DEMO MANUAL DC086 BATTERY CHARGER DESCRIPTIO LT1510 Constant-Voltage/ Constant-Current Lithium-Ion Battery Charger U Demonstration board DC086 is a complete lithium-ion battery charger designed for 1-, 2- or 3-cell applications (other rechargeable battery types can also be charged, see page three). The LT ®1510 is used in a high efficiency current mode step-down switching topology, capable of providing up to 1.5A of charging current. This demo board uses all surface mount components, resulting in a circuit occupying approximately 1 square inch of board area with less than 0.3 in. (7.6mm) height. Jumpers J1 and J2, located on the demo board, are used to select the correct charging voltage for the number of cells being charged (4.2V, 8.4V or 12.6V). Charging current is programmed for 1.3A by resistor R1. The DC input voltage must be at least 3V greater than the output voltage. When the input voltage is removed, an external low current MOSFET (Q1) provides a disconnect for the output voltage divider resistors and the chip goes into a sleep mode, draining approximately 3µA from the battery. , LTC and LT are registered trademarks of Linear Technology Corporation. W U WW PERFOR A CE SU ARY PARAMETER CONDITIONS LIMITS VOUT + 3V ≤ VIN ≤ 28V* VIN Battery Voltage (VBAT) When Charging Terminates 4.2 ±0.7% 8.4V ±0.7% 12.6V ±0.7% VIN = 10V VIN = 15V VIN = 20V 1.3A ±5% Maximum Battery Charging Current Note: Good thermal PC board layout techniques are required when operating near maximum power levels to prevent excessive junction temperatures. Note: For 0.5% battery-voltage accuracy, replace R3 to R8 with 0.1% resistors. *For VIN > 25V, C1 should be replaced with a higher voltage rating capacitor. W U U TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO Component Side Demo Board Charging Efficiency 96 94 VCC = 15V VBAT = 8.4V EFFICIENCY (%) 92 90 88 86 84 82 80 0.1 0.3 0.5 0.7 0.9 1.1 1.3 BATTERY CHARGING CURRENT (A) 1.5 DM086 • TPC01 1 DEMO MANUAL DC086 BATTERY CHARGER U W W PACKAGE A D SCHE ATIC DIAGRA S J3 GND J4 VIN D1 MBRS140L 1 2 1, 4 L1 CTX33-2 33µH 2, 3 C2 0.22µF 3 4 D3 MMBD914 5 6 7 8 GND GND SW VCC BOOST VCC GND PROG LT1510 OVP VC SENSE BAT GND GND GND GND J1 R3 4.99k 0.25% 16 TOP VIEW D2 MBRS140L GND 1 16 GND SW 2 15 VCC2 BOOST 3 14 VCC1 15 14 C1 10µF 13 12 R9 1k C5 0.1µF 11 10 9 Q1 2N7002 J2 R4 R5 R6 R7 R8 3.52k 4.99k 3.52k 4.99k 3.52k 0.25% 0.25% 0.25% 0.25% 0.25% R2 300Ω R1 3.83k 0.25% C3 1µF 16V IBAT VBAT + C4 J6 VIN GND 4 13 PROG OVP 5 12 VC SENSE 6 11 BAT GND 7 10 GND GND 8 9 S PACKAGE 16-LEAD PLASTIC SO + Li-Ion 22µF GND BATTERY LT1510CS J5 FOUR CORNER PINS ARE FUSED TO INTERNAL DIE ATTACH PADDLE FOR HEAT SINKING TO PC BOARD PROGRAM OUTPUT VOLTAGE BATTERY J1 J2 VOLTAGE CLOSED CLOSED 4.2V CLOSED OPEN 8.4V OPEN OPEN 12.6V USE GENEROUS AMOUNTS OF PC BOARD COPPER AROUND LEADS (SEE LT1510 DATA SHEET AND DESIGN NOTE 124) DM086 • SCHEMATIC Figure 1. Demo Board Schematic PARTS LIST REFERENCE DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE C1 1 1E106ZY5U-C304F-T THCS50EIE106Z 10µF 25V 20% Y5U Ceramic Capacitor Tokin United Chemicon/Marcon (408) 432-8020 (708) 696-2000 C2 1 12063C224MAT2A 0.22µF 25V 20% X7R Ceramic Capacitor AVX (207) 282-5111 C3 1 1206YG105ZAT2A 1µF 16V Y5V Ceramic Capacitor AVX (207) 282-5111 C4 1 TPSD226M025R0200 22µF 25V 20% Tantalum Capacitor AVX (207) 282-5111 C5 1 12065C104MAT2A 0.1µF 50V 20% X7R Ceramic Capacitor AVX (207) 282-5111 D1, D2 2 MBRS140LT3 1A 40V Schottky Diode Motorola (602) 244-3550 D3 1 MMBD914LT1 100V Silicon Diode Motorola (602) 244-3550 J1, J2 2 TSW-102-07-G-S 0.1"cc, 0.025"sq. 2-Pin Jumper Samtech (800) 726-8329 J3 to J6 4 1502-2 0.090" Turret Terminal Keystone (718) 956-8900 L1 1 CTX33-2 33µH 2A SMT Inductor Coiltronics (407) 241-7876 Q1 1 2N7002 N-Channel MOSFET Transistor Siliconix (800) 554-5565 R1 1 CR1206F3K83CT 3.83k 1/4W 0.25% Chip Resistor IRC (512) 992-7900 R2 1 CR32-301J-T 300Ω 1/8W 5% Chip Resistor AVX (207) 282-5111 R3, R5, R7 3 CR1206F4K99CT 4.99k 1/4W 0.25% Chip Resistor IRC (512) 992-7900 R4, R6, R8 3 CR1206F3K52CT 3.52k 1/4W 0.25% Chip Resistor IRC (512) 992-7900 R9 1 CR32-102J-T 1k 1/8W 5% Chip Resistor AVX (207) 282-5111 U1 1 LT1510CS SO-16 Battery Charger IC LTC (408) 432-1900 2 DEMO MANUAL DC086 BATTERY CHARGER U OPERATIO The DC086 demonstration board is intended for evaluating the LT1510 switching regulator battery charger IC. Solder terminals are provided for easy hookup to a power supply and to a lithium-ion battery to be charged. The correct charging voltage for either 1, 2 or 3 cells is selectable by a combination of jumpers (J1 and J2) on the board. See the schematic diagram for jumper information. Current limit is set for 1.29A by resistor R1. With a suitable input power supply and a discharged battery connected to the demo board, the battery will begin charging at the programmed current limit of 1.29A. As the battery charges, the voltage rises and approaches the program voltage of either 4.2V, 8.4V or 12.6V. The charger will then maintain a constant voltage across the battery, with the charging current decreasing to zero over time as the battery reaches a fully charged condition. The IC goes into a sleep mode when the input voltage is removed. In the sleep mode, the drain from the battery due to the LT1510 is approximately 3µA. An additional source of battery drain is due to the leakage current of Schottky diode D1. Selecting a low leakage Schottky diode such as a Motorola MBRD340 or a low leakage 3A silicon diode can minimize this current drain. Some lithium-ion battery manufacturers recommend terminating the constant-voltage float mode after the charge current has dropped below a specific level (typically 50mA to 100mA) and a specific amount of time has elapsed (typically from 30 to 90 minutes). This may extend the life of the battery, but check with the manufacturer of the battery you are using for details. Included on the board is an area for breadboarding a timing circuit. Other Battery Types Although the demo board was designed for charging Li-Ion batteries, simple modifications will allow other battery types to be charged. Sealed lead-acid batteries are charged using a currentlimited constant voltage. Over a 0°C to 40°C temperature range, a charge voltage of 2.35V/cell can be used with no charge termination needed. The maximum charge current is determined by the battery manufacturer and is typically 0.25C or less. To use the demo board for charging sealed Note: C is the capacity rating of the battery in Ampere-Hours. lead-acid batteries, reprogram the OVP (overvoltage protection) feedback resistor divider for the correct battery charging voltage using the following formula: V RF = R3 OUT – 1 VREF where RF = total resistance between OVP pin and BAT pin, VREF = 2.465V, select R3 = 4.99k, 1% or less. Maximum charging current (up to 1.5A) is programmed by R1 using the following formula: R1 = (2000)(2.465) ICHARGE where 2.465V = reference voltage present at PROG pin. The maximum charging current (or current limit) is 2000 times the current out of the PROG pin. This current has both AC and DC components present; therefore, to provide high DC accuracy, averaging components R2 and C3 are required. For nickel-cadmium and nickel-metal-hydride batteries, the normal charging method is constant current. Fast charging requires some method to detect full charge and terminate the high charge current. Some methods often used to indicate full charge include battery temperature rise and observing battery voltage profile during charging. LT1510 Step-Down Switching Regulator The LT1510 is designed for constant-voltage and/or constant-current operation with a 0.5% voltage accuracy and a 5% current accuracy. An external resistor voltage divider programs the output voltage, while a single resistor (or a programming current from a DAC) sets the maximum charging current . An internal 2A NPN switch operating at 200kHz provides high efficiency with low inductor values using a minimum number of external components. The charging current sense resistor is included on the die and can be wired for sensing charging current at either the positive or negative side of the battery. Refer to the LT1510 data sheet for complete product specifications and design notes DN111 and DN124 for additional application information. 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. 3 DEMO MANUAL DC086 BATTERY CHARGER U W PCB LAYOUT AUD FILW Component Side Silkscreen Component Side Component Side Solder Mask Solder Side U PC FAB DRAWI G 3.000 4 SYMBOL DIAMETER NUMBER OF HOLES NONE 0.010 10 B 0.015 17 C 0.035 80 D 0.040 4 E 0.095 4 F 0.070 2 TOTAL HOLES 117 F E C B E 2.000 E 0.150 Linear Technology Corporation F DD DD 0.150 E NOTES: 1. BOARD MATERIAL IS FR-4, 0.062" THICK, 2 0Z COPPER 2. PCB WILL BE DOUBLE-SIDED WITH PLATED THROUGH HOLES 3. SOLDER MASK BOTH SIDES WITH PC4014. SILKSCREEN COMPONENT SIDE. USE WHITE NONCONDUCTIVE INK 4. ALL DIMENSIONS IN INCHES ±0.005" DC086 • PC DWG LT/GP 0696 500 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1996