TO INNER LAYERS.
1.00
0.85
0.80
12° MAX
0.05 MAX
0.02 NOM
0.30
0.25
0.18
SEATING
PLANE
COPLANARITY
0.08
0.20 REF
COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2
Figure 77. 32-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
5 mm × 5 mm Body, Very Thin Quad
(CP-32-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model
Temperature
Package Description
Package Option
CP-32-8
CP-32-8
AD8260ACPZ-R71
AD8260ACPZ-RL1
AD8260ACPZ-WP1
AD8260-EVALZ1
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
32-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
32-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
32-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
Evaluation Board
CP-32-8
1 Z = RoHS Compliant Part.
©2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07192-0-5/08(0)
Rev. 0 | Page 32 of 32
相关型号：
AD8264ACPZ
SPECIALTY ANALOG CIRCUIT, QCC40, 6 X 6 MM, ROHS COMPLIANT, MO-220VJJD-2, LFCSP-40
ROCHESTER
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