Datasheet AD8534ARU, AD8534AR, AD8534AN, AD8532ARU, AD8532ARM Datasheet (Analog Devices)

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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.
a
Low Cost, 250 mA Output
Single-Supply Amplifiers
GENERAL DESCRIPTION
The AD8531, AD8532, and AD8534 are single, dual and quad rail-to-rail input and 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/µs slew rate and low distortion. All are guaranteed to oper­ate from a 3 volt single supply as well as a 5 volt 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 µA per amplifier at 5 volts, 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 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, and AD8534 are specified over the extended industrial (–40°C to +85°C) temperature range. The AD8531. The AD8532 is available in 8-lead plastic DIP, SOIC, MSOP, TSSOP surface-mount packages. The AD8534 is available in 14-lead plastic DIP, narrow SO-14 and 14-lead TSSOP surface-mount packages. All TSSOP, SOT, and SC70 versions are available in tape and reel only.
FEATURES Single-Supply Operation: 2.7 Volts to 6 Volts 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
APPLICATIONS Multimedia Audio LCD Driver ASIC Input or Output Amplifier Headphone Driver
PIN CONFIGURATIONS
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 2000
14-Lead DIP, SOIC, and TSSOP
(N, R, and RU Suffixes)
AD8534
1
2
3
4
14
13
12
11
OUT A
–IN A
+IN A
V+
V–
+IN D
–IN D
OUT D
5
6
7
10
9
8
+IN B
–IN B
OUT B
OUT C
–IN C
+IN C
8-Lead DIP, SOIC, TSSOP, and MSOP
(N, R, RU, and RM Suffixes)
AD8532
1
2
3
4
8
7
6
5
OUT A
–IN A
+IN A
V–
+IN B
–IN B
OUT B
V+
8-Lead DIP, SOIC, TSSOP, and MSOP
(N, R, RU, and RM Suffixes)
NULL
–IN A
+IN A
V–
V+
OUT A
NULL
NC
1
2
3
4
8
7
6
5
AD8531
5-Lead SC70 and SOT-23
(KS and RT Suffixes)
1
2
3
5
4
IN A
+IN A
V+
OUT A
AD8531
V
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AD8531/AD8532/AD8534–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage V
OS
25 mV
–40°C T
A
+85°C30mV
Input Bias Current I
B
550 pA
–40°C T
A
+85°C60pA
Input Offset Current I
OS
125 pA
–40°C T
A
+85°C30pA
Input Voltage Range 0 3 V Common-Mode Rejection Ratio CMRR V
CM
= 0 V to 3 V 38 45 dB
Large Signal Voltage Gain A
VO
RL = 2 k, VO = 0.5 V to 2.5 V 25 V/mV
Offset Voltage Drift ∆V
OS
/T20µV/°C
Bias Current Drift ∆I
B
/T 50 fA/°C
Offset Current Drift ∆IOS/T 20 fA/°C
OUTPUT CHARACTERISTICS
Output Voltage High V
OH
IL = 10 mA 2.85 2.92 V –40°C T
A
+85°C 2.8 V
Output Voltage Low V
OL
IL = 10 mA 60 100 mV –40°C T
A
+85°C 125 mV
Output Current I
OUT
±250 mA
Closed-Loop Output Impedance Z
OUT
f = 1 MHz, AV = 1 60
POWER SUPPLY
Power Supply Rejection Ratio PSRR V
S
= 3 V to 6 V 45 55 dB
Supply Current/Amplifier I
SY
VO = 0 V 0.70 1 mA –40°C TA +85°C 1.25 mA
DYNAMIC PERFORMANCE
Slew Rate SR RL = 2 k 3.5 V/µs Settling Time t
S
To 0.01% 1.6 µs
Gain Bandwidth Product GBP 2.2 MHz Phase Margin φo 70 Degrees Channel Separation CS f = 1 kHz, RL = 2 k 65 dB
NOISE PERFORMANCE
Voltage Noise Density e
n
f = 1 kHz 45 nV/Hz f = 10 kHz 30 nV/Hz
Current Noise Density i
n
f = 1 kHz 0.05 pA/Hz
Specifications subject to change without notice.
(@ VS = 3.0 V, VCM = 1.5 V, TA = 25C unless otherwise noted)
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ELECTRICAL CHARACTERISTICS
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage V
OS
25 mV
–40°C T
A
+85°C30mV
Input Bias Current I
B
550 pA
–40°C T
A
+85°C60pA
Input Offset Current I
OS
125 pA
–40°C T
A
+85°C30pA
Input Voltage Range 0 5 V Common-Mode Rejection Ratio CMRR V
CM
= 0 V to 5 V 38 47 dB
Large Signal Voltage Gain A
VO
RL = 2 k, VO = 0.5 V to 4.5 V 15 80 V/mV
Offset Voltage Drift ∆V
OS
/T –40°C TA +85°C20µV/°C
Bias Current Drift ∆I
B
/T 50 fA/°C
Offset Current Drift ∆IOS/T 20 fA/°C
OUTPUT CHARACTERISTICS
Output Voltage High V
OH
IL = 10 mA 4.9 4.94 V –40°C T
A
+85°C 4.85 V
Output Voltage Low V
OL
IL = 10 mA 50 100 mV –40°C T
A
+85°C 125 mV
Output Current I
OUT
±250 mA
Closed-Loop Output Impedance Z
OUT
f = 1 MHz, AV = 1 40
POWER SUPPLY
Power Supply Rejection Ratio PSRR V
S
= 3 V to 6 V 45 55 dB
Supply Current/Amplifier I
SY
VO = 0 V 0.75 1.25 mA –40°C TA +85°C 1.75 mA
DYNAMIC PERFORMANCE
Slew Rate SR RL = 2 k 5V/µs Full-Power Bandwidth BW
p
1% Distortion 350 kHz
Settling Time t
S
To 0.01% 1.4 µs
Gain Bandwidth Product GBP 3 MHz Phase Margin φo 70 Degrees Channel Separation CS f = 1 kHz, RL = 2 k 65 dB
NOISE PERFORMANCE
Voltage Noise Density e
n
f = 1 kHz 45 nV/Hz f = 10 kHz 30 nV/Hz
Current Noise Density i
n
f = 1 kHz 0.05 pA/Hz
Specifications subject to change without notice.
AD8531/AD8532/AD8534
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(@ VS = 5.0 V, VCM = 2.5 V, TA = 25C unless otherwise noted)
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AD8531/AD8532/AD8534
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ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage (VS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND to V
S
Differential Input Voltage2 . . . . . . . . . . . . . . . . . . . . . . . ±6 V
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Operating Temperature Range . . . . . . . . . . . –40°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; 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.
2
For supplies less than +6 volts, the differential input voltage is equal to ± VS.
2.5
2
1.5
1
0.5
0
0 20 40 60 80 100 120 140 160 180 200
R
LOAD –
V
OUT
+V
OH
–V
OL
Figure 1. Output Voltage vs. Load. VS = ±2.5 V, RL Is Connected to GND (0 V)
PACKAGE INFORMATION
Package Type JA*
JC
Unit
5-Lead SC70 (KS) 376 126 °C/W 5-Lead SOT-23 (RT) 230 146 °C/W 8-Lead SOIC (R) 158 43 °C/W 8-Lead MSOP (RM) 210 45 °C/W 8-Lead TSSOP (RU) 240 43 °C/W 8-Lead Plastic DIP (N) 103 43 °C/W 14-Lead Plastic DIP (N) 83 39 °C/W 14-Lead SOIC (R) 120 36 °C/W 14-Lead TSSOP (RU) 240 43 °C/W
*θJA is specified for the worst case conditions, i.e., θJA is specified for device in socket
for P-DIP packages; θJA is specified for device soldered onto a circuit board for surface-mount packages.
ORDERING GUIDE
Model Temperature Range Package Description Package Option Branding Information
AD8531AKS* –40°C to +85°C 5-Lead SC70 KS-5 A7B AD8531AR –40°C to +85°C 8-Lead SOIC SO-8 AD8531ART* –40°C to +85°C 5-Lead SOT-23 RT-5 A7A
AD8532AR –40°C to +85°C 8-Lead SOIC SO-8 AD8532ARM* –40°C to +85°C 8-Lead MSOP RM-8 ARA AD8532AN –40°C to +85°C 8-Lead Plastic DIP N-8 AD8532ARU* –40°C to +85°C 8-Lead TSSOP RU-8
AD8534AR –40°C to +85°C 14-Lead SOIC SO-14 AD8534AN –40°C to +85°C 14-Lead Plastic DIP N-14 AD8534ARU* –40°C to +85°C 14-Lead TSSOP RU-14
*Available in reels only.
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 the AD8531/AD8532/AD8534 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.
WARNING!
ESD SENSITIVE DEVICE
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INPUT OFFSET VOLTAGE – mV
QUANTITY – Amplifiers
300
500
400
200
100
12
10 8 6 4 20 2 4
VS = 2.7V
V
CM
= 1.35V
T
A
= 25ⴗC
Figure 2. Input Offset Voltage Distribution
TEMPERATURE C
35 15 5 25 45 65
85
INPUT BIAS CURRENT – pA
5
8
7
4
2
6
3
VS = 5V, 3V
V
CM
= VS/2
Figure 5. Input Bias Current vs. Temperature
LOAD CURRENT – mA
0.01 0.1 10001 10 100
OUTPUT VOLTAGE – mV
1000
100
0.1
10
1
VS = 2.7V
TA = 25ⴗC
SOURCE
SINK
Figure 8. Output Voltage to Supply Rail vs. Load Current
Typical Performance Characteristics–AD8531/AD8532/AD8534
REV. C
–5–
INPUT OFFSET VOLTAGE – mV
QUANTITY – Amplifiers
300
12
10 8 6 4 20 2 4
500
400
200
100
VS = 5V
V
CM
= 2.5V
T
A
= 25ⴗC
Figure 3. Input Offset Voltage Distribution
COMMON-MODE VOLTAGE – Volts
01234 5
INPUT BIAS CURRENT – pA
5
8
7
4
2
6
3
1
VS = 5V
T
A
= 25ⴗC
Figure 6. Input Bias Current vs. Common-Mode Voltage
LOAD CURRENT – mA
0.01 0.1 10001 10 100
OUTPUT VOLTAGE – mV
10000
100
0.01
10
1000
1
VS = 5V
T
A
= 25ⴗC
SOURCE
SINK
Figure 9. Output Voltage to Supply Rail vs. Load Current
TEMPERATURE C
35 15 5 25 45 65
85
INPUT OFFSET VOLTAGE – mV
5
2
3
6
8
4
7
VS = 5V
V
CM
= 2.5V
Figure 4. Input Offset Voltage vs. Temperature
TEMPERATURE C
35 15 5 25 45 65 85
INPUT OFFSET CURRENT – pA
3
2
0
4
1
1
2
5
6
VS = 5V, 3V
V
CM
= VS/2
Figure 7. Input Offset Current vs. Temperature
FREQUENCY – Hz
1k 10k 100k 1M 10M 100M
VS = 2.7V
R
L
= NO LOAD
T
A
= 25ⴗC
80
60
40
20
0
GAIN – dB
45
90
135
180
PHASE SHIFT – De
g
rees
Figure 10. Open-Loop Gain and Phase vs. Frequency
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AD8531/AD8532/AD8534–Typical Performance Characteristics
REV. C
–6–
FREQUENCY – Hz
1k 10k 100k 1M 10M 100M
80
60
40
20
0
GAIN – dB
45
90
135
180
PHASE SHIFT – Degrees
VS = 5V
R
L
= NO LOAD
T
A
= 25ⴗC
Figure 11. Open-Loop Gain & Phase vs. Frequency
FREQUENCY – Hz
1k 10k
100M
100k 1M 10M
IMPEDANCE –
160
140
120
100
80
60
40
20
VS = 5V
TA = 25ⴗC
AV = 10
A
V
= 1
180
200
0
Figure 14. Closed-Loop Output Impedance vs. Frequency
FREQUENCY – Hz
CURRENT NOISE DENSITY – pA/ Hz
1
0.1
0.01 10 100 100k
1k
10k
VS = 5V
T
A
= 25ⴗC
Figure 17. Current Noise Density vs. Frequency
FREQUENCY – Hz
OUTPUT SWING – Volts p-p
5
4
0
1k 10k 10M100k 1M
3
2
1
VS = 2.7V
T
A
= 25ⴗC
R
L
= 2k
V
IN
= 2.5V p-p
Figure 12. Closed-Loop Output Voltage Swing vs. Frequency
100V/div
MARKER 41␮V/ Hz
VS = 5V A
V
= 1000
T
A
= 25ⴗC
FREQUENCY = 1kHz
90
100
0%
10
Figure 15. Voltage Noise Density vs. Frequency
FREQUENCY – Hz
COMMON-MODE REJECTION – dB
110
100
40
1k 10k 10M100k 1M
80
70
50
90
60
VS = 5V
T
A
= 25ⴗC
Figure 18. Common-Mode Rejec­tion vs. Frequency
FREQUENCY – Hz
OUTPUT SWING – Volts p-p
5
4
0
1k 10k 10M100k 1M
3
2
1
VS = 5V
T
A
= 25ⴗC
R
L
= 2k
V
IN
= 4.9V p-p
Figure 13. Closed-Loop Output Voltage Swing vs. Frequency
MARKER 25.9 ␮V/ Hz
200
V/div
100
90
10
0%
VS = 5V A
V
= 1000
T
A
= 25ⴗ C
FREQUENCY = 10kHz
Figure 16. Voltage Noise Density vs. Frequency
80
60
40
20
0
POWER SUPPLY REJECTION – dB
100
120
140
60
40
20
FREQUENCY – Hz
1k 10k 100k 1M 10M100
VS = 2.7V
TA = 25ⴗC
PSRR–
PSRR+
Figure 19. Power Supply Rejection vs. Frequency
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AD8531/AD8532/AD8534
REV. C
–7–
80
60
40
20
0
POWER SUPPLY REJECTION – dB
FREQUENCY – Hz
1k
10k
100k 1M 10M100
100
120
140
60
40
20
PSRR–
PSRR+
VS = 5V
T
A
= 25ⴗC
Figure 20. Power Supply Rejection vs. Frequency
CAPACITANCE – pF
10 100 100001000
SMALL SIGNAL OVERSHOOT – %
50
40
0
30
20
10
–OS
+OS
VS = 5V T
A
= 25ⴗC
R
L
= 600
Figure 23. Small Signal Overshoot vs. Load Capacitance
SUPPLY VOLTAGE – Volts
SUPPLY CURRENT/AMPLIFIER – mA
0.80
0.30
0.00
0.75 1.00
1.50 2.00 2.50 3.00
0.70
0.40
0.20
0.10
0.60
0.50
TA = 25ⴗC
Figure 26. Supply Current per Amplifier vs. Supply Voltage
CAPACITANCE – pF
10 100 100001000
SMALL SIGNAL OVERSHOOT – %
50
40
0
30
20
10
–OS
+OS
VS = 2.7V
T
A
= 25ⴗC
R
L
= 2k
Figure 21. Small Signal Overshoot vs. Load Capacitance
CAPACITANCE – pF
10 100 100001000
SMALL SIGNAL OVERSHOOT – %
50
40
0
30
20
10
–OS
+OS
VS = 2.7V T
A
= 25ⴗC
R
L
= 600
Figure 24. Small Signal Overshoot vs. Load Capacitance
500 ns/DIV
20mV/DIV
VS = 1.35V V
IN
= ⴞ50mV
A
V
= 1
R
L
= 2k
C
L
= 300pF
T
A
= 25ⴗC
0V
Figure 27. Small Signal Transient Response
SMALL SIGNAL OVERSHOOT – %
50
40
0
30
20
10
60
CAPACITANCE – pF
10 100 100001000
–OS
+OS
VS = 5V T
A
= 25ⴗC
R
L
= 2k
Figure 22. Small Signal Overshoot vs. Load Capacitance
TEMPERATURE – C
SUPPLY CURRENT/AMPLIFIER – mA
0.9
0.65
0.5
40
200 20406080
0.85
0.7
0.6
0.55
0.8
0.75
VS = 5V
VS = 3V
Figure 25. Supply Current per Amplifier vs. Temperature
500 ns/DIV
20mV/DIV
VS = 2.5V
V
IN
= ⴞ50mV
A
V
= 1
R
L
= 2k
C
L
= 300pF
TA = 25ⴗC
0V
Figure 28. Small Signal Transient Response
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AD8531/AD8532/AD8534
REV. C
–8–
100
90
10
0%
VS = 2.5V A
V
= 1
R
L
= 2k
T
A
= 25ⴗC
500mV
500ns
Figure 29. Large Signal Transient Response
APPLICATIONS THEORY OF OPERATION
The AD8531/AD8532/AD8534 is an all-CMOS, high output current drive, rail-to-rail input/output operational amplifier. This is the latest entry in Analog Devices’ expanding family of single-supply devices for the multimedia and telecom market­places. Its high output current drive and stability with heavy capacitive loads makes the AD8531/AD8532/AD8534 an excel­lent choice as a drive amplifier for LCD panels.
Figure 32 illustrates a simplified equivalent circuit for the AD8531/ AD8532/AD8534. Like many rail-to-rail input amplifier configu­rations, it is comprised of two differential pairs, one n-channel (M1–M2) and one p-channel (M3–M4). These differential pairs are biased by 50 µA 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–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 through the use of transistors M11–M14.
In order to achieve rail-to-rail output swings, the AD8531/ AD8532/AD8534 design employs a complementary common­source output stage (M15–M16). However, the output voltage swing is directly dependent on the load current, as the difference between the output voltage and the supply is determined by the AD8531/AD8532/AD8534’s output transistors on-channel resistance (see Figures 8 and 9). 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 open­loop gain of the device) exhibits a strong dependence to the total load resistance at the output of the AD8531/AD8532/AD8534.
50␮A
100A 100␮A
20A
V
B2
M5
M8
M12
M15
M16
M11
OUT
M3
M4
M2
M1
IN–
IN+
V
B3
M6
M7 M10
20A
M13
50␮A
V+
V–
M9
M14
Figure 32. AD8531/AD8532/AD8534 Simplified Equivalent Circuit
Short-Circuit Protection
As a result of the design of the output stage for maximum load current capability, the AD8531/AD8532/AD8534 does not have any internal short-circuit protection circuitry. Direct connection of the AD8531/AD8532/AD8534’s output to the positive supply in single-supply applications will destroy the device. In those 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 33, can be used. The resistor, connected within the feedback loop of the amplifier, will have 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
R
X
20
V
OUT
V
IN
AD8532
Figure 33. Output Short-Circuit Protection
VS = 1.35V A
V
= 1
R
L
= 2k
T
A
= 25ⴗC
500ns
500mV
100
90
10
0%
Figure 30. Large Signal Transient Response
1V
10␮s
1V
0%
10
90
100
Figure 31. No Phase Reversal
Page 9
AD8531/AD8532/AD8534
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Power Dissipation
Although the AD8531/AD8532/AD8534 is capable of providing load currents to 250 mA, the usable output load current drive capability will be 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 150°C, and should never be exceeded for the device could suffer premature failure. Accurately measuring power dissipation of an integrated circuit is not always a straightforward exercise, so Figure 34 has been provided as a design aid for either setting a safe output current drive level or in selecting a heatsink for the three package options available on the AD8531/AD8532/AD8534.
TEMPERATURE – C
1.5
1
0
0 10025 50 75
0.5
85
TJ MAX = 150ⴗC FREE AIR NO HEATSINK
PDIP
JA
= 103ⴗC/W
SOIC
JA
= 158ⴗC/W
TSSOP
JA
= 240ⴗC/W
SOT-23
JA
= 236ⴗC/W
SC70
JA
= 376ⴗC/W
POWER DISSIPATION – Watts
Figure 34. Maximum Power Dissipation vs. Ambient Temperature
These thermal resistance curves were determined using the AD8531/AD8532/AD8534 thermal resistance data for each package and a maximum junction temperature of 150°C. The following formula can be used to calculate the internal junction temperature of the AD8531/AD8532/AD8534 for any application:
TJ = P
DISS
× θJA + T
A
where TJ = junction temperature;
P
DISS
= power dissipation;
θ
JA
= package thermal resistance,
junction-to-case; and
T
A
= Ambient temperature of the circuit.
To calculate the power dissipated by the AD8531/AD8532/ AD8534, the following equation can be used:
P
DISS
= I
LOAD
× (VS–V
OUT
)
where I
LOAD
= is output load current;
V
S
= is supply voltage; and
V
OUT
= is 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 1 illustrates the AD8531/ AD8532/AD8534 output voltage as a function of load resistance.
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 might seem. In many cases power cannot be directly measured. This 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. The other is to directly measure the circuit’s supply current.
Calculating Power by Measuring Ambient and Case Temperature
Given the two equations for calculating junction temperature:
T
J
= TA + P θ
JA
where TJ is junction temperature, and TA is ambient tempera­ture. θ
JA
is the junction to ambient thermal resistance.
T
J
= TC + P θ
JC
where TC is case temperature and θJA and θJC are given in the data sheet.
The two equations can be solved for P (power):
T
A
+ P θJA = TC + P θ
JC
P = (TA – TC )/ (θ
JC
θJA)
Once power has been determined it is necessary to go back and calculate the junction temperature to assure 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 definitely not touching it. Measuring the package could be diffi­cult. A very small bimetallic junction glued to the package could be used or it could 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. This could 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 you must be sure all of the current is being deliv­ered by the supply pin you are measuring. 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.
Input Overvoltage Protection
As with any semiconductor device, whenever the condition exists for the input to exceed either supply voltage, the device’s input overvoltage characteristic must be considered. When an overvoltage occurs, the amplifier could 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 (Figure 32), the AD8531/ AD8532/AD8534 does not have any internal current limiting resistors, so fault currents can quickly rise to damaging levels.
Page 10
AD8531/AD8532/AD8534
REV. C
–10–
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. For more information on general overvoltage character­istics of amplifiers refer to the 1993 Seminar Applications Guide, available from the Analog Devices Literature Center.
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 is free from reasonable input voltage range restrictions provided that input voltages no greater than the supply voltage rails are applied. Although the device’s out­put will not change phase, large currents can flow through internal junctions to the supply rails, as was pointed out in the previous 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.
Capacitive Load Drive
The AD8531/AD8532/AD8534 exhibits excellent capacitive load driving capabilities. It can drive up to 10 nF directly as shown in Figures 21 through 24. However, even though the device is stable, a capacitive load does not come without a penalty in bandwidth. As shown in Figure 35, the bandwidth is reduced to under 1 MHz for loads greater than 10 nF. A “snub­ber” network on the output won’t increase the bandwidth, but it does significantly reduce the amount of overshoot for a given capacitive load. A snubber consists of a series R-C network (R
S
, CS), as shown in Figure 36, connected from the output of the device to ground. This network operates in parallel with the load capacitor, C
L
, to provide phase lag compensation. The actual
value of the resistor and capacitor is best determined empirically.
CAPACITIVE LOAD – nF
4
3.5
0
0.01 1000.1
BANDWIDTH – MHz
110
2
1.5
1
0.5
3
2.5
VS = 2.5V R
L
= 1k
TA = 25ⴗC
Figure 35. Unity-Gain Bandwidth vs. Capacitive Load
5V
R
S
5
V
OUT
V
IN
100mV p-p
AD8532
C
L
47nF
C
S
1F
Figure 36. Snubber Network Compensates for Capacitive Loads
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, C
S
is deter-
mined—10 µF is a good starting point. This value is reduced to the smallest value for acceptable performance (typically, 1 µF). For the case of a 47 nF load capacitor on the AD8531/AD8532/ AD8534, the optimal snubber network is a 5 in series with 1 µF. The benefit is immediately apparent as seen in the scope photo in Figure 37. The top trace was taken with a 47 nF load and the bottom trace with the 5 Ω—1 µF snubber network in place. The amount of overshoot and ringing is dramatically reduced. Table I below illustrates a few sample snubber networks for large load capacitors:
Table I. Snubber Networks for Large Capacitive Loads
Load Capacitance Snubber Network (CL)(R
S
, CS)
0.47 nF 300 , 0.1 µF
4.7 nF 30 , 1 µF 47 nF 5 , 1 µF
47nF LOAD
ONLY
SNUBBER
IN CIRCUIT
100
90
10
0%
50mV
10␮s
50mV
Figure 37. Overshoot and Ringing Is Reduced by Adding a Snubber Network in Parallel with the 47 nF Load
Page 11
AD8531/AD8532/AD8534
REV. C
–11–
A 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 rail-to-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 which feature low power, with sourcing outputs of 30 mA or less. Figure 38 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.
C2
0.1␮F
R2
10k 1%
V
OUT1
=
3.3V @ 100mA
R5
0.2
C5 100F/16V TANTALUM
R1 10k 1%
C1
0.1␮F
V
S
5V
V
OUT2
=
3.3V C4
1F
6
2
3
4
V
OUT
COMMON
C3
0.1␮F
V
C
ON/OFF CONTROL INPUT CMOS HI (OR OPEN) = ON
LO = OFF
V
S
COMMON
R3
(SeeText)
R4
3.3k
U2
AD8531
U1
REF196
Figure 38. A High Output Current Reference/Regulator
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 measured 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–C1. U2 replicates the U1 voltage within a few millivolts, but at a higher current output at V
OUT1
, 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.
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–C5 output network. With values as shown, the transient is about 20 mV peak and settles to within 2 mV in less than 10 µs for either polarity. Although room exists for optimizing the transient response, any changes to the R5–C5 network should be verified by experiment to preclude the possi­bility of excessive ringing with some capacitor types.
To scale V
OUT2
to another (higher) output level, the optional
resistor R3 (shown dotted) is added, causing, the new V
OUT1
to
become:
V
OUT1=VOUT 2
× 1+
R2 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, resistor R4 must be used with U1 to speed ON-OFF switching.
A Single-Supply, Balanced Line Driver
The circuit in Figure 39 is a unique line driver circuit topology used in professional audio applications and has been 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 common-mode 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.
R
L
600
C1
22␮F
A2
7
6
5
3
1
2
A1
5V
R1
10k
R2
10k
R11 10k
R7 10k
6
7
5
A1
12V
5V
R8 100k
R9
100k
C2
1F
R12
10k
R14
50
A2
1
2
3
R3
10k
R6
10k
R13
10k
C3
47␮F
V
O1
V
O2
C4
47␮F
A1, A2 = 1/2 AD8532
GAIN =
R3 R2
SET: R7, R10, R11 = R2
SET: R6, R12, R13 = R3
V
IN
R10
10k
R5
50
Figure 39. A Single-Supply, Balanced Line Driver for Multimedia and Automotive Applications
Page 12
AD8531/AD8532/AD8534
REV. C
–12–
A Single-Supply Headphone Amplifier
Because of its speed and large output drive, the AD8531/AD8532/ AD8534 makes an excellent headphone driver, as illustrated in Figure 40. 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 µF to prevent power supply noise from contami- nating the audio signal.
The audio signal is then ac-coupled to each input through a 10 µF 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 µF 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 op amps output stage by limiting 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.
1/2
AD8532
16
50k
270␮F
LEFT HEADPHONE
10F
50k
50k
100k
10F
LEFT
INPUT
1/2
AD8532
16
50k
270␮F
RIGHT HEADPHONE
10F
50k
50k
100k
10F
RIGHT
INPUT
V
V 5V
1F/0.1F
V 5V
Figure 40. A Single-Supply, Stereo Headphone Driver
A Single-Supply, Two-Way Loudspeaker Crossover Network
Active filters are useful in loudspeaker crossover networks for reasons 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 Sallen-Key (SK) and multiple-feedback (MFB) filter architectures are use­ful in implementing active crossover networks. The circuit shown in Figure 41 is a single-supply, two-way active crossover which combines the advantages of both filter topologies. 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 two-way example, the LO signal is a dc-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 a HP section, covering frequencies 500 Hz.
V
IN
3
2
1
U1A
AD8532
V
S
4
R1
31.6k
C1
0.01␮F
C2
0.01␮F
R2
31.6k
R5
31.6k
R6
31.6k
R4
49.9
HI
LO
500Hz
AND UP
DC – 500Hz
6
5
7
C3
0.01␮F
U1B
AD8532
C4
0.02␮F
R7
15.8k
R3
49.9
270␮F
270␮F
100k
V
S
10␮F
100k
100k
C
IN
10␮F
R
IN
100k
0.1F 100F/25V
V
S
TO U1
5V
COM
+
100k
+
Figure 41. A Single-Supply, Two-Way Active Crossover
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 II provides a design aid to adaptation, with suggested standard component values for other frequencies.
Table II. RC Component Selection for Various Crossover Frequencies
Crossover R1/C1 (U1A)
1
Frequency (Hz) R5/C3 (U1B)
2
100 160 kΩ/0.01 µF 200 80.6 kΩ/0.01 µF 319 49.9 kΩ/0.01 µF 500 31.6 kΩ/0.01 µF 1 k 16 k/0.01 µF 2 k 8.06 k/0.01 µF 5 k 3.16 k/0.01 µF 10 k 1.6 k/0.01 µF
NOTES Applicable for filter α = 2.
1
For Sallen-Key stage U1A: R1 = R2, and C1 = C2, etc.
2
For Multiple Feedback stage U1B: R6 = R5, R7 = R5/2, and
C4 = 2C3.
For additional information on the active filters and active cross­over networks, please consult the data sheet for the OP279, a dual rail-to-rail high-output current operational amplifier.
Page 13
AD8531/AD8532/AD8534
REV. C
–13–
Direct Access Arrangement for Telephone Line Interface
Figure 42 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. 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 signal on a single supply to the transformer. Because of the high output current drive and low dropout voltage of the AD8531/AD8532/ AD8534s, the largest signal available on a single 5 V supply is approximately 4.5 V p-p into a 600 transmission system. Amplifier A3 is configured as a difference amplifier for two reasons: (1) It prevents the transmit signal from interfering with the receive signal and (2) it extracts the receive signal from the transmission line for amplification by A4. A4s gain can be adjusted in the same manner as A1s to meet the modems input signal requirements. Standard resistor values permit the use of SIP (Single In-line Package) format resistor arrays.
6.2V
6.2V
TRANSMIT
TxA
RECEIVE
RxA
C1
0.1␮F
R1
10k
R2
9.09k
2k
P1 Tx GAIN ADJUST
A1
A2
A3
A4
A1, A2 = 1/2 AD8532 A3, A4 = 1/2 AD8532
R3
360
1:1
T1
TO TELEPHONE
LINE
1
2
3
7
6
5
2
3
1
6
5
7
10␮F
R7 10k
R8 10k
R5
10k
R6
10k
R9
10k
R14
14.3k
R10
10k
R11
10k
R12
10k
R13
10k
C2
0.1␮F
P2 Rx GAIN ADJUST
2k
Z
O
600
5V DC
MIDCOM 671-8005
Figure 42. A Single-Supply Direct Access Arrangement for Modems
Page 14
AD8531/AD8532/AD8534
REV. C
–14–
* AD8531/AD8532/AD8534 SPICE Macro-model 3/96, REV. C * 5-Volt Version ARG / ADSC * * Copyright 1996 by Analog Devices * * Refer to “README.DOC” file for License Statement. Use of this model * indicates your acceptance of the terms and provisions in the License * Statement. * * Node assignments * noninverting input * | inverting input * | | positive supply * | | | negative supply * ||||output * ||||| .SUBCKT AD8531/AD8532/AD8534_5 1 2 99 50 40 * * INPUT STAGE * M1 32650NIXL=6UW=25U M2 47650NIXL=6UW=25U M3 8255PIXL=6UW=25U M4 9755PIXL=6UW=25U EOS 7 1 POLY(1) 25 98 5E-3 0.451 IIN1 1 98 5P IIN2 2 98 5P IOS 2 1 0.5P I1 99 5 50U I2 6 50 50U R1 99 3 4.833K R2 99 4 4.833K R3 8 50 4.833K R4 9 50 4.833K D3 5 99 DX D4 50 6 DX * * GAIN STAGE * EREF 98 0 POLY(2) 99 0 50 0 0 0.5 +0.5 G1 98 21 POLY(2) 4 3 9 8 0 +145U +145U RG 21 98 18.078E6 CC 21 40 14P D1 21 22 DX D2 23 21 DX V1 99 22 1.37 V2 23 50 1.37 *
* COMMON MODE GAIN STAGE * ECM 24 98 POLY(2) 1 98 2 98 0 0.5 +0.5 R5 24 25 1E6 R6 25 98 10K C1 24 25 0.75P * * OUTPUT STAGE * ISY 99 50 450.4U GSY 99 50 POLY(1) 99 50 -3.334E-4 6.667E-5 EP 99 39 POLY(1) 98 21 0.78925 1 EN 38 50 POLY(1) 21 98 0.78925 1 M15 40 39 99 99 POX L=1.5U W=1500U M16 40 38 50 50 NOX L=1.5U W=1500U C15 40 39 50P C16 40 38 50P .MODEL DX D(RS=1 CJO=0.1P) .MODEL NIX NMOS(VTO=0.75 KP=205.5U RD=1 RS=1 RG=1 RB=1 +CGSO=4E-9 +CGDO=4E-9 CGBO=16.667E-9 CBS=2.34E-13 CBD=2.34E-13) .MODEL NOX NMOS(VTO=0.75 KP=195U RD=.5 RS=.5 RG=1 RB=1 +CGSO=66.667E-12 +CGDO=66.667E-12 CGBO=125E-9 CBS=2.34E-13 CBD=2.34E-13) .MODEL PIX PMOS(VTO=-0.75 KP=205.5U RD=1 RS=1 RG=1 RB=1 +CGSO=4E-9 +CGDO=4E-9 CBDO=16.667E-9 CBS=2.34E-13 CBD=2.34E-13) .MODEL POX PMOS(VTO=-0.75 KP=195U RD=.5 RS=.5 RG=1 RB=1 +CGSO=66.667E-12 +CGDO=66.667E-12 CGBO=125E-9 CBS=2.34E-13 CBD=2.34E-13) .ENDS
Page 15
AD8531/AD8532/AD8534
REV. C
–15–
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic DIP
(N-8)
8
14
5
0.430 (10.92)
0.348 (8.84)
0.280 (7.11)
0.240 (6.10)
PIN 1
SEATING PLANE
0.022 (0.558)
0.014 (0.356)
0.060 (1.52)
0.015 (0.38)
0.210 (5.33) MAX
0.130 (3.30) MIN
0.070 (1.77)
0.045 (1.15)
0.100
(2.54)
BSC
0.160 (4.06)
0.115 (2.93)
0.325 (8.25)
0.300 (7.62)
0.015 (0.381)
0.008 (0.204)
0.195 (4.95)
0.115 (2.93)
8-Lead TSSOP
(RU-8)
8
5
4
1
0.122 (3.10)
0.114 (2.90)
0.256 (6.50)
0.246 (6.25)
0.177 (4.50)
0.169 (4.30)
PIN 1
0.0256 (0.65) BSC
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.0118 (0.30)
0.0075 (0.19)
0.0433 (1.10) MAX
0.0079 (0.20)
0.0035 (0.090)
0.028 (0.70)
0.020 (0.50)
8 0
14-Lead TSSOP
(RU-14)
14
8
7
1
0.201 (5.10)
0.193 (4.90)
0.256 (6.50)
0.246 (6.25)
0.177 (4.50)
0.169 (4.30)
PIN 1
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.0118 (0.30)
0.0075 (0.19)
0.0256 (0.65)
BSC
0.0433 (1.10) MAX
0.0079 (0.20)
0.0035 (0.090)
0.028 (0.70)
0.020 (0.50)
8 0
14-Lead Plastic DIP
(N-14)
14
17
8
0.795 (20.19)
0.725 (18.42)
0.280 (7.11)
0.240 (6.10)
PIN 1
0.325 (8.25)
0.300 (7.62)
0.015 (0.381)
0.008 (0.204)
0.195 (4.95)
0.115 (2.93)
SEATING PLANE
0.022 (0.558)
0.014 (0.356)
0.060 (1.52)
0.015 (0.38)
0.210 (5.33) MAX
0.130 (3.30) MIN
0.070 (1.77)
0.045 (1.15)
0.100
(2.54)
BSC
0.160 (4.06)
0.115 (2.93)
Page 16
AD8531/AD8532/AD8534
REV. C
–16–
C01099b–0–8/00 (rev. C)
PRINTED IN U.S.A.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead SOIC
(SO-8)
14-Lead SOIC
(SO-14)
8-Lead MSOP
(RM-8)
0.009 (0.23)
0.005 (0.13)
0.028 (0.70)
0.016 (0.40)
6 0
0.037 (0.95)
0.030 (0.75)
85
4
1
0.122 (3.10)
0.114 (2.90)
PIN 1
0.0256 (0.65) BSC
0.122 (3.10)
0.114 (2.90)
0.193 (4.90)
BSC
SEATING PLANE
0.006 (0.15)
0.002 (0.05)
0.016 (0.40)
0.010 (0.25)
0.043 (1.10) MAX
0.1968 (5.00)
0.1890 (4.80)
85
41
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.1574 (4.00)
0.1497 (3.80)
0.0688 (1.75)
0.0532 (1.35)
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.0500 (1.27)
BSC
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8 0
0.0196 (0.50)
0.0099 (0.25)
x 45
14 8
71
0.3444 (8.75)
0.3367 (8.55)
0.2440 (6.20)
0.2284 (5.80)
0.1574 (4.00)
0.1497 (3.80)
PIN 1
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.0688 (1.75)
0.0532 (1.35)
0.0500 (1.27)
BSC
0.0099 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8 0
0.0196 (0.50)
0.0099 (0.25)
x 45
5-Lead SOT-23
(RT-5)
0.1181 (3.00)
0.1102 (2.80)
PIN 1
0.0669 (1.70)
0.0590 (1.50)
0.1181 (3.00)
0.1024 (2.60)
1 3
4 5
0.0748 (1.90) BSC
0.0374 (0.95) BSC
2
0.0079 (0.20)
0.0031 (0.08)
0.0217 (0.55)
0.0138 (0.35)
10
0
0.0197 (0.50)
0.0138 (0.35)
0.0059 (0.15)
0.0019 (0.05)
0.0512 (1.30)
0.0354 (0.90)
SEATING PLANE
0.0571 (1.45)
0.0374 (0.95)
5-Lead SC70
(KS-5)
0.012 (0.30)
0.006 (0.15)
0.004 (0.10)
0.000 (0.00)
0.039 (1.00)
0.031 (0.80)
SEATING PLANE
0.043 (1.10)
0.031 (0.80)
0.007 (0.18)
0.004 (0.10)
0.012 (0.30)
0.004 (0.10)
0.016 (0.40)
0.004 (0.10)
3
5
4
1
2
0.087 (2.20)
0.071 (1.80)
PIN 1
0.094 (2.40)
0.071 (1.80)
0.026 (0.65) BSC
0.053 (1.35)
0.045 (1.15)
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