Freescale Semiconductor User’s Guide Document Number: KT34671UG Rev. 1.0, 3/2008 Using the High Input Voltage Charger for Single Cell Li-Ion Batteries (KIT34671EPEVBE) 1 Purpose This User Guide helps the Lithium-Ion (Li-Ion) battery charger designer understand the MC34671 and its evaluation board. It illustrates the design procedure when using the MC34671 to design a Li-Ion battery charger, and the way to get the best performance from the MC34671. 2 Scope The MC34671 is a low-cost high input voltage linear charger for single cell Li-Ion batteries in a tiny 2x3mm UDFN package. It features high accuracy output voltage and charge current. Its high input voltage of 28V eliminates the over-voltage protection circuit required in handheld devices. It uses an external resistor to set the CC-mode charge current up to 600mA. The end of charge (EOC) current is preset to 10% of the CC-mode charge current by the factory. When the battery voltage is below the trickle charge threshold of 2.7V, the MC34671 charges the battery with 20% of the CC-mode charge current. Three indication pins © Freescale Semiconductor, Inc., 2008. All rights reserved. Contents 1 2 3 4 5 6 7 8 9 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Application Diagram . . . . . . . . . . . . . . . . . . . . 2 Evaluation Board Specification . . . . . . . . . . . 3 Component Selection . . . . . . . . . . . . . . . . . . . 5 Layout Design . . . . . . . . . . . . . . . . . . . . . . . . . 6 Evaluation Board Configuration . . . . . . . . . . 8 Test Setup with the Evaluation Board. . . . . 10 References. . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Application Diagram (PPR, CHG, and FAST) can be simply interfaced to the system or LEDs to report the charge status. Its internal thermal foldback control reduces the charge current automatically, whenever the die temperature reaches the thermal limit threshold of 110°C, to keep the charger safe. When there is no input power, or when the MC34671 is disabled, the charger draws less than a 1.0µA leakage current from the battery. 3 3.1 Application Diagram Standalone Charger The MC34671 can be used as a standalone Li-Ion charger. Figure 1 is the typical application circuit. Two LEDs indicate the charge status. DC Input BAT VIN CIN COUT RED GREEN GND 470 MC34671 Li+ RISET ISET 470 CHG PPR FAST EN Figure 1. The Standalone Li-Ion Charger 3.2 Embedded Charger When the MC34671 is embedded in the system, the system MCU can control the charger through the EN pin and get the charge status through PPR, CHG, and FAST pins. Figure 2 is the typical application circuit. DC Input BAT VIN CIN COUT Li+ VIO GND 100Kx3 MC34671 ISET RISET CHG MCU PPR FAST EN OFF ON Figure 2. The Li-Ion Charger Embedded in the Hand Held System 2 Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor Evaluation Board Specification 4 Evaluation Board Specification The evaluation board is designed to work as a standalone charger, or as an embedded charger in a handheld system. Figure 3 shows its schematic circuit. Table 1 is the BOM list of the evaluation board. The normal operation range of the evaluation board is: VIN_MIN = 4.3V, VIN_MAX = 11V ICHG_MAX = 600mA TP7 TP6 BAT VBAT ISET /FAST 1 2 TP2 1 TP1 VIN 1 INPUT J8 JP4 HDR_1X2 1 JP1 HDR_1X2 1 2 1 J1 C1 1.0uF C2 2.2UF C4 47UF C5 47UF C6 47UF J7 JP2 HDR_1X3 3 JP7 D1 GREEN HDR_1X2 U1 2 3 JP3 HDR_1X2 J5 4 ISET EN FAST 8 9 TP5 HDR_1X2 VL R5 100K 7 J6 TP9 6 TP10 1 2 /EN BAT BAT CHG 5 1 BAT PPR 1 /CHG TP4 JP8 JP9 HDR_1X3 1 R1 470 OHM VIN R2 470 OHM 1 2 EPAD R3 100K GND R4 100K 1 2 R8 8.66K 3 D2 RED R7 17.4K 2 1 JP6 1 1 1 2 HDR_1X2HDR_1X2 /PPR TP3 1 JP5 R6 17.8K 2 C3 1.0uF 1 2 J4 BAT 2 VIN VL J3 TP8 1 VL 2 1 J2 MC34671AEP J10 GND 1 1 J9 GND Figure 3. The Schematic Circuit of the Evaluation Board Table 1. The Components on the Evaluation Board Designator Footprint Part Value Part Number Description C1 CC0603 1.0µF C1608X5R1C105K 16V, X5R ceramic, 10% TDK C2 CC0603 2.2µF C1608X5R1C225K 6.3V, X5R ceramic, 10% TDK C3 CC0603 1.0µF C1608X5R1C105K 16V, X5R ceramic, 10% TDK C4 CC1206 47µF C3216X5R0J476M 6.3V, X5R ceramic, 20% TDK C5 CC1206 47µF C3216X5R0J476M 6.3V, X5R ceramic, 20% TDK C6 CC1206 47µF C3216X5R0J476M 6.3V, X5R ceramic, 20% TDK R1 RC0603 470 CR0603JW471E MF, 5%, 1/10W BOURNS R2 RC0603 470 CR0603JW471E MF, 5%, 1/10W BOURNS Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor Vendor 3 Evaluation Board Specification Table 1. The Components on the Evaluation Board Designator Footprint Part Value Part Number Description Vendor R3 RC0603 100K CR0603-JW-104ELF MF, 5%, 1/10W BOURNS R4 RC0603 100K CR0603-JW-104ELF MF, 5%, 1/10W BOURNS R5 RC0603 100K CR0603-JW-104ELF MF, 5%, 1/10W BOURNS R6 RC0603 17.8K RK73H1JTTD1782F MF, 1%, 1/10W KOA SPEER R7 RC0603 17.4K RK73H1JTTD1742F MF, 1%, 1/10W KOA SPEER R8 RC0603 8.66K RK73H1JTTD8661F MF, 1%, 1/10W KOA SPEER D1 LED0603 GREEN LTST-C190KGKT Ultra-bright Green LED LITE ON D2 LED0603 RED LTST-C190KRKT Ultra-bright Red LED LITE ON TP1 TP VIN TP-105-01-00 Test Point COMPONENTS TP2 TP GND TP-105-01-00 Test Point COMPONENTS TP3 TP PPR TP-105-01-00 Test Point COMPONENTS TP4 TP CHG TP-105-01-00 Test Point COMPONENTS TP5 TP EN TP-105-01-00 Test Point COMPONENTS TP6 TP BAT TP-105-01-00 Test Point COMPONENTS TP7 TP GND TP-105-01-00 Test Point COMPONENTS TP8 TP ISET TP-105-01-00 Test Point COMPONENTS TP9 TP FAST TP-105-01-00 Test Point COMPONENTS TP10 TP GND TP-105-01-00 Test Point COMPONENTS JP1 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP2 HDR103 3-PIN 826629-3 TH 100MIL SP 375H TYCO JP3 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP4 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP5 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP6 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP7 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP8 HDR102 2-PIN 826629-2 TH 100MIL SP 375H TYCO JP9 HDR103 3-PIN 826629-3 TH 100MIL SP 375H TYCO U1 2x3 UDFN-8 MC34671AEP Single Cell Li+ Battery Charger IC, Linear FREESCALE Freescale does not assume liability, endorse, or warrant components from external manufacturers that are referenced in circuit drawings or tables. While Freescale offers 4 Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor Component Selection component recommendations in this configuration, it is the customer’s responsibility to validate their application. 5 5.1 Component Selection Input capacitor C1 The input capacitor is used to minimize the input voltage transient that may cause instability. A ceramic capacitor of 1.0µF or above is required for most applications. X5R and X7R dielectrics have better temperature stability. The evaluation board uses 1.0µF X5R ceramic capacitors. Considering the maximum input voltage rating of the MC34671 is 28V, the input capacitor must have 16V DC rated voltage. 5.2 Output capacitors C2, C4, C5, and C6 The output capacitor is used for stable operation. A ceramic capacitor minimum of a 2.2µF is required. On the evaluation board, a C2 of 2.2µF is necessary. The large capacitors of C4, C5, and C6 are used to simulate the situation in the cell phone application where big capacitance is put in parallel with the Li-Ion battery. The user may remove C4, C5, and C6 if their system doesn’t need such large capacitance. C4, C5, and C6 do not affect the performance of the MC34671. Because the highest output voltage of the MC34671 is 4.2V, a 6.3V DC rated voltage is high enough for the output capacitors. 5.3 Charge current setting resistors R6, R7, and R8 The resistor between the ISET pin and GND sets the charge current by the following equation: ICHG = 2667 / (RISET+96) (A) where RISET is in units of Ω, ICHG is in units of amps. A metal film with a 1% tolerance resistor should be used for temperature stability. As a result, the charge current will be accurate over the whole temperature range. On the evaluation board, three resistors with two pin header jumpers are used for the user to conveniently configure different charge current values. Table 2 shows the charge current with the different settings of pin headers JP7 and JP8. Table 2. The Charge Current Settings JP7 JP8 Charge Current Open Open 150mA Short Open 300mA Open Short 450mA Short Short 600mA Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor 5 Layout Design 6 6.1 Layout Design Layout The KIT34671EPEVBE PCB board has two copper layers. The component side of the KIT34671EPEVBE is provided to locate all components. Figure 4 is an overview of the board, followed by the layout of each layer. Figure 4. The Overview of the Evaluation Board 6 Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor Layout Design Figure 5. The Silkscreen Layer of the Evaluation Board Figure 6. The Component Side Layer of the Evaluation Board Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor 7 Evaluation Board Configuration Figure 7. The Solder Side Layer of the Evaluation Board 6.2 • • • • 7 7.1 Layout considerations Place decoupling capacitors C1 and C2 as close as possible to the VIN pin and BAT pin respectively. Place the charge current setting resistor as close as possible to the ISET pin to minimize the parasitic capacitance between the ISET pin and ground. Use wide traces to connect input power to the VIN pin and BAT pin to the battery. To get better thermal performance, put the EPAD pin of the MC34671 on a large ground plane on the component side, and use a via array to connect the EPAD pin to the ground layer, or the large ground plane on the other layer. Evaluation Board Configuration Pin Headers The JP1 pin header links the external DC power supply to the VIN pin of the MC34671. This allows the user to measure the current from the DC power supply to the evaluation board when using a current meter between pin 1 and pin 2 of JP1. The default setting of JP1 is to short pins 1 and 2. The JP2 pin header selects the voltage to supply the D1 and D2 LED indicators. Shorting pins 1 and 2 selects VIN to power the LEDs. Shorting pins 2 and 3 selects the BAT pin to power the LEDs. 8 Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor Evaluation Board Configuration IMPORTANT: DO NOT APPLY HIGHER THAN 12V DC INPUT VOLTAGE TO VIN IF PINS 1 and 2 ARE SHORTED. The absolute maximum voltage at the PPR and CHG pin is 12V. When applying higher than a 12V input voltage, select BAT to power the LEDs. The JP3 pin header allows the user to disable the MC34671 when shorting pins 1 and 2. Leaving it open enables the MC34671. The JP4 pin header links the BAT pin and the external battery connector. It allows the user to measure the charging current from the MC34671 into the battery with a current meter between pins 1 and 2. The default setting is to short pins 1 and 2. JP5 and JP6 are used to let the user supply an I/O logic voltage to PPR and CHG, so the system can interface to the PPR and CHG signals with the same voltage level. When using LEDs to indicate the charging status, leave JP5 and JP6 open. When interfacing the PPR and CHG signal to the system, short pins 1 and 2 of JP5 and JP6, and leave JP2 open. JP7 and JP8 set the charge current. The current values related to JP7 and JP8 settings are shown in Table 2. JP9 selects the power supply for pulling up the voltage of the FAST signal. Shorting pins 1 and 2 selects the externally supplied I/O logic voltage. Shorting pins 2 and 3 selects the battery voltage. The default configuration of the evaluation board is a standalone charger. The default settings of the evaluation board are shown in Table 3. Table 3. The Default Settings of the Pin Headers for Standalone Chargers Pin Header Jumpers Default Setting JP1 Shorted JP2 1 and 2 shorted JP3 Open JP4 Shorted JP5 Open JP6 Open JP7 Shorted JP8 Shorted JP9 1 and 2 shorted When using the evaluation board to connect to the system, please apply the required I/O logic voltage at the VL pad of the evaluation board and set the pin header jumpers as shown in Table 4. Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor 9 Test Setup with the Evaluation Board Table 4. The Settings of the Pin Headers for an Embedded Charger Connecting to the System Pin Header Jumpers 7.2 Default Setting JP1 Shorted JP2 Open JP3 Open JP4 Shorted JP5 Shorted JP6 Shorted JP7 Shorted JP8 Shorted JP9 2 and 3 shorted Connector Pads There are 10 connecting pads (J1 to J10 with corresponding names) on the evaluation board to let the user simply connect the board to their system. The GND pads link power ground of the MC34671. The INPUT pad connects an external DC power supply to the evaluation board. The PPR, CHG, EN, FAST, and ISET pads link to the corresponding pins of the MC34671. The VL pad is used for the user to supply a logic I/O voltage to the evaluation board, in case the application system needs a logic voltage level to interface to the PPR, CHG, and FAST pins of the MC34671. The VBAT pad connects the positive pole of the Li+ battery being charged. 7.3 Test points The KIT34671 evaluation board provides 7 signal test points and 3 ground test points for users to conveniently hookup multi-meters and oscilloscope probes to evaluate the MC34671. The test points connect the pins of the MC34671 with the same name directly. 8 Test Setup with the Evaluation Board The test setup is shown in Figure 8. Connect a DC power source with a larger than 1.0A current limit to the INPUT pad on the evaluation board. Connect the positive and negative polarities of the Li+ battery to the VBAT pad and the GND pad on the evaluation board respectively. Use a current meter and a voltage meter to measure the charge current and the voltage respectively. Turn on the power supply and the evaluation board starts charging the battery. 10 Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor Test Setup with the Evaluation Board A V A DC Power Source Li+ Battery Figure 8. The Test Set Up for the Evaluation Board Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor 11 References 9 References • • 12 MC34671PG Quick Reference MC34671 Data Sheet Using the High Input Voltage Charger for Single Cell Li-Ion Batteries, Rev. 1.0 Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com E-mail: [email protected] USA/Europe or Locations Not Listed: Freescale Semiconductor Technical Information Center, CH370 1300 N. Alma School Road Chandler, Arizona 85224 +1-800-521-6274 or +1-480-768-2130 [email protected] Europe, Middle East, and Africa: Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen, Germany +44 1296 380 456 (English) +46 8 52200080 (English) +49 89 92103 559 (German) +33 1 69 35 48 48 (French) [email protected] Japan: Freescale Semiconductor Japan Ltd. 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