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Low Cost, 250 mA Output, Single-Supply Amplifiers AD8531/AD8532/AD8534
FEATURES
Single-supply operation: 2.7 V to 6 V High output current: 250 mA Low supply current: 750 A/amplifier Wide bandwidth: 3 MHz Slew rate: 5 V/s No phase reversal Low input currents Unity gain stable Rail-to-rail input and output
PIN CONFIGURATIONS
OUT A 1 V- 2 +IN A 3
4
AD8531
5
V+
-IN A
Figure 1. 5-Lead SC70 and 5-Lead SOT-23 (KS and RJ Suffixes)
NC 1
AD8531
8 7 6 5
NC V+ OUT A
01099-002
01099-004
APPLICATIONS
Multimedia audio LCD drivers ASIC input or output amplifiers Headphone drivers
-IN A 2 +IN A 3 V- 4
NC
NC = NO CONNECT
Figure 2. 8-Lead SOIC (R Suffix)
GENERAL DESCRIPTION
The AD8531, AD8532, and AD8534 are single, dual, and quad rail-to-rail input/output single-supply amplifiers featuring 250 mA output drive current. This high output current makes these amplifiers excellent for driving either resistive or capacitive loads. AC performance is very good with 3 MHz bandwidth, 5 V/s slew rate, and low distortion. All are guaranteed to operate from a 3 V single supply as well as a 5 V supply. The very low input bias currents enable the AD853x to be used for integrators, diode amplification, and other applications requiring low input bias current. Supply current is only 750 A per amplifier at 5 V, allowing low current applications to control high current loads. Applications include audio amplification for computers, sound ports, sound cards, and set-top boxes. The AD853x family is very stable, and it is capable of driving heavy capacitive loads such as those found in LCDs. The ability to swing rail-to-rail at the inputs and outputs enables designers to buffer CMOS DACs, ASICs, or other wide output swing devices in single-supply systems. The AD8531/AD8532/AD8534 are specified over the extended industrial temperature range (-40C to +85C). The AD8531 is available in 8-lead SOIC, 5-lead SC70, and 5-lead SOT-23 packages. The AD8532 is available in 8-lead SOIC, 8-lead MSOP, and 8-lead TSSOP surface-mount packages. The AD8534 is available in narrow 14-lead SOIC and 14-lead TSSOP surface-mount packages.
Rev. F
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.
OUT A 1 -IN A +IN A V-
2 3 4 8 7 6 5
V+ OUT B -IN B +IN B
01099-003
AD8532
Figure 3. 8-Lead SOIC, 8-Lead TSSOP, and 8-Lead MSOP (R, RU, and RM Suffixes)
OUT A 1 -IN A +IN A V+
2 3 4
14 OUT D 13 -IN D 12 +IN D
AD8534
11 V- 10 +IN C 9 8
+IN B 5 -IN B OUT B
6 7
-IN C OUT C
Figure 4. 14-Lead SOIC and 14-Lead TSSOP (R and RU Suffixes)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)1996-2008 Analog Devices, Inc. All rights reserved.
01099-001
AD8531/AD8532/AD8534 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Pin Configurations ........................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Electrical Characteristics............................................................. 3 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Typical Performance Characteristics ............................................. 6 Theory of Operation ...................................................................... 11 Short-Circuit Protection............................................................ 11 Power Dissipation....................................................................... 11 Power Calculations for Varying or Unknown Loads............. 12 Calculating Power by Measuring Ambient and Case Temperature ................................................................................ 12 Calculating Power by Measuring Supply Current ................. 12 Input Overvoltage Protection ................................................... 12 Output Phase Reversal............................................................... 13 Capacitive Load Drive ............................................................... 13 Applications Information .............................................................. 14 High Output Current, Buffered Reference/Regulator........... 14 Single-Supply, Balanced Line Driver ....................................... 14 Single-Supply Headphone Amplifier....................................... 15 Single-Supply, 2-Way Loudspeaker Crossover Network....... 15 Direct Access Arrangement for Telephone Line Interface ... 16 Outline Dimensions ....................................................................... 17 Ordering Guide .......................................................................... 20
REVISION HISTORY
1/08--Rev. E to Rev. F Changes to Layout ............................................................................ 5 Changes to Figure 12 and Figure 13............................................... 7 Changes to Figure 38...................................................................... 11 Changes to Input Overvoltage Protection Section..................... 12 Changes to Figure 43...................................................................... 14 Updated Outline Dimensions ....................................................... 17 Changes to Ordering Guide .......................................................... 20 4/05--Rev. D to Rev. E Updated Format..................................................................Universal Changes to Pin Configurations....................................................... 1 Changes to Table 4............................................................................ 5 Updated Outline Dimensions ....................................................... 18 Changes to Ordering Guide .......................................................... 19 10/02--Rev. C to Rev. D Deleted 8-Lead PDIP (N-8) .............................................. Universal Deleted 14-Lead PDIP (N-14) .......................................... Universal Edits to Figure 34...............................................................................9 Updated Outline Dimensions ........................................................15 8/96--Revision 0: Initial Version
Rev. F | Page 2 of 20
AD8531/AD8532/AD8534 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
VS = 3.0 V, VCM = 1.5 V, TA = 25C, unless otherwise noted. Table 1.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift Bias Current Drift Offset Current Drift OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin Channel Separation NOISE PERFORMANCE Voltage Noise Density Current Noise Density Symbol VOS -40C TA +85C IB -40C TA +85C IOS -40C TA +85C CMRR AVO VOS/T IB/T IOS/T VOH VOL IOUT ZOUT PSRR ISY VCM = 0 V to 3 V RL = 2 k, VO = 0.5 V to 2.5 V 0 38 45 25 20 50 20 2.92 60 250 60 45 55 0.70 100 125 1 5 Conditions Min Typ Max 25 30 50 60 25 30 3 Unit mV mV pA pA pA pA V dB V/mV V/C fA/C fA/C V V mV mV mA dB mA mA V/s s MHz Degrees dB nV/Hz nV/Hz pA/Hz
IL = 10 mA -40C TA +85C IL = 10 mA -40C TA +85C f = 1 MHz, AV = 1 VS = 3 V to 6 V VO = 0 V -40C TA +85C RL = 2 k To 0.01%
2.85 2.8
1 1.25
SR tS GBP o CS en in
f = 1 kHz, RL = 2 k f = 1 kHz f = 10 kHz f = 1 kHz
3.5 1.6 2.2 70 65 45 30 0.05
Rev. F | Page 3 of 20
AD8531/AD8532/AD8534
VS = 5.0 V, VCM = 2.5 V, TA = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift Bias Current Drift Offset Current Drift OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Full-Power Bandwidth Settling Time Gain Bandwidth Product Phase Margin Channel Separation NOISE PERFORMANCE Voltage Noise Density Current Noise Density Symbol VOS -40C TA +85C IB -40C TA +85C IOS -40C TA +85C CMRR AVO VOS/T IB/T IOS/T VOH VOL IOUT ZOUT PSRR ISY VCM = 0 V to 5 V RL = 2 k, VO = 0.5 V to 4.5 V -40C TA +85C 0 38 15 47 80 20 50 20 4.94 50 250 40 45 55 0.75 100 125 1 5 Conditions Min Typ Max 25 30 50 60 25 30 5 Unit mV mV pA pA pA pA V dB V/mV V/C fA/C fA/C V V mV mV mA dB mA mA V/s kHz s MHz Degrees dB nV/Hz nV/Hz pA/Hz
IL = 10 mA -40C TA +85C IL = 10 mA -40C TA +85C f = 1 MHz, AV = 1 VS = 3 V to 6 V VO = 0 V -40C TA +85C RL = 2 k 1% distortion To 0.01%
4.9 4.85
1.25 1.75
SR BWp tS GBP o CS en in
f = 1 kHz, RL = 2 k f = 1 kHz f = 10 kHz f = 1 kHz
5 350 1.4 3 70 65 45 30 0.05
Rev. F | Page 4 of 20
AD8531/AD8532/AD8534 ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Supply Voltage (VS) Input Voltage Differential Input Voltage1 Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec)
1
Rating 7V GND to VS 6 V -65C to +150C -40C to +85C -65C to +150C 300C
2.5 -VOL 2.0 +VOH
1.5
VOUT
1.0 0.5
01099-005
For supplies less than 6 V, the differential input voltage is equal to VS.
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; the functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
0
0
20
40
60
80
100 120 RLOAD ()
140
160
180
200
Figure 5. Output Voltage vs. Load, VS = 2.5 V, RLOAD Is Connected to GND (0 V)
THERMAL RESISTANCE
JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 4.
Package Type 5-Lead SC70 (KS) 5-Lead SOT-23 (RJ) 8-Lead SOIC (R) 8-Lead MSOP (RM) 8-Lead TSSOP (RU) 14-Lead SOIC (R) 14-Lead TSSOP (RU) JA 376 230 158 210 240 120 240 JC 126 146 43 45 43 36 43 Unit C/W C/W C/W C/W C/W C/W C/W
ESD CAUTION
Rev. F | Page 5 of 20
AD8531/AD8532/AD8534 TYPICAL PERFORMANCE CHARACTERISTICS
500
QUANTITY (Amplifiers)
VS = 2.7V VCM = 1.35V TA = 25C
INPUT BIAS CURRENT (pA)
8 7 6 5 4 3
VS = 5V, 3V VCM = VS/2
400
300
200
100
01099-006
-12
-10
-8 -6 -4 -2 0 INPUT OFFSET VOLTAGE (mV)
2
4
-35
-15
5 25 45 TEMPERATURE (C)
65
85
Figure 6. Input Offset Voltage Distribution
Figure 9. Input Bias Current vs. Temperature
500
QUANTITY (Amplifiers)
VS = 5V VCM = 2.5V TA = 25C
INPUT BIAS CURRENT (pA)
VS = 5V TA = 25C 8 7 6 5 4 3 2
01099-010
400
300
200
100
01099-007
-12
-10
-8 -6 -4 -2 0 INPUT OFFSET VOLTAGE (mV)
2
4
0
1 2 3 4 COMMON-MODE VOLTAGE (V)
5
Figure 7. Input Offset Voltage Distribution
Figure 10. Input Bias Current vs. Common-Mode Voltage
6 5
INPUT OFFSET CURRENT (pA)
-2
INPUT OFFSET VOLTAGE (mV)
VS = 5V VCM = 2.5V
VS = 5V, 3V VCM = VS/2
-3 -4 -5 -6 -7
01099-008
4 3 2 1 0
01099-011
-8
-1 -2
-35
-15
5 25 45 TEMPERATURE (C)
65
85
-35
-15
5 25 45 TEMPERATURE (C)
65
85
Figure 8. Input Offset Voltage vs. Temperature
Figure 11. Input Offset Current vs. Temperature
Rev. F | Page 6 of 20
01099-009
2
AD8531/AD8532/AD8534
1000
OUTPUT VOLTAGE (mV)
VS = 2.7V TA = 25C
VS = 5V RL = NO LOAD TA = 25C 80
GAIN (dB) PHASE SHIFT (Degrees)
100
SOURCE SINK
60 40 20 0
45 90 135 180
10
1
0.1
01099-012
0.01 0.001
0.01
0.1 1 LOAD CURRENT (mA)
10
100
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
Figure 12. Output Voltage to Supply Rail vs. Load Current
1000
Figure 15. Open-Loop Gain and Phase Shift vs. Frequency
5
VS = 5V TA = 25C
100
OUTPUT VOLTAGE (mV) OUTPUT SWING (V p-p)
4
VS = 2.7V TA = 25C RL = 2k VIN = 2.5V p-p
10
SOURCE
3
SINK 1
2
0.1
01099-013
1
01099-016
0.01 0.001
0.01
0.1 1 LOAD CURRENT (mA)
10
100
0 1k
10k
100k FREQUENCY (Hz)
1M
Figure 13. Output Voltage to Supply Rail vs. Load Current
5
Figure 16. Closed-Loop Output Swing vs. Frequency
VS = 2.7V RL = NO LOAD TA = 25C 80
GAIN (dB) PHASE SHIFT (Degrees) OUTPUT SWING (V p-p)
4
VS = 5V TA = 25C RL = 2k VIN = 4.9V p-p
60 40 20 0
45 90 135 180
3
2
1
01099-017
01099-014
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
0 1k
10k
100k FREQUENCY (Hz)
1M
Figure 14. Open-Loop Gain and Phase Shift vs. Frequency
Figure 17. Closed-Loop Output Swing vs. Frequency
Rev. F | Page 7 of 20
01099-015
10M
10M
AD8531/AD8532/AD8534
200 180 160 140
IMPEDANCE ()
VS = 5V TA = 25C
CURRENT NOISE DENSITY (pA/Hz)
1
VS = 5V TA = 25C
120 100 80 60 40
01099-018
0.1
AV = 10 AV = 1
20 0 1k 10k 100k 1M LOAD CURRENT (mA) 10M
100M
0.01 10
100
1k FREQUENCY (Hz)
10k
100k
Figure 18. Closed-Loop Output Impedance vs. Frequency
110 100 90 80 70 60 50 40 1k
Figure 21. Current Noise Density vs. Frequency
100 90
10 0%
01099-019
COMMON-MODE REJECTION (dB)
VS = 5V AV = 1000 TA = 25C FREQUENCY = 1kHz
VS = 5V TA = 25C
100V/DIV
MARKER 41V/Hz
10k
100k FREQUENCY (Hz)
1M
10M
Figure 19. Voltage Noise Density vs. Frequency (1 kHz)
140 120
POWER SUPPLY REJECTION (dB)
Figure 22. Common-Mode Rejection vs. Frequency
100 90
VS = 5V AV = 1000 TA = 25C FREQUENCY = 10kHz
VS = 2.7V TA = 25C
100 80 60 PSSR- 40 20 0 -20 -40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M
01099-023
200V/DIV
PSSR+
10 0%
01099-020
MARKER 25.9V/Hz
10M
Figure 20. Voltage Noise Density vs. Frequency (10 kHz)
Figure 23. Power Supply Rejection vs. Frequency
Rev. F | Page 8 of 20
01099-022
01099-021
AD8531/AD8532/AD8534
140 120
POWER SUPPLY REJECTION (dB)
VS = 5V TA = 25C
SMALL SIGNAL OVERSHOOT (%)
50
100 80 PSSR- 60 40 20 0 -20
01099-024
40
VS = 5V TA = 25C RL = 600
30 -OS +OS
PSSR+
20
10
01099-027
-40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M
10M
0 10
100 1000 CAPACITANCE (pF)
10000
Figure 24. Power Supply Rejection vs. Frequency
50
Figure 27. Small Signal Overshoot vs. Load Capacitance
50
SMALL SIGNAL OVERSHOOT (%)
40
SMALL SIGNAL OVERSHOOT (%)
VS = 2.7V TA = 25C RL = 2k
40
VS = 2.7V TA = 25C RL = 600
30 -OS 20 +OS 10
01099-025
30
20 -OS 10 +OS 0 10 100 1000 CAPACITANCE (pF)
01099-028
0 10
100 1000 CAPACITANCE (pF)
10000
10000
Figure 25. Small Signal Overshoot vs. Load Capacitance
60 VS = 5V TA = 25C RL = 2k
Figure 28. Small Signal Overshoot vs. Load Capacitance
0.90 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 -40 VS = 5V
SMALL SIGNAL OVERSHOOT (%)
50
40 -OS 30 +OS 20
SUPPLY CURRENT/AMPLIFIER (mA)
01099-026
0 10
100 1000 CAPACITANCE (pF)
10000
-20
0
20 40 TEMPERATURE (C)
60
80
Figure 26. Small Signal Overshoot vs. Load Capacitance
Figure 29. Supply Current per Amplifier vs. Temperature
Rev. F | Page 9 of 20
01099-029
10
VS = 3V
AD8531/AD8532/AD8534
0.8 0.7 0.6 0.5 0.4 0.3 0.2
01099-030
TA = 25C
100 90
SUPPLY CURRENT/AMPLIFIER (mA)
VS = 2.5V AV = 1 RL = 2k TA = 25C
10 0% 500mV 500ns
01099-033 01099-035 01099-034
0.1 0 0.75
1.00
1.50 2.00 SUPPLY VOLTAGE (V)
2.50
3.00
Figure 30. Supply Current per Amplifier vs. Supply Voltage
Figure 33. Large Signal Transient Response
VS = 1.35V VIN = 50mV AV = 1 RL = 2k CL = 300pF TA = 25C
20mV/DIV
100 90
VS = 1.35V AV = 1 RL = 2k TA = 25C
0V
10 0%
01099-031
500mV
500ns
500 ns/DIV
Figure 31. Small Signal Transient Response
Figure 34. Large Signal Transient Response
1V 100 90
10s
20mV/DIV
0V
VS = 2.5V VIN = 50mV AV = 1 RL = 2k CL = 300pF TA = 25C
01099-032
10 0% 1V
500ns/DIV
Figure 32. Small Signal Transient Response
Figure 35. No Phase Reversal
Rev. F | Page 10 of 20
AD8531/AD8532/AD8534 THEORY OF OPERATION
The AD8531/AD8532/AD8534 are all CMOS, high output current drive, rail-to-rail input/output operational amplifiers. Their high output current drive and stability with heavy capacitive loads make the AD8531/AD8532/AD8534 excellent choices as drive amplifiers for LCD panels. Figure 36 illustrates a simplified equivalent circuit for the AD8531/AD8532/AD8534. Like many rail-to-rail input amplifier configurations, it comprises two differential pairs, one N-channel (M1 to M2) and one P-channel (M3 to M4). These differential pairs are biased by 50 A current sources, each with a compliance limit of approximately 0.5 V from either supply voltage rail. The differential input voltage is then converted into a pair of differential output currents. These differential output currents are then combined in a compound folded-cascade second gain stage (M5 to M9). The outputs of the second gain stage at M8 and M9 provide the gate voltage drive to the rail-to-rail output stage. Additional signal current recombination for the output stage is achieved using M11 to M14. To achieve rail-to-rail output swings, the AD8531/AD8532/ AD8534 design employs a complementary, common source output stage (M15 to M16). However, the output voltage swing is directly dependent on the load current because the difference between the output voltage and the supply is determined by the AD8531/AD8532/AD8534's output transistors on channel resistance (see Figure 12 and Figure 13). The output stage also exhibits voltage gain by virtue of the use of common source amplifiers; as a result, the voltage gain of the output stage (thus, the open-loop gain of the device) exhibits a strong dependence on the total load resistance at the output of the AD8531/ AD8532/AD8534.
V+
SHORT-CIRCUIT PROTECTION
As a result of the design of the output stage for the maximum load current capability, the AD8531/AD8532/AD8534 do not have any internal short-circuit protection circuitry. Direct connection of the output of the AD8531/AD8532/AD8534 to the positive supply in single-supply applications destroys the device. In applications where some protection is needed, but not at the expense of reduced output voltage headroom, a low value resistor in series with the output, as shown in Figure 37, can be used. The resistor, connected within the feedback loop of the amplifier, has very little effect on the performance of the amplifier other than limiting the maximum available output voltage swing. For single 5 V supply applications, resistors less than 20 are not recommended.
5V VIN RX 20
AD8532
VOUT
01099-037
Figure 37. Output Short-Circuit Protection
POWER DISSIPATION
Although the AD8531/AD8532/AD8534 are capable of providing load currents to 250 mA, the usable output load current drive capability is limited to the maximum power dissipation allowed by the device package used. In any application, the absolute maximum junction temperature for the AD8531/AD8532/AD8534 is 150C. The maximum junction temperature should never be exceeded because the device could suffer premature failure. Accurately measuring power dissipation of an integrated circuit is not always a straightforward exercise; therefore, Figure 38 is provided as a design aid for either setting a safe output current drive level or selecting a heat sink for the package options available on the AD8531/AD8532/AD8534.
1.5 TJ MAX = 150C FREE AIR NO HEAT SINK
50A
100A
100A M11
20A
M5 VB2 M1 IN- M6 VB3 M9 M3 M4 M2 M8
M12
M15 OUT
POWER DISSIPATION (W)
IN+
M16 M14
SOIC 1.0 JA = 158C/W MSOP JA = 210C/W
SOT-23 JA = 230C/W
20A 50A M7 M10 M13
01099-036
V-
SC70 0.5 = 376C/W JA TSSOP JA = 240C/W 0 0 25 50 TEMPERATURE (C) 75 85
Figure 36. Simplified Equivalent Circuit
100
Figure 38. Maximum Power Dissipation vs. Ambient Temperature
Rev. F | Page 11 of 20
01099-038
AD8531/AD8532/AD8534
The thermal resistance curves were determined using the AD8531/AD8532/AD8534 thermal resistance data for each package and a maximum junction temperature of 150C. The following formula can be used to calculate the internal junction temperature of the AD8531/AD8532/AD8534 for any application: TJ = PDISS x JA + TA where: TJ is the junction temperature. PDISS is the power dissipation. JA is the package thermal resistance, junction-to-case. TA is the ambient temperature of the circuit. To calculate the power dissipated by the AD8531/AD8532/ AD8534, the following equation can be used: PDISS = ILOAD x (VS - VOUT) where: ILOAD is the output load current. VS is the supply voltage. VOUT is the output voltage. The quantity within the parentheses is the maximum voltage developed across either output transistor. As an additional design aid in calculating available load current from the AD8531/AD8532/AD8534, Figure 5 illustrates the output voltage of the AD8531/AD8532/AD8534 as a function of load resistance. TJ = TC + PDISS JA where: TC is the case temperature. JA and JC are given in the data sheet. The two equations can be solved for P (power) TA + PDISS JA = TC + PJC PDISS = (TA - TC)/(JC - JA) Once power is determined, it is necessary to go back and calculate the junction temperature to ensure that it has not been exceeded. The temperature measurements should be directly on the package and on a spot on the board that is near the package but not touching it. Measuring the package could be difficult. A very small bimetallic junction glued to the package can be used, or measurement can be done using an infrared sensing device if the spot size is small enough.
CALCULATING POWER BY MEASURING SUPPLY CURRENT
Power can be calculated directly, knowing the supply voltage and current. However, supply current may have a dc component with a pulse into a capacitive load, which can make rms current very difficult to calculate. It can be overcome by lifting the supply pin and inserting an rms current meter into the circuit. For this to work, be sure the current is being delivered by the supply pin being measured. This is usually a good method in a single-supply system; however, if the system uses dual supplies, both supplies may need to be monitored.
POWER CALCULATIONS FOR VARYING OR UNKNOWN LOADS
Often, calculating power dissipated by an integrated circuit to determine if the device is being operated in a safe range is not as simple as it may seem. In many cases, power cannot be directly measured, which may be the result of irregular output waveforms or varying loads; indirect methods of measuring power are required. There are two methods to calculate power dissipated by an integrated circuit. The first can be done by measuring the package temperature and the board temperature, and the other is to directly measure the supply current of the circuit.
INPUT OVERVOLTAGE PROTECTION
As with any semiconductor device, whenever the condition exists for the input to exceed either supply voltage, the input overvoltage characteristic of the device must be considered. When an overvoltage occurs, the amplifier can be damaged, depending on the magnitude of the applied voltage and the magnitude of the fault current. Although not shown here, when the input voltage exceeds either supply by more than 0.6 V, pn junctions internal to the AD8531/AD8532/AD8534 energize, allowing current to flow from the input to the supplies. As illustrated in the simplified equivalent input circuit (see Figure 36), the AD8531/AD8532/AD8534 do not have any internal current limiting resistors; therefore, fault currents can quickly rise to damaging levels. This input current is not inherently damaging to the device, as long as it is limited to 5 mA or less. For the AD8531/AD8532/ AD8534, once the input voltage exceeds the supply by more than 0.6 V, the input current quickly exceeds 5 mA. If this condition continues to exist, an external series resistor should be added. The size of the resistor is calculated by dividing the maximum overvoltage by 5 mA. For example, if the input voltage could reach 10 V, the external resistor should be (10 V/5 mA) = 2 k. This resistance should be placed in series with either or both inputs if they are exposed to an overvoltage condition.
CALCULATING POWER BY MEASURING AMBIENT AND CASE TEMPERATURE
Given the two equations for calculating junction temperature TJ = TA + PDISS JA where: TJ is the junction temperature. TA is the ambient temperature. JA is the junction to ambient thermal resistance.
Rev. F | Page 12 of 20
AD8531/AD8532/AD8534
OUTPUT PHASE REVERSAL
Some operational amplifiers designed for single-supply operation exhibit an output voltage phase reversal when their inputs are driven beyond their useful common-mode range. The AD8531/ AD8532/AD8534 are free from reasonable input voltage range restrictions, provided that input voltages no greater than the supply voltage rails are applied. Although the output of the device does not change phase, large currents can flow through internal junctions to the supply rails, which was described in the Input Overvoltage Protection section. Without limit, these fault currents can easily destroy the amplifier. The technique recommended in the Input Overvoltage Protection section should therefore be applied in those applications where the possibility of input voltages exceeding the supply voltages exists.
5V
AD8532
VIN
100mV p-p
Figure 40. Snubber Network Compensates for Capacitive Loads
CAPACITIVE LOAD DRIVE
The AD8531/AD8532/AD8534 exhibit excellent capacitive load driving capabilities. They can drive up to 10 nF directly, as shown in Figure 25 through Figure 28. However, even though the device is stable, a capacitive load does not come without a penalty in bandwidth. As shown in Figure 39, the bandwidth is reduced to less than 1 MHz for loads greater than 10 nF. A snubber network on the output does not increase the bandwidth, but it does significantly reduce the amount of overshoot for a given capacitive load. A snubber consists of a series RC network (RS, CS), as shown in Figure 40, connected from the output of the device to ground. This network operates in parallel with the load capacitor, CL, to provide phase lag compensation. The actual value of the resistor and capacitor is best determined empirically.
4.0 3.5 3.0
BANDWIDITH (MHz)
The first step is to determine the value of the resistor, RS. A good starting value is 100 . This value is reduced until the small signal transient response is optimized. Next, CS is determined; 10 F is a good starting point. This value is reduced to the smallest value for acceptable performance (typically, 1 F). For the case of a 47 nF load capacitor on the AD8531/AD8532/AD8534, the optimal snubber network is 5 in series with 1 F. The benefit is immediately apparent, as seen in Figure 41. The top trace was taken with a 47 nF load, and the bottom trace was taken with the 5 in series with a 1 F snubber network in place. The amount of overshoot and ringing is dramatically reduced. Table 5 illustrates a few sample snubber networks for large load capacitors. Table 5. Snubber Networks for Large Capacitive Loads
Load Capacitance (CL) 0.47 nF 4.7 nF 47 nF
50mV 47nF LOAD 90 ONLY 100
Snubber Network (RS, CS) 300 , 0.1 F 30 , 1 F 5 , 1 F
VS = 2.5V RL = 1k TA = 25C
2.5 2.0 1.5 1.0
01099-039
SNUBBER 10 IN CIRCUIT 0% 50mV 10s
01099-041
0.5 0 0.01
Figure 41. Overshoot and Ringing Are Reduced by Adding a Snubber Network in Parallel with the 47 nF Load
0.1
1 CAPACITIVE LOAD (nF)
10
100
Figure 39. Unity-Gain Bandwidth vs. Capacitive Load
Rev. F | Page 13 of 20
01099-040
RS 5 CS 1F
VOUT CL 47nF
AD8531/AD8532/AD8534 APPLICATIONS INFORMATION
HIGH OUTPUT CURRENT, BUFFERED REFERENCE/REGULATOR
Many applications require stable voltage outputs relatively close in potential to an unregulated input source. This low dropout type of reference/regulator is readily implemented with a railto-rail output op amp and is particularly useful when using a higher current device, such as the AD8531/AD8532/AD8534. A typical example is the 3.3 V or 4.5 V reference voltage developed from a 5 V system source. Generating these voltages requires a three terminal reference, such as the REF196 (3.3 V) or the REF194 (4.5 V), both of which feature low power, with sourcing outputs of 30 mA or less. Figure 42 shows how such a reference can be outfitted with an AD8531/AD8532/AD8534 buffer for higher currents and/or voltage levels, plus sink and source load capability.
VS 5V C1 0.1F R2 10k 1%
for optimizing the transient response, any changes to the R5 to C5 network should be verified by experiment to preclude the possibility of excessive ringing with some capacitor types. To scale VOUT2 to another (higher) output level, the optional resistor R3 (shown dotted in Figure 42) is added, causing the new VOUT1 to become
R2 VOUT1 = VOUT2 x 1 + R3 The circuit can either be used as shown, as a 5 V to 3.3 V reference/regulator, or with on/off control. By driving Pin 3 of U1 with a logic control signal as noted, the output is switched on/off. Note that when on/off control is used, R4 must be used with U1 to speed on/off switching.
SINGLE-SUPPLY, BALANCED LINE DRIVER
The circuit in Figure 43 is a unique line driver circuit topology used in professional audio applications. It was modified for automotive and multimedia audio applications. On a single 5 V supply, the line driver exhibits less than 0.7% distortion into a 600 load from 20 Hz to 15 kHz (not shown) with an input signal level of 4 V p-p. In fact, the output drive capability of the AD8531/AD8532/AD8534 maintains this level for loads as small as 32 . For input signals less than 1 V p-p, the THD is less than 0.1%, regardless of load. The design is a transformerless, balanced transmission system where output commonmode rejection of noise is of paramount importance. As with the transformer-based system, either output can be shorted to ground for unbalanced line driver applications without changing the circuit gain of 1. Other circuit gains can be set according to the equation in the diagram. This allows the design to be easily configured for inverting, noninverting, or differential operation.
R3 10k 2 3 R2 10k 5V C1 22F VIN 2 3 A1 1 7 A2 1 R6 10k R5 50 C3 47F VOUT1
AD8531
VOUT1 = 3.3V @ 100mA
U2
R1 10k 1% C3 0.1F VC ON/OFF CONTROL INPUT CMOS HI (OR OPEN) = ON LO = OFF VS COMMON 3 R3 (See Text) 6 VOUT2 = 3.3V
C2 0.1F C5 100F/16V TANTALUM R5 0.2
2 U1 REF196 4
C4 1F R4 3.3k
VOUT COMMON
Figure 42. High Output Current Reference/Regulator
SET: R7, R10, R11 = R2 SET: R6, R12, R13 = R3
Transient performance of the reference/regulator for a 100 mA step change in load current is also quite good and is largely determined by the R5 to C5 output network. With values as shown, the transient is about 20 mV peak and settles to within 2 mV in less than 10 s for either polarity. Although room exists
Figure 43. Single-Supply, Balanced Line Driver for Multimedia and Automotive Applications
Rev. F | Page 14 of 20
01099-043
The low dropout performance of this circuit is provided by stage U2, an AD8531 connected as a follower/buffer for the basic reference voltage produced by U1. The low voltage saturation characteristic of the AD8531/AD8532/AD8534 allows up to 100 mA of load current in the illustrated use, as a 5 V to 3.3 V converter with good dc accuracy. In fact, the dc output voltage change for a 100 mA load current delta measures less than 1 mV. This corresponds to an equivalent output impedance of < 0.01 . In this application, the stable 3.3 V from U1 is applied to U2 through a noise filter, R1 to C1. U2 replicates the U1 voltage within a few millivolts, but at a higher current output at VOUT1, with the ability to both sink and source output current(s), unlike most IC references. R2 and C2 in the feedback path of U2 provide additional noise filtering.
01099-042
R7 10k 12V 6 A1 5 R9 100k
5V R8 100k C2 1F
RL 600
R1 10k A1, A2 = 1/2 AD8532 GAIN = R3 R2 R10 10k
R11 R12 10k 10k 6 5 A2 7 R13 10k
R14 50
C4 47F VOUT2
AD8531/AD8532/AD8534
SINGLE-SUPPLY HEADPHONE AMPLIFIER
Because of its speed and large output drive, the AD8531/ AD8532/AD8534 make an excellent headphone driver, as illustrated in Figure 44. Its low supply operation and rail-to-rail inputs and outputs give a maximum signal swing on a single 5 V supply. To ensure maximum signal swing available to drive the headphone, the amplifier inputs are biased to V+/2, which in this case is 2.5 V. The 100 k resistor to the positive supply is equally split into two 50 k resistors, with their common point bypassed by 10 F to prevent power supply noise from contaminating the audio signal. The audio signal is then ac-coupled to each input through a 10 F capacitor. A large value is needed to ensure that the 20 Hz audio information is not blocked. If the input already has the proper dc bias, the ac coupling and biasing resistors are not required. A 270 F capacitor is used at the output to couple the amplifier to the headphone. This value is much larger than that used for the input because of the low impedance of the headphones, which can range from 32 to 600 . An additional 16 resistor is used in series with the output capacitor to protect the output stage of the op amp by limiting the capacitor discharge current. When driving a 48 load, the circuit exhibits less than 0.3% THD+N at output drive levels of 4 V p-p.
V 5V V 5V 50k 1F/0.1F
TO U1
This active crossover exhibits less than 0.4% THD+N at output levels of 1.4 V rms using general-purpose, unity-gain HP/LP stages. In this 2-way example, the LO signal is a dc-to-500 Hz LP woofer output, and the HI signal is the HP (>500 Hz) tweeter output. U1B forms an LP section at 500 Hz, while U1A provides an HP section, covering frequencies 500 Hz.
C1 0.01F R1 31.6k C2 0.01F VIN RIN 100k CIN 10F R2 31.6k 3 2 4 VS U1A R3 49.9 270F + 500Hz AND UP HI 100k
AD8532
1
R5 31.6k
R6 31.6k R7 15.8k C4 0.02F 6 7 5 U1B 10F C3 0.01F
R4 49.9
270F +
DC - 500Hz LO
VS 100k
100k
100k
AD8532
VS
0.1F
5V 100F/25V COM
01099-045
Figure 45. A Single-Supply, 2-Way Active Crossover
50k LEFT INPUT 10F 1/2 AD8532 16 270F LEFT HEADPHONE 50k 100k
10F
V 50k
The crossover example frequency of 500 Hz can be shifted lower or higher by frequency scaling of either resistors or capacitors. In configuring the circuit for other frequencies, complementary LP/HP action must be maintained between sections, and component values within the sections must be in the same ratio. Table 6 provides a design aid to adaptation, with suggested standard component values for other frequencies. For additional information on the active filters and active crossover networks, refer to the data sheet for the OP279, a dual rail-torail, high output current, operational amplifier.
Table 6. RC Component Selection for Various Crossover Frequencies 1
Crossover Frequency (Hz) 100 200 319 500 1k 2k 5k 10 k
1 2
50k RIGHT INPUT
10F
1/2 AD8532
16 270F
RIGHT HEADPHONE 50k
01099-044
10F
100k
Figure 44. Single-Supply, Stereo Headphone Driver
SINGLE-SUPPLY, 2-WAY LOUDSPEAKER CROSSOVER NETWORK
Active filters are useful in loudspeaker crossover networks because of small size, relative freedom from parasitic effects, the ease of controlling low/high channel drive, and the controlled driver damping provided by a dedicated amplifier. Both SallenKey (SK) and multiple-feedback (MFB) filter architectures are useful in implementing active crossover networks. The circuit shown in Figure 45 is a single-supply, 2-way active crossover that combines the advantages of both filter topologies.
R1/C1 (U1A) 2 , R5/C3 (U1B) 3 160 k/0.01 F 80.6 k/0.01 F 49.9 k/0.01 F 31.6 k/0.01 F 16 k/0.01 F 8.06 k/0.01 F 3.16 k/0.01 F 1.6 k/0.01 F
Applicable for Filter A = 2. For Sallen-Key stage U1A: R1 = R2, and C1 = C2, and so on. 3 For multiple feedback stage U1B: R6 = R5, R7 = R5/2, and C4 = 2C3.
Rev. F | Page 15 of 20
AD8531/AD8532/AD8534
DIRECT ACCESS ARRANGEMENT FOR TELEPHONE LINE INTERFACE
Figure 46 illustrates a 5 V only transmit/receive telephone line interface for 600 transmission systems. It allows full duplex transmission of signals on a transformer-coupled 600 line in a differential manner. 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 signal on a single supply to the transformer. Because of the high output current drive and low dropout voltage of the AD8531/AD8532/AD8534, the largest signal available on a single 5 V supply is approximately 4.5 V p-p into a 600 transmission system. A3 is configured as a difference amplifier for two reasons: it prevents the transmit signal from interfering with the receive signal, and it extracts the receive signal from the transmission line for amplification by A4. The gain of A4 can be adjusted in the same manner as that of A1 to meet the input signal requirements of the modem. Standard resistor values permit the use of single in-line package (SIP) format resistor arrays.
TO TELEPHONE LINE 1:1 ZO 600 T1 MIDCOM 671-8005 6.2V 6.2V 5V DC R6 10k 6 7 A2 5 10F R9 10k R11 10k R12 10k 2 3 A3 1 R10 10k R13 R14 10k 14.3k 6 5 A4 R7 10k R8 10k R3 360 R5 10k P1 Tx GAIN ADJUST 2k 1 A1
R2 9.09k 2 3
C1 R1 10k 0.1F
TRANSMIT TxA
P2 Rx GAIN ADJUST 2k 7
RECEIVE RxA
A1, A2 = 1/2 AD8532 A3, A4 = 1/2 AD8532
Figure 46. Single-Supply Direct Access Arrangement for Modems
Rev. F | Page 16 of 20
01099-046
C2 0.1F
AD8531/AD8532/AD8534 OUTLINE DIMENSIONS
2.20 2.00 1.80 1.35 1.25 1.15 PIN 1 1.00 0.90 0.70
5 1 2 4 3
2.40 2.10 1.80
0.65 BSC 1.10 0.80 0.40 0.10 0.46 0.36 0.26
0.10 MAX
0.30 0.15
SEATING PLANE
0.22 0.08
0.10 COPLANARITY COMPLIANT TO JEDEC STANDARDS MO-203-AA
Figure 47. 5-Lead Thin Shrink Small Outline Transistor Package [SC70] (KS-5) Dimensions shown in millimeters
2.90 BSC
5
4
1.60 BSC
1 2 3
2.80 BSC
PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC
1.45 MAX
0.22 0.08 10 5 0 0.60 0.45 0.30
0.15 MAX
0.50 0.30
SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MO-178-A A
Figure 48. 5-Lead Small Outline Transistor Package [SOT-23] (RJ-5) Dimensions shown in millimeters
5.00 (0.1968) 4.80 (0.1890)
4.00 (0.1574) 3.80 (0.1497)
8 1
5 4
6.20 (0.2441) 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) 0.25 (0.0099) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
0.51 (0.0201) 0.31 (0.0122)
COMPLIANT TO JEDEC STANDARDS MS-012-A A CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 49. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
Rev. F | Page 17 of 20
012407-A
AD8531/AD8532/AD8534
3.20 3.00 2.80
3.20 3.00 2.80 PIN 1
8
5
1
5.15 4.90 4.65
4
0.65 BSC 0.95 0.85 0.75 0.15 0.00 0.38 0.22 SEATING PLANE 1.10 MAX 8 0 0.80 0.60 0.40
0.23 0.08
COPLANARITY 0.10
COMPLIANT TO JEDEC STANDARDS MO-187-AA
Figure 50. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
3.10 3.00 2.90
8
5
4.50 4.40 4.30
1 4
6.40 BSC
PIN 1 0.65 BSC 0.15 0.05 COPLANARITY 0.10 0.30 0.19 1.20 MAX SEATING 0.20 PLANE 0.09
8 0
0.75 0.60 0.45
COMPLIANT TO JEDEC STANDARDS MO-153-AA
Figure 51. 8-Lead Thin Shrink Small Outline Package [TSSOP] (RU-8) Dimensions shown in millimeters
5.10 5.00 4.90
14
8
4.50 4.40 4.30
1 7
6.40 BSC
PIN 1 1.05 1.00 0.80 0.65 BSC 1.20 MAX 0.15 0.05 0.30 0.19
0.20 0.09
SEATING COPLANARITY PLANE 0.10
8 0
0.75 0.60 0.45
COMPLIANT TO JEDEC STANDARDS MO-153-AB-1
Figure 52. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters
Rev. F | Page 18 of 20
AD8531/AD8532/AD8534
8.75 (0.3445) 8.55 (0.3366)
14 1 8 7
4.00 (0.1575) 3.80 (0.1496)
6.20 (0.2441) 5.80 (0.2283)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122)
1.75 (0.0689) 1.35 (0.0531) SEATING PLANE
0.50 (0.0197) 0.25 (0.0098) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
COMPLIANT TO JEDEC STANDARDS MS-012-AB CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 53. 14-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-14) Dimensions shown in millimeters and (inches)
Rev. F | Page 19 of 20
060606-A
AD8531/AD8532/AD8534
ORDERING GUIDE
Model AD8531AKS-R2 AD8531AKS-REEL7 AD8531AKSZ-R2 1 AD8531AKSZ-REEL71 AD8531ART-REEL AD8531ART-REEL7 AD8531ARTZ-REEL1 AD8531ARTZ-REEL71 AD8531AR AD8531AR-REEL AD8531ARZ1 AD8531ARZ-REEL1 AD8532AR AD8532AR-REEL AD8532AR-REEL7 AD8532ARZ1 AD8532ARZ-REEL1 AD8532ARZ-REEL71 AD8532ARM-R2 AD8532ARM-REEL AD8532ARMZ-R21 AD8532ARMZ-REEL1 AD8532ARU AD8532ARU-REEL AD8532ARUZ1 AD8532ARUZ-REEL1 AD8534AR AD8534AR-REEL AD8534ARZ1 AD8534ARZ-REEL1 AD8534ARU AD8534ARU-REEL AD8534ARUZ1 AD8534ARUZ-REEL1
1
Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
Package Description 5-Lead SC70 5-Lead SC70 5-Lead SC70 5-Lead SC70 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead TSSOP 8-Lead TSSOP 8-Lead TSSOP 8-Lead TSSOP 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead TSSOP 14-Lead TSSOP 14-Lead TSSOP 14-Lead TSSOP
Package Option KS-5 KS-5 KS-5 KS-5 RJ-5 RJ-5 RJ-5 RJ-5 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RU-8 RU-8 RU-8 RU-8 R-14 R-14 R-14 R-14 RU-14 RU-14 RU-14 RU-14
Branding A7B A7B A0Q A0Q A7A A7A A0P A0P
ARA ARA A0R A0R
Z = RoHS Compliant Part.
(c)1996-2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D01099-0-1/08(F)
Rev. F | Page 20 of 20

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