OPA2544 Datasheet, PDF (7/10 Pages) Burr-Brown (TI) – High-Voltage, High-Current DUAL OPERATIONAL AMPLIFIER

APPLICATIONS INFORMATION
Figure 1 shows the OPA2544 connected as a basic non-
inverting amplifier. The OPA2544 can be used in virtually
any op amp configuration. Power supply terminals should be
bypassed with low series impedance capacitors. The tech-
nique shown, using a ceramic and tantalum type in parallel,
is recommended. Power supply wiring should have low
series impedance and inductance.
+35V
V+
10µF
0.1µF
G = 1+ ^R2 = 3
R₁
R₁
R₂
5kΩ
10kΩ
The safe output current decreases as V_CE increases. Output
short-circuit is a very demanding case for SOA. A short-
circuit to ground forces the full power supply voltage (V+
or V–) across the conducting transistor. With V_S = ±35V
the safe output current is 1.5A (at 25°C). The short-circuit
current is approximately 4A which exceeds the SOA. This
situation will activate the thermal shutdown circuit in the
OPA2544. For further insight on SOA, consult AB-039.
CURRENT LIMIT
The OPA2544 has an internal current limit set for approxi-
mately 4A. This current limit decreases with increasing
junction temperature as shown in the typical curve, Current
Limit versus Temperature. This, in combination with the
thermal shutdown circuit, provides protection from many
types of overload. It may not, however, protect for short-
circuit to ground, depending on the power supply voltage,
ambient temperature, heat sink and signal conditions.
1/2
V_O
OPA2544
V_IN
0.1µF
Z_L
10µF
+
V–
–35V
FIGURE 1. Basic Circuit Connections.
SAFE OPERATING AREA
Stress on the output transistors is determined by the output
current and the voltage across the conducting output transis-
tor, V_CE. The power dissipated by the output transistor is
equal to the product of the output current and the voltage
across the conducting transistor, V_CE. The Safe Operating
Area (SOA curve, Figure 2) shows the permissible range of
voltage and current.
SAFE OPERATING AREA
10
4
Current-Limited
Output current may
1 ^{be limited to less}
than 4A—see text.
T_C = 85°C
0.4
T_C = 25°C
T_C = 125°C
0.1
1
2
5
10
20
|V_S – V_O| (V)
50
100
FIGURE 2. Safe Operating 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 con-
ducting output transistor. Power dissipation can be mini-
mized by using the lowest possible power supply voltage
necessary to assure the required output voltage swing.
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.
HEATSINKING
Most applications require a heat sink to assure that the
maximum junction temperature is not exceeded. The heat
sink required depends on the power dissipated and on
ambient conditions. Consult Application Bulletin AB-038
for information on determining heat sink requirements.
The heat sink tab of the plastic package is connected to the
V– power supply terminal. Lowest thermal resistance can be
achieved by mounting the tab directly to a heat sink. If the
heat sink cannot be electrically “hot” at V– power supply
potential, insulating hardware must be used.
THERMAL PROTECTION
The OPA2544 has thermal shutdown that protects the ampli-
fier from damage. Any tendency to activate the thermal
shutdown circuit during normal operation is indication of
excessive power dissipation or an inadequate heat sink.
The thermal protection activates at a junction temperature
of approximately 155°C. For reliable operation, junction
temperature should be limited to 150°C, maximum. To
estimate the margin of safety in a complete design (includ-
ing heat sink), increase the ambient temperature until the
thermal protection is activated. Use worst-case load and
signal conditions. For good reliability, the thermal protec-
®
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OPA2544