Document
OBSOLETE:
FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
Features
nn Guaranteed 1% Initial Tolerance nn Guaranteed 0.3% Load Regulation nn Guaranteed 5A Output Current nn 100% Thermal Limit Burn-In nn 12A Transient Output Current
Applications
nn High Power Linear Regulator nn Battery Chargers nn Power Driver nn Constant-Current Regulator
Typical Application
Parallel Regulators for Higher Current*
LT338A
0.01Ω∗∗
VIN VIN VOUT
ADJ
5V 8A
LT350A
VIN VOUT ADJ
0.016Ω** 121Ω 1%
365Ω 1%
138/338 TA01
*THIS CIRCUIT WILL NOT WORK WITH LM VERSION DEVICES **CURRENT SHARING RESISTORS DEGRADE REGULATION TO 1%
LT138A/LT338A LM138/LM338 5A Positive Adjustable Voltage Regulator
Description
The LT®138A series of adjustable regulators provide 5A output current over an output voltage range of 1.2V to 32V. The internal voltage reference is trimmed to less than 1%, enabling a very tight output voltage. In addition to excellent line and load regulation, with full overload protection, the LT138A incorporates new current limiting circuitry allowing large transient load currents to be handled for short periods. Transient load currents of up to 12A can be supplied without limiting, eliminating the need for a large output capacitor. The LT138A is an improved version of the popular LM138 with improved circuit design and advanced process techniques to provide superior performance and reliability. The graph below shows the significant improvement in output voltage tolerance achieved by using the LT138A or LT338A.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
OUTPUT VOLTAGE ERROR (%)
Output Voltage Error
12
11
10
9 8
2% RESISTORS LM338
7 6
1% RESISTORS LM338
5 LT338A
4 2% RESISTORS 3 LT338A 2 1% RESISTORS
1
0 1 10 100 OUTPUT VOLTAGE (V)
138A/338A TA02
For more information www.linear.com/LT138A
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1
LT138A/LT339A LM138/LM338
Absolute Maximum Ratings (Note 1)
Power Dissipation............................... Internally Limited Input-to-Output Voltage Differential.......................... 35V Operating Junction Temperature Range
LT138A/LM138.................................. – 55°C to 150°C LT338A/LM338..................................... 0°C to 125°C
Storage Temperature Range.................. –65°C to 150°C Lead Temperature (Soldering, 10 sec).................... 300°C
Preconditioning
100% Thermal Limit Burn-In
Pin Configuration
BOTTOM VIEW VIN
2
1
CASE IS OUTPUT
ADJ (GND*)
K PACKAGE 2-LEAD TO-3 METAL CAN TJMAX = 150°C, θJA = 35°C/W, θJA = 1°C/W (LT138A/LT138) TJMAX = 125°C, θJA = 35°C/W, θJA = 1°C/W (LT338A/LT338)
OBSOLETE PACKAGE
FRONT VIEW
3 2 1
P PACKAGE 3-LEAD PLASTIC TO-3P TJMAX = 125°C, θJA = 45°C/W
OBSOLETE PACKAGE
VIN VOUT ADJ
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2 For more information www.linear.com/LT138A
LT138A/LT338A LM138/LM338
E lectrical Characteristics The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 2)
SYMBOL PARAMETER
CONDITIONS
LT138A MIN TYP MAX
LM138 MIN TYP MAX
VREF Reference Voltage
ΔVOUT ΔVIN ΔVOUT ΔVOUT
Line Regulation Load Regulation
Thermal Regulation
IOUT = 10mA, TJ = 25°C 3V ≤ (VIN – VOUT) ≤ 35V, 10mA ≤ IOUT ≤ 5A, P ≤ 50W 3V ≤ (VIN – VOUT) ≤ 35V, (Note 3)
10mA ≤ IOUT ≤ 5A, (Note 3) VOUT ≤ 5V VOUT ≥ 5V VOUT ≤ 5V VOUT ≥ 5V 20ms Pulse
l l
l l
1.238 1.225
1.250 1.250
0.005 0.02
5 0.1 20 0.3 0.002
1.262 1.270
1.119
1.24
0.01 0.005 0.04 0.02
15 5 0.3 0.1 30 20 0.6 0.3 0.01 0.002
1.29
0.01 0.04
15 0.3 30 0.6 0.01
IADJ ΔIADJ
ISC
Ripple Rejection
Adjust Pin Current Adjust Pin Current Change
Minimum Load Current Current Limit
VOUT = 10V, f = 120Hz CADJ = 0µF CADJ = 10µF
10mA ≤ IOUT ≤ 5A, 3V ≤ (VIN – VOUT) ≤ 35V (VIN – VOUT) = 35V (VIN – VOUT) ≤ 10V DC 0.5ms Peak
l l 60
60 75
60 60 75
l 45 100
45 100
l 0.2 5
0.2 5
l 3.5 5
3.5 5
l5 l6
8 12
58 6 12
ΔVOUT ΔTemp
Temperature Stability
(VIN – VOUT) = 30V, TJ = 25ºC
l
12 12
1 1
ΔVOUT ΔTime
Long-Term Stability
TA = 125ºC, 1000 Hours
0.3 1
0.3 1
en RMS Output Noise (% of VOUT) 10HZ ≤ f ≤ 10kHz
θJC Thermal Resistance Junction-to-Case
K Package
0.001
1
0.003
1
UNITS V V
%/V %/V
mV % mV % %/W
dB dB µA µA
mA
A A A %
%
% ºC/W
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
SYMBOL PARAMETER
CONDITIONS
LT138A
LM138
MIN TYP MAX MIN TYP MAX UNITS
VREF Reference Voltage
ΔVOUT ΔVIN ΔVOUT ΔVOUT
Line Regulation Load Regulation
Thermal Regulation
IOUT = 10mA
1.238 1.250 1.262
3V ≤ (VIN – VOUT) ≤ 35V, 10mA ≤ IOUT ≤ 5A, P ≤ 50W
l 1.225 1.250 1.270 1.19 1.24 1.29
3V ≤ (VIN – VOUT) ≤ 35V, (Note 3) l
0.005 0.01 0.02 0.04
0.005 0.03 0.02 0.06
10mA ≤ IOUT ≤ 5A, (Note 3) VOUT ≤ 5V VOUT ≥ 5V VOUT ≤ 5V VOUT ≥ 5V 20ms Pulse
l l
5 0.1 20 0.3 0.002
15 0.3 30 0.6 0..