FEATURES
Unity Gain Bandwidth: 5.5 MHz
Low Voltage Offset: 1.0 mV
Slew Rate: 7.5 V/s
Single-Supply Operation: 5 V to 18 V
High Output Current: 70 mA
Low Supply Current: 800 A/Amplifier
Stable with Large Capacitive Loads
Rail-to-Rail Inputs and Outputs
APPLICATIONS
LCD Gamma and V
Modems
Portable Instrumentation
Direct Access Arrangement
GENERAL DESCRIPTION
The AD8614 (single) and AD8644 (quad) are single-supply,
5.5 MHz bandwidth, rail-to-rail amplifiers optimized for LCD
monitor applications.
They are processed using Analog Devices high voltage, high speed,
complementary bipolar process—HV XFCB. This proprietary
process includes trench isolated transistors that lower internal
parasitic capacitance which improves gain bandwidth, phase margin and capacitive load drive. The low supply current of 800 µA
(typ) per amplifier is critical for portable or densely packed designs.
In addition, the rail-to-rail output swing provides greater dynamic
range and control than standard video amplifiers provide.
These products operate from supplies of 5 V to as high as
18 V. The unique combination of an output drive of 70 mA,
high slew rates, and high capacitive drive capability makes the
AD8614/AD8644 an ideal choice for LCD applications.
The AD8614 and AD8644 are specified over the temperature
range of –20°C to +85°C. They are available in 5-lead SOT-23,
14-lead TSSOP and 14-lead SOIC surface mount packages in
tape and reel.
COM
Drivers
Operational Amplifiers
AD8614/AD8644
PIN CONFIGURATIONS
5-Lead SOT-23
(RT Suffix)
14-Lead TSSOP
(RU Suffix)
OUT A
2IN A
1IN A
1IN B
2IN B
OUT B
114
V1
78
AD8644
14-Lead Narrow Body SO
(R Suffix)
OUT D
2IN D
1IN DV2
1IN C
2IN C
OUT C
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Operating Temperature Range . . . . . . . . . . . –20°C to +85°C
Junction Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Range (Soldering, 60 sec) . . . . . . . . 300°C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
f = 1 kHz12nV/√Hz
f = 10 kHz11nV/√Hz
f = 10 kHz1pA/√Hz
Package Type
5-Lead SOT-23 (RT)230140°C/W
S
14-Lead TSSOP (RU)18035°C/W
1
JA
JC
Unit
14-Lead SOIC (R)12056°C/W
NOTE
1
θJA is specified for worst-case conditions, i.e., θ
onto a circuit board for surface mount packages.
is specified for device soldered
JA
ORDERING GUIDE
TemperaturePackagePackage
ModelRangeDescriptionOption
AD8614ART
AD8644ARU
AD8644AR
NOTES
1
Available in 3,000 or 10,000 piece reels.
2
Available in 2,500 piece reels only.
1
–20°C to +85°C5-Lead SOT-23RT-5
2
–20°C to +85°C14-Lead TSSOP RU-14
2
–20°C to +85°C14-Lead SOICR-14
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.
WARNING!
Although the AD8614/AD8644 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.
ESD SENSITIVE DEVICE
–2–REV. 0
Page 3
Typical Performance Characteristics –
GAIN – dB
FREQUENCY – Hz
1k
100M
10k100k1M10M
80
60
40
20
0
45
90
135
180
5V # VS # 18V
R
L
= 1MV
CL = 40pF
T
A
= 258C
PHASE SHIFT – Degrees
TIME – 500ns/Div
VS = 5V # VS # 18V
R
L
= 2kV
CL = 200pF
AV = 1
T
A
= 258C
V
S
2
VOLTAGE – 50mV/Div
COMMON-MODE VOLTAGE – Volts
400
0
2400
22.5
2.5
21.520.5
0.51.5
300
200
2200
2300
100
2100
VS = 62.5V
INPUT BIAS CURRENT – nA
AD8614/AD8644
50
VS = 18V
R
= 2kV
45
L
T
= 258C
A
40
35
30
25
20
15
10
SMALL SIGNAL OVERSHOOT – %
5
0
1010k1001k
+OS
2OS
CAPACITANCE – pF
Figure 1. Small Signal Overshoot vs.
Load Capacitance
7.5
VS = 5V
6.5
R
= 2kV
L
CL = 200pF
5.5
AV = 1
= 258C
T
4.5
A
3.5
2.5
1.5
VOLTAGE – 1V/Div
0.5
20.5
21.5
22.5
TIME – 1ms/Div
Figure 4. Large Signal Transient
Response
12
8
0.1%
4
0
24
28
OUTPUT SWING FROM 0 TO 6 V
212
0
0.1%
1.01.5 2.0 2.5 3.0
0.53.5
SETTLING TIME – ms
0.01%
0.01%
Figure 2. Settling Time
29
VS = 18V
25
R
= 2kV
L
CL = 200pF
21
AV = 1
17
= 258C
T
A
13
9
5
VOLTAGE – 4V/Div
1
23
27
211
TIME – 1ms/Div
Figure 5. Large Signal Transient
Response
Figure 3. Open-Loop Gain and Phase
vs. Frequency
Figure 6. Small Signal Transient
Response
10k
1k
100
10
DOUTPUT VOLTAGE – mV
1
0.001100
Figure 7. Output Voltage to Supply
Rail vs. Load Current
5V # VS # 18V
T
= 258C
A
0.01
LOAD CURRENT – mA
SINK
SOURCE
0.1110
1,000
900
TA = 258C
800
700
600
500
400
300
200
SUPPLY CURRENT/AMPLIFIER – mA
100
0
010123456789
SUPPLY VOLTAGE – 6Volts
Figure 8. Supply Current vs. Supply
Voltage
–3–REV. 0
Figure 9. Input Bias Current vs.
Common-Mode Voltage
Page 4
AD8614/AD8644
TEMPERATURE – 8C
SUPPLY CURRENT/AMPLIFIER – mA
1.0
0.9
0.5
235 215
5 25456585
0.8
0.7
0.6
VS = 18V
VS = 5V
400
300
VS = 69V
200
100
0
2100
2200
INPUT BIAS CURRENT – nA
2300
2400
29927 25 23 21
COMMON-MODE VOLTAGE – Volts
01357
Figure 10. Input Bias Current vs.
Common-Mode Voltage
6
5
VS = 5V
A
= 1
VCL
4
R
= 2kV
L
= 258C
T
A
3
2
OUTPUT SWING – V p-p
1
0
1001k10M
10k100k1M
FREQUENCY – Hz
Figure 13. Maximum Output Swing
vs. Frequency
180
160
140
120
100
80
60
QUANTITY – Amplifiers
40
20
0
21.5 2120.5
22
INPUT OFFSET VOLTAGE – mV
2.5V # VS # 9V
T
= 258C
A
0 0.5 1 1.5
2
Figure 11. Input Offset Voltage
Distribution
20
18
16
VS = 18V
14
A
= 1
VCL
R
= 2kV
L
12
= 258C
T
A
10
8
6
OUTPUT SWING – V p-p
4
2
0
1001k10M10k100k1M
FREQUENCY – Hz
Figure 14. Maximum Output Swing
vs. Frequency
Figure 12. Supply Current vs.
Temperature
300
5V # VS # 18V
= 258C
T
A
240
180
120
IMPEDANCE – V
60
0
1k10k100k1M10M
AV = 10
AV = 100
FREQUENCY – Hz
AV = 1
Figure 15. Closed-Loop Output
Impedance vs. Frequency
5V # VS # 18V
T
= 258C
A
40
20
GAIN – dB
0
1k10k100M
Figure 16. Closed-Loop Gain vs.
Frequency
FREQUENCY – Hz
100k1M10M
140
5V # VS # 18V
T
= 258C
120
A
100
80
60
40
20
COMMON-MODE REJECTION – dB
0
1001k10M
10k100k1M
FREQUENCY – Hz
Figure 17. Common-Mode Rejection
vs. Frequency
–4–REV. 0
100
80
60
40
20
POWER-SUPPLY REJECTION – dB
0
1001k
10k100k
FREQUENCY – Hz
VS = 18V
T
PSRR+
PSRR2
= 258C
A
1M
10M
Figure 18. Power-Supply Rejection
vs. Frequency
Page 5
AD8614/AD8644
VOLTAGE NOISE DENSITY – nV Hz
FREQUENCY – Hz
100
10
1
1010010k1k
VS = 18V
T
A
= 258C
9
8
7
6
5
4
3
SLEW RATE – V/ms
AV = 1
2
R
= 2kV
L
CL = 200pF
1
= 258C
T
A
0
4681012141618
220
0
SUPPLY VOLTAGE – V
SR+
SR2
Figure 19. Slew Rate vs. Supply
Voltage
100
10
VOLTAGE NOISE DENSITY – nV Hz
1
1010010k1k
FREQUENCY – Hz
Figure 20. Voltage Noise Density
vs. Frequency
APPLICATIONS SECTION
Theory of Operation
The AD8614/AD8644 are processed using Analog Devices’ high
voltage, high speed, complementary bipolar process—HV XFCB.
This process includes trench isolated transistors that lower parasitic
capacitance.
Figure 22 shows a simplified schematic of the AD8614/AD8644.
The input stage is rail-to-rail, consisting of two complementary
differential pairs, one NPN pair and one PNP pair. The input stage
is protected against avalanche breakdown by two back-to-back
diodes. Each input has a 1.5 kΩ resistor that limits input current
during over-voltage events and furnishes phase reversal protection
if the inputs are exceeded. The two differential pairs are connected
to a double-folded cascode. This is the stage in the amplifier with
the most gain. The double folded cascode differentially feeds the
output stage circuitry. Two complementary common emitter transistors are used as the output stage. This allows the output to swing
to within 125 mV from each rail with a 10 mA load. The gain of the
output stage, and thus the open loop gain of the op amp, depends on
the load resistance.
VS = 5V
T
= 258C
A
Figure 21. Voltage Noise Density vs.
Frequency
The AD8614/AD8644 have no built-in short circuit protection.
The short circuit limit is a function of high current roll-off of the
output stage transistors and the voltage drop over the resistor
shown on the schematic at the output stage. The voltage over this
resistor is clamped to one diode during short circuit voltage events.
Output Short-Circuit Protection
To achieve a wide bandwidth and high slew rate, the output of
the AD8614/AD8644 is not short-circuit protected. Shorting
the output directly to ground or to a supply rail may destroy the
device. The typical maximum safe output current is 70 mA.
In applications where some output current protection is needed,
but not at the expense of reduced output voltage headroom, a low
value resistor in series with the output can be used. This is shown
in Figure 23. The resistor is connected within the feedback loop
of the amplifier so that if V
is shorted to ground and V
OUT
IN
swings up to 18 V, the output current will not exceed 70 mA.
For 18 V single supply applications, resistors less than 261 Ω are
not recommended.
V
CC
2
1.5kV
V
EE
+
1.5kV
V
V
CC
CC
Figure 22. Simplified Schematic
–5–REV. 0
V
OUT
Page 6
AD8614/AD8644
18V
V
IN
AD86x4
261V
V
OUT
Figure 23. Output Short-Circuit Protection
Input Overvoltage Protection
As with any semiconductor device, whenever the condition exists for
the input to exceed either supply voltage, attention needs to be paid
to the input overvoltage characteristic. As an overvoltage occurs, the
amplifier could be damaged, depending on the voltage level and the
magnitude of the fault current. When the input voltage exceeds
either supply by more than 0.6 V, internal pin junctions energize,
allowing current to flow from the input to the supplies. Observing
Figure 22, the AD8614/AD8644 has 1.5 kΩ resistors in series with
each input, which helps limit the current. This input current is not
inherently damaging to the device as long as it is limited to 5 mA or
less. If the voltage is large enough to cause more than 5 mA of current to flow, an external series resistor should be added. The size of
this resistor is calculated by dividing the maximum overvoltage by
5 mA and subtracting the internal 1.5 kΩ resistor. For example, if
the input voltage could reach 100 V, the external resistor should be
(100 V/5 mA) – 1.5 kΩ = 18.5 kΩ. This resistance should be placed
in series with either or both inputs if they are subjected to the overvoltages. For more information on general overvoltage characteristics
of amplifiers refer to the 1993 System Applications Guide, available
from the Analog Devices Literature Center.
Output Phase Reversal
The AD8614/AD8644 is immune to phase reversal as long as the
input voltage is limited to within the supply rails. Although the
device’s output will not change phase, large currents due to
input overvoltage could result, damaging the device. In applications where the possibility of an input voltage exceeding the
supply voltage exists, overvoltage protection should be used, as
described in the previous section.
Power Dissipation
The maximum power that can be safely dissipated by the
AD8614/AD8644 is limited by the associated rise in junction
temperature. The maximum safe junction temperature is 150°C,
and should not be exceeded or device performance could suffer.
If this maximum is momentarily exceeded, proper circuit operation will be restored as soon as the die temperature is reduced.
Leaving the device in an “overheated” condition for an extended
period can result in permanent damage to the device.
To calculate the internal junction temperature of the AD86x4,
the following formula can be used:
T
= P
J
DISS
×θ
JA
+ T
A
where: TJ = AD86x4 junction temperature;
P
= AD86x4 power dissipation;
DISS
θ
= AD86x4 package thermal resistance, junction-to-
JA
ambient; and
T
= Ambient temperature of the circuit.
A
The power dissipated by the device can be calculated as:
P
where: I
= I
DISS
is the AD86x4 output load current;
LOAD
V
is the AD86x4 supply voltage; and
S
V
is the AD86x4 output voltage.
OUT
LOAD
× (V
– V
S
OUT
)
Figure 24 provides a convenient way to see if the device is being
overheated. The maximum safe power dissipation can be found
graphically, based on the package type and the ambient temperature around the package. By using the previous equation, it
is a simple matter to see if P
exceeds the device’s power
DISS
derating curve. To ensure proper operation, it is important to
observe the recommended derating curves shown in Figure 24.
1.5
14-LEAD SOIC PACKAGE
u
= 1208C/W
JA
1.0
14-LEAD TSSOP PACKAGE
u
= 1808C/W
JA
0.5
5-LEAD SOT-23 PACKAGE
u
= 2308C/W
JA
MAXIMUM POWER DISSIPATION – Watts
0
–35–15525456585
AMBIENT TEMPERATURE – 8C
Figure 24. Maximum Power Dissipation vs. Temperature
for 5-Lead and 14-Lead Package Types
Unused Amplifiers
It is recommended that any unused amplifiers in the quad package be configured as a unity gain follower with a 1 kΩ feedback
resistor connected from the inverting input to the output, and
the noninverting input tied to the ground plane.
Capacitive Load Drive
The AD8614/AD8644 exhibits excellent capacitive load driving
capabilities. Although the device is stable with large capacitive
loads, there is a decrease in amplifier bandwidth as the capacitive
load increases.
When driving heavy capacitive loads directly from the AD8614/
AD8644 output, a snubber network can be used to improve the
transient response. This network consists of a series R-C connected
from the amplifier’s output to ground, placing it in parallel with the
capacitive load. The configuration is shown in Figure 25. Although
this network will not increase the bandwidth of the amplifier, it will
significantly reduce the amount of overshoot.
5V
V
AD86x4
V
IN
R
X
C
X
OUT
C
L
Figure 25. Snubber Network Compensation for Capacitive
Loads
–6–REV. 0
Page 7
The optimum values for the snubber network should be determined
U1-A
R1
2kV
4
C1
100mF
5V
1
10
2
3
5
5V
V
DD
V
DD
LEFT
OUT
AD1881
(AC'97)
RIGHT
OUT
V
SS
R3
20V
7
8
6
9
R4
20V
C2
100mF
NOTE: ADDITIONAL PINS
OMITTED FOR CLARITY
U1-B
U1 = AD8644
R2
2kV
28
35
36
U1-A
R1
2kV
4
C1
100mF
5V
1
10
2
3
5
5V
V
DD
V
DD
LEFT
OUT
AD1881
(AC97)
RIGHT
OUT
V
SS
R3
20V
7
8
6
9
R4
20V
C2
100mF
NOTE: ADDITIONAL PINS
OMITTED FOR CLARITY
U1-B
U1 = AD8644
R2
2kV
R6
20kV
R6
20kV
V
REF
R5
10kV
R5
10kV
AV == +6dB WITH VALUES SHOWN
R6
R5
38
35
27
36
empirically based on the size of the capacitive load. Table I shows a
few sample snubber network values for a given load capacitance.
Table I. Snubber Networks for Large Capacitive Loads
Load CapacitanceSnubber Network
(CL)(R
, CS)
S
0.47 nF300 Ω, 0.1 µF
4.7 nF30 Ω, 1 µF
47 nF5 Ω, 1 µF
Direct Access Arrangement
Figure 26 shows a schematic for a 5 V single supply transmit/receive
telephone line interface for 600 Ω transmission systems. It allows
full duplex transmission of signals on a transformer-coupled 600 Ω
line. Amplifier A1 provides gain that can be adjusted to meet the
modem output drive requirements. Both A1 and A2 are configured
to apply the largest possible differential signal to the transformer.
The largest signal available on a single 5 V supply is approximately
4.0 V p-p into a 600 Ω transmission system. Amplifier A3 is configured as a difference amplifier to extract the receive information from
the transmission line for amplification by A4. A3 also prevents the
transmit signal from interfering with the receive signal. The gain of
A4 can be adjusted in the same manner as A1’s to meet the modem’s
input signal requirements. Standard resistor values permit the use of
SIP (Single In-Line Package) format resistor arrays. Couple this with
the AD8644 14-lead SOIC or TSSOP package and this circuit can
offer a compact solution.
AD8614/AD8644
Figure 27. A PC-99 Compliant Headphone/Line Out Amplifier
If gain is required from the output amplifier, four additional
resistors should be added as shown in Figure 28. The gain of
the AD8644 can be set as:
R
A
6
=
V
R
5
TO TELEPHONE
Z
600V
A1, A2 = 1/2 AD8644
A3, A4 = 1/2 AD8644
Figure 26. A Single-Supply Direct Access Arrangement for
Modems
A One-Chip Headphone/Microphone Preamplifier Solution
Because of its high output current performance, the AD8644
makes an excellent amplifier for driving an audio output jack in
a computer application. Figure 27 shows how the AD8644 can
be interfaced with an ac codec to drive headphones or speakers
LINE
1:1
O
T1
MIDCOM
671-8005
R3
360V
6.2V
6.2V
R9
10kV
R11
10kV
R12
10kV
2
3
Tx GAIN
ADJUST
R5
10kV
R6
10kV
R10
10kV
A3
P1
2kV
1
7
1
R2
A1
A2
R13
10kV
9.09kV
2
3
6
5
R14
14.3kV
6
5
R1
10kV
A4
C1
0.1mF
10mF
P2
Rx GAIN
ADJUST
2kV
7
5V DC
C2
0.1mF
TRANSMIT
R7
10kV
R8
10kV
RECEIVE
TxA
RxA
Figure 28. A PC-99-Compliant Headphone/Speaker
Amplifier with Gain
Input coupling capacitors are not required for either circuit as
the reference voltage is supplied from the AD1881.
R4 and R5 help protect the AD8644 output in case the output
jack or headphone wires are accidentally shorted to ground.
The output coupling capacitors C1 and C2 block dc current
from the headphones and create a high-pass filter with a corner
frequency of:
f
=
dB
−
3
Where RL is the resistance of the headphones.
1
CR R
214π
+
()
L
–7–REV. 0
Page 8
AD8614/AD8644
The remaining two amplifiers can be used as low voltage
microphone preamplifiers. A single AD8614 can be used as a
stand-alone microphone preamplifier. Figure 29 shows this
implementation.
MIC 1 IN
AD1881
(AC'97)
MIC 2 IN
V
REF
10kV
= 20dB
A
V
21
10kV
AV = +20dB
22
27
1kV
1kV
1mF
1mF
5V
2.2kV
MIC 1
5V
2.2kV
MIC 2
Figure 29. Microphone Preamplifier
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
SPICE Model Availability
The SPICE model for the AD8614/AD8644 amplifier is available
and can be downloaded from the Analog Devices’ web site at
http://www.analog.com. The macro-model accurately simulates
a number of AD8614/AD8644 parameters, including offset voltage, input common-mode range, and rail-to-rail output swing.
The output voltage versus output current characteristic of the
macro-model is identical to the actual AD8614/AD8644 performance, which is a critical feature with a rail-to-rail amplifier model.
The model also accurately simulates many ac effects, such as gain
bandwidth product, phase margin, input voltage noise, CMRR and
PSRR versus frequency, and transient response. Its high degree of
model accuracy makes the AD8614/AD8644 macro-model one of
the most reliable and true-to-life models available for any amplifier.
C3735–8–10/99
0.177 (4.50)
0.006 (0.15)
0.002 (0.05)
SEATING
PLANE
0.201 (5.10)
0.193 (4.90)
14
0.169 (4.30)
1
PIN 1
0.0256
(0.65)
BSC
14-Lead TSSOP
(RU Suffix)
8
0.256 (6.50)
7
0.0433
(1.10)
0.0118 (0.30)
0.0075 (0.19)
MAX
0.0079 (0.20)
0.0035 (0.090)
0.0669 (1.70)
0.0590 (1.50)
0.0512 (1.30)
0.0354 (0.90)
0.246 (6.25)
PIN 1
0.0059 (0.15)
0.0019 (0.05)
0.028 (0.70)
88
08
0.020 (0.50)
5-Lead SOT-23
0.1181 (3.00)
0.1102 (2.80)
1 3
2
0.0748 (1.90)
BSC
0.0197 (0.50)
0.0138 (0.35)
(RT Suffix)
4 5
0.1181 (3.00)
0.1024 (2.60)
0.0374 (0.95) BSC
0.0571 (1.45)
0.0374 (0.95)
SEATING
PLANE
108
08
0.1574 (4.00)
0.1497 (3.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.0079 (0.20)
0.0031 (0.08)
0.0217 (0.55)
0.0138 (0.35)
14-Lead Narrow SOIC
(R Suffix)
0.3444 (8.75)
0.3367 (8.55)
148
PIN 1
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
0.0500
0.2440 (6.20)
71
0.2284 (5.80)
0.0688 (1.75)
0.0532 (1.35)
0.0099 (0.25)
0.0075 (0.19)
0.0196 (0.50)
0.0099 (0.25)
8ⴗ
0ⴗ
0.0500 (1.27)
0.0160 (0.41)
PRINTED IN U.S.A.
x 45ⴗ
–8–
REV. 0
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