Linear Technology DC1887A Quick setup guide

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dc1887af
DEMO MANUAL DC1887A
Description
LTC3128
High Efficiency 2-Cell Supercapacitor
Charger and Balancer Converter
Demonstration circuit 1887 is a DC/DC supercapacitor
buck-boost charger and balancer converter featuring the
LT C
®
3128.TheDC1887Aoperatesover1.72Vto5.5Vinput
and charges the output up to 5.5V. Also, the LTC3128 has
2% precision input current limit, which allows the circuitto
operateeffectivelywithcurrentlimitedinputpowersources
like the USB. The 1.2MHz switching frequency operation
results in a small and efficient circuit. The converter pro-
vides high output voltage accuracy (typically ±2%) over
a1.72V to 5.5V input. The demonstration circuit can be
easily modified to generate different output voltages.
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
Specifications are at TA= 25°C
PARAMETER CONDITIONS VALUE
Minimum Input Voltage IOUT = 0A to 1A 1.72V
Maximum Input Voltage IOUT = 0A to 1A 5.5V
VOUT VIN = 1.72V to 5.5V, IOUT = 0A 4.2V ±2%
Input Current Limit (Programmable to 3A) VIN = 1.72V to 5.5V 0.9A
Nominal Switching Frequency 1.2MHz
The DC1887 has a small circuit footprint. It is a high per-
formance and cost effective solution for charging and
balancing supercapacitors. Please read the LTC3128 data
sheet along with this manual.
Design files for this circuit board are available at
http://www.linear.com/demo
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dc1887af
DEMO MANUAL DC1887A
Quick start proceDure
Demonstration circuit 1887 is easy to set up to evaluate
the performance of the LTC3128. For proper measure-
ment equipment setup refer to Figure 1 and follow the
procedure below:
NOTE: When measuring the input or output voltage
ripple, care must be taken to minimize the length of
oscilloscope probe ground lead. Measure the input
or output voltage ripple by connecting the probe tip
directly across the VIN or VOUT and GND terminals as
shown in Figure 2.
NOTE: Make sure that the input voltage VIN does not
exceed 5.5V.
4. Set the input voltage to 3.3V and check for the proper
output voltage of 4.2V. If there is no output, temporarily
disconnect the load to make sure that the load is not
set too high.
5. Once the proper output voltage is established, adjust the
load and observe the output voltage regulation, ripple
voltage, efficiency and other parameters.
6. Note that the output voltage VOUT will vary with load.
This is due to the current source nature of the LTC3128
power converter. As the output voltage increases the
output current will decrease in order to maintain the
input current below the preset limit.
The LTC3128 circuit maximizes the output current while
keeping the input current within the preset current limit.
Thiskeepsthesupercapacitorchargingtime to a minimum.
CHANGING THE OUTPUT VOLTAGE
To change the output voltage from the programmed 4.2V,
change the voltage divider resistors connected to the
LTC3128 FB pin (see the schematic on page 5).
Figure 2. Measuring Input or Output Ripple
Figure 1. Proper Measurement Equipment Setup
+ –
VOUT GND
COUT
1. With power off, connect the input power supply to VIN
and GND.
2. Keep the load set to 0A or disconnected.
3. Turn the input power source on and slowly increase the
input voltage. Be careful not to exceed 5.5V.
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dc1887af
DEMO MANUAL DC1887A
Quick start proceDure
Figure 3. The Output Current Decreases as the Supercap Voltage
Increases Due to Precise Input Current Limit.
Figure 4. The Supercap Supplies Most of the Pulsed Load Current.
The LTC3128 Makes a Small Contribution to Load Current as
Shown in Figure 3.
Figure 5. The DC1887 Ramps the Output Slowly at Start-Up
without Generating an Input Current Surge.
CONVERTER OUTPUT CURRENT
The DC1887 output current capability depends on the
input voltage and programmed input current limit. Typical
performance of the DC1887A is shown in Figure 3. As can
be seen from Figure 3, the output current decreases as
the output voltage is approaching the programmed output
voltage of 4.2V.
OUTPUT LOAD STEP RESPONSE
The load step response of DC1887A is dependent on the
supercap used. If higher load steps need to be handled
more output capacitance can be added in order to keep
the voltage transients at the desired level. The load step
transients are shown in Figure 4.
START-UP AND CURRENT LIMIT FUNCTION
The DC1887 features an input current limit circuit that
controls the inrush current and output voltage ramp at
start-up and during recharge cycles. The input current
limit of DC1887 is set to 900mA and it should be suitable
for operation from a USB port. The input current limit can
be seen in Figure 5. While charging the supercap, the cur-
rent is constant. Once the output voltage is close to the
set point the current limit is reduced in order to prevent
output voltage overshoot.
The input current limit can be programmed up to 3A by
changing the resistor R8 in the Schematic Diagram.
OUTPUT VOLTAGE BALANCING
TheLTC3128 can chargetwo output capacitors inseries that
are not identical. The internal capacitor voltage balancing
circuit can compensate for the difference in capacitance by
moving the charge from the capacitor at a higher voltage
(smallercap)toacapacitor withalower voltage(biggercap).
To see this effect, monitor VMID (VC3) and VOUT with a
scope as shown in Figure 5. The trace 1 in Figure 5 is
showing the top cap voltage (VC3 = VOUT – VMID).
VOUT (V)
1
IOUT (A)
1.2
0.8
0.6
1.0
0.4
0.2
042 3
dc1887 F03
4.53.51.5 2.5
2V INPUT
3.3V INPUT
5V INPUT
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dc1887af
DEMO MANUAL DC1887A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C2, C3 CAP, X5R, 10µF, 25V, 10%, 0805 AVX, 08053D106KAT2A
2 2 C1, C4 CAP, X5R, 10µF, 25V, 10%, 1206 MURATA, GRM31CR61E106KA12L
3 1 C5 CAP, NPO, 120pF, 25V, 10%, 0603 AVX, 06033A121JAT2A
4 3 C6, C7, C10 CAP, X5R, 1µF, 25V, 10%, 0603 AVX, 06033D105KAT2A
5 1 C8 SUPERCAP, 5.5V, 330mF MURATA, DMF3Z5R5H334M3DTA0
6 2 C9, C12 SUPERCAP, 10.0F, 2.7V, 10mm × 30mm ILLINOIS CAP, 106DCN2R7Q
7 1 L1 IND, POWER INDUCTOR, 3.3µH COILCRAFT: XAL6030-332MEB
8 1 R1 RES, CHIP, 1.87M, 1%, 0603 VISHAY, CRCW06031M87FKEA
9 1 R2 RES, CHIP, 0, 0603 VISHAY, CRCW06030000Z0EA
10 1 R3 RES, CHIP, 301k, 1%, 0603 VISHAY, CRCW0603301KFKEA
11 2 R5, R6 RES, CHIP, 1M, 1%, 0603 VISHAY, CRCW06031M00FKEA
12 1 R7 RES, CHIP, 127k, 1%, 0603 VISHAY, CRCW0603127KFKEA
13 1 R8 RES, CHIP, 12.1k, 0.1%, 0603 VISHAY, TNPW060312K1BEEA
14 1 U1 LTC3128EUFD, QFN 4mm × 5mm LINEAR TECHNOLOGY, LTC3128EUFD
Additional Demo Board Circuit Components
1 0 C11 (OPT) CAP, 0603
2 0 R4 OPT RES, CHIP OPTIONAL
Hardware: For Demo Board Only
1 10 E1 TO E10 TESTPOINT, TURRET, 0.095" MILL-MAX, 2501-2-00-80-00-00-07-0
2 1 JP1 0.079 SINGLE ROW HEADER, 3 PIN SAMTEC, TMM-103-02-L-S
3 2 JP3, JP4 0.079 DOUBLE ROW HEADER, 2X3 PIN SAMTEC, TMM-103-02-L-D
4 3 JP1, JP3, JP4 SHUNT SAMTEC, 2SN-BK-G
5 4 STAND OFF STAND OFF KEYSTONE, 8833
6 1 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 1887A
7 1 STENCIL STENCIL DC1887A
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DEMO MANUAL DC1887A
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
VOUT
1.72V - 5.5V
4.2V / 1A
VIN GND
Goran P.
GND PGOOD
PFO
MID
0.1%
RUN
ON OFF
RSENS
PFI VIN VOUT
PFI
VPWR
VPWR
VIN VOUT
OPT
VOUT
VIN
VOUT
VIN
VOUT
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
Goran P.PRODUCTION
210-16-13
__
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
Goran P.PRODUCTION
210-16-13
__
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
Goran P.PRODUCTION
210-16-13
__
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] 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
2
Tuesday, November 12, 2013
11
BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER
HZ
N/A
LTC3128EUFD
DEMO CIRCUIT 1887A
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] 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
2
Tuesday, November 12, 2013
11
BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER
HZ
N/A
LTC3128EUFD
DEMO CIRCUIT 1887A
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] 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
2
Tuesday, November 12, 2013
11
BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER
HZ
N/A
LTC3128EUFD
DEMO CIRCUIT 1887A
JP3
MODE
JP3
MODE
1 2 3 4 5 6
E4E4
BAL
C8
330mF
5.5V
BAL
C8
330mF
5.5V
2
V+
1
3
C11 1uF C11 1uF
E3E3 E2E2
E8E8
E10E10
C2
10uF
C2
10uF
C3
10uF
C3
10uF
E6E6
U1
LTC3128EUFD
U1
LTC3128EUFD
GND
20
SW1 1
SW2 17
GND
6
GND
21
VOUTP 16
SW2 18
SW1 19
RSENP
2
RSENS
3
VIN
7VOUTP 15
VOUTS 14
MID 13
PGOOD 12
FB 11
MAXV 10
PFI
9
PFO 8
RUN
4
PROG
5
R2 0R2 0
E9E9
C4
10uF
10V C4
10uF
10V
JP4
PULL UP SOURCE
JP4
PULL UP SOURCE
1 2 3 4 5 6
R8
12.1k
R8
12.1k
E7E7
R5 1Meg R5 1Meg
R3
301K
R3
301K
R1
1.87Meg
R1
1.87Meg
L1
3.3uH
L1
3.3uH
+
C9
10F
+
C9
10F
C7
1uF
C7
1uF
C6
1uF
C6
1uF
E1E1
R4
OPT
R4
OPT
+
C12
10F
+
C12
10F
C1
10uF 10V
C1
10uF 10V
JP1JP1
1
2
3
C5
120pF
C5
120pF
R6 1Meg R6 1Meg
E5E5
+
C10
10uF
+
C10
10uF
R7
127k
R7
127k
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dc1887af
DEMO MANUAL DC1887A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2014
LT 0214 • 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
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