DEMO MANUAL DC1870A
LT3081
1.5A Single Resistor Rugged
Linear Regulator with Monitors
Description
DC1870A is a 1.5A low dropout linear regulator featuring
LT
®
3081.
The device is designed for rugged industrial ap-
plications and can be paralleled for higher output current
or heat spreading. Besides paralleling, the LT3081 also
presents other features including adjustability to zero V
OUT
,
reverse protection for input and output-to-input voltages,
temperature monitor, output current monitor, etc.
A key feature of the LT3081 is the extended safe operating
area (SOA). With the precision zero TC 50μA reference
current source, a single resistor programs the output
voltage to any level between zero and 34.5V.
Internal protection circuitry includes reverse-battery and
reverse-current protection, current limiting and thermal
limiting.
The LT3081 is offered in the packages of 16-lead TSSOP,
7-lead TO-220, 7-lead DD-Pak, and a 12-lead 4mm ×
4mm DFN.
The LT3081 data sheet gives a complete description of
the device, operation and application information. The data
sheet should be read in conjunction with this quick start
guide for working on or modifying the DC1870A.
Design files for this circuit board are available at
http://www.linear.com/demo
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.
performance summary
SYMBOL
V
IN
V
OUT
PARAMETER
Input Supply Range
Output Voltage
Specifications are at T
A
= 25°C
MIN
2.8
1.164
1.455
1.746
2.425
3.201
4.85
11.64
1.2
1.5
1.8
2.5
3.3
5
12
TYP
MAX
36
1.248
1.56
1.872
2.6
3.432
5.2
12.48
UNITS
V
V
V
V
V
V
V
V
CONDITIONS
V
OUT
= 1.2V, I
OUT1
= 1mA
Shunt at 1, 2 for JP1
Shunt at 3, 4 for JP1
Shunt at 5, 6 for JP1
Shunt at 7, 8 for JP1
Shunt at 9, 10 for JP1
Shunt at 11, 12 for JP1
Shunt at 13, 14 for JP1 and R7 Stuffed as 243kΩ
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DEMO MANUAL DC1870A
Quick start proceDure
DC1870A is easy to set up to evaluate the performance
of the LT3081. Refer to Figure 1 for proper measurement
equipment setup and follow the procedure below:
NOTE: When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the terminals
of the input or output capacitors. See Figure 2 for proper
scope probe technique.
1. Use JP1 to set the desired output voltage.
2. With power off, connect the input power supply to V
IN
and GND.
3. Turn on the power at the V
IN
.
NOTE: Make sure that the V
IN
voltage does not exceed
36V.
4. Check for the proper output voltages:
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
5. Once the proper output voltages are established, adjust
the loads within the operating range and observe the
output voltage regulation, efficiency and other param-
eters.
NOTE: Make sure that the power dissipation is limited
below the thermal limit.
Figure 1. DC1870A Proper Equipment Setup
V
IN
OR V
OUT
GND
DC1870A F02
Figure 2. Measuring Input or Output Ripple
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DEMO MANUAL DC1870A
thermal image
An example thermal image shows the temperature distribu-
tion on the PC board. The test is done in still air at room
temperature with 2.3W power dissipation in the LT3081
IC. This gives an IC junction-to-ambient thermal resistance
of
θ
JA
= 16°C/W on the demo board.
Figure 3. Temperature Rise at 2.3W Dissipation
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DEMO MANUAL DC1870A
parts list
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
1
2
3
QTY
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
6
1
1
REFERENCE
CIN2
C1
C4
R1
R2
R3
R4
R5
R6
R9
R13
R14
U1
CIN1
C2, C3 (Opt)
R7, R8, R12 (Opt)
E1, E2, E3, E4, E5, E6
JP1
XJP1
PART DESCRIPTION
Cap., X5R 10µF 50V 20% 1210
Cap., X5R 22µF 16V 20% 1206
Cap., X7R 0.01µF 25V 10% 0603
Res., Chip 24.3k 0.1W 1% 0603
Res., Chip 30.1k 0.1W 1% 0603
Res., Chip 36.5k 0.1W 1% 0603
Res., Chip 49.9k 0.1W 1% 0603
Res., Chip 66.5k 0.1W 1% 0603
Res., Chip 100k 0.1W 1% 0603
Res., Chip 499Ω 0.125W 1% 0805
Res., Chip 499Ω 0.1W 1% 0603
Res., Chip 1k 0.1W 5% 0603
I.C., Linear Regulator TSSOP16-FE/TSSOP16-BB
Cap., Aluminum 10µF 50V 10% OSCON-CE-5
Cap., 0603
Res., 0603
Turret, Testpoint
Headers, 2 × 7 (2mm Ctrs.)
Shunt, 2mm Ctrs.
Mill Max 2501-2-00-80-00-00-07-0
Samtec TMM-107-02-L-D
Samtec 2SN-BK-G
MANUFACTURER/PART NUMBER
Taiyo Yuden UMK325BJ106MM-T
Taiyo Yuden EMK316BJ226ML-T
AVX 06033C103KAT2A
Vishay CRCW060324K3FKEA
Vishay CRCW060330K1FKEA
Vishay CRCW060336K5FKEA
Vishay CRCW060349K9FKEA
Vishay CRCW060366K5FKEA
Vishay CRCW0603100KFKEA
Vishay CRCW0805499RFKEA
Vishay CRCW0603499RFKEA
Vishay CRCW06031K00JNEA
Linear Technology Corporation LT3081EFE#PBF
Sun Electronics 50CE10BSS
Required Circuit Components
Additional Demo Board Circuit Components
Hardware: For Demo Board Only
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5
4
3
2
1
ECO REV
DATE
May 20, 2011
May 06, 2013
REVISION HISTORY
APPROVED
DESCRIPTION
1st PROTOTYPE
PRODUCTION
EDWIN LI
EDWIN LI
-
1
2
D
D
VOUT
ADJ.,
+
schematic Diagram
GND
GND
IMON
C
C
B
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
B
CUSTOMER NOTICE
APPROVALS
TECHNOLOGY
TITLE: SCHEMATIC
NOTES: UNLESS OTHERWISE SPECIFIED.
www.linear.com
A
A
1. ALL CAPACITORS AND RESISTORS ARE 0603.
2. JUMPERS SHOWN IN DEFAULT POSITIONS
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES.
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APP ENG.
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
C:\PADS PROJECTS\1870A(LT3081EFE)\SCH\1870A_03_REV2.DSN
SIZE
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
IC NO.
REV.
2
SCALE = NONE
3
DATE:
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DEMO MANUAL DC1870A
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