DC1887A - Demo Manual

DEMO MANUAL DC1887A
LTC3128
High Efficiency 2-Cell Supercapacitor
Charger and Balancer Converter
Description
Demonstration circuit 1887 is a DC/DC supercapacitor
buck-boost charger and balancer converter featuring the
LTC®3128. The DC1887A operates over 1.72V to 5.5V input
and charges the output up to 5.5V. Also, the LTC3128 has
2% precision input current limit, which allows the circuit to
operate effectively with current limited input power sources
like the USB. The 1.2MHz switching frequency operation
results in a small and efficient circuit. The converter provides high output voltage accuracy (typically ±2%) over
a 1.72V to 5.5V input. The demonstration circuit can be
easily modified to generate different output voltages.
Performance Summary
The DC1887 has a small circuit footprint. It is a high performance 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
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.
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
dc1887af
1
DEMO MANUAL DC1887A
Quick Start Procedure
Demonstration circuit 1887 is easy to set up to evaluate
the performance of the LTC3128. For proper measurement 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.
+
VOUT
–
COUT
GND
Figure 2. Measuring Input or Output Ripple
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.
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.
This keeps the supercapacitor charging time 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 1. Proper Measurement Equipment Setup
dc1887af
2
DEMO MANUAL DC1887A
Quick Start Procedure
CONVERTER OUTPUT CURRENT
START-UP AND CURRENT LIMIT FUNCTION
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.
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 current is constant. Once the output voltage is close to the
set point the current limit is reduced in order to prevent
output voltage overshoot.
1.2
1.0
The input current limit can be programmed up to 3A by
changing the resistor R8 in the Schematic Diagram.
IOUT (A)
0.8
0.6
OUTPUT VOLTAGE BALANCING
0.4
2V INPUT
3.3V INPUT
5V INPUT
0.2
0
1
1.5
2
2.5
3
VOUT (V)
3.5
4
4.5
dc1887 F03
Figure 3. The Output Current Decreases as the Supercap Voltage
Increases Due to Precise Input Current Limit.
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.
The LTC3128 can charge two output capacitors in series 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
(smaller cap) to a capacitor with a lower voltage (bigger cap).
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).
Figure 5. The DC1887 Ramps the Output Slowly at Start-Up
without Generating an Input Current Surge.
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.
dc1887af
3
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
STAND OFF
5
4
STAND OFF
KEYSTONE, 8833
6
1
FAB, PRINTED CIRCUIT BOARD
DEMO CIRCUIT 1887A
7
1
STENCIL
STENCIL DC1887A
dc1887af
4
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
RSENS
GND
1.72V - 5.5V
VIN
5
E9
E4
VIN
E1
E8
C11
1uF
OPT
C10
10uF
+
6
OFF
ON
2
JP1
RUN
4
5
2
3
1
C5
120pF
C4
10uF
10V
C1
10uF
10V
VOUT
VIN
PFI
4
R8
12.1k
0.1%
C7
1uF
R4
OPT
C6
1uF
R2 0
U1
LTC3128EUFD
MAXV
PFO
PGOOD
MID
FB
VOUTS
VOUTP
VOUTP
CUSTOMER NOTICE
PROG
RSENS
RSENP
RUN
VIN
PFI
3.3uH
10
8
12
13
11
14
15
16
3
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
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.
5
3
2
4
7
9
1
SW1
L1
3
SW2
4
17
GND
18
SW2
PFI
JP3
MODE
1
3
19
SW1
GND
20
GND
6
VOUT
21
VOUT
VIN
4
6
5
2
3
1
JP4
PULL UP SOURCE
C3
10uF
C8
330mF
5.5V
C9
10F
E10
E7
E5
E3
E6
VPWR
PFO
PGOOD
GND
MID
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
R6
1Meg
R5
1Meg
C12
10F
VOUT
VPWR
VIN
+
+
DATE
10-16-13
VOUT
4.2V / 1A
Goran P.
E2
APPROVED
DESCRIPTION
1
PRODUCTION
REVISION HISTORY
DATE:
N/A
SIZE
2
LTC3128EUFD
DEMO CIRCUIT 1887A
Tuesday, November 12, 2013
IC NO.
1
SHEET 1
OF 1
2
REV.
TECHNOLOGY
HZ
TITLE:
SCHEMATIC
Goran P.
BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER
SCALE = NONE
APP ENG.
PCB DES.
APPROVALS
127k
R7
R3
301K
R1
1.87Meg
VOUT
2
REV
V+
C2
10uF
3 BAL
__
ECO
2
2
1
D
5
A
B
C
D
DEMO MANUAL DC1887A
Schematic Diagram
dc1887af
5
DEMO MANUAL DC1887A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) 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 LTC 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 LTC 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. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC 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 LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1887af
6
Linear Technology Corporation
LT 0214 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2014
Similar pages