LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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OBSOLETE PRODUCT
DATA SHEET FOR REFERENCE ONLY
Consult www.linear.com for possible alternate source.
FEATURES
s Guaranteed 0.8% Initial Tolerance
s Guaranteed 0.4% Load Regulation
s Guaranteed 10A Output Current
s 100% Thermal Limit Burn-In
s 24A Transient Output Current
s Standard Adjustable Pinout
s Operates to 35V
U
APPLICATIO S
s System Power Supplies
s High Power Linear Regulator
s Battery Chargers
s Power Driver
s Constant Current Regulator
LT1038
10A Positive
Adjustable Voltage
Regulator
DESCRIPTIO
The LT®1038 is a three terminal regulator which is capable
of providing in excess of 10A output current over 1.2V to
32V range. The device is packaged in a standard T0-3
power package and is plug-in compatible with industry
standard adjustable regulators, such as the LM117 and
LM138. Also, the LT1038 is a functional replacement for
the LM396.
In addition to excellent load and line regulations, the
LT1038 is fully protected by current limiting, safe area
protection and thermal shutdown. New current limiting
circuitry allows transient load currents up to 24A to be
supplied for 500µs without causing the regulator to cur-
rent limit and drop out of regulation during the transient.
On-chip trimming of initial reference voltage to ±0.8%
combined with 0.4% load regulation minimize errors in all
high current applications. Further, the LT1038 is manufac-
tured with standard bipolar processing and has Linear
Technology’s high reliability.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIONS
5V, 10A Regulator
VIN 8V
+
1µF
LT1038
VIN VOUT
ADJ
121
1% +
365
1%
5V
AT 10A
10µF
1038 TA01
Load Regulation
0.2
VIN = 15V
VOUT = 10V
0.1 PRELOAD = 100mA
0
IOUT = 6A
– 0.1 IOUT = 10A
– 0.2
– 0.3
– 0.4
– 75 – 50 – 25 0 25 50 75 100 125 150
TEMPERATURE (°C)
1038 TA02
1


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
ABSOLUTE AXI U RATI GS
(Note 1)
Power Dissipation ............................... Internally Limited
Input to Output Voltage Differential ......................... 35V
Operating Junction Temperature Range
LT1038M Control Circuitry ................ –55°C to 150°C
LT1038M Power Transistor ............... –55°C to 200°C
LT1038C Control Circuitry ..................... 0°C to 125°C
LT1038C Power Transistor .................... 0°C to 175°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
BOTTOM VIEW
VIN
2
ORDER PART
NUMBER
LT1038MK
1
CASE
ADJ IS OUTPUT
LT1038CK
K PACKAGE
2-LEAD TO-3 METAL CAN
TJMAX = 3°C, θJA = 35°C/W
OBSOLETE PACKAGE
PRECO DITIO I G 100% Thermal Limit Burn-in
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 2)
SYMBOL
VREF
VOUT
VIN
VOUT
IOUT
IADJ
IADJ
ISC
VOUT
Temp
VOUT
Time
en
θJC
PARAMETER
Reference Voltage
Line Regulation
Load Regulation
Thermal Regulation
Ripple Rejection
Adjust Pin Current
Adjust Pin Current Change
Minimum Load Current
Current Limit
Temperature Stability
Long Term Stability
RMS Output Noise
(% of VOUT)
Thermal Resistance
Junction to Case
CONDITIONS
IOUT = 20mA, Tj = 25°C
3V (VIN – VOUT) 35V
20mA IOUT 10A, P 75W
3V (VIN – VOUT) 35V,
IOUT = 20mA (Note 3)
20mA IOUT 10A (Note 3)
3V (VIN – VOUT) 35V
3V (VIN – VOUT) 35V
20ms Pulse
VOUT = 10V, f = 120Hz
CADJ = 0µF
CADJ = 10µF
20mA IOUT 10A
3V (VIN – VOUT) 35V
(VIN – VOUT) = 35V
(VIN – VOUT) 20V
(VIN – VOUT) 10V
DC
Transient (0.5ms)
(VIN – VOUT) = 30V, Tj = 25°C
TA = 125°C, 1000 Hours
10Hz f 10kHz
Power Transistor
Control Circuity
LT1038M
MIN TYP MAX
1.24 1.25 1.26
q 1.22 1.25 1.285
LT1038C
MIN TYP MAX
1.23 1.25 1.275
1.22 1.25 1.285
UNITS
V
V
0.005 0.01
q 0.02 0.03
0.005
0.02
0.02
0.03
%/V
%/V
0.1 0.4
q 0.3 0.8
0.002 0.005
0.1
0.3
0.002
0.6
1.0
0.01
%
%
%/W
q
q 60
q
60
75 60
50 100
60
75
50 100
dB
dB
µA
q 0.2 3
q 7 20
q 10
0.2 3
7 20
10
µA
mA
mA
q 10
14
14
22
10 14
12 22
12
12
q 12
1
A
A
A
%
0.3 1
0.3 1
%
0.001
0.001
%
q1
0.5
1 °C/W
0.5 °C/W
2


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Unless otherwise specified, these specifications apply:
VIN – VOUT = 5V and IOUT = 5A. These specifications are applicable for
power dissipations up to 75W. At input-output voltage differentials greater
than 10V, achievable output current and power dissipation decrease due to
protection circuitry.
Note 3: See thermal regulation specifications for changes in output voltage
due to heating effects. Load and line regulation are measured at a constant
junction temperature by low duty cycle pulse testing.
TYPICAL PERFOR A CE CHARACTERISTICS
Dropout Voltage
4
VOUT = 100mV
3
IOUT = 10A
IOUT = 6A
2
IOUT = 2A
1
– 75 – 50 – 25 0 25 50 75 100 125 150
TEMPERATURE (°C)
1038 TA02
Output Impedance
10
VIN = 15V
VOUT = 10V
1 IOUT = 1A
0.1
0.01
0.001
CADJ = 0µF
COUT = 0µF
CADJ = 10µF
COUT = 10µF
0.0001
10
100 1k 10k 100k
FREQUENCY (Hz)
1M
1038 G04
Adjustment Current
65
60
55
50
45
40
35
30
– 75 – 50 – 25 0 25 50 75 100 125 150
TEMPERATURE (°C)
1038 G02
Minimum Operating Current
10
8
Tj = 150°C
6 Tj = 25°C
4 Tj = – 55°C
2
0
0 5 10 15 20 25 30 35 40
INPUT-OUTPUT DIFFERENTIAL (V)
1038 G05
Temperature Stability
1.27
1.26
1.25
1.24
1.23
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1038 G03
Ripple Rejection
100
CADJ = 10µF
80
CADJ = 0µF
60
40
VIN – VOUT = 5V
20 IOUT = 1A
f = 120Hz
Tj = 25°C
0
0 5 10 15
20
25
OUTPUT VOLTAGE (V)
30 35
1038 G06
3


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
TYPICAL PERFOR A CE CHARACTERISTICS
Ripple Rejection
100
CADJ = 10µF
80
VIN = 15V
VOUT = 10V
IOUT = 1A
60
CADJ = 0µF
40
20
0
10 100 1k 10k 100k 1M
FREQUENCY (Hz)
1038 G07
Current Limit
28
VIN = 10V
24
VOUT = 5V
TCASE = 25°C
20
PRELOAD = 10A
16
PRELOAD = 0A
12
8
4
0
0.1
1 10
TIME (ms)
100
LTXXX GXX
Ripple Rejection
80
CADJ = 10µF
70
60 CADJ = 0µF
50 VIN = 15V
VOUT = 10V
f = 120Hz
TCASE = 25°C
40
0.1
1
OUTPUT CURRENT (A)
10
1038 G08
Current Limit
28
PRELOAD CURRENT = 0A
24 TCASE = 25°C
20
VIN – VOUT = 10V
16
12 VIN – VOUT = 15V
8 VIN – VOUT = 20V
4 VIN – VOUT = 30V
0
0.1 1
10 100
TIME (ms)
Load Transient Response
1038 G11
3
VIN = 15V
2 VOUT = 10V
1 TCASE = 25°C
PRELOAD = 200mA
0
– 1 CL = 0µF; CADJ = 0µF
–2
CL = 1µF; CADJ = 10µF
–3
6
4
2
0
0
10 20
TIME (µs)
30
40
1038 G13
Current Limit
32
PEAK CURRENT LIMIT
DC CURRENT LIMIT
TCASE = 25°C
24 PRELOAD = 0A
PRELOAD = 10A
16
PRELOAD = 2A
8
0
0 10 20 30 40
INPUT-OUTPUT DIFFERENTIAL (V)
1195 G20
Line Transient Response
1.5 VOUT = 10V
1.0 IOUT = 100mA
Tj = 25°C
0.5 CL = 1µF; CL = 10µF
0
– 0.5
–1.0 COUT = 0A
CADJ = 0A
–1.5
1.0
0.5
0
0
10 20
TIME (µs)
30
40
1038 G12
4


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
APPLICATIO S I FOR ATIO
General
The LT1038 develops a 1.25V reference voltage between
the output and the adjustment terminal (see Figure 1). By
placing a resistor, R1, between these two terminals, a
constant current is caused to flow through R1 and down
through R2 to set the overall output voltage. Normally this
current is the specified minimum load current of 10mA or
20mA. Because IADJ is very small and constant when
compared with the current through R1, it represents a
small error and can usually be ignored.
Bypass Capacitors
Input bypassing using a 1µF tantalum or 25µF electrolytic
is recommended when the input filter capacitors are more
than 5 inches from the device. Improved ripple rejection
(80dB) can be accomplished by adding a 10µF capacitor
from the ADJ pin to ground. Increasing the size of the
capacitor to 20µF will help ripple rejection at low output
voltage since the reactance of this capacitor should be
small compared to the voltage setting resistor, R2. For
improved AC transient response and to prevent the possi-
bility of oscillation due to unknown reactive load, a 1µF
capacitor is also recommended at the output. Because of
their low impedance at high frequencies, the best type of
capacitor to use is solid tantalum.
If a very large output capacitor is used, such as a 100µF
shown in Figure 2, the regulator could be damaged or
destroyed if the input is accidentally shorted to ground or
crowbarred, due to the output capacitor discharging into
the output terminal of the regulator. To prevent this, a
diode, D1 as shown, is recommended to safely discharge
the capacitor.
Load Regulation
Because the LT1038 is a three-terminal device, it is not
possible to provide true remote load sensing. Load regu-
lation will be limited by the resistance of the wire connect-
ing the regulator to the load. The data sheet specification
for load regulation is measured at the bottom of the
package. Negative side sensing can be a true Kelvin
connection if the bottom of resistor R2 is returned to the
negative side of the load. Although it may not be immedi-
ately obvious, best load regulation is obtained when the
top of the resistor divider, R1, is connected directly to the
case, not to the load. This is illustrated in Figure 3. If R1
were connected to the load, the effective resistance be-
tween the regulator and the load would be:
Rp

R2 + R1
R1 
Rp = Parasitic Line Resistance
Protection Diodes
The LT1038 does not require a protection diode from the
adjustment terminal to the output (see Figure 2). Im-
proved internal circuitry eliminates the need for this diode
when the adjustment pin is bypassed with a capacitor to
improve ripple rejection.
Connected as shown, Rp is not multiplied by the divider
ratio. Rp is about 0.004per foot using 16 gauge wire.
This translates to 4mV/ft at 1A load current, so it is
important to keep the lead between the regulator and the
load as short as possible, and use large wire or PC board
traces.
LT1038
VIN VIN VOUT
VOUT
ADJ
IADJ
50µA
VREF R1
VOUT
=
VREF
(1
+
R2
R1
)
+
IADJ
R2
R2
1038 F01
D1
1N4002
LT1038
VIN VIN VOUT
+ VOUT
ADJ R1 *
COUT
100µF
CADJ +
10µF
R2 *NOT NEEDED
1038 F02
Rp
LT1038
PARASITIC
LINE RESISTANCE
VIN VIN
VOUT
ADJ CONNECT
R1 TO CASE
R1
R2
RL
CONNECT R2
TO LOAD
1038 F03
Figure 1. Basic Adjustable Regulator
Figure 2
Figure 3. Connections for
Best Load Regulation
5


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
TYPICAL APPLICATIO S
Paralleling Regulators
LT1038
VIN VIN VOUT
ADJ
LT1038
2 FEET #18 WIRE*
VOUT
=
1.25
(1
+
R2
R1
)
IOUT = 0A TO 20A
0.015
VIN VOUT
ADJ
* THE #18 WIRE ACTS AS
BALLAST RESISTANCE
R1 INSURING CURRENT SHARING
120BETWEEN BOTH DEVICES
R2
1038 TA03
10A Variable Regulator*
T1
TRIAD
F-269U
110V AC
1N4003
C30B
20
3 T2 4
201
C30B
2
1N4003
1µF 560
L
1MHz
+
1N4003
C1
50,000µF
LT1038
VIN VOUT
ADJ
LT1004-1.2
LT1004-2.5
15V 16k*
+
750* 1.5k
0V TO 35V
0A TO 10A
100µF
20k
OUTPUT
ADJUST
82k
15k 8
2+
–15V
47
LT1011
200k
11k*
10k
31
0.1µF
1N4148
15V NC
8 100pF
–15V
4
3 2N3904
1
*1% FILM RESISTOR
L-DALE TO-5 TYPE
T2-STANCOR 11Z-2003
7
LT1011
+ 2 10k
1
15k
GENERAL PURPOSE REGULATOR WITH SCR PREREGULATOR TO LOWER
POWER DISSIPATION. ABOUT 4V DIFFERENTIAL IS MAINTAINED ACROSS
15V
8 +3
6
LM301A
7 2
15V 4
1µF –15V
THE LT1038 INDEPENDENT OF OUTPUT VOLTAGE AND LOAD CURRENT.
LT1004-1.2
16k*
2.7k
–15V
11k*
1038 TA04
6


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
TYPICAL APPLICATIO S
Improving Ripple Rejection
VIN
+
1µF
LT1038
VIN VOUT
ADJ
5V
R1
121
1%
R2 +
365
1%
C1*
10µF
*C1 IMPROVES RIPPLE
REJECTION. XC SHOULD
BE SMALL COMPARED TO R2.
1038 TA05
1.2V to 25V Adjustable Regulator
LT1038
VIN VIN
VOUT
ADJ
+ C1*
1µF
R2
5k
R1
121
+
VOUT††
C2
1µF
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS
OPTIONAL—IMPROVES TRANSIENT RESPONSE
†† VOUT = 1.25V (1 + R2/R1)
1038 TA06
5V Regulator with Shutdown
VIN
+
LT1038
VIN VOUT
ADJ
1µF
1k
TTL
2N3904
1k
5V
121
1%
365
1%
1038 TA07
Remote Sensing
LT1038
VIN VIN
VOUT
ADJ
RETURN
Rp
(MAX DROP 300mV)
25
121
365
VIN
72
6
LM301A
1
3 1k
8
4 5µF
+
100pF
25
5V
OUTPUT
RL
RETURN
1038 TA08
Temperature Compensated Lead Acid Battery Charger
10A
VIN
LT1038
VIN VOUT
ADJ
12110k*
1%
THERMALLY
50COUPLED
25k
2N3906
+
12V
CHARGE
2k*
2N3904
50k*
*LOAD ON BATTERY 200µA
WHEN NOT CHARGING
1038 TA09
SCHE ATIC DIAGRA
VIN
310310190
50
5.6k
Q11
Q4 Q6
Q9
Q2
Q15
30k Q5
4k
Q1 130Q8
Q3
160k
180
Q7
Q14
3k
12.4k
Q10
Q12 Q13
Q16
C1
30pF
4.1k 6k 10k
5.1k
Q24
20k
300
Q19
1.6k
Q18
Q20
Q17
Q23
6.7k 12k
200
Q26
Q27
120
Q28
Q21
C3 400160
5pF
Q22
16k
Q25
D1
6.3V
18k
D2
6.3V
C2
30pF
2.4k
160
3
12k
0.005
ADJ
VOUT 1038 SD
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
7


LT1038 (Linear Technology)
10Amp Positive Adjustable Voltage Regulator

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LT1038
TYPICAL APPLICATIO S
15V
1µF
Lamp Flasher
LT1038
VIN VOUT
ADJ
+10µF
12V
OFF
1k
12k
2N3904
12k
+10µF
+10µF
12k
1039 TA10
Automatic Light Control
LT1038
VIN VOUT
ADJ
1.2k
1039 TA11
Protected High Current Lamp Driver
LT1038
12V
10A
VOUT
VIN
15V
ADJ
TTL OR
CMOS
10k
1039 TA12
PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted.
0.320 – 0.350
(8.13 – 8.89)
0.420 – 0.480
(10.67 – 12.19)
0.760 – 0.775
(19.30 – 19.69)
K Package
2-Lead TO-3 Metal Can
(60mil Diameter Leads)
(LTC DWG # 05-08-1312)
0.060 – 0.135
(1.524 – 3.429)
0.210 – 0.220
(5.33 – 5.59)
1.177 – 1.197
(29.90 – 30.40)
0.655 – 0.675
(16.64 – 17.15)
0.151 – 0.161
(3.86 – 4.09)
DIA, 2 PLACES
0.058 – 0.062
(1.47 – 1.57)
0.425 – 0.435
(10.80 – 11.05)
0.067 – 0.077
(1.70 – 1.96)
OBSOLETE PACKAGE
0.167 – 0.177
(4.24 – 4.49)
R
0.490 – 0.510
(12.45 – 12.95)
R
K2(TO-3) 1098
RELATED PARTS
PART NUMBER
LT1084
LT1581
LT1584
LT1585
DESCRIPTION
Low Dropout, 0.01% Load Regulation
Low Dropout, 430mV at 10A
Low Dropout, 0.05% Load Regulation
Low Dropout, 0.05% Load Regulation
8 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q www.linear.com
COMMENTS
7.5A Max Current Output
Best Replacement
7A Max Current Output
5A Max Current Output
1038fa LT/TP 0701 1.5K REV A • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2000




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