Linear Technology DC1887A Quick setup guide

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)

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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dc1887af

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

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

OFF

RSENS

PFI

VIN

VOUT

PFI

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: (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

Tuesday, November 12, 2013

BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER

N/A

LTC3128EUFD

DEMO CIRCUIT 1887A

SIZE

DATE:

IC NO. REV.

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

Tuesday, November 12, 2013

BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER

N/A

LTC3128EUFD

DEMO CIRCUIT 1887A

SIZE

DATE:

IC NO. REV.

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

Tuesday, November 12, 2013

BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER

N/A

LTC3128EUFD

DEMO CIRCUIT 1887A

JP3

MODE

JP3

MODE

1 2

3 4

5 6

E4E4

BAL

330mF

5.5V

BAL

330mF

5.5V

V+

C11

1uF

C11

1uF

E3E3

E2E2

E8E8

E10E10

10uF

E6E6

LTC3128EUFD

GND

SW1 1

SW2 17

GND

VOUTP 16

SW2 18

SW1 19

RSENP

RSENS

VIN

7VOUTP 15

VOUTS 14

MID 13

PGOOD 12

FB 11

MAXV 10

PFI

PFO 8

RUN

PROG

R2 0R2 0

E9E9

10uF

10V

10uF

10V

JP4

PULL UP SOURCE

JP4

PULL UP SOURCE

1 2

3 4

5 6

12.1k

E7E7

1Meg

301K

1.87Meg

3.3uH

10F

1uF

E1E1

OPT

C12

10F

C12

10F

10uF

10V

10uF

10V

JP1JP1

120pF

1Meg

E5E5

C10

10uF

C10

10uF

127k

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dc1887af

DEMO MANUAL DC1887A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ●FAX: (408) 434-0507 ●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

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