LT1038 10A Positive Adjustable Voltage Regulator
OBSOLETE PRODUCT DATA SHEET FOR REFERENCE ONLY Consult www.linear.com for possible alternate source.
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FEATURES ■ ■ ■ ■ ■ ■ ■
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.
Guaranteed 0.8% Initial Tolerance Guaranteed 0.4% Load Regulation Guaranteed 10A Output Current 100% Thermal Limit Burn-In 24A Transient Output Current Standard Adjustable Pinout Operates to 35V
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 current limit and drop out of regulation during the transient.
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System Power Supplies High Power Linear Regulator Battery Chargers Power Driver Constant Current Regulator
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 manufactured with standard bipolar processing and has Linear Technology’s high reliability. , LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIONS 5V, 10A Regulator
Load Regulation
LT1038 VIN VOUT
VIN ≥ 8V
+
ADJ
5V AT 10A 121Ω 1%
1µF
+ 10µF
365Ω 1% 1038 TA01
OUTPUT VOLTAGE DEVIATION (%)
0.2 0.1
VIN = 15V VOUT = 10V PRELOAD = 100mA
0 – 0.1
IOUT = 6A IOUT = 10A
– 0.2 – 0.3 – 0.4 – 75 – 50 – 25
0 25 50 75 100 125 150 TEMPERATURE (°C) 1038 TA02
1
LT1038
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ABSOLUTE
AXI U RATI GS
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(Note 1) BOTTOM VIEW
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
ORDER PART NUMBER
VIN 2
LT1038MK LT1038CK
1 CASE IS OUTPUT
ADJ K PACKAGE 2-LEAD TO-3 METAL CAN
TJMAX = 3°C, θJA = 35°C/W
OBSOLETE PACKAGE
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PRECO DITIO I G 100% Thermal Limit Burn-in ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) SYMBOL
PARAMETER
VREF
Reference Voltage
CONDITIONS IOUT = 20mA, Tj = 25°C 3V ≤ (VIN – VOUT) ≤ 35V 20mA ≤ IOUT ≤ 10A, P ≤ 75W
∆VOUT ∆VIN
Line Regulation
∆VOUT ∆IOUT
Load Regulation
ISC
1.26
1.23
1.25
1.275
V
1.25
1.285
1.22
1.25
1.285
V
MAX
UNITS
0.005 0.02
0.02 0.03
%/V %/V
20mA ≤ IOUT ≤ 10A (Note 3) 3V ≤ (VIN – VOUT) ≤ 35V 3V ≤ (VIN – VOUT) ≤ 35V
●
0.1 0.3
0.4 0.8
0.1 0.3
0.6 1.0
% %
0.002
0.005
0.002
0.01
%/W
● ●
60
60 75
●
50
20mA ≤ IOUT ≤ 10A 3V ≤ (VIN – VOUT) ≤ 35V
●
Minimum Load Current
(VIN – VOUT) = 35V (VIN – VOUT) ≤ 20V
● ●
Current Limit
(VIN – VOUT) ≤ 10V DC Transient (0.5ms)
●
(VIN – VOUT) = 30V, Tj = 25°C ∆VOUT ∆Temp
Temperature Stability
∆VOUT ∆Time
Long Term Stability
TA = 125°C, 1000 Hours
en
RMS Output Noise (% of VOUT)
10Hz ≤ f ≤ 10kHz
θJC
Thermal Resistance Junction to Case
Power Transistor Control Circuity
2
LT1038C TYP
0.01 0.03
VOUT = 10V, f = 120Hz CADJ = 0µF CADJ = 10µF
Adjust Pin Current Change
1.25
1.22
MIN
0.005 0.02
Ripple Rejection
∆IADJ
1.24
MAX
●
20ms Pulse
Adjust Pin Current
LT1038M TYP
3V ≤ (VIN – VOUT) ≤ 35V, IOUT = 20mA (Note 3)
Thermal Regulation
IADJ
●
MIN
●
60
dB dB 100
µA
100
50
0.2
3
0.2
3
µA
7
20 10
7
20 10
mA mA
10 14
14 22
10 12
14 22
A A
1
2
1
2
A %
1
2
1
0.3
1
0.3
0.001 ●
60 75
1
0.001 1 0.5
% %
1 0.5
°C/W °C/W
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.
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TYPICAL PERFOR A CE CHARACTERISTICS Dropout Voltage
Adjustment Current
Temperature Stability 1.27
65
∆VOUT = 100mV
3 IOUT = 10A IOUT = 6A 2 IOUT = 2A
REFERENCE VOLTAGE (V)
60
ADJUSTMENT CURRENT (µA)
55 50 45 40
1 – 75 – 50 – 25
30 – 75 – 50 – 25
0 25 50 75 100 125 150 TEMPERATURE (°C)
1.25
1.24
CADJ = 0µF COUT = 0µF
0.1
CADJ = 10µF COUT = 10µF
0.01
Ripple Rejection
10
100
8
80
CADJ = 10µF QUIESCENT CURRENT (mA)
1
0.001
Tj = 150°C 6
Tj = 25°C Tj = – 55°C
4
2
100
10k 1k FREQUENCY (Hz)
100k
1M 1038 G04
CADJ = 0µF 60
40 VIN – VOUT = 5V IOUT = 1A f = 120Hz Tj = 25°C
20
0
0.0001 10
25 50 75 100 125 150 TEMPERATURE (°C) 1038 G03
Minimum Operating Current
VIN = 15V VOUT = 10V IOUT = 1A
0
1038 G02
Output Impedance 10
1.23 –50 –25
0 25 50 75 100 125 150 TEMPERATURE (°C)
1038 TA02
OUTPUT IMPEDANCE (Ω)
1.26
35
RIPPLE REJECTION (dB)
INPUT-OUTPUT DIFFERENTIAL (V)
4
0 0
25 30 35 5 10 15 20 INPUT-OUTPUT DIFFERENTIAL (V)
40
1038 G05
0
5
20 15 10 25 OUTPUT VOLTAGE (V)
30
35
1038 G06
3
LT1038 U W
TYPICAL PERFOR A CE CHARACTERISTICS Ripple Rejection
Ripple Rejection
40
70
60
50
20
40
10k 1k FREQUENCY (Hz)
100k
1M
CADJ = 0µF
VIN = 15V VOUT = 10V f = 120Hz TCASE = 25°C
PRELOAD = 0A
12 8
20 VIN – VOUT = 10V 16
0
0
100
1
TIME (ms)
10
100
TIME (ms) LTXXX GXX
1038 G11
Load Transient Response 3
OUTPUT VOLTAGE DEVIATION (V)
2 1
VIN = 15V VOUT = 10V TCASE = 25°C PRELOAD = 200mA
0 CL = 0µF; CADJ = 0µF
–1 –2
CL = 1µF; CADJ = 10µF
LOAD CURRENT (A)
–3 6 4 2 0 0
10
20 TIME (µs)
30
CL = 1µF; CL = 10µF
0.5
VOUT = 10V IOUT = 100mA Tj = 25°C
0 – 0.5 COUT = 0A CADJ = 0A
–1.5
VIN – VOUT = 30V
0.1
1.0
–1.0
VIN – VOUT = 20V
8 4
10
VIN – VOUT = 15V
12
4
1
Line Transient Response
OUTPUT VOLTAGE DEVIATION (V)
PRELOAD = 10A
40 1195 G20
1.5
PRELOAD CURRENT = 0A TCASE = 25°C
24 OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
28
VIN = 10V VOUT = 5V TCASE = 25°C
20
20 10 30 INPUT-OUTPUT DIFFERENTIAL (V)
0
Current Limit
24
40 1038 G13
4
PRELOAD = 2A 8
1038 G08
Current Limit 28
0.1
PRELOAD = 10A 16
10
1038 G07
16
24
0
1 OUTPUT CURRENT (A)
0.1
INPUT VOLTAGE CHANGE (V)
100
OUTPUT CURRENT (A)
CADJ = 0µF
10
PEAK CURRENT LIMIT DC CURRENT LIMIT TCASE = 25°C PRELOAD = 0A
CADJ = 10µF RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
80
60
32
VIN = 15V VOUT = 10V IOUT = 1A
CADJ = 10µF
0
Current Limit
80
100
1.0 0.5 0 0
10
20 TIME (µs)
30
40 1038 G12
LT1038
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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 possibility 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. Protection Diodes The LT1038 does not require a protection diode from the adjustment terminal to the output (see Figure 2). Improved internal circuitry eliminates the need for this diode when the adjustment pin is bypassed with a capacitor to improve ripple rejection.
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 regulation will be limited by the resistance of the wire connecting 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 immediately 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 between the regulator and the load would be: R2 + R1 Rp • R = Parasitic Line Resistance R1 p
Connected as shown, Rp is not multiplied by the divider ratio. Rp is about 0.004Ω per 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.
D1 1N4002
VIN
VIN
LT1038 VOUT ADJ
VOUT VREF
VIN
LT1038 VIN VOUT
R1
ADJ
IADJ 50µA R2 ) + IADJ R2 R1 1038 F01
+ R1
*
VOUT COUT 100µF
VIN
LT1038 VOUT
CONNECT R1 TO CASE
ADJ
RL
R1 R2
R2 VOUT = VREF (1 +
VIN
Rp PARASITIC LINE RESISTANCE
CADJ 10µF
+
R2
*NOT NEEDED
1038 F02
CONNECT R2 TO LOAD 1038 F03
Figure 1. Basic Adjustable Regulator
Figure 2
Figure 3. Connections for Best Load Regulation
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LT1038 U
TYPICAL APPLICATIO S Paralleling Regulators
VIN
VIN
LT1038 VOUT
2 FEET #18 WIRE*
ADJ
VOUT = 1.25 (1 + 0.015Ω
LT1038 VIN
IOUT = 0A TO 20A
R2 ) R1
VOUT * THE #18 WIRE ACTS AS BALLAST RESISTANCE R1 INSURING CURRENT SHARING 120Ω BETWEEN BOTH DEVICES
ADJ
R2 1038 TA03
10A Variable Regulator* T1 TRIAD F-269U
L 1MHz
C30B
VIN 1N4003
20Ω 3
110V AC 20Ω
+
T2
1
LT1038 VOUT ADJ
C1 50,000µF
750Ω*
1.5k
+
0V TO 35V 0A TO 10A 100µF
4 2
LT1004-1.2
C30B LT1004-2.5 1N4003
1N4003
1µF
560Ω
16k*
15V
82k
LT1004-1.2
15k
8 2
3 10k
200k
–15V
+
4 LT1011
–
–15V 4
–
–15V
NC 100pF 2N3904
3
LT1011 1
+
10k
2
6
1
+
8 6
15V
3
LM301A 7
15k GENERAL PURPOSE REGULATOR WITH SCR PREREGULATOR TO LOWER POWER DISSIPATION. ABOUT 4V DIFFERENTIAL IS MAINTAINED ACROSS THE LT1038 INDEPENDENT OF OUTPUT VOLTAGE AND LOAD CURRENT.
2.7k
0.1µF 15V 8
7
16k*
11k*
7
1
1N4148
*1% FILM RESISTOR L-DALE TO-5 TYPE T2-STANCOR 11Z-2003
20k OUTPUT ADJUST
15V
– 4 1µF –15V
2 11k* 1038 TA04
LT1038 U
TYPICAL APPLICATIO S Improving Ripple Rejection VIN
VIN
LT1038 VOUT
5V
+
VIN
VIN
R1 121Ω 1%
ADJ
1µF
LT1038 VOUT
VOUT††
VIN
R1 121Ω
ADJ
LT1038 VOUT
VIN
5V 121Ω 1%
ADJ
+ 1µF
+ R2 365Ω 1%
5V Regulator with Shutdown
1.2V to 25V Adjustable Regulator
+
C1* 1µF
C1* 10µF
+
R2 5k
C2† 1µF
1k 2N3904
TTL
365Ω 1%
1k *C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE SMALL COMPARED TO R2.
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS † OPTIONAL—IMPROVES TRANSIENT RESPONSE †† VOUT = 1.25V (1 + R2/R1) 1038 TA06
1038 TA05
Remote Sensing
VIN
Temperature Compensated Lead Acid Battery Charger 10A
Rp (MAX DROP 300mV)
LT1038 VOUT VIN ADJ
1038 TA07
VIN
VIN
5V OUTPUT
LT1038 VOUT ADJ
121Ω 1%
VIN 7 6
–
LM301A
+
25Ω
1
121Ω
2
50Ω
10k*
THERMALLY COUPLED
+
25k
3 1k
RL
–
2N3906
12V
8 4
+
365Ω
5µF
2k*
CHARGE
100pF
50k*
2N3904 RETURN 25Ω
RETURN
*LOAD ON BATTERY ≈ 200µA WHEN NOT CHARGING
1038 TA08
1038 TA09
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SCHE ATIC DIAGRA
VIN
Q24 310Ω
310Ω
190Ω
50Ω
5.6k
20k 300Ω Q23
Q11
200Ω Q4
Q6
Q27
Q9
Q26
Q2
Q15 30k
Q21 C3 5pF
3k Q18
4k
Q1
130Ω
D1 6.3V
400Ω 160Ω
18k 16k Q25
D2 6.3V
Q17 C1 30pF
Q12 Q13 Q3 160k
Q20
Q10
Q8
Q28
Q22
Q16
12.4k
12k 120Ω
1.6k
Q14
Q5
6.7k
Q19
C2 30pF
2.4k
160Ω
Q7 3Ω 180Ω
4.1k
6k
10k
5.1k
12k 0.005Ω
ADJ
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
VOUT
1038 SD
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LT1038 U
TYPICAL APPLICATIO S Lamp Flasher VIN
15V
12V
LT1038 VOUT
Automatic Light Control
Protected High Current Lamp Driver
ADJ
1µF
+
ADJ 12k
OFF
VOUT
VIN
15V
ADJ
1.2k
TTL OR CMOS
10µF
+
1k
12V 10A
LT1038
LT1038 VIN VOUT
10µF
2N3904 12k
10µF
10k
+
1039 TA12
1039 TA11
12k
1039 TA10
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PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted. K Package 2-Lead TO-3 Metal Can (60mil Diameter Leads) (LTC DWG # 05-08-1312) 1.177 – 1.197 (29.90 – 30.40) 0.655 – 0.675 (16.64 – 17.15)
0.760 – 0.775 (19.30 – 19.69)
0.320 – 0.350 (8.13 – 8.89)
0.060 – 0.135 (1.524 – 3.429)
0.420 – 0.480 (10.67 – 12.19)
0.210 – 0.220 (5.33 – 5.59)
0.167 – 0.177 (4.24 – 4.49) R
0.425 – 0.435 (10.80 – 11.05) 0.058 – 0.062 (1.47 – 1.57)
0.151 – 0.161 (3.86 – 4.09) DIA, 2 PLACES
0.067 – 0.077 (1.70 – 1.96)
0.490 – 0.510 (12.45 – 12.95) R
K2(TO-3) 1098
OBSOLETE PACKAGE
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DESCRIPTION
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Linear Technology Corporation
1038fa LT/TP 0701 1.5K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2000
