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dc1948af
DEMO MANUAL DC1948A
Description
LT3090
–36V, 600mA Negative Linear Regulator
with Programmable Current Limit
Demonstration circuit 1948A is a 600mA low dropout
negative linear regulator featuring the LT
®
3090. This device
is designed for applications requiring negative output volt-
age, high current with no heat sink, output adjustability to
zero and low dropout voltage.
The LT3090 features fast transient response, high PSRR
and low output noise. The LT3090 supplies 600mA at a
typical dropout voltage of 300mV. Operating quiescent cur-
rent is nominally 1mA and drops to << 1μA in shutdown.
A single resistor adjusts the LT3090’s precision program-
mable current limit. The LT3090’s positive or negative
current monitor either sources a current (0.5mA/A) or
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
sinks a current (1mA/A) proportional to output current.
Built-in protection includes reverse output protection,
internal current limit with foldback and thermal shutdown
with hysteresis.
The LT3090 is offered in a 10 pin DFN package and a
16-lead MSOP package.
The LT3090 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 1948A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1948A
Specifications are at TA = 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range VOUT = 1.2V, IOUT1 = 1mA –36 –1.5 V
VOUT Output Voltage Shunt at 1, 2 for JP1 –1.286 –1.25 –1.213 V
Shunt at 3, 4 for JP1 –2.575 –2.5 –2.425 V
Shunt at 5, 6 for JP1 –5.15 –5 –4.85 V
Shunt at 7, 8 for JP1 –12.36 –12 –11.64 V
Shunt at 9, 10 for JP1 –15.45 –15 –14.55 V
Shunt at 11, 12 for JP1 and R10 Stuffed as 357kΩ –18.54 –18 –17.46 V
IOUT Output Current R1 = 10k, (Note 1) 600 mA
Note 1. This is for the typical condition when VIN – VOUT < 5V. Current limit varies with different values of VIN – VOUT. Refer to the LT3090 data sheet
for details.
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dc1948af
DEMO MANUAL DC1948A
Quick start proceDure
Demonstration circuit 1948A is easy to set up to evalu-
ate the performance of the LT3090. 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 JP2 to set the desired output voltage.
2. Put JP4 on ON position.
3. With power off, connect the input power supply to VIN
and GND.
4. Turn on the power at the VIN.
NOTE. Make sure that the VIN voltage does not exceed
–36V.
5. 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.
6. 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 2. Measuring Input or Output Ripple
Figure 1. DC1948A Proper Equipment Setup
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DEMO MANUAL DC1948A
positive or negative current monitor configuration
cable Drop compensation configuration
Figure 5. Temperature Rise at 2.1W Dissipation
There are both positive and negative current monitors on
the LT3090. The configurations for these two monitors are
different. When the positive current monitor is in use, JP1
needs to be configured on IMP position and JP3 needs to
be configured on +3V position. Meantime a +3V external
power supply needs to be connected to +3V turret. Figure 3
shows this configuration.
When the negative current monitor is in use, JP1 needs
to be configured on VIN position and JP3 needs to be
configured on IMN position. There is no external power
supply needed. Figure 4 shows this configuration.
thermal image
Figure 3. Positive Current Monitor Configuration
Figure 4. Negative Current Monitor Configuration
Demo Circuit 1948A can be configured to evaluate the
cable drop compensation on the LT3090. Note that cable
drop compensation is only using negative current monitor
configuration. JP1, JP3 and R12 shall be configured. JP1
needs to be configured on VIN position. JP3 needs to be
configured on CDC position. R12 needs be replaced by a
calculated value which has the following relationship with
the total output cable impedance (RCBL) below. R12 and
RCBL are both in kΩ:
R12 = RCBL • 1k
An example thermal image shows the temperature distri-
bution on board. The test is complete in still air at room
temperature with 2.1W power dissipation in the LT3090.
This gives the IC case-to-ambient thermal resistance of
about θJA = 24°C/W on the demo board.
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DEMO MANUAL DC1948A
parts list
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C1, CIN2 CAP, X7R 4.7µF 50V 10% 1206 TDK C3216X7R1H475KT
2 1 C2 CAP, X7R 0.1µF 16V 10% 0603 AVX 0603YC104KAT2A
3 1 C4 CAP, X7R 1µF 10V 10% 0603 TAIYO YUDEN LMK107BJ105KA
4 1 R1 RES, CHIP 10k 0.1W 1% 0805 VISHAY CRCW080510K0FKTA
5 1 R2 RES, CHIP 49.9k 0.1W 1% 0805 VISHAY CRCW080549K9FKTA
6 1 R4 RES, CHIP 2k 0.06W 1% 0603 VISHAY CRCW06032K00FKEA
7 1 R5 RES, CHIP 24.9k 0.06W 1% 0603 VISHAY CRCW060324K9FKEA
8 1 R6 RES, CHIP 49.9k 0.06W 1% 0603 VISHAY CRCW060349K9FKEA
9 1 R7 RES, CHIP 100k 0.06W 1% 0603 VISHAY CRCW0603100KFKEA
10 1 R8 RES, CHIP 243k 0.06W 1% 0603 VISHAY CRCW0603243KFKEA
11 1 R9 RES, CHIP 301k 0.06W 1% 0603 VISHAY CRCW0603301KFKEA
12 1 R11 RES, CHIP 1k 0.06W 1% 0603 VISHAY CRCW06031K00FKEA
13 1 R12, R14 RES, CHIP 0Ω 0.25W 5A 0603 VISHAY CRCW06030000Z0EA
14 1 U1 IC, NEGATIVE LINEAR REG DFN(10) (DD) 3mm × 3mm LINEAR TECHNOLOGY CORPORATION LT3090EDD
Additional Demo Board Circuit Components
1 1 CIN1 CAP, ALUM 10µF 50V 10% SUNCON 50CE10BSS
2 0 C3 (OPT) CAP, 1206
3 0 R10, R13, R15 (OPT) RES, 0603
Hardware: For Demo Board Only
1 8 E1, E2, E3, E4, E6,
E7, E8, E9
TURRET, TESTPOINT MILL MAX 2501-2-00-80-00-00-07-0
21 JP1 HEADERS, DBL ROW 2 × 2 2mm CTRS SAMTEC TMM-102-02-L-D
31 JP2 HEADERS, DBL ROW 2 × 6 2mm CTRS SAMTEC TMM-106-02-L-D
4 1 JP3 HEADERS, DBL ROW 2 × 3 2mm CTRS SAMTEC TMM-103-02-L-D
5 1 JP4 HEADERS, 2mm CTRS SAMTEC ASP-157349-01
6 4 XJP1, XJP2, XJP3,
XJP4
SHUNT, 2mm CTRS SAMTEC 2SN-BK-G
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DEMO MANUAL DC1948A
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.
schematic Diagram
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
REVISION HISTORY
DESCRIPTION DATE
APPROVED
ECO REV
EDWIN LIPRODUCTION
2
Aug 20, 2013
REVISION HISTORY
DESCRIPTION DATE
APPROVED
ECO REV
EDWIN LIPRODUCTION
2
Aug 20, 2013
REVISION HISTORY
DESCRIPTION DATE
APPROVED
ECO REV
EDWIN LIPRODUCTION
2
Aug 20, 2013
SIZE
MODIFY DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
11
EDWIN LI
SIZE
MODIFY DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
11
EDWIN LI
SIZE
MODIFY DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
11
EDWIN LI
GND
GND
+3V
+3V
GND
GND
IMONP
IMONP
VOUT
-600mA
Max
VOUT
-600mA
Max
IMONN
IMONN
SHDN
SHDN
+
+
*
*
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dc1948af
DEMO MANUAL DC1948A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2013
LT 0913 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LT C for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LT C from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LT C assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LT C currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LT C applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
