Description Demonstration circuit 887 is a DC/DC supercapacitor buck-boost charger and balancer converter featuring the LTC 8. The DC887A operates over.7v to 5.5V input and charges the output up to 5.5V. Also, the LTC8 has % precision input current limit, which allows the circuit to operate effectively with current limited input power sources like the USB. The.MHz switching frequency operation results in a small and efficient circuit. The converter provides high output voltage accuracy (typically ±%) over a.7v to 5.5V input. The demonstration circuit can be easily modified to generate different output voltages. DEMO MANUAL DC887A LTC8 High Efficiency -Cell Supercapacitor Charger and Balancer Converter The DC887 has a small circuit footprint. It is a high performance and cost effective solution for charging and balancing supercapacitors. Please read the LTC8 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. Performance Summary Specifications are at T A = 5 C PARAMETER CONDITIONS VALUE Minimum Input Voltage I OUT = 0A to A.7V Maximum Input Voltage I OUT = 0A to A 5.5V V OUT V IN =.7V to 5.5V, I OUT = 0A.V ±% Input Current Limit (Programmable to A) V IN =.7V to 5.5V 0.9A Nominal Switching Frequency.MHz dc887af
DEMO MANUAL DC887A Quick Start Procedure Demonstration circuit 887 is easy to set up to evaluate the performance of the LTC8. For proper measurement equipment setup refer to Figure 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 or and terminals as shown in Figure. + V OUT C OUT Figure. Measuring Input or Output Ripple. With power off, connect the input power supply to V IN and.. Keep the load set to 0A or disconnected.. 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 V IN does not exceed 5.5V.. Set the input voltage to.v and check for the proper output voltage of.v. 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 V OUT will vary with load. This is due to the current source nature of the LTC8 power converter. As the output voltage increases the output current will decrease in order to maintain the input current below the preset limit. The LTC8 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.v, change the voltage divider resistors connected to the LTC8 FB pin (see the schematic on page 5). Figure. Proper Measurement Equipment Setup dc887af
DEMO MANUAL DC887A Quick Start Procedure CONVERTER OUTPUT CURRENT The DC887 output current capability depends on the input voltage and programmed input current limit. Typical performance of the DC887A is shown in Figure. As can be seen from Figure, the output current decreases as the output voltage is approaching the programmed output voltage of.v. IOUT (A)..0 0.8 0.6 0. 0. 0 V INPUT.V INPUT 5V INPUT.5.5 V OUT (V) Figure. The Output Current Decreases as the Supercap Voltage Increases Due to Precise Input Current Limit. OUTPUT LOAD STEP RESPONSE The load step response of DC887A 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..5.5 dc887 F0 START-UP AND CURRENT LIMIT FUNCTION The DC887 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 DC887 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. The input current limit can be programmed up to A by changing the resistor R8 in the Schematic Diagram. OUTPUT VOLTAGE BALANCING The LTC8 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 V MID (VC) and V OUT with a scope as shown in Figure 5. The trace in Figure 5 is showing the top cap voltage (VC = V OUT V MID ). Figure 5. The DC887 Ramps the Output Slowly at Start-Up without Generating an Input Current Surge. Figure. The Supercap Supplies Most of the Pulsed Load Current. The LTC8 Makes a Small Contribution to Load Current as Shown in Figure. dc887af
DEMO MANUAL DC887A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components C, C CAP, X5R, 0µF, 5V, 0%, 0805 AVX, 0805D06KATA C, C CAP, X5R, 0µF, 5V, 0%, 06 MURATA, GRMCR6E06KAL C5 CAP, NPO, 0pF, 5V, 0%, 060 AVX, 060AJATA C6, C7, C0 CAP, X5R, µf, 5V, 0%, 060 AVX, 060D05KATA 5 C8 SUPERCAP, 5.5V, 0mF MURATA, DMFZ5R5HMDTA0 6 C9, C SUPERCAP, 0.0F,.7V, 0mm 0mm ILLINOIS CAP, 06DCNR7Q 7 L IND, POWER INDUCTOR,.µH COILCRAFT: XAL600-MEB 8 R RES, CHIP,.87M, %, 060 VISHAY, CRCW060M87FKEA 9 R RES, CHIP, 0, 060 VISHAY, CRCW0600000Z0EA 0 R RES, CHIP, 0k, %, 060 VISHAY, CRCW0600KFKEA R5, R6 RES, CHIP, M, %, 060 VISHAY, CRCW060M00FKEA R7 RES, CHIP, 7k, %, 060 VISHAY, CRCW0607KFKEA R8 RES, CHIP,.k, 0.%, 060 VISHAY, TNPW060KBEEA U LTC8EUFD, QFN mm 5mm LINEAR TECHNOLOGY, LTC8EUFD Additional Demo Board Circuit Components 0 C (OPT) CAP, 060 0 R OPT RES, CHIP OPTIONAL Hardware: For Demo Board Only 0 E TO E0 TESTPOINT, TURRET, 0.095" MILL-MAX, 50--00-80-00-00-07-0 JP 0.079 SINGLE ROW HEADER, PIN SAMTEC, TMM-0-0-L-S JP, JP 0.079 DOUBLE ROW HEADER, X PIN SAMTEC, TMM-0-0-L-D JP, JP, JP SHUNT SAMTEC, SN-BK-G 5 STAND OFF STAND OFF KEYSTONE, 88 6 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 887A 7 STENCIL STENCIL DC887A dc887af
5 5 DEMO MANUAL DC887A Schematic Diagram REVISION HISTORY ECO REV DESCRIPTION APPROVED DATE PRODUCTION Goran P. 0-6- D D L.uH R 0 JP MODE.V / A PFI PFI E8 SW 8 SW 7 SW 9 SW 5 6 E V+ R OPT + C9 0F MID C8 0mF 5.5V C 0uF BAL R.87Meg U LTC8EUFD E6 P 6 P 5 S PFI 9 7 + C 0F R 0K E.7V - 5.5V C C FB C7 uf E C 0uF 0V JP C0 0uF + RUN PGOOD C 0uF MID E5 RUN ON OFF R5 Meg E PGOOD RSENP RSENS PFO 8 C6 uf C 0uF 0V R6 Meg RSENS R7 PFO MAXV 0 PROG 5 E9 E7 B B R8.k 0.% C uf OPT VPWR JP PULL UP SOURCE 5 6 7k C5 0pF 6 0 VPWR E0 60 McCarthy Blvd. Milpitas, CA 9505 Phone: (08)-900 APPROVALS CUSTOMER NOTICE LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; TECHNOLOGY Fax: (08)-0507 HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. HZ LTC Confidential-For Customer Use Only VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED APP ENG. Goran P. TITLE: SCHEMATIC A A CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT BUCK-BOOST SUPERCAPACITOR CHARGER AND BALANCER PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. www.linear.com IC NO. LTC8EUFD REV. DEMO CIRCUIT 887A SIZE N/A Tuesday, November, 0 SHEET OF DATE: THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. SCALE = NONE 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. dc887af 5
DEMO MANUAL DC887A 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 0 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 60 McCarthy Blvd. Milpitas, CA 9505 Copyright 00, Linear Technology Corporation 6 LT 0 PRINTED IN USA Linear Technology Corporation 60 McCarthy Blvd., Milpitas, CA 9505-77 (08) -900 FAX: (08) -0507 www.linear.com LINEAR TECHNOLOGY CORPORATION 0 dc887af