1
dc2041af
DEMO MANUAL DC2041A
Description
LTC3255EMSE
Wide VIN Range Fault Protected
50mA Step-Down Charge Pump
Demonstration circuit 2041A is a switched-capacitor
step-down power supply featuring the LT C
®
3255. The
LTC3255 has the ability to step down voltage 2:1 to ef-
ficiently regulate output voltages less than half the VIN
voltage reducing the input current needed. As VIN reduces
below twice VOUT, the LTC3255 will automatically switch
to 1:1 mode.
The LTC3255 also has an integrated shunt regulator al-
lowing it to provide a regulated output from a 4mA to
20mA current loop.
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
The LTC3255 is a robust device that can survive reverse-
polarity input supplies with current limit and overtem-
perature protection.
Refer to the LTC3255 data sheet for more details on the
electrical and timing specifications.
Design files for this circuit board are available at
http://www.linear.com/demo
Specifications are at TA = 25°C
7.4mA DC Supply from 4mA to 20mA Current Loop Available Output Current
vs Input Current
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Supply Range 4 48 V
VOUT 2.4 12.5 V
IOUT Shunt Jumper = OFF (SHUNT = GND)
Shunt Jumper = ON (SHUNT = BIAS) IIN = 4mA
50
7.4
7.8
mA
mA
VIN
EN 220k
10µF
DC2041A F01
0.1µF
4mA TO 20mA INPUT
>10V COMPLIANCE 1µF
1µF
OUTPUT
3.3V
7.4mA
LTC3255
GND
C+C–
SHUNT
BIAS
PGOOD
+
–
PGOOD
FB
VOUT
2.15M
1.21M
4 8 12 14 20
6 10 16 18
INPUT CURRENT (mA)
AVAILABLE OUTPUT CURRENT (mA)
16
31
34
37
40
10
25
13
28
7
4
22
19
DC2041A F02
INCREASED
IOUT CAPABILITY
AVAILABLE
IOUT
INPUT
CURRENT
2
dc2041af
DEMO MANUAL DC2041A
Quick start proceDure
The DC2041 is easy to set up to evaluate the performance
of the LTC3255 with the shunt disabled. Refer to Figure 1
for proper measurement equipment setup with the shunt
disabled and follow the evaluation procedure below. To
evaluate the LTC3255 with the shunt enabled, go to the
SHUNT ENABLED section.
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 VIN or
VOUT and GND terminals. See Figure 2 for proper scope
probe technique.
1. Set the EN jumper, JP1, on the DC2041 board to the
ON position.
2. Set the SHUNT jumper, JP3, to the OFF position.
3. Set the VOUT jumper, JP2, to the desired output voltage.
NOTE. Do not set the VOUT jumper to the OPT setting un-
less the appropriate resistor is installed in R7. The VOUT
jumper OPT position is to allow an alternate VOUT setting.
This can be accomplished by adding a resistor to R7 to
set the output to a desired voltage. Refer to the LTC3255
data sheet to calculate the appropriate value for R7.
4. With power off, connect a 0V to 48V, 100mA power
supply to VIN and GND with a voltmeter as shown in
Figure 1.
5. Turn on the VIN input power supply and increase the
supply until the VOUT voltage is in regulation and the
PGOOD voltage is pulled to VOUT.
NOTE. Make sure that the input voltages do not exceed 60V.
6. With VIN at least 1V above VOUT, increase the load on
VOUT from 0mA to 50mA and observe the input current.
The output ripple may also be observed using an oscil-
loscope with the probe connected as shown in Figure 2.
7. With a 50mA load on VOUT, increase VIN until the cur-
rent on VIN drops to approximately ½ the VOUT current.
8. Refer to the LTC3255 data sheet for more details on
how the LTC3255 operates.
9. When done, turn off all loads and power supplies.
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dc2041af
DEMO MANUAL DC2041A
Quick start proceDure
+
–
+–
PS1
0V TO 48V
100mA Supply
+ –
+–
+
–L1
0mA TO
100mA Load
–+
DC2041 F01
Figure 1. Proper Measurement Equipment Setup with Shunt Disabled
Figure 2. Measuring Input or Output Ripple
GND
VIN
4
dc2041af
DEMO MANUAL DC2041A
sHunt enaBLeD
The DC2041 is easy to set up to evaluate the performance
of the LTC3255 with the shunt enabled. Refer to Figure 3
for proper measurement equipment setup of the LTC3255
with the shunt enabled and follow the evaluation procedure.
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 VIN or
VOUT and GND terminals. See Figure 2× for proper scope
probe technique.
1. Set the EN jumper, JP1, on the DC2041 board to the
ON position.
2. Set the SHUNT jumper, JP3, to the ON position.
3. Set the VOUT jumper, JP2, to the desired output voltage.
NOTE. Do not set the VOUT jumper to the OPT setting un-
less the appropriate resistor is installed in R7. The VOUT
jumper OPT position is to allow an alternate VOUT setting.
This can be accomplished by adding a resistor to R7 to
set the output to a desired voltage. Refer to the LTC3255
data sheet to calculate the appropriate value for R7.
4. With power off, connect a 0V to 48V, 100mA power
supply to a controlled current source, a 250Ω ¼ Watt
resistor, VIN and GND with a voltmeter and ammeter
as shown in Figure 3.
5. Turn on the VIN input power supply, PS1, and increase
the supply above twice the VOUT voltage setting plus
9V. (VPS1 > 2VOUT + 2V + VCS1 + VRS1 + Vammeter).
For example, if VOUT is set to 3.3V, set PS1 above
3.3V • 2 + 9V or 15.6V.
NOTE. Make sure that the input voltages do not exceed 60V.
6. Turn on and set the input current source to 4mA. Ob-
serve the voltage across the VIN and GND terminals
and across the VOUT and GND terminals. The output
ripple may also be observed using an oscilloscope
with the probe connected as shown in Figure 2.
7. Increase the load on VOUT to about 7.4mA and observe
the input current, input voltage and output voltage.
8. Increase the input current source from 4mA to 20mA.
Observe the voltage across the VIN and GND terminals
and across the VOUT and GND terminals. Adjust PS1
as per equation described in step 5 if needed.
9. Increase the load on VOUT to about 38mA and observe
the output voltage. Observe the input current and input
voltage as the load on VOUT is changed.
10. Refer to the LTC3255 data sheet for more details on
how the LTC3255 operates.
11. When done, turn off all loads and power supplies.
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dc2041af
DEMO MANUAL DC2041A
sHunt enaBLeD
+
–
+–
+–
CS1
4mA TO 20mA
CURRENT SOURCE
–+
PS1 SUPPLY
V > (2VOUT +24V)
+ VCS1 + VRS1
VMAX = 60V
–+
+
–
–
+
L1
0mA TO
40mA Load
–+
DC2041 F03
Figure 3. Proper Measurement Equipment Setup with Shunt Enabled
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dc2041af
DEMO MANUAL DC2041A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 CAP CER, 1µF, 25V, X7R 10% 0603 MURATA, GRM188R71E105KA12D
2 1 C2 CAP CER, 1µF, 100V, X7R 10% 0805 TDK, C2012X7S2A105K
3 1 C3 CAP CER, 10µF, 25V, 10% X7R 1206 MURATA, GRM31CR71E106KA12L
4 1 C5 CAP CER, 10pF, 50V, 5% NP0 0402 MURATA, GRM1555C1H100JA01D
5 1 C7 CAP CER, 0.1µF, 16V, 10%, X7R 0402 MURATA, GRM155R71C104KA88D
6 1 R3 RES 1.1M, 1/16W, 1%, 0402 SMD VISHAY, CRCW04021M10FKED
7 1 R4 RES 383kΩ, 1/16W, 1%, 0402 SMD VISHAY, CRCW0402383KFKED
8 1 R5 RES 215kΩ, 1/16W, 1%, 0402 SMD VISHAY, CRCW0402215KFKED
9 1 R6 RES 133kΩ, 1/16W, 1%, 0402 SMD VISHAY, CRCW0402133KFKED
10 1 R8 RES 220kΩ, 1/16W, 5%, 0402 SMD VISHAY, CRCW0402220KJNED
11 2 R12 RES 121kΩ, 1/16W, 1%, 0402 SMD VISHAY, CRCW0402121KFKED
12 1 U1 50mA STEP-DOWN CHARGE PUMP LINEAR TECH., LTC3255EMSE#PBF
Additional Demo Board Circuit Components
13 1 C4 CAP CER 2.2µF, 100V, 10%, X7R 1206 MURATA, GRM31CR72A225KA7
14 0 C6 CAP, 0603 SMD OPT
15 0 C8 CAP, 1206 SMD OPT
16 1 R1 RES 0.0Ω, 1/8W, 0805 SMD VISHAY, CRCW08050000Z0EA
17 2 R2, R10 RES 10kΩ, 1/16W, 5%, 0402 SMD VISHAY, CRCW040210K0JNED
18 0 R7 RES, 0402 SMD OPT
19 2 R9, R11 RES 10.0M, 1/16W, 5%, 0402 SMD VISHAY, CRCW040210M0JNED
20 0 R13, R14, R15 RES, 0805 SMD OPT
Hardware: For Demo Board Only
21 4 E1, E2, E3, E4 TP, TURRET, 0.094", PBF MILL-MAX, 2501-2-00-80-00-00-07-0
22 4 E5, E6, E7, E8 TURRET, 0.061 DIA MILL-MAX, 2308-2-00-80-00-00-07-0
23 2 JP1, JP3 HEADER, 3 PIN, 1 ROW .079CC SAMTEC, TMM-103-02-L-S
24 3 JP1-JP3 SHUNT, 2mm SAMTEC, 2SN-KB-G
25 1 JP2 HEADER, 2.0mm, 2 × 5 SAMTEC, TMM-105-02-L-D
26 4 MH1-MH4 STAND-OFF, NYLON 0.375" TALL EYSTONE, 8832 (SNAP ON)
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dc2041af
DEMO MANUAL DC2041A
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
ALL CAPACITORS ARE 0402, 10%
1. ALL RESISTORS ARE 0402, 1%, 1/16W
2. INSTALL SHUNTS AS SHOWN.
NOTE: UNLESS OTHERWISE SPECIFIED
OPTIONAL FILTER COMPONENTS
*
4.0V - 48V50mA
*
5V
3.3V
12V
OPT
2.5V
M. MERCHANTPRODUCTION FAB 31 - 5 - 62
REVISION HISTORY
ETADNOITPIRCSED APPROVEDECO REV
2
DEMO CIRCUIT 2041A
11
WIDE VIN RANGE FAULT PROTECTED
N/A LTC3255EMSE
NC
MARTY M.
06 - 05 - 13
50mA STEP - DOWN CHARGE PUMP
SIZE
DATE:
.VER.ON CI
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 McCarthy Blvd.
LTC Confidential-For Customer Use Only
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
VIN_P
VIN_P
VIN
VIN
E2
VOUT
R14
OPT
0805
R9
10.0M
5% R6
133k
E6
GND
E1
VIN
C8
OPT
100V
1206
C2
1uF
100V
0805
R3
1.1M
JP1
EN
ON
OFF
1
3
2
R4
383k
E3
GND
R2
10K
5%
R15
OPT
0805
R1
0
0805
JP3
SHUNT
ON
OFF
1
3
2
C1
1uF
25V
0603
C3
10uF
25V
1206
E8
GND
C5
10pF
50V
R13
OPT
0805
R8
220K
5%
R7
OPT
C6
OPT
100V
0603 R5
215k
E5
EN
R11
10.0M
5%
JP2
VOUT
C7
0.1uF
16V
E4
GND
R10
10K
5%
E7
PGOOD
C4
2.2uF
100V
1206
U1
LTC3255EMSE
6
3
45
2
9
1
11
8
10
7
EN
FB
SHUNT PGOOD
VOUT
C-C+
GNDGND
VIN
BIAS
R12
121k
8
dc2041af
DEMO MANUAL DC2041A
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
