DEMO MANUAL DC1729A
LT3086
40V, 2.1A Low Dropout Adjustable
Linear Regulator with Monitoring
and Cable Drop Compensation
DESCRIPTION
Demonstration circuit 1729A is a 2.1A low dropout adjust-
able linear regulator featuring the
LT
®
3086.
The device is
designed with multiple features and operates over a wide
1.4V to 40V input supply range. The LT3086 requires only
one resistor to set the output voltage from 0.4V to 32V
and it is stable with ceramic output capacitors requiring
a minimum of 10μF.
The key features of the LT3086 include programmable
cable drop compensation, master/slave configuration for
paralleling of multiple devices for higher load current and
heat spreading, output current and temperature monitor-
ing, and programmable power good flag.
The LT3086 is offered in the packages of 16-lead DFN,
16-lead TSSOP, 7-lead DD-PAK, and a 7-lead TO-220.
The LT3086 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 demo circuit 1729A.
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
1.55
0.97
1.164
1.455
3.201
4.85
11.64
2.1
1
1.2
1.5
3.3
5
12
TYP
MAX
40
1.03
1.236
1.545
3.399
5.15
12.36
UNITS
V
V
V
V
V
V
V
A
CONDITIONS
V
OUT
= 1V, 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 and R10 Stuffed as 232k
I
OUT
Maximum Output Current
(Note 1)
Note 1:
The maximum output current 2.1A is when the internal current
limit is active and when V
IN
-V
OUT
is smaller than 9V. For the maximum
output current under other conditions, please refer to the data sheet.
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DEMO MANUAL DC1729A
QUICK START PROCEDURE
Demonstration circuit 1729A is easy to set up to evalu-
ate the performance of the LT3086. 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 ter-
minals 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 VIN
and GND.
3. Turn on the power at the VIN.
Note:
Make sure that the VIN voltage does not exceed 40V.
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
parameters.
Note:
Make sure that the power dissipation is limited
below the thermal limit.
Figure 1. DC1729A Proper Equipment Setup
V
IN
OR V
OUT
GND
Figure 2. Measuring Input or Output Ripple
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DEMO MANUAL DC1729A
THERMAL IMAGE
An example thermal image shows the temperature distri-
bution on the board. The test is done in still air at room
temperature with 2.2W power dissipation in the LT3086.
This gives the IC case-to-ambient thermal resistance
θ
JA
= 23°C/W on the demo board.
Figure 3. Temperature Rise at 2.2W Dissipation
CABLE DROP COMPENSATION
The power good setting jumper JP2 on the DC1729A is
used for setting the power good threshold for the cor-
responding output voltages. JP2 needs to be configured
at the same position as JP1 for any specific output volt-
ages. For example, when JP1 is configured on 7 and 8 for
3.3V
OUT
, JP2 also needs to be configured on 7 and 8 for
the correct power good setting for 3.3V
OUT
.
POWER GOOD SETTING
The cable drop compensation on the DC1729A can be
turned on by placing R4 (R
CDC
) with a value which is gov-
erned by the following equation provided in the data sheet:
R
CDC
=
R
MON
•R
SET
3000 •R
WIRE
Please note that when cable drop compensation is activated,
it also changes the power good threshold. R23 needs to
be the same value as R4 in order to keep the same output
voltage power good threshold at the load.
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DEMO MANUAL DC1729A
PARTS LIST
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1
2
3
4
1
2
3
4
QTY
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
0
0
9
2
1
2
REFERENCE
C1
C2
C3
R1, R12
R3
R5
R6
R7
R8
R9
R14
R15
R16
R17
R18
R20
U1
C4
C5
R2, R4, R10, R11, R13, R19, R21, R23
R22
E1, E2, E3, E4, E5, E6, E7, E8, E9
JP1, JP2
JP3
XJP1, XJP2
PART DESCRIPTION
CAP., X7R, 10µF 50V, 10%, 1210
CAP., X5R, 22µF 16V, 10%, 1206
CAP., X7R, 10nF 25V, 10%, 0603
RES., CHIP, 100k, 1/16W, 1% 0603
RES., CHIP, 357Ω, 1/16W, 1% 0603
RES., CHIP, 12.1k, 1/16W, 1% 0603
RES., CHIP, 16.2k, 1/16W, 1% 0603
RES., CHIP, 22.1k, 1/16W, 1% 0603
RES., CHIP, 57.6k, 1/16W, 1% 0603
RES., CHIP, 90.9k, 1/16W, 1% 0603
RES., CHIP, 82.5k, 1/16W, 1% 0603
RES., CHIP, 51.1k, 1/16W, 1% 0603
RES., CHIP, 19.1k, 1/16W, 1% 0603
RES., CHIP, 13.7k, 1/16W, 1% 0603
RES., CHIP, 10k, 1/16W, 1% 0603
RES., CHIP, 1.1k, 1/16W, 1% 0603
I.C., LT3086EFE, TSSOP16EFE-BB
CAP., OPT 0603
CAP., SMT, 10µF 50V, 50CE10BSS
RES., CHIP, OPT 0603
RES., CHIP, OPT 0805
TP, TURRET, 0.094"
JMP, 2X6, 0.079"
JMP, 1X2, 0.079"
SHUNT, 0.079" CENTER
SANYO, 50CE10BSS
OPT
OPT
MILL-MAX, 2501-2-00-80-00-00-07-0
SULLINS, NRPN062PAEN-RC
SULLINS, NRPN021PAEN-RC
SAMTEC, 2SN-BK-G
MANUFACTURER/PART NUMBER
MURATA, GRM32ER71H106KA12L
AVX, 1206YD226KAT2A
AVX, 06033C103KAT2A
VISHAY, CRCW0603100KFKEA
VISHAY, CRCW0603357RFKEA
VISHAY, CRCW060312K1FKEA
VISHAY, CRCW060316K2FKEA
VISHAY, CRCW060322K1FKEA
VISHAY, CRCW060357K6FKEA
VISHAY, CRCW060390K9FKEA
VISHAY, CRCW060382K5FKEA
VISHAY, CRCW060351K1FKEA
VISHAY, CRCW060319K1FKEA
VISHAY, CRCW060313K7FKEA
NIC, NRC06F1002TRF
VISHAY, CRCW06031K10FKEA
LINEAR TECH., LT3086EFE
Required Circuit Components
Additional Demo Board Circuit Components
Hardware-For Demo Board Only
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4
5
4
3
2
D
1
D
SCHEMATIC DIAGRAM
C
C
+
B
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.
TECHNOLOGY
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3
4
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2
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DEMO MANUAL DC1729A
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