OPA548 [BB]
High-Voltage, High-Current OPERATIONAL AMPLIFIER; 高电压，大电流运算放大器
| 型号： | OPA548 |
| 厂家： | 
BURR-BROWN CORPORATION |
| 描述： | High-Voltage, High-Current OPERATIONAL AMPLIFIER |
| 文件： | 总16页 (文件大小：286K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
OPA548
®
OPA548
OPA548
www.burr-brown.com/databook/OPA548.html
High-Voltage, High-Current
OPERATIONAL AMPLIFIER
DESCRIPTION
FEATURES
The OPA548 is a low cost, high-voltage/high-current
operational amplifier ideal for driving a wide variety
of loads. A laser-trimmed monolithic integrated cir-
cuit provides excellent low-level signal accuracy and
high output voltage and current.
● WIDE SUPPLY RANGE
Single Supply: +8V to +60V
Dual Supply: ±4V to ±30V
● HIGH OUTPUT CURRENT:
3A Continuous
The OPA548 operates from either single or dual sup-
plies for design flexibility. In single supply operation,
the input common-mode range extends below ground.
5A Peak
● WIDE OUTPUT VOLTAGE SWING
● FULLY PROTECTED:
Thermal Shutdown
The OPA548 is internally protected against over-
temperature conditions and current overloads. In addi-
tion, the OPA548 was designed to provide an accurate,
user-selected current limit. Unlike other designs which
use a “power” resistor in series with the output current
path, the OPA548 senses the load indirectly. This
allows the current limit to be adjusted from 0 to 5A
with a resistor/potentiometer or controlled digitally
with a voltage-out or current-out DAC.
Adjustable Current Limit
● OUTPUT DISABLE CONTROL
● THERMAL SHUTDOWN INDICATOR
● HIGH SLEW RATE: 10V/µs
● LOW QUIESCENT CURRENT
● PACKAGES:
The Enable/Status (E/S) pin provides two functions.
An input on the pin not only disables the output stage
to effectively disconnect the load but also reduces the
quiescent current to conserve power. The E/S pin
output can be monitored to determine if the OPA548
is in thermal shutdown.
7-Lead TO-220
7-Lead DDPAK Surface-Mount
APPLICATIONS
● VALVE, ACTUATOR DRIVER
● SYNCHRO, SERVO DRIVER
● POWER SUPPLIES
The OPA548 is available in an industry-standard
7-lead staggered TO-220 package and a 7-lead DDPAK
surface-mount plastic power package. The copper tab
allows easy mounting to a heat sink or circuit board
for excellent thermal performance. It is specified for
operation over the extended industrial temperature
range, –40°C to +85°C. A SPICE macromodel is
available for design analysis.
● TEST EQUIPMENT
● TRANSDUCER EXCITATION
● AUDIO AMPLIFIER
V+
VI–N
OPA548
VO
VI+N
ILIM
RCL
(1/4W Resistor)
RCL sets the current limit
value from 0 to 5A.
E/S
V–
International Airport Industrial Park
•
Mailing Address: PO Box 11400, Tucson, AZ 85734
FAXLine: (800) 548-6133 (US/Canada Only)
•
Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/
•
•
Cable: BBRCORP
•
Telex: 066-6491
•
FAX: (520) 889-1510
•
Immediate Product Info: (800) 548-6132
©1997 Burr-Brown Corporation
PDS-1389B
Printed in U.S.A. October, 1997
SPECIFICATIONS
At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted.
OPA548T, F
TYP
PARAMETER
CONDITION
MIN
MAX
UNITS
OFFSET VOLTAGE
Input Offset Voltage
vs Temperature
V
CM = 0, IO = 0
±2
±30
30
±10
mV
µV/°C
µV/V
T
T
A = –40°C to +85°C
vs Power Supply
VS = ±4V to ±30V
100
INPUT BIAS CURRENT(1)
Input Bias Current(2)
vs Temperature
VCM = 0V
–100
±0.5
±5
–500
nA
nA/°C
nA
A = –40°C to +85°C
CM = 0V
Input Offset Current
V
±50
NOISE
Input Voltage Noise Density, f = 1kHz
Current Noise Density, f = 1kHz
90
200
nV/√Hz
fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range: Positive
Negative
Linear Operation
Linear Operation
CM = (V–) –0.1V to (V+) –3V
(V+) –3
(V–) –0.1
80
(V+) –2.3
(V–) –0.2
95
V
V
dB
Common-Mode Rejection
V
INPUT IMPEDANCE
Differential
Common-Mode
107 || 6
109 || 4
Ω || pF
Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain
V
V
O = ±25V, RL = 1kΩ
O = ±25V, RL = 8Ω
90
98
90
dB
dB
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
Full Power Bandwidth
Settling Time: ±0.1%
RL = 8Ω
G = 1, 50Vp-p, RL = 8Ω
1
MHz
V/µs
kHz
µs
10
See Typical Curve
15
G = –10, 50V Step
RL = 8Ω, G = +3, Power = 10W
Total Harmonic Distortion + Noise, f = 1kHz
0.02(3)
%
OUTPUT
Voltage Output, Positive
Negative
I
O = 3A
O = –3A
O = 0.6A
O = –0.6A
(V+) –4.1
(V–) +3.7
(V+) –2.4
(V–) +1.3
±3
(V+) –3.7
(V–) +3.3
(V+) –2.1
(V–) +1.0
V
V
V
V
A
I
I
Positive
Negative
I
Maximum Continuous Current Output: dc
ac
3
Arms
Leakage Current, Output Disabled, dc
Output Current Limit
Current Limit Range
Current Limit Equation
Current Limit Tolerance(1)
See Typical Curve
0 to ±5
A
A
mA
I
LIM = (15000)(4.75)/(13750Ω + RCL)
RCL = 14.8kΩ (ILIM = ±2.5A),
RL = 8Ω
±100
±250
Capacitive Load Drive
See Typical Curve(4)
OUTPUT ENABLE /STATUS (E/S) PIN
Shutdown Input Mode
V
V
E/S High (output enabled)
E/S Low (output disabled)
E/S Pin Open or Forced High
E/S Pin Forced Low
E/S Pin High
(V–) +2.4
V
V
µA
µA
µs
µs
(V–) +0.8
IE/S High (output enabled)
–65
–70
1
IE/S Low (output disabled)
E/S Pin Low
Output Disable Time
Output Enable Time
3
Thermal Shutdown Status Output
Normal Operation
Thermally Shutdown
Sourcing 20µA
Sinking 5µA, TJ > 160°C
(V–) +2.4
(V–) +3.5
(V–) +0.35
+160
V
V
°C
°C
(V–) +0.8
Junction Temperature, Shutdown
Reset from Shutdown
+140
POWER SUPPLY
Specified Voltage
Operating Voltage Range
Quiescent Current
±30
V
V
mA
mA
±4
±30
±20
I
I
LIM Connected to V–, IO = 0
LIM Connected to V–, IO = 0
±17
±6
Quiescent Current, Shutdown Mode
TEMPERATURE RANGE
Specified Range
Operating Range
–40
–40
–55
+85
+125
+125
°C
°C
°C
Storage Range
Thermal Resistance, θJC
7-Lead DDPAK, 7-Lead TO-220
7-Lead DDPAK, 7-Lead TO-220
Thermal Resistance, θJA
7-Lead DDPAK, 7-Lead TO-220
f > 50Hz
dc
2
2.5
°C/W
°C/W
No Heat Sink
65
°C/W
NOTES: (1) High-speed test at TJ = +25°C. (2) Positive conventional current flows into the input terminals. (3) See “Total Harmonic Distortion+Noise vs Frequency” in
the Typical Performance Curves section for additional power levels. (4) See “Small-Signal Overshoot vs Load Capacitance” in the Typical Performance Curves section.
®
OPA548
2
CONNECTION DIAGRAMS
PACKAGE/ORDERING INFORMATION
Top Front View
PACKAGE
DRAWING TEMPERATURE
PRODUCT
PACKAGE
NUMBER(1)
RANGE
OPA548T
7-Lead Stagger-Formed TO-220
327
–40°C to +85°C
7-Lead
Stagger-Formed
TO-220
7-Lead
DDPAK
Surface-Mount
OPA548F(2) 7-Lead DDPAK Surface-Mount
328
–40°C to +85°C
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book. (2) Available on Tape and
Reel.
1
2
3
4
1 2 3 4
5
5
6
7
6 7
ELECTROSTATIC
DISCHARGE SENSITIVITY
VI+N
VI–N
ILIM V+ E/S
V– VO
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
VI+N
VI–N
ILIM V+ E/S
V– VO
NOTE: Tabs are electrically connected to V– supply.
ESD damage can range from subtle performance degrada-
tion to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet its
published specifications.
ABSOLUTE MAXIMUM RATINGS(1)
Output Current ................................................................. See SOA Curve
Supply Voltage, V+ to V– ................................................................... 60V
Input Voltage ....................................................... (V–)–0.5V to (V+)+0.5V
Input Shutdown Voltage ........................................................................ V+
Operating Temperature ................................................. –40°C to +125°C
Storage Temperature..................................................... –55°C to +125°C
Junction Temperature ...................................................................... 150°C
Lead Temperature (soldering 10s)(2) ................................................................. 300°C
NOTE: (1) Stresses above these ratings may cause permanent damage.
(2) Vapor-phase or IR reflow techniques are recommended for soldering the
OPA548F surface mount package. Wave soldering is not recommended due to
excessive thermal shock and “shadowing” of nearby devices.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility
for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or
licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support
devices and/or systems.
®
3
OPA548
TYPICAL PERFORMANCE CURVES
At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted.
OPEN-LOOP GAIN AND PHASE
vs FREQUENCY
INPUT BIAS CURRENT vs TEMPERATURE
–160
–140
–120
–100
–80
100
No Load
RL = 8Ω
80
60
40
20
0
0
VS = ±5V
G
–45
–90
–135
–180
RL = 8Ω
No
VS = ±30V
Load
φ
–60
–40
–20
–75
–50
–25
0
25
50
75
100 125
1
10
100
1k
10k
100k
1M
10M
Temperature (°C)
Frequency (Hz)
CURRENT LIMIT vs TEMPERATURE
CURRENT LIMIT vs SUPPLY VOLTAGE
±5
±4
±3
±2
±1
0
±5
±4
±3
±2
±1
0
+ILIM
–ILIM
RCL = 4.02kΩ
RCL = 4.02kΩ
RCL = 14.7kΩ
RCL = 57.6kΩ
RCL = 14.7kΩ
RCL = 57.6kΩ
–75
–50
–25
0
25
50
75
100
125
0
±5
±10
±15
±20
±25
±30
Temperature (°C)
Supply Voltage (V)
INPUT BIAS CURRENT
QUIESCENT CURRENT vs TEMPERATURE
vs COMMON-MODE VOLTAGE
±20
±18
±16
±14
±12
±10
±8
–200
–150
–100
–50
0
IQ
VS = ±5V
VS = ±30V
VS = ±30V
IQ Shutdown
±6
VS = ±5V
75
±4
–75
–50
–25
0
25
50
100
125
–30
–20
–10
0
10
20
30
Temperature (°C)
Common-Mode Voltage (V)
®
OPA548
4
TYPICAL PERFORMANCE CURVES (CONT)
At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted.
POWER SUPPLY REJECTION
vs FREQUENCY
COMMON-MODE REJECTION vs FREQUENCY
100
80
60
40
20
0
100
80
60
40
20
0
+PSRR
–PSRR
10
100
1k
10k
100k
1M
10
–75
20
100
1k
10k
100k
1M
Frequency (Hz)
Frequency (Hz)
OPEN-LOOP GAIN, COMMON-MODE REJECTION,
AND POWER SUPPLY REJECTION vs TEMPERATURE
VOLTAGE NOISE DENSITY vs FREQUENCY
100
95
90
85
80
110
500
400
300
200
100
0
AOL
105
100
95
PSRR
CMRR
90
–50
–25
0
25
50
75
100
125
1
10
100
1k
10k
100k
1M
Temperature (°C)
Frequency (Hz)
GAIN-BANDWIDTH PRODUCT AND
SLEW RATE vs TEMPERATURE
TOTAL HARMONIC DISTORTION+NOISE
vs FREQUENCY
1.25
1
13
1
0.1
G = +3
RL = 8Ω
GBW
20W
12
11
10
9
10W
1W
0.75
0.5
0.25
0
0.1W
SR+
0.01
0.001
SR–
8
–75
–50
–25
0
25
50
75
100
125
100
1k
Frequency (Hz)
10k 20k
Temperature (°C)
®
5
OPA548
TYPICAL PERFORMANCE CURVES (CONT)
At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted.
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
OUTPUT VOLTAGE SWING vs TEMPERATURE
5
4
3
2
1
0
5
4
3
2
1
0
IO = +3A
IO = –3A
(V+) –VO
(V–) –VO
IO = +0.6A
IO = –0.6A
0
1
2
Output Current (A)
3
4
–75
–40
0
–50
–25
0
25
50
75
100
125
Temperature (°C)
MAXIMUM OUTPUT VOLTAGE SWING
vs FREQUENCY
OUTPUT LEAKAGE CURRENT
vs APPLIED OUTPUT VOLTAGE
30
25
20
15
10
5
10
5
Maximum Output
RL = 8Ω
Voltage Without
Slew Rate Induced
Distortion
RCL = ∞
RCL = 0
0
–5
–10
Output Disabled
VE/S < (V–) + 0.8V
0
1k
10k
100k
Frequency (Hz)
1M
–30
–20
–10
0
10
20
30
40
Output Voltage (V)
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
20
18
16
14
12
10
8
14
12
10
8
Typical distribution
of packaged units.
Typical production
distribution of
packaged units.
6
6
4
4
2
2
0
0
–10 –9 –8 –7 –6 –5 –4 –3 –2 –1
0
1
2
3
4
5
6
7
8
9
10
10 20 30 40 50 60 70 80 90 100 110 120 130
Offset Voltage Drift (µV/°C)
Offset Voltage (mV)
®
OPA548
6
TYPICAL PERFORMANCE CURVES (CONT)
At TCASE = +25°C, VS = ±30V and E/S pin open, unless otherwise noted.
LARGE-SIGNAL STEP RESPONSE
SMALL-SIGNAL OVERSHOOT
G = 3, CL = 1000pF, RL = 8Ω
vs LOAD CAPACITANCE
50
40
G = +1
30
20
G = –1
10
0
0
2k
4k
6k
8k 10k 12k 14k 16k 18k 20k
5µs/div
Load Capacitance (pF)
SMALL-SIGNAL STEP RESPONSE
G = 1, CL = 1000pF
SMALL-SIGNAL STEP RESPONSE
G = 3, CL = 1000pF
2µs/div
2µs/div
®
7
OPA548
With the OPA548, the simplest method for adjusting the
current limit uses a resistor or potentiometer connected
between the ILIM pin and V– according to the equation:
APPLICATIONS INFORMATION
Figure 1 shows the OPA548 connected as a basic non-
inverting amplifier. The OPA548 can be used in virtually
any op amp configuration.
15000 4.75
(
)(
)
RCL
=
–13750Ω
ILIM
Power supply terminals should be bypassed with low series
impedance capacitors. The technique shown, using a ce-
ramic and tantalum type in parallel is recommended. In
addition, we recommend a 0.01µF capacitor between V+
and V– as close to the OPA548 as possible. Power supply
wiring should have low series impedance.
The low level control signal (0 to 330µA) also allows the
current limit to be digitally controlled.
Figure 3 shows a simplified schematic of the internal cir-
cuitry used to set the current limit. Leaving the ILIM pin open
programs the output current to zero, while connecting ILIM
directly to V– programs the maximum output current limit,
typically 5A.
V+
10µF
R2
R1
+
G = 1+
0.1µF(2)
SAFE OPERATING AREA
R1
R2
Stress on the output transistors is determined both by the
output current and by the output voltage across the conduct-
ing output transistor, VS – VO. The power dissipated by the
output transistor is equal to the product of the output current
and the voltage across the conducting transistor, VS – VO.
The Safe Operating Area (SOA curve, Figure 2) shows the
permissible range of voltage and current.
5
E/S
7
2
6
VO
OPA548
VIN
3
ZL
1
(1)
ILIM
4
0.1µF(2)
0.01µF(2)
10µF
+
SAFE OPERATING AREA
10
V–
Current-Limited
NOTE: (1) ILIM connected to V– gives the maximum current
limit, 5A (peak). (2) Connect capacitors directly to package
power supply pins.
TC = 25°C
PD = 50W
PD = 26W
Output current can
be limited to less
than 3A—see text.
1
FIGURE 1. Basic Circuit Connections.
PD = 10W
POWER SUPPLIES
TC = 85°C
The OPA548 operates from single (+8V to +60V) or dual
(±4V to ±30V) supplies with excellent performance. Most
behavior remains unchanged throughout the full operating
voltage range. Parameters which vary significantly with
operating voltage are shown in the typical performance
curves.
Pulse Operation Only
(Limit rms current to ≤ 3A)
TC = 125°C
0.1
1
2
5
10
20
50
100
VS
– VO (V)
FIGURE 2. Safe Operating Area.
Some applications do not require equal positive and negative
output voltage swing. Power supply voltages do not need to
be equal. The OPA548 can operate with as little as 8V
between the supplies and with up to 60V between the
supplies. For example, the positive supply could be set to
55V with the negative supply at –5V, or vice-versa.
The safe output current decreases as VS – VO increases. Out-
put short-circuits are a very demanding case for SOA. A
short-circuit to ground forces the full power supply voltage
(V+ or V–) across the conducting transistor. Increasing the
case temperature reduces the safe output current that can be
tolerated without activating the thermal shutdown circuit of
the OPA548. For further insight on SOA, consult Applica-
tion Bulletin AB-039.
ADJUSTABLE CURRENT LIMIT
The OPA548 features an accurate, user-selected current
limit. Current limit is set from 0 to 5A by controlling the
input to the ILIM pin. Unlike other designs which use a power
resistor in series with the output current path, the OPA548
senses the load indirectly. This allows the current limit to be
set with a 0 to 330µA control signal. In contrast, other
designs require a limiting resistor to handle the full output
current (5A in this case).
AMPLIFIER MOUNTING
Figure 4 provides recommended solder footprints for both the
TO-220 and DDPAK power packages. The tab of both pack-
ages is electrically connected to the negative supply, V–. It
may be desirable to isolate the tab of TO-220 package from its
®
OPA548
8
RESISTOR METHOD
DAC METHOD (Current or Voltage)
Max IO = ILIM
Max IO = ILIM
(4.75) (15000)
±ILIM
=
±ILIM =15000 ISET
13750Ω + RCL
13750Ω
13750Ω
4.75V
4.75V
ISET
3
3
D/A
RCL
0.01µF
(optional, for noisy
environments)
4
4
V–
V–
ISET = ILIM/15000
SET = (V–) + 4.75V – (13750Ω) (ILIM)/15000
15000 (4.75V)
ILIM
RCL
=
– 13750Ω
V
OPA547 CURRENT LIMIT: 0 to 5A
DESIRED
CURRENT LIMIT
RESISTOR(1)
(RCL
CURRENT
(ISET
VOLTAGE
(VSET
)
)
)
0A
1A
2.5A
3A
4A
5A
I
LIM Open
57.6kΩ
14.7kΩ
10kΩ
0µA
67µA
167µA
200µA
267µA
333µA
(V–) + 4.75V
(V–) + 3.8V
(V–) + 2.5V
(V–) + 2V
(V–) + 1.1V
(V–)
4.02kΩ
ILIM Connected to V–
NOTE: (1) Resistors are nearest standard 1% values.
FIGURE 3. Adjustable Current Limit.
(1)
7-Lead DDPAK
(Package Drawing #328)
7-Lead TO-220
(Package Drawing #327)
0.51
0.04
0.05
0.035
0.05
0.105
Mean dimensions in inches. Refer to end of data sheet
or Appendix C of Burr-Brown Data Book for tolerances
and detailed package drawings.
NOTE: (1) For improved thermal performance increase footprint area.
See Figure 6, “Thermal Resistance vs Circuit Board Copper Area”.
FIGURE 4. TO-220 and DDPAK Solder Footprints.
mounting surface with a mica (or other film) insulator (see
Figure 5). For lowest overall thermal resistance it is best to
isolate the entire heat sink/OPA548 structure from the mount-
ing surface rather than to use an insulator between the semi-
conductor and heat sink.
dissipation. Figure 6 shows typical thermal resistance from
junction-to-ambient as a function of the copper area
POWER DISSIPATION
Power dissipation depends on power supply, signal, and load
conditions. For dc signals, power dissipation is equal to
the product of output current times the voltage across the
For best thermal performance, the tab of the DDPAK sur-
face-mount version should be soldered directly to a circuit
board copper area. Increasing the copper area improves heat
®
9
OPA548
THERMAL RESISTANCE
vs ALUMINUM PLATE AREA
Aluminum Plate Area
Flat, Rectangular
18
16
14
12
10
8
Vertically Mounted
in Free Air
Aluminum Plate
θ
0.030in Al
0.050in Al
Aluminum
Plate Thickness
0.062in Al
5
Optional mica or film insulator
for electrical isolation. Adds
approximately 1°C/W.
0
1
2
3
4
6
7
8
OPA548
TO-220 Package
Aluminum Plate Area (inches2)
FIGURE 5. TO-220 Thermal Resistance vs Aluminum Plate Area.
THERMAL RESISTANCE vs
CIRCUIT BOARD COPPER AREA
50
Circuit Board Copper Area
OPA548F
40
30
20
10
0
Surface Mount Package
1oz copper
OPA548
Surface Mount Package
0
1
2
3
4
5
Copper Area (inches2)
FIGURE 6. DDPAK Thermal Resistance vs Circuit Board Copper Area.
conducting output transistor. Power dissipation can be mini-
mized by using the lowest possible power supply voltage
necessary to assure the required output voltage swing.
tion of the amplifier but may have an undesirable effect on
the load.
Any tendency to activate the thermal protection circuit
indicates excessive power dissipation or an inadequate heat
sink. For reliable operation, junction temperature should be
limited to 125°C, maximum. To estimate the margin of
safety in a complete design (including heat sink) increase the
ambient temperature until the thermal protection is trig-
gered. Use worst-case load and signal conditions. For good
reliability, thermal protection should trigger more than 35°C
above the maximum expected ambient condition of your
application. This produces a junction temperature of 125°C
at the maximum expected ambient condition.
For resistive loads, the maximum power dissipation occurs
at a dc output voltage of one-half the power supply voltage.
Dissipation with ac signals is lower. Application Bulletin
AB-039 explains how to calculate or measure power dissi-
pation with unusual signals and loads.
THERMAL PROTECTION
Power dissipated in the OPA548 will cause the junction
temperature to rise. The OPA548 has thermal shutdown
circuitry that protects the amplifier from damage. The ther-
mal protection circuitry disables the output when the junc-
tion temperature reaches approximately 160°C, allowing the
device to cool. When the junction temperature cools to
approximately 140°C, the output circuitry is again enabled.
Depending on load and signal conditions, the thermal pro-
tection circuit may cycle on and off. This limits the dissipa-
The internal protection circuitry of the OPA548 was de-
signed to protect against overload conditions. It was not
intended to replace proper heat sinking. Continuously run-
ning the OPA548 into thermal shutdown will degrade reli-
ability.
®
OPA548
10
HEAT SINKING
Combining equations (1) and (2) gives:
Most applications require a heat sink to assure that the
maximum operating junction temperature (125°C) is not
exceeded. In addition, the junction temperature should be
kept as low as possible for increased reliability. Junction
temperature can be determined according to the equation:
TJ = TA + PD(θJC + θCH + θHA
)
(3)
TJ, TA, and PD are given. θJC is provided in the specification
table, 2.5°C/W (dc). θCH can be obtained from the heat sink
manufacturer. Its value depends on heat sink size, area, and
material used. Semiconductor package type, mounting screw
torque, insulating material used (if any), and thermal
joint compound used (if any) also affect θCH. A typical θCH
for a TO-220 mounted package is 1°C/W. Now we can solve
TJ = TA + PDθJA
(1)
(2)
where, θJA = θJC + θCH + θHA
TJ = Junction Temperature (°C)
TA = Ambient Temperature (°C)
for θHA
:
PD = Power Dissipated (W)
θJC = Junction-to-Case Thermal Resistance (°C/W)
θCH = Case-to-Heat Sink Thermal Resistance (°C/W)
TJ – TA
PD
θHA
θHA
=
=
– θ + θCH
JC
(
)
125°C – 40°C
θHA
= Heat Sink-to-Ambient Thermal Resistance (°C/W)
– 2.5°C/W +1°C/W = 13.5°C/W
(
)
5W
θJA = Junction-to-Air Thermal Resistance (°C/W)
Figure 7 shows maximum power dissipation versus ambient
temperature with and without the use of a heat sink. Using
a heat sink significantly increases the maximum power
dissipation at a given ambient temperature as shown.
To maintain junction temperature below 125°C, the heat
sink selected must have a θHA less than 14°C/W. In other
words, the heat sink temperature rise above ambient must be
less than 67.5°C (13.5°C/W x 5W). For example, at 5 Watts
Thermalloy model number 6030B has a heat sink
temperature rise of 66°C above ambient (θHA = 66°C/5W =
13.2°C/W), which is below the 67.5°C required in this
example. Figure 7 shows power dissipation versus ambient
temperature for a TO-220 package with a 6030B heat sink.
The difficulty in selecting the heat sink required lies in
determining the power dissipated by the OPA548. For dc
output into a purely resistive load, power dissipation is
simply the load current times the voltage developed across
the conducting output transistor, PD = IL(Vs–VO). Other
loads are not as simple. Consult Application Bulletin AB-
039 for further insight on calculating power dissipation.
Once power dissipation for an application is known, the
proper heat sink can be selected.
Another variable to consider is natural convection vs forced
convection air flow. Forced-air cooling by a small fan can
lower θCA (θCH + θHA) dramatically. Heat sink manufactures
provide thermal data for both of these cases. For additional
information on determining heat sink requirements, consult
Application Bulletin AB-038.
MAXIMUM POWER DISSIPATION
vs AMBIENT TEMPERATURE
10
As mentioned earlier, once a heat sink has been selected the
complete design should be tested under worst-case load and
signal conditions to ensure proper thermal protection.
PD = (TJ (max) – TA) /θJA
TO-220 with Thermalloy
6030B Heat Sink
TJ (max) = 150°C
8
6
4
2
0
θ
= 16.7°C/W
JA
With infinite heat sink
ENABLE/STATUS (E/S) PIN
(
θJA = 2.5°C/W),
max PD = 50W at TA = 25°C.
The Enable/Status Pin provides two functions: forcing this
pin low disables the output stage, or, E/S can be monitored
to determine if the OPA548 is in thermal shutdown. One or
both of these functions can be utilized on the same device
using single or dual supplies. For normal operation (output
enabled), the E/S pin can be left open or pulled high (at least
2.4V above the negative rail). A small value capacitor
connected between the E/S pin and V– may be required for
noisy applications.
DDPAK
= 26°C/W
(3 in one oz
θ
JA
2
copper mounting pad)
DDPAK or TO-220
= 65°C/W (no heat sink)
θ
JA
0
25
50
75
100
125
Ambient Temperature (°C)
FIGURE 7. Maximum Power Dissipation vs Ambient
Temperature.
Output Disable
A unique feature of the OPA548 is its output disable capa-
bility. This function not only conserves power during idle
periods (quiescent current drops to approximately 6mA) but
also allows multiplexing in low frequency (f<20kHz), mul-
tichannel applications. Signals greater than 20kHz may
cause leakage current to increase in devices that are shut-
down. Figure 18 shows the two OPA548s in a switched
amplifier configuration. The on/off state of the two amplifi-
ers is controlled by the voltage on the E/S pin.
Heat Sink Selection Example
A TO-220 package is dissipating 5 Watts. The maximum
expected ambient temperature is 40°C. Find the proper heat
sink to keep the junction temperature below 125°C (150°C
minus 25°C safety margin).
®
11
OPA548
To disable the output, the E/S pin is pulled low, no greater
than 0.8V above the negative rail. Typically the output is
shutdown in 1µs. Figure 8 provides an example of how to
implement this function using a single supply. Figure 9 gives
a circuit for dual supply applications. To return the output to
an enabled state, the E/S pin should be disconnected (open) or
pulled to at least (V–) + 2.4V. It should be noted that pulling
the E/S pin high (output enabled) does not disable internal
thermal shutdown.
V+
5V
OPA548
2.49kΩ
E/S
TTL
V–
Zetex
ZVN3310
OR
HCT
V+
FIGURE 10. Thermal Shutdown Status with a Single Supply.
OPA548
E/S
5V
V+
V–
CMOS or TTL
1kΩ
OPA548
2N3906
FIGURE 8. Output Disable with a Single Supply.
E/S
22kΩ
470Ω
Zetex
ZVN3310
V+
V–
5V
FIGURE 11. Thermal Shutdown Status with Dual Supplies.
OPA548
E/S
1
6
Output Disable and Thermal Shutdown Status
As mentioned earlier, the OPA548’s output can be disabled
and the disable status can be monitored simultaneously.
Figures 12 and 13 provide examples interfacing to the E/S
pin while using a single supply and dual supplies, respec-
tively.
5
(1)
HCT or TTL In
1
4
4N38
Optocoupler
V–
OUTPUT STAGE COMPENSATION
NOTE: (1) Optional—may be required to limit leakage
current of optocoupler at high temperatures.
The complex load impedances common in power op amp
applications can cause output stage instability. For normal
operation output compensation circuitry is typically not
required. However, if the OPA548 is intended to be
driven into current limit, an R/C network may be required.
Figure 14 shows an output series R/C compensation (snub-
ber) network which generally provides excellent stability.
FIGURE 9. Output Disable with Dual Supplies.
Thermal Shutdown Status
Internal thermal shutdown circuitry shuts down the output
when the die temperature reaches approximately 160°C, reset-
ting when the die has cooled to 140°C. The E/S pin can be
monitored to determine if shutdown has occurred. During
normal operation the voltage on the E/S pin is typically 3.5V
above the negative rail. Once shutdown has occurred this
voltage drops to approximately 350mV above the negative rail.
A snubber circuit may also enhance stability when driving
large capacitive loads (>1000pF) or inductive loads (motors,
loads separated from the amplifier by long cables). Typi-
cally 3Ω to 10Ω in series with 0.01µF to 0.1µF is adequate.
Some variations in circuit value may be required with
certain loads.
Figure 10 gives an example of monitoring shutdown in a
single supply application. Figure 11 provides a circuit for
dual supplies. External logic circuitry or an LED could be
used to indicate if the output has been thermally shutdown,
see Figure 16.
OUTPUT PROTECTION
Reactive and EMF-generating loads can return load cur-
rent to the amplifier, causing the output voltage to exceed
the power supply voltage. This damaging condition can
®
OPA548
12
V+
V+
R2
R1
R1
5kΩ
R2
20kΩ
G = –
= –4
VIN
OPA548
D1
E/S
OPA548
V–
10Ω
(Carbon)
D2
Motor
Open Drain
HCT
(Output Disable)
(Thermal Status
Shutdown)
0.01µF
V–
D1, D2 : Motorola MUR410.
FIGURE 12. Output Disable and Thermal Shutdown Status
with a Single Supply.
FIGURE 14. Motor Drive Circuit.
V+
5V
5V
1
6
5
4
OPA548
E/S
7.5kΩ
1W
TTL Out
1
6
2
(1)
Zetex
ZVN3310
4N38
5
4
Optocoupler
HCT or TTL In
2
4N38
Optocoupler
V–
NOTE: (1) Optional—may be required to limit leakage
current of optocoupler at high temperatures.
FIGURE 13. Output Disable and Thermal Shutdown Status with Dual Supplies.
be avoided with clamp diodes from the output terminal to
the power supplies as shown in Figure 14. Schottky
rectifier diodes with a 5A or greater continuous rating are
recommended.
VCL, is connected to the noninverting input of the op amp
and used as a voltage reference, thus eliminating the need for
an external reference. The feedback resistors are selected to
gain VCL to the desired output voltage level.
VOLTAGE SOURCE APPLICATION
PROGRAMMABLE POWER SUPPLY
Figure 15 illustrates how to use the OPA548 to provide an
accurate voltage source with only three external resistors.
First, the current limit resistor, RCL, is chosen according to
the desired output current. The resulting voltage at the ILIM
pin is constant and stable over temperature. This voltage,
A programmable source/sink power supply can easily be
built using the OPA548. Both the output voltage and output
current are user-controlled. Figure 16 shows a circuit using
potentiometers to adjust the output voltage and current while
Figure 17 uses digital-to-analog converters. An LED tied to
the E/S pin through a logic gate indicates if the OPA548 is
in thermal shutdown.
®
13
OPA548
R1
R2
V+
VO = VCL (1 + R2/R1)
15000 (4.75V)
4.75V
13750Ω
V–
IO
=
VCL
13750Ω + RCL
ILIM
For Example:
RCL
0.01µF
If ILIM = 3A, RCL = 10kΩ
10kΩ • 4.75V
(Optional, for noisy
environments)
VCL
=
= 2V
20
(10kΩ + 13750Ω)
Uses voltage developed at ILIM pin
as a moderately accurate reference
voltage.
Desired VO = 20V,G =
= 10
2
R1 = 1kΩ and R2 = 9kΩ
FIGURE 15. Voltage Source.
1kΩ
9kΩ
9kΩ
G = 1 +
= 10
1kΩ
+5V
+30V
V+
10.5kΩ
2
5
6
VO = 1.2V to 25V(1)
IO = 0 to 5A
OPA548
0.12V to 2.5V
E/S
10kΩ
7
1
Output
Adjust
4
74HCT04
ILIM
R ≥ 250Ω
3
499Ω
V–
+5V
V–
Thermal
Shutdown Status
(LED)
0V to 4.75V
1kΩ
Current
Limit
Adjust
NOTES: (1) For VO ≤ 0V, V– ≤ –1V.
(2) Optional: Improves noise
immunity.
0.01µF(2)
20kΩ
FIGURE 16. Resistor-Controlled Programmable Power Supply.
®
OPA548
14
1kΩ
9kΩ
–5V
VREF
OUTPUT ADJUST
+30V
G = 10
+5V
VREF A
+5V
RFB A
V
O = 0.8 to 25V(1)
IO = 0 to 5A
OPA548
10pF
IOUT A
1/2
OPA2336
74HCT04
1/2 DAC7800/1/2(3)
DAC A
R ≥ 250Ω
E/S
V–
AGND A
ILIM
Thermal
(LED)
Shutdown Status
VREF B
RFB B
10pF
IOUT B
1/2
OPA2336
1/2 DAC7800/1/2(3)
DAC B
0.01µF(2)
DGND
AGND B
CURRENT LIMIT ADJUST
NOTES: (1) For VO ≤ 0V, V– ≤ –1V. (2) Optional, improves noise immunity. (3) Chose DAC780X based on
digital interface: DAC7800 - 12-bit interface, DAC7801 - 8-bit interface + 4 bits, DAC7802 - serial interface.
(4) Can use OPA2237, IO = 100mA to 5A.
FIGURE 17. Digitally-Controlled Programmable Power Supply.
R1
R2
VIN1
OPA548
ILIM
AMP1
E/S
RCL1
RCL2
Close for high current
(Could be open drain
output of a logic gate).
VO
R3
R4
VE/S
VIN2
V–
AMP2
E/S
FIGURE 19. Multiple Current Limit Values.
VE/S > (V–) +2.4V: Amp 1 is on, Amp 2 if off
VO = –VIN1 R2
VO
OPA548
(R )
As VO increases,
ILIM decreases.
1
ILIM
VE/S < (V–) +2.4V: Amp 2 is on, Amp 1 if off
VO = –VIN2 R4
RCL
(R )
3
FIGURE 20. Single Quadrant V • I Limiting.
FIGURE 18. Switched Amplifier.
®
15
OPA548
R1
R2
1kΩ
4kΩ
V+
4kΩ
1kΩ
G = 1 +
= 5(1)
0.25Ω
800Ω
OPA548
ILIM
V–
VIN
VO
IO = 10A (peak)(2)
V+
800Ω
0.25Ω
OPA548
ILIM
V–
R3
R4
1kΩ
4kΩ
NOTES: (1) Works well for G < 10. Input offset causes output current to flow between amplifiers
with G > 10. Gains (resistor ratios) of the two amplifiers should be carefully matched to ensure
equal current sharing. (2) As configured (ILIM connected to V–) output current limit is set to 10A
(peak). Each amplifier is limited to 5A (peak). Other current limit values may be obtained, see
Figure 3, “Adjustable Current Limit”.
FIGURE 21. Parallel Output for Increased Output Current.
®
OPA548
16
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