AD AD8392ACP-R2

Low Power, High Output Current, Quad Op Amp,
Dual-Channel ADSL/ADSL2+ Line Driver
AD8392
PIN CONFIGURATIONS
VEE1, 2 1
28 GND
PD0 1, 2
2
27 NC
PD1 1, 2
3
26 NC
+VIN1
4
–VIN1
5
1
25 +VIN2
2
24 –VIN2
VOUT1
6
VCC1, 2
7
NC
8
21 VCC3, 4
VOUT3
9
20 VOUT4
23 VOUT2
22 NC
AD8392
–VIN3 10
3
+VIN3 11
19 –VIN4
4
18
+VIN4
NC 12
17 PD1 3, 4
NC 13
16
PD0 3, 4
GND 14
15
VEE3, 4
NC = NO CONNECT
+VIN2
NC
VCOM1, 2
GND
PD0 1, 2
VEE1, 2
PD1 1, 2
Figure 1. AD8392ARE, 28-Lead TSSOP/EP
+VIN1
Four current feedback, high current amplifiers
Ideal for use as ADSL/ADSL2+ dual-channel Central Office
(CO) line drivers
Low power operation
Power supply operation from ±5 V (+10 V) up to ±12 V (+24 V)
Less than 3 mA/Amp quiescent supply current for full
power ADSL/ADSL2+ CO applications (20.4 dBm line
power, 5.5 CF)
Three active power modes plus shutdown
High output voltage and current drive
400 mA peak output drive current
44 V p-p differential output voltage
Low distortion
−72 dBc @1 MHz second harmonic
−82 dBc @ 1 MHz third harmonic
High speed: 900 V/µs differential slew rate
Additional functionality of AD8392ACP
On-chip common-mode voltage generation
04802-0-001
FEATURES
32 31 30 29 28 27 26 25
The AD8392 is available in two thermally enhanced packages, a
28-lead TSSOP EP (AD8392ARE) and a 5 mm × 5 mm 32-lead
LFCSP (AD8392ACP). Four bias modes are available via the use
of two digital bits (PD1, PD0).
VOUT3
6
–VIN3
7
NC
8
AD8392
3
9
4
NC
23
–VIN2
22
VOUT2
21
NC
20
VCC3, 4
19
VOUT4
18
–VIN4
17
NC
10 11 12 13 14 15 16
04802-0-002
5
+VIN4
4
NC
PD1 3, 4
VCC1, 2
VEE3, 4
3
PD0 3, 4
VOUT1
2
GND
The AD8392 is comprised of four high output current, low
power consumption, operational amplifiers. It is particularly
well suited for the CO driver interface in digital subscriber line
systems, such as ADSL and ADSL2+. The driver is capable of
providing enough power to deliver 20.4 dBm to a line, while
compensating for losses due to hybrid insertion and back
termination resistors. In addition, the low distortion, fast slew
rate, and high output current capability make the AD8392 ideal
for many other applications, including medical, instrumentation, DAC output drivers, and other high peak current circuits.
24
1
VCOM3, 4
GENERAL DESCRIPTION
2
NC
ADSL/ADSL2+ CO line drivers
XDSL line drives
High output current, low distortion amplifiers
DAC output buffer
–VIN1
+VIN3
APPLICATIONS
NC 1
Figure 2. AD8392ACP, 32-Lead LFCSP 5 mm × 5 mm
Additionally, the AD8392ACP provides VCOM pins for on-chip
common mode voltage generation.
The low power consumption, high output current, high output
voltage swing, and robust thermal packaging enable the AD8392
to be used as the CO line drivers in ADSL and other xDSL systems, as well as other high current, single-ended or differential
amplifier applications.
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
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
AD8392
TABLE OF CONTENTS
Specifications..................................................................................... 3
Power Management ................................................................... 12
Absolute Maximum Ratings............................................................ 5
Driving Capacitive Loads.......................................................... 12
Thermal Resistance ...................................................................... 5
Thermal Considerations............................................................ 13
ESD Caution.................................................................................. 5
Typical ADSL/ADSL2+ Application ........................................ 13
Typical Performance Characteristics ............................................. 6
Multitone Power Ratio............................................................... 14
Theory of Operation ...................................................................... 11
Lightning and AC Power Fault ................................................. 15
Applications..................................................................................... 12
Outline Dimensions ....................................................................... 16
Supplies, Grounding, and Layout ............................................. 12
Ordering Guide .......................................................................... 16
Resistor Selection........................................................................ 12
REVISION HISTORY
7/04—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
AD8392
SPECIFICATIONS
VS = ±12 V or +24 V, RL = 100 Ω, G = +5, PD = (0, 0), T = 25°C, unless otherwise noted.
Table 1.
Parameter
DYNAMIC PERFORMANCE
−3 dB Small Signal Bandwidth
−3 dB Large Signal Bandwidth
Peaking
Slew Rate
NOISE/DISTORTION PERFORMANCE
Second Harmonic Distortion
Third Harmonic Distortion
Multitone Input Power Ratio
Voltage Noise (RTI)
+Input Current Noise
−Input Current Noise
INPUT CHARACTERISTICS
RTI Offset Voltage
+Input Bias Current
−Input Bias Current
Input Resistance
Input Capacitance
Common-Mode Rejection Ratio
OUTPUT CHARACTERISTICS
Differential Output Voltage Swing
Single-Ended Output Voltage Swing
Linear Output Current
POWER SUPPLY
Operating Range (Dual Supply)
Operating Range (Single Supply)
Total Quiescent Current
PD1, PD0 = (0, 0)
PD1, PD0 = (0, 1)
PD1, PD0 = (1, 0)
PD1, PD0 = (1, 1) (Shutdown State)
PD = 0 Threshold
PD = 1 Threshold
+Power Supply Rejection Ratio
−Power Supply Rejection Ratio
Min
Typ
30
20
850
−5.0
64
42.0
21.0
Unit
Test Conditions/Comments
40
25
0.05
900
MHz
MHz
dB
V/µs
VOUT = 0.1 V p-p, RF = 2 kΩ
VOUT = 4 V p-p, RF = 2 kΩ
VOUT = 0.1 V p-p, RF = 2 kΩ
VOUT = 20 V p-p, RF = 2 kΩ
−72
−82
−70
4.3
10
13
dBc
dBc
dBc
nV/√Hz
pA/√Hz
pA/√Hz
fC = 1 MHz, VOUT = 2 V p-p
fC = 1 MHz, VOUT = 2 V p-p
26 kHz to 2.2 MHz, ZLINE = 100 Ω Differential Load
f = 10 kHz
f = 10 kHz
f = 10 kHz
mV
µA
µA
kΩ
pF
dB
V+IN − V−IN
∆VOUT
∆VOUT
RL = 10 Ω, fC = 100 kHz
±3.0
5.0
10.0
400
2.0
68
+5.0
10.0
15.0
44.0
22.0
400
46.0
23.0
V
V
mA
±12
24
V
V
7.0
4.0
3.3
1.2
0.8
mA/Amp
mA/Amp
mA/Amp
mA/Amp
V
V
dB
dB
±5
10
6.0
3.6
2.8
0.4
1.8
64
76
Max
68
79
Rev. 0 | Page 3 of 16
(∆VOS, DM (RTI))/(∆VIN, CM)
∆VOS, DM (RTI)/∆VCC, ∆VCC = ±1 V
∆VOS, DM (RTI)/∆VEE, ∆VEE = ±1 V
AD8392
VS = ±5 V or +10 V, RL = 100 Ω, G = +5, PD = (0, 0), T = 25°C, unless otherwise noted.
Table 2.
Parameter
DYNAMIC PERFORMANCE
−3 dB Small Signal Bandwidth
−3 dB Large signal Bandwidth
Peaking
Slew Rate (Rise)
Slew Rate (Fall)
NOISE/DISTORTION PERFORMANCE
Second Harmonic Distortion
Third Harmonic Distortion
Voltage Noise (RTI)
+Input Current Noise
−Input Current Noise
INPUT CHARACTERISTICS
RTI Offset Voltage
+Input Bias Current
−Input Bias Current
Input Resistance
Input Capacitance
Common-Mode Rejection Ratio
OUTPUT CHARACTERISTICS
Differential Output Voltage Swing
Single-Ended Output Voltage Swing
Linear Output Current
POWER SUPPLY
Operating Range (Dual Supply)
Operating Range (Single Supply)
Total Quiescent Current
PD1, PD0 = (0, 0)
PD1, PD0 = (0, 1)
PD1, PD0 = (1, 0)
PD1, PD0 = (1, 1) (Shutdown State)
PD = 0 Threshold
PD = 1 Threshold
+Power Supply Rejection Ratio
−Power Supply Rejection Ratio
Min
Typ
30
20
300
400
−5.0
62
14.0
7.0
Unit
Test Conditions/Comments
40
25
0.05
350
450
MHz
MHz
dB
V/µs
V/µs
VOUT = 0.1 V p-p, RF = 2 kΩ
VOUT = 4 V p-p, RF = 2 kΩ
VOUT = 0.1 V p-p, RF = 2 kΩ
VOUT = 7 V p-p, RF = 2 kΩ
VOUT = 7 V p-p, RF = 2 kΩ
−72
−82
4.3
10
13
dBc
dBc
nV/√Hz
pA/√Hz
pA/√Hz
fC = 1 MHz, VOUT = 2 V p-p
fC = 1 MHz, VOUT = 2 V p-p
f = 10 kHz
f = 10 kHz
f = 10 kHz
mV
µA
µA
kΩ
pF
dB
V+IN − V−IN
∆VOUT
∆VOUT
RL = 10 Ω, fC = 100 kHz
±3.0
5.0
10.0
400
2.0
66
+5.0
10.0
15.0
16.0
8.0
400
18.0
9.0
V
V
mA
±12
+24
V
V
6.0
4.0
3.0
1.0
0.8
mA/Amp
mA/Amp
mA/Amp
mA/Amp
V
V
dB
dB
±5
+10
5.4
3.5
2.6
0.4
1.8
72
64
Max
76
68
Rev. 0 | Page 4 of 16
(∆VOS, DM (RTI))/(∆VIN, CM)
∆VOS, DM (RTI)/∆VCC, ∆VCC = ±1 V
∆VOS, DM (RTI)/∆VEE, ∆VEE = ±1 V
AD8392
ABSOLUTE MAXIMUM RATINGS
Rating
±13 V (+26 V)
See Figure 3
−65°C to +150°C
−40°C to +85°C
300°C
150°C
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.
RMS output voltages should be considered. If RL is referenced
to VS− as in single-supply operation, the total power is VS × IOUT.
In single supply with RL to VS−, worst case is VOUT = VS/2.
Airflow increases heat dissipation, effectively reducing θJA. Also,
more metal directly in contact with the package leads from
metal traces, through holes, ground, and power planes reduces
the θJA.
Figure 3 shows the maximum safe power dissipation in the
package versus the ambient temperature for the LFCSP-32 and
TSSOP-28/EP packages on a JEDEC standard 4-layer board. θJA
values are approximations.
7
TJ = 150°C
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, i.e., θJA is specified
for device soldered in circuit board for surface-mount packages.
Table 4. Thermal Resistance
Package Type
LFCSP-32 (CP)
TSSOP-28/EP (RE)
θJA
27.27
35.33
Unit
°C/W
°C/W
Maximum Power Dissipation
6
5
LFCSP-32
4
TSSOP-28/EP
3
2
1
0
–40 –30 –20 –10
The power dissipated in the package (PD) is the sum of the
quiescent power dissipation and the power dissipated in the
package due to the load drive for all outputs. The quiescent
power is the voltage between the supply pins (VS) times the
quiescent current (IS). Assuming that the load (RL) is midsupply,
the total drive power is VS/2 × IOUT, some of which is
dissipated in the package and some in the load (VOUT × IOUT).
0
10 20 30 40 50
TEMPERATURE (°C)
60
70
80
90
04802-0-003
Parameter
Supply Voltage
Power Dissipation
Storage Temperature
Operating Temperature Range
Lead Temperature Range (Soldering 10 sec)
Junction Temperature
MAXIMUM POWER DISSIPATION (W)
Table 3.
Figure 3. Maximum Power Dissipation vs. Temperature for a 4-Layer Board
See the Thermal Considerations section for additional thermal
design guidance.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the
human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic
discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of
functionality.
Rev. 0 | Page 5 of 16
AD8392
TYPICAL PERFORMANCE CHARACTERISTICS
950
–45
CREST FACTOR = 5.45
CREST FACTOR = 5.45
900
PD (0, 0)
POWER CONSUMPTION (mW)
MULTITONE POWER RATIO (dBc)
–50
–55
–60
PD (1, 0)
PD (0, 1)
PD (0, 0)
–65
850
800
PD (0, 1)
750
700
PD (1, 0)
650
16
17
19
18
OUTPUT POWER (dBm)
20
21
550
15
16
17
18
19
OUTPUT POWER (dBm)
21
Figure 7. Power Consumption vs. Output Power (26 kHz to 2.2 MHz)
ADSL/ADSL2+ Circuit (Figure 32)
VS = ±12 V, RLOAD = 100 Ω, CF = 5.45
Figure 4. MTPR vs. Output Power (1.75 MHz Empty Bin)
ADSL/ADSL2+ Circuit (Figure 32)
VS = ±12 V, RLOAD = 100 Ω, CF = 5.45
–50
–50
HD2 PD (1, 0)
HD2 PD (1, 0)
HD2 PD (0, 1)
HD2 PD (0, 1)
–60
HARMONIC DISTORTION (dBc)
HARMONIC DISTORTION (dBc)
20
04802-0-007
–70
15
04802-0-004
600
–70
HD2 PD (0, 0)
–80
HD3 PD (1, 0)
HD3 PD (0, 0)
–90
–60
–70
HD2 PD (0, 0)
HD3 PD (1, 0)
–80
HD3 PD (0, 0)
–90
HD3 PD (0, 1)
1
FREQUENCY (MHz)
10
–100
0.1
1
FREQUENCY (MHz)
Figure 8. Harmonic Distortion vs. Frequency
Dual Differential Driver Circuit (Figure 30)
VS = ±5 V, RLOAD = 100 Ω, G = +5, VOUT = 2 V p-p
Figure 5. Harmonic Distortion vs. Frequency
Dual Differential Driver Circuit (Figure 30)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VOUT = 2 V p-p
–50
–50
HD2 PD (1, 0)
HD2 PD (0, 1)
HD2 PD (1, 0)
HD2 PD (0, 1)
–60
HARMONIC DISTORTION (dBc)
–60
–70
–80
HD2 PD (0, 0)
HD3 PD (0, 0)
HD3 PD (0, 1)
–90
HD3 PD (1, 0)
–100
–80
HD2 PD (0, 0)
HD3 PD (0, 0)
HD3 PD (0, 1)
–90
HD3 PD (1, 0)
–100
1
FREQUENCY (MHz)
10
–120
0.1
1
FREQUENCY (MHz)
Figure 9. Harmonic Distortion vs. Frequency
Quad Op Amp Circuit (Figure 29)
VS = ±5 V, RLOAD = 100 Ω, G = +5, VOUT = 2 V p-p
Figure 6. Harmonic Distortion vs. Frequency
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VOUT = 2 V p-p
Rev. 0 | Page 6 of 16
10
04802-0-009
–120
0.1
–70
–110
–110
04802-0-006
HARMONIC DISTORTION (dBc)
10
04802-0-008
–100
0.1
04802-0-005
HD3 PD (0, 1)
AD8392
15
15
10
10
PD (0, 0)
PD (0, 0)
5
5
GAIN (dB)
–5
PD (0, 1)
0
–5
–10
–10
–15
–15
PD (1, 0)
10
FREQUENCY (MHz)
100
1000
–20
0.1
Figure 10. Small Signal Frequency Response
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VOUT = 100 mV p-p
100
1000
0
–10
75Ω
100Ω
–20
SIGNAL FEEDTHROUGH (dB)
10
5
GAIN (dB)
10
FREQUENCY (MHz)
Figure 13. Small Signal Frequency Response
Quad Op Amp Circuit (Figure 29)
VS = ±5 V, RLOAD = 100 Ω, G = +5, VOUT = 100 mV p-p
15
0
25Ω
50Ω
–5
–10
1Ω
–15
4.7Ω
–30
–40
–50
–60
–70
–80
10Ω
1
10
FREQUENCY (MHz)
100
–90
04802-0-011
–20
0.1
1
04802-0-013
1
PD (1, 0)
04802-0-010
–20
0.1
1000
–100
0.1
Figure 11. Small Signal Frequency Response vs. Load
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, G = +5, VOUT = 100 mV p-p
1
10
FREQUENCY (MHz)
100
1000
Figure 14. Signal Feedthrough vs. Frequency
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, G = +5, VIN = 800 mV p-p, PD (1, 1)
15
15
10
10
PD (0, 0)
5
PD (0, 1)
GAIN (dB)
0
–5
–5
–10
–10
–15
–15
PD (1, 0)
1
10
FREQUENCY (MHz)
100
1000
04802-0-012
PD (1, 0)
–20
0.1
PD (0, 0)
PD (0, 1)
0
–20
0.1
Figure 12. Large Signal Frequency Response
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VOUT = 4 V p-p
1
10
FREQUENCY (MHz)
100
Figure 15. Large Signal Frequency Response
Quad Op Amp Circuit (Figure 29)
VS = ±5 V, RLOAD = 100 Ω, G = +5, VOUT = 4 V p-p
Rev. 0 | Page 7 of 16
1000
04802-0-015
GAIN (dB)
5
04802-0-014
GAIN (dB)
PD (0, 1)
0
AD8392
2.5
0.06
2.0
OUTPUT VOLTAGE (V)
1.5
0.02
0
–0.02
1.0
0.5
0
–0.5
–1.0
–1.5
–0.04
–6
–4
–2
0
2
TIME (µs)
4
6
8
10
–2.5
–10
–8
–6
–4
–2
0
2
TIME (µs)
4
6
8
10
Figure 19. Large Signal Pulse Response
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, 4 V Step
Figure 16. Small Signal Pulse Response
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, 100 mV Step
PD PINS
OUTPUT
1
1
OUTPUT
2
004802-0-017
004802-0-020
2
PD PINS
CH1 200mVΩ BW CH2 1.00mVΩ BW M 50.0ns
A CH2
CH1 200mVΩBW CH2 1.00VΩBW
2.38V
M 400ns
CH2
2.38V
Figure 20. Power-Down Time: PD (0, 0) to PD (1, 1)
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VOUT = 1 V p-p
Figure 17. Power-Up Time: PD (1, 1) to PD (0, 0)
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VOUT = 1 V p-p
∆: 460ns
@: –1.32µs
∆: 420ns
@: 2.84µs
C1 p-p
27.0V
C2 p-p
21.4V
C1 p-p
6.00V
C2 p-p
21.8V
1
2
1
2
INPUT
CH1 5.00VΩ
CH2 5.00VΩ
M1.00µs
CH1
004802-0-021
OUTPUT
OUTPUT
INPUT
CH1 1.00VΩ
700mV
CH2 5.00VΩ
M1.00µs
CH1
800mV
Figure 21. Output Overdrive Recovery
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +5, VIN = 6 V p-p
Figure 18. Input Overdrive Recovery
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, RLOAD = 100 Ω, G = +1, VIN = 27 V p-p
Rev. 0 | Page 8 of 16
04802-0-019
–8
04802-0-016
–2.0
–0.06
–10
004802-0-018
OUTPUT VOLTAGE (V)
0.04
0
0
–10
–10
–20
–20
–30
–30
CROSSTALK (dB)
–40
–50
ADSL CHANNEL 3, 4
–60
ADSL CHANNEL 1, 2
–70
–40
–50
DIFF CHANNEL 3, 4
–60
–80
–90
0.1
1
10
FREQUENCY (MHz)
100
04802-0-022
–80
–90
0.1
1
10
FREQUENCY (MHz)
100
Figure 25. Crosstalk vs. Frequency
Dual Differential Driver Circuit (Figure 30)
VS = ±12 V, G = +5, RLOAD = 100 Ω, VIN = 200 mV p-p
Figure 22. Crosstalk vs. Frequency
ADSL/ADSL2+ Circuit (Figure 32)
VS = ±12 V, G = +11, RLOAD = 100 Ω, VIN = 200 mV p-p
45
0
VS = ±12V
–10
DIFFERENTIAL OUTPUT SWING (V)
40
–20
CROSSTALK (dB)
DIFF CHANNEL 1, 2
–70
04802-0-025
CROSSTALK (dB)
AD8392
–30
–40
–50
–60
CHANNEL 1
–70
CHANNEL 2
CHANNEL 3
–80
35
30
25
20
VS = ±5V
15
100
10
10
Figure 23. Crosstalk vs. Frequency
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, G = +5, RLOAD = 100 Ω, VIN = 200 mV p-p
40
50
60
70
RESISTIVE LOAD (Ω)
80
90
100
10
0.1
1
10
100
FREQUENCY (kHz)
1000
Figure 24. Voltage Noise vs. Frequency
100
–INOISE
10
1
0.01
+INOISE
0.1
1
10
100
FREQUENCY (kHz)
Figure 27. Current Noise vs. Frequency
Rev. 0 | Page 9 of 16
1000
04802-0-027
CURRENT NOISE (pA/ Hz)
1000
04802-0-024
VOLTAGE NOISE (nV/ Hz)
30
Figure 26. Differential Output Swing vs. RLOAD
ADSL/ADSL2+ Circuit (Figure 32)
G = +11
100
1
0.01
20
04802-0-026
1
10
FREQUENCY (MHz)
04802-0-023
CHANNEL 4
–90
0.1
AD8392
180
1G
1k
60
100
40
10
20
1
0
0.1
–20
0.01
–40
0.001
–60
1k
10k
100k
1M
10M
–80
1G
100M
FREQUENCY (Hz)
OUTPUT IMPEDANCE (Ω)
80
PHASE (Degrees)
10k
04802-0-028
100
10
PD (0, 0)
PD (0, 1)
1
0.1
0.01
0.01
0.1
10
1
100
1000
FREQUENCY (MHz)
Figure 28. Open-Loop Transimpedance and Phase
Figure 31. Output Impedance vs. Frequency
Quad Op Amp Circuit (Figure 29)
VS = ±12 V, G = +5, PD (0, 0)
280kΩ
100nF
866Ω
6.19Ω
162Ω
49.9Ω
2kΩ
226Ω
499Ω
VCM
04802-0-033
100Ω
100Ω
100nF
162Ω
2kΩ
100nF
2kΩ
6.19Ω
866Ω
280kΩ
Figure 29. Quad Op Amp Circuit
100nF
Figure 32. ADSL/ADSL2+ Circuit
49.9Ω
2kΩ
1kΩ
100Ω
2kΩ
100nF
49.9Ω
Figure 30. Dual Differential Driver Circuit
Rev. 0 | Page 10 of 16
04802-0-032
100nF
04802-0-030
TRANSIMPEDANCE (Ω)
120
TRANSIMPEDANCE
100k
0.0001
100
PD (1, 0)
140
10M
1M
100
160
PHASE
04802-0-031
100M
AD8392
THEORY OF OPERATION
Of course, for a real amplifier there are additional poles that
contribute excess phase, and there is a value for RF below which
the amplifier is unstable. Tolerance for peaking and desired
flatness determines the optimum RF in each application.
RF
The open-loop transimpedance is analogous to the open-loop
voltage gain of a voltage feedback amplifier. Figure 33 shows a
simplified model of a current feedback amplifier. Since RIN is
proportional to 1/gm, the equivalent voltage gain is just TZ × gm,
where gm is the transconductance of the input stage. Basic
analysis of the follower with gain circuit yields
RG
RIN
IIN
VIN
VO
TZ (S )
= G×
VIN
TZ (S ) + G × RIN + RF
R IN =
VOUT
Figure 33. Simplified Block Diagram
where:
G = 1+
TZ
RN
04802-0-034
The AD8392 is a current feedback amplifier with high (400 mA)
output current capability. With a current feedback amplifier, the
current into the inverting input is the feedback signal, and the
open-loop behavior is that of a transimpedance, dVO/dIIN or TZ.
The AD8392 is capable of delivering 400 mA of output current
while swinging to within 2 V of either power supply rail. The
AD8392 also has a power management system included on-chip.
It features four user-programmable power levels (three active
power modes as well as the provision for complete shutdown).
RF
RG
1
≈ 50 Ω
gm
Since G × RIN << RF for low gains, a current feedback amplifier
has relatively constant bandwidth versus gain, the 3 dB point
being set when |TZ| = RF.
Rev. 0 | Page 11 of 16
AD8392
APPLICATIONS
As with all high speed amplifiers, close attention should be paid
to supply decoupling, grounding, and overall board layout. Low
frequency supply decoupling should be provided with 10 µF
tantalum capacitors from each supply to ground. In addition, all
supply pins should be decoupled with 0.1 µF quality ceramic
chip capacitors placed as close as possible to the driver. An
internal low impedance ground plane should be used to provide
a common ground point for all driver and decoupling capacitor
ground requirements. Whenever possible, separate ground
planes should be used for analog and digital circuitry.
High speed layout techniques should be followed to minimize
parasitic capacitance around the inverting inputs. Some practical examples of these techniques are keeping feedback traces as
short as possible and clearing away ground plane in the area of
the inverting inputs. Input and output traces should be kept
short and as far apart from each other as practical to avoid
crosstalk. When used as a differential driver, all differential
signal traces should be kept as symmetrical as possible.
The AD8392 exhibits low output impedance for the three active
states. However, the output impedance in the shutdown state
(PD1, 0 = 1, 1) is undefined.
DRIVING CAPACITIVE LOADS
When driving a capacitive load, most op amps exhibit peaking
in their frequency response. In general, to minimize peaking or
to ensure device stability for larger values of capacitive loads, a
small series resistor can be added between the op amp output
and the load capacitor. Figure 34 shows the frequency response
of the AD8392 for various capacitive loads without any series
resistance. In this condition, the maximum recommended
capacitive load is around 20 pF. As shown in Figure 35, the
addition of a 5.1 Ω series resistor limits peaking to approximately 3 dB when driving capacitive loads up to 100 pF.
20
15
20pF
10
15pF
499Ω
2kΩ
VIN
–10
In current feedback amplifiers, selection of feedback and gain
resistors can impact harmonic distortion performance, bandwidth, and gain flatness. Care should be exercised in the selection of these resistors so that optimum performance is achieved.
Table 5 shows some suggested resistor values for use in a variety
of gain settings. These values are suggested as a good starting
point when designing for any application.
10pF
1kΩ
CL
50Ω
–15
0.1
1
10
100
1000
FREQUENCY (MHz)
Figure 34. AD8392 Capacitive Load Frequency Response
without Series Resistance
20
100pF
15
Table 5. Resistor Selection Guide
47pF
22pF
RG
Open
1.5k
249
82.5
10
5
0
499Ω
2kΩ
–5
POWER MANAGEMENT
5.1Ω
VIN
–10
The AD8392 can be configured in any of three active bias states
as well as a shutdown state via the use of two sets of digitally
programmable logic pins. Pins PD(0, 1) 1, 2 control Amplifiers 1
and 2, while PD(0, 1) 3, 4 control Amplifiers 3 and 4. These pins
can be controlled directly with either 3.3 V or 5 V CMOS logic
by using the GND pins as a reference. If left unconnected, the
PD pins float low, placing the amplifier in the full bias mode.
Refer to the Specifications for the per amplifier quiescent current for each of the available bias states.
Rev. 0 | Page 12 of 16
CL
50Ω
–15
0.1
1
1kΩ
10
100
1000
FREQUENCY (MHz)
Figure 35. AD8392 Capacitive Load Frequency Response
with Series Resistance
04802-0-035
GAIN (dB)
RF
2.0k
1.5k
1.0k
750
0
–5
RESISTOR SELECTION
Gain
1
2
5
10
5
04802-0-034
The AD8392 can be powered from either single or dual supplies,
with the total supply voltage ranging from 10 V to 24 V. For
optimum performance, a well regulated low ripple supply
should be used.
GAIN (dB)
SUPPLIES, GROUNDING, AND LAYOUT
AD8392
When using a quad, high output current amplifier, such as the
AD8392, special consideration should be given to system level
thermal design. In applications such as ADSL/ADSL2+, the
AD8392 could be required to dissipate as much as 1.4 W or
more on chip. Under these conditions, particular attention
should be paid to the thermal design in order to maintain safe
operating temperatures on the die. To aid in the thermal design,
the thermal information in the Thermal Resistance section can
be combined with what follows here.
The information in Table 4 and Figure 3 is based on a standard
JEDEC 4-layer board and a maximum die temperature of
150°C. To provide additional guidance and design suggestions, a
thermal study was performed under a set of conditions more
closely aligned with an actual ADSL/ADSL2+ application.
This data is only provided as guidance to assist in the thermal
design process. Due diligence should be performed with regards
to power dissipation because there are many factors that can
affect thermal performance.
TYPICAL ADSL/ADSL2+ APPLICATION
In a typical ADSL/ADSL2+ application, a differential line driver
is used to take the signal from the analog front end (AFE) and
drive it onto the twisted pair telephone line. Referring to the
typical circuit representation in Figure 37, the differential input
appears at VIN+ and VIN− from the AFE, while the differential
output is transformer coupled to the telephone line at tip and
ring. The common-mode operating point, generally midway
between the supplies, is set through VCOM.
R3
R4
VIN+
In a typical ADSL/ADSL2+ line card, component density usually dictates that most of the copper plane used for thermal
dissipation be internal. Additionally, each ADSL/ADSL2+ port
may be allotted only 1 square inch, or even less, of board space.
For these reasons, a special thermal test board was constructed
for this study. The 4-layer board measured approximately
4 inches × 4 inches and contained two internal 1 oz copper
ground planes, each measuring 2 inches × 3 inches. The top
layer contained signal traces and an exposed copper strip
¼ inch × 3 inches to accommodate heat sinking, with no other
copper on the top or bottom of the board.
Three 28-lead TSSOPs were placed on the board representing
six ADSL channels, or one channel per square inch of copper,
with each channel dissipating 700 mW on-chip (1.4 W per
package). The die temperature is then measured in still air and
in a wind tunnel with calibrated airflow of 100 LFM, 200 LFM,
and 400 LFM. Figure 36 shows the power dissipation versus the
ambient temperature for each airflow condition. The figure
assumes a maximum die temperature of 135°C. No heat sink
was used.
4.5
TJ = 135°C
VOA
VP
TIP
Rm
RBIAS
RIN
R2
ROUT
1:N
VCOM
R1
R2
RBIAS
VIN–
R4
VP
Rm
RING
VOA
R3
04802-0-037
THERMAL CONSIDERATIONS
Figure 37. Typical ADSL/ADSL2+ Application Circuit
In ADSL/ADSL2+ applications, it is common practice to
conserve power by using positive feedback to synthesize the
output resistance, thereby lowering the required ohmic value of
the line matching resistors, Rm. The circuit in Figure 37 is
somewhat unique in that the positive feedback introduced via
R3 has the effect of synthesizing the input resistance as well.
The following definitions and equations can be used to calculate
the resistor values necessary to obtain the desired gain, input
resistance, and output resistance for a given application. For
simplicity the following calculations assume a lossless
transformer.
4.0
The following values are used in the design equations and are
assumed already known or chosen by the designer.
200LFM
VIN
RIN
N
VLINE
Rm
3.0
2.5
STILL AIR
2.0
100LFM
1.5
1.0
5
15
25
35
45
55
65
AMBIENT TEMPERATURE (°C)
75
85
04802-0-036
POWER DISSIPATION (W)
400LFM
3.5
R2
VP
RL
Figure 36. Power Dissipation vs. Ambient
Temperature and Air Flow 28-Lead TSSOP/EP
Rev. 0 | Page 13 of 16
Differential input voltage
Desired differential input resistance
Transformer turns ratio
Differential output voltage at tip and ring
Each is typically 5% to 15% of the transformer reflected
line impedance
Recommended in the amplifier data sheet
Voltage at the + inputs to the amplifier, approximately ½
VIN (must be less than VIN for positive input resistance)
Transformer reflected line impedance
AD8392
Additional definitions for calculating resistor values include:
MULTITONE POWER RATIO
VOA
Voltage at the amplifier outputs
k
Matching resistance reduction factor
AV
Gain from VIN to transformer primary
Negative feedback factor
β
Positive feedback factor
α
Note: R1 must be calculated before β and α.
The DMT signal used in ADSL/ADSL2+ systems carries data in
discrete tones or bins, which appear in the frequency domain in
evenly spaced 4.3125 kHz intervals. In applications using this
type of waveform, multitone power ratio (MTPR) is a commonly used measure of linearity. Generally, there are two types
of MTPR that designers are typically concerned with: in-band
and out-of-band MTPR. In-band MTPR is defined as the
measured difference from the peak of one tone that is loaded
with data to the peak of an adjacent tone that is intentionally
left empty. Out-of-band MTPR is more loosely defined as the
spurious emissions that occur in the receive band located
between 25.875 kHz and the first downstream tone at 138 kHz.
Figure 38 and Figure 39 show the AD8392 in-band MTPR for a
5.5 crest factor waveform for empty bins in the ADSL and
extended ADSL2+ bandwidths. Figure 40 shows the AD8392
out-of-band MTPR for the same waveform.
VOA =
β=
VLINE (1 + k )
N
k=
2 Rm
RL
AV =
R1
R1 + 2 R2
VLINE
N VIN
α = β (1 − k )
With the above known quantities and definitions, the remaining
resistors can readily be calculated.
R1 =
R4 =
2VP R2
VOA − VP
–20
R IN (VIN − VP )
2 VIN
–30
–40
AV R4 (2 R1 Rm + R1 RL − α R1 RL − 2α R2 RL )
R3 =
α RL (R1 + 2 R2 )
R BIAS =
–50
72.2dB
–60
–70
–80
α R3 R4
R4 − α (R3 + R4 )
–90
After building the circuit with the closest 1% resistor values,
the actual gain, input resistance, and output resistance can be
verified with the following equations.
GAIN (VIN to LINE ) =
R IN =
N
R4
R4 ⎞ R4
⎛
β (k + 1)⎜1 +
+
⎟−
⎝ R3 R BIAS ⎠ R3
2
⎛ 2 Rm + RL
1
− AV β⎜⎜
R4
⎝ R4 RL
–110
–120
CENTER 647kHz
1kHz/
SPAN 10kHz
04802-0-038
–100
Figure 38. In-Band MTPR at 647 kHz
–20
–30
–40
⎞
⎟
⎟
⎠
–50
–60
64.4dB
–70
2 Rm N 2
⎛
⎜
⎛ R4 R BIAS
⎞⎜
R1 + 2R2
⎟
1 − ⎜⎜
⎟
R4 R BIAS
⎜
R1
R4
R
(
)
+
BIAS ⎠
⎝
⎜ R3 + R4 + R
BIAS
⎝
–80
⎞
⎟
⎟
⎟
⎟
⎠
–90
–100
–110
–120
CENTER 1.75MHz
1kHz/
SPAN 10kHz
Figure 39. In-Band MTPR at 1.751 MHz
Rev. 0 | Page 14 of 16
04802-0-039
ROUT =
AD8392
–20
LIGHTNING AND AC POWER FAULT
–30
–40
–50
–60
–70
–80
–90
–110
–120
START 3kHz
14.2kHz/
STOP 145kHz
04802-0-040
–100
The AD8392 can be used is as an ADSL/ADSL2+ line driver. In
this application, the line driver is transformer-coupled to the
twisted pair telephone line and could be subjected to large line
transients resulting from events such as lightning strikes or
downed power lines. In this type of environment, additional
circuitry may be required to protect the AD8392 from damage
that may occur as a result of these events. Using a minimal
amount of external protection, the AD8392 has successfully
passed overvoltage and overcurrent compliance testing per the
ITU K-20 specification. For details on the external protection
circuitry, contact the high current driver product line at
[email protected]
Figure 40. Out-of-Band MTPR
Rev. 0 | Page 15 of 16
AD8392
OUTLINE DIMENSIONS
9.80
9.70
9.60
BOTTOM VIEW
28
15
4.50
4.40
4.30
1
EXPOSED
PAD
(Pins Down)
6.40
BSC
3.00
BSC
14
PIN 1
0.65
BSC
1.20
MAX
0.30
0.19
0.15
0.00
3.50
BSC
1.05
1.00
0.80
SEATING
PLANE
0.20
0.09
8°
0°
0.75
0.60
0.45
COMPLIANT TO JEDEC STANDARDS MO-153AET
Figure 41. 28-Lead Thin Shrink Small Outline with Exposed Pad [TSSOP/EP]
(RE-28-1)
Dimensions shown in millimeters
5.00
BSC SQ
0.60 MAX
32
25
24
PIN 1
INDICATOR
0.50
BSC
4.75
BSC SQ
TOP
VIEW
0.50
0.40
0.30
12° MAX
PIN 1
INDICATOR
0.60 MAX
1
3.25
3.10 SQ
2.95
BOTTOM
VIEW
17
16
9
8
0.25 MIN
3.50 REF
0.80 MAX
0.65 TYP
0.05 MAX
0.02 NOM
1.00
0.85
0.80
SEATING
PLANE
0.30
0.23
0.18
0.20 REF
COPLANARITY
0.08
COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2
Figure 42. 32-Lead Lead Frame Chip Scale Package [LFCSP]
5 mm × 5 mm Body (CP-32-2)
Dimensions shown in millimeters
ORDERING GUIDE
Model
AD8392ARE
AD8392ARE-REEL
AD8392ARE-REEL7
AD8392ACP-R2
AD8392ACP-REEL
AD8392ACP-REEL7
Temperature Range
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
Package Description
28-Lead Thin Shrink Small Outline Package (TSSOP)
28-Lead Thin Shrink Small Outline Package (TSSOP)
28-Lead Thin Shrink Small Outline Package (TSSOP)
32-Lead Lead Frame Chip Scale Package (LFCSP)
32-Lead Lead Frame Chip Scale Package (LFCSP)
32-Lead Lead Frame Chip Scale Package (LFCSP)
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
D04802–0–7/04(0)
Rev. 0 | Page 16 of 16
Package Outline
RE-28-1
RE-28-1
RE-28-1
CP-32-2
CP-32-2
CP-32-2