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Positive Voltage Regulators
The LM323,A are monolithic integrated circuits which supply a fixed
positive 5.0 V output with a load driving capability in excess of 3.0 A. These
three–terminal regulators employ internal current limiting, thermal shutdown,
and safe–area compensation. The A–suffix is an improved device with
superior electrical characteristics and a 2% output voltage tolerance. These
regulators are offered with a 0° to +125°C temperature range in a low cost
plastic power package.
Although designed primarily as a fixed voltage regulator, these devices
can be used with external components to obtain adjustable voltages and
currents. These devices can be used with a series pass transistor to supply
up to 15 A at 5.0 V.
• Output Current in Excess of 3.0 A
• Available with 2% Output Voltage Tolerance
• No External Components Required
• Internal Thermal Overload Protection
• Internal Short Circuit Current Limiting
• Output Transistor Safe–Area Compensation
• Thermal Regulation and Ripple Rejection Have Specified Limits
LM323, A
3–AMPERE, 5 VOLT
POSITIVE
VOLTAGE REGULATORS
SEMICONDUCTOR
TECHNICAL DATA
T SUFFIX
PLASTIC PACKAGE
CASE 221A
Pin 1. Input
2. Ground
3. Output
1
2
3
Heatsink surface is connected to Pin 2.
Simplified Application
Input
Cin*
0.33µF
LM323, A
Output
CO**
A common ground is required between the input and the output voltages. The input
voltagemust remain typically 2.5 V above the output voltage even during the low point
on the input ripple voltage.
* Cin is required if regulator is located an appreciable
* distancefrompowersupplyfilter.(SeeApplications
* Information for details.)
** CO is not needed for stability; however, it does
** improve transient response.
ORDERING INFORMATION
Output
Voltage
Device Tolerance
Operating
Temperature
Range
Package
LM323T
LM323AT
4%
2%
TJ = 0° to +125°C
Plastic
Power
MOTOROLA ANALOG IC DEVICE DATA
© Motorola, Inc. 1996
Rev 0
1
LM323, A
Figure 9. Dropout Voltage
2.5
Iout = 3.0 A
2.0
8.0
6.0
1.5 Iout = 1.0 A
Iout = 0.5 A
1.0
∆Vout = 50 mV
0.5–90
–50 –10 30 70 110 150
TJ, JUNCTION TEMPERATURE (°C)
190
4.0
2.0
0
5.0
Figure 10. Short Circuit Current
TJ = 0°C
TJ = 25°C
TJ = 125°C
10 15 20
Vin, INPUT VOLTAGE (Vdc)
25
Figure 11. Line Transient Response
0.8
0.6
0.4
Iout = 150 mA
CO = 0
TJ = 25°C
0.2
0
–0.2
–0.4
–0.6
1.0
0.5
00
10 20
t, TIME (µs)
30
40
Figure 12. Load Transient Response
0.3
0.2 Vin = 10 V
0.1
CO = 0
TJ = 25°C
0
–0.1
–0.2
–0.3
1.5
1.0
0.5
0
0
10 20 30
t, TIME (µs)
40
APPLICATIONS INFORMATION
Design Considerations
The LM323,A series of fixed voltage regulators are
designed with Thermal Overload Protection that shuts down
the circuit when subjected to an excessive power overload
condition, Internal Short Circuit Protection that limits the
maximum current the circuit will pass, and Output Transistor
Safe–Area Compensation that reduces the output short
circuit current as the voltage across the pass transistor is
increased.
In many low current applications, compensation
capacitors are not required. However, it is recommended that
the regulator input be bypassed with a capacitor if the
regulator is connected to the power supply filter with long wire
lengths, or if the output load capacitance is large. An input
bypass capacitor should be selected to provide good
high–frequency characteristics to insure stable operation
under all load conditions. A 0.33 µF or larger tantalum, mylar,
or other capacitor having low internal impedance at high
frequencies should be chosen. The bypass capacitor should
be mounted with the shortest possible leads directly across
the regulator’s input terminals. Normally good construction
techniques should be used to minimize ground loops and
lead resistance drops since the regulator has no external
sense lead.
MOTOROLA ANALOG IC DEVICE DATA
5