Freescale Semiconductor Advance Information Document Number: MC34671 Rev. 1.0, 01/2008 High Input Voltage 600mA Charger for Single-cell Li-Ion Batteries 34671 The MC34671 is a cost-effective fully-integrated battery charger for POWER MANAGEMENT IC Li-Ion or Li-Polymer batteries. The high input voltage, up to 28V, eliminates the input over-voltage-protection circuit required in handheld devices such as cell phones, Bluetooth accessories and MP3 players. A typical charge cycle includes trickle, constant-current (CC) and constant-voltage (CV) charge modes. The CC-mode current is programmable up to 600mA with an external resistor. The voltage across the external resistor is also used to monitor the actual charge EP SUFFIX (PB-FREE) 98ASA10774D current. The constant voltage is fixed at 4.2V with 0.7% accuracy over 8-PIN UDFN a -20°C to 70°C temperature range. The trickle-mode current is preset to 20% of the CC-mode current when the battery voltage is lower than the trickle-mode threshold. The end-of-charge (EOC) current threshold is preset to 10% of the CC-mode current to save the board space and ORDERING INFORMATION cost. A charge current thermal foldback feature limits the charge current when the IC internal temperature rises to a preset threshold. Temperature Device Package Range (TA) The MC34671 also protects the system with its input over-voltage protection (OVP) feature. In addition, the MC34671 has a 2.6V falling MC34671AEP/R2 -40°C to 85°C 8-UDFN power-on-reset (POR) threshold, making it perfect to work with current limited power supplies. Three indication pins (PPR, CHG and FAST) can be simply interfaced to a microprocessor or LEDs. When no power supply is connected, or when disabled, the charger draws less than 1.0µA leakage current from the battery. Features • No external MOSFET, reverse-blocking diode or current-sense resistor are required • Guaranteed maximum 600mA programmable CC-mode current • ±0.7% voltage accuracy over -20°C to 70°C • ±5% current accuracy over -40°C to 85°C • 28V maximum voltage for the power input with 11V over-voltage protection threshold • 2.6V minimum input operating voltage • Trickle charge for fully discharged batteries • Charge current monitor • Charge current thermal foldback • Pb-free packaging designated by suffix code EP 34671 VIN CIN VIN GND CHG ON OFF TO BATTERY BAT COUT ISET RISET VIO PPR EN FAST Figure 1. 34671 Simplified Application Diagram * This document contains certain information on a new product. Specifications and information herein are subject to change without notice. © Freescale Semiconductor, Inc., 2007-8. All rights reserved. TO MCU INTERNAL BLOCK DIAGRAM INTERNAL BLOCK DIAGRAM VIN BAT – VIN Monitor Internal Supply + VREF Charge Control REF ISET – PPR + VOS IREF VIN + – + BAT – – + Die Temp 110°C CHG EN Logic Control + – IEOC FAST GND Figure 2. 34671 Simplified Internal Block Diagram 34671 2 Analog Integrated Circuit Device Data Freescale Semiconductor PIN CONNECTIONS PIN CONNECTIONS VIN 1 8 BAT PPR 2 7 ISET CHG 3 6 FAST EN 4 5 GND EPAD Figure 3. 34671 Pin Connections Table 1. 34671 Pin Definitions A functional description of each pin can be found in the Functional Pin Description section beginning on page 11. Pin Number Pin Name Pin Function Formal Name Definition 1 VIN Input Input supply 2 PPR Output Power present indicator 3 CHG Output Charge indicator 4 EN Input Enable Enable logic input. 5 GND Ground Ground Ground. 6 FAST Output Fast charge indicator 7 ISET Output CC-mode current setting and charge current monitor 8 BAT Output Charger output EPAD EPAD N/A Exposed pad The supply input. Indication of the input power status. Open drain output. Indication of the charge status. Open drain output. Indication of the fast charge status. Open drain output. CC-mode current setting and monitoring pin. The charger output pin. Connect this pin to the Li-Ion battery. Exposed pad for thermal dissipation enhancement. Must be soldered on the large ground plane on the PCB to increase the thermal dissipation. The pad must be connected to GND electrically. 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 3 ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device. Ratings Symbol Value Unit ELECTRICAL RATINGS Input Voltage Range V VIN Pin VIN PPR and CHG Pins EN, BAT, ISET, and FAST Pins -0.3 to 28 VPPR, VCHG -0.3 to 12 VEN, VBAT, VISET, VFAST -0.3 to 5.5 ESD Voltage(1) V Human Body Model (HBM) VESD Machine Model (MM) ±2000 ±200 THERMAL RATINGS Operating Temperature °C Ambient TA -40 to 85 Junction TJ -40 to 150 TSTG -65 to 150 RθJC 10 RθJA 70 TPPRT Note 4 Storage Temperature Thermal Resistance(2) °C/W Junction-to-Case Junction-to-Ambient Peak Package Reflow Temperature During °C Reflow(3),(4) °C Notes 1. ESD testing is performed in accordance with the Human Body Model (HBM) (CZAP = 100pF, RZAP = 1500Ω), and the Machine Model (MM) (CZAP = 200pF, RZAP = 0Ω). 2. 3. 4. Device mounted on the Freescale EVB test board per JEDEC DESD51-2. Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may cause malfunction or permanent damage to the device. Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package Reflow Temperature and Moisture Sensitivity Levels (MSL), Go to www.freescale.com, search by part number [e.g. remove prefixes/suffixes and enter the core ID to view all orderable parts. (i.e. MC33xxxD enter 33xxx), and review parametrics. 34671 4 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions VIN = 5.0V, -40°C ≤ TA ≤ 85°C, CIN = 1.0µF, COUT = 2.2µF (see Figure 1), unless otherwise noted. Typical values noted reflect the approximate parameter means at VIN = 5.0V and TA = 25°C under nominal conditions, unless otherwise noted. Characteristic Symbol Min Typ Max Unit Input Voltage Range(5) VIN 2.6 - 10 V VIN Pin Supply Current IIN Charger enabled(6) - 1400 - Charger disabled - - 350 POWER INPUT Regulated Output Voltage µA VBAT V VIN = 5.0V; IBAT = 10mA; TA = 25°C 4.185 4.20 4.215 VIN = 5.0V; IBAT = 10mA; TA = -20 to 70°C 4.170 4.20 4.230 VIN = 5.0V; IBAT = 10mA; TA = -40 to 85°C 4.158 4.20 4.230 - 500 700 Power MOSFET On Resistance RDS(ON) VBAT = 4V; IBAT = 500mA; ICHG = 600mA BAT Pin Standby Current mΩ ISTDBY VIN not powered or charger disabled µA - - 1.0 Rising VIN threshold 3.0 - 3.9 Falling VIN threshold - 2.4 2.6 Rising threshold - - 60 Falling threshold 1.0 - 22 VOVP 10 11 12 V VOVPHYS - 400 - mV Constant Current Mode Charge Current Range(7) ICHG 50 - 600 mA ICHG Accuracy ICHG Power On Reset VPOR VIN-BAT Offset Voltage V VOS Over-voltage Protection Rising Threshold Over-voltage Protection Threshold Hysteresis mV CHARGE CURRENT For ICHG between 300mA to 600mA (7) For ICHG between 50mA to 300mA (Tested at 300mA) Trickle-mode Charge Current ITRKL End-of-Charge (EOC) Threshold IEOC When ICHG is set to 300mA ISET Pin Voltage for ICHG Reference(7) VISET % 95 100 105 90 100 110 16 20 24 20 30 40 - 1.0 - % ICHG mA V Notes 5. Refer to the Power-on-Reset parameter for VIN turn on and turn off values. 6. 7. Supply current does not include the current delivered to the battery through the BAT pin. Not tested. Guaranteed by design. 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 5 ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics (continued) Characteristics noted under conditions VIN = 5.0V, -40°C ≤ TA ≤ 85°C, CIN = 1.0µF, COUT = 2.2µF (see Figure 1), unless otherwise noted. Typical values noted reflect the approximate parameter means at VIN = 5.0V and TA = 25°C under nominal conditions, unless otherwise noted. Characteristic Symbol Min Typ Max Unit VTRKL 2.6 2.7 2.8 V VTRKLHYS 40 100 150 mV VRECH 4.060 4.100 4.140 V VTHRCHG - 25 50 mV EN Input High Threshold Voltage VIH 1.5 - - V EN Input Low Threshold Voltage VIL - - 0.5 V EN Input Leakage Current IEN - 2.0 7.5 µA - mA 12 15 CHARGE THRESHOLDS Trickle-mode Rising Threshold Voltage Trickle-mode Threshold Voltage Hysteresis Recharge Falling Threshold Voltage Recharge Threshold Voltage Hysteresis LOGIC INPUT AND OUTPUT VEN = 3.0V PPR and CHG Sink Current When the Output is Low IPCSINKL VCHG =VPPR = 0.6V PPR and CHG Leakage Current When the Output is High-impedance IPCLEAKH VCHG =VPPR = 5.0V FAST Sink Current When the Output is Low - - 1.0 0.3 - - - - 1.0 95 110 125 IFSINKL VFAST = 0.5.0V FAST Leakage Current When the Output is High-impedance µA mA IFLEAKH VFAST = 3.0V µA CHARGE CURRENT THERMAL FOLDBACK Current Foldback Die Temperature Limit TLIMIT °C 34671 6 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS Table 4. Dynamic Electrical Characteristics Characteristics noted under conditions VIN = 5.0V, -40°C ≤ TA ≤ 85°C, CIN = 1µF, COUT = 2.2µF (Figure 1), unless otherwise noted. Typical values noted reflect the approximate parameter means at VIN = 5.0V and TA = 25°C under nominal conditions, unless otherwise noted. Characteristic Symbol Min Typ Max Unit tEOC 6.0 8.0 10 ms fOSC 40.0 50.0 60.0 kHz END OF CHARGE EOC Filter Time OSCILLATOR Oscillation Frequency 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 7 ELECTRICAL CHARACTERISTICS ELECTRICAL PERFORMANCE CURVES Battery Voltage (V) 4.5 300 Battery Voltage 4.0 250 3.5 200 3.0 150 2.5 100 Charge Current 2.0 1.5 0 20 40 60 80 50 Charge Current (mA) 350 5.0 0 100 120 Constant Charge Current (mA) ELECTRICAL PERFORMANCE CURVES 350 300 RISET=8.80 kΩ 250 200 150 RISET=17.8 kΩ 100 50 0 4 5 6 7 8 VIN (V) Charge Time ( min) Figure 4. Complete Charge Cycle VIN = 5.0V, ICHG=300mA, TA = 25°C VBAT ( V) 4.1 4.0 3.9 3.8 3.7 3.6 6 7 8 9 10 11 Trickle Charge Current (mA) 4.2 5 80 70 60 50 RISET=8.80 kΩ 40 30 20 RISET=17.80 kΩ 10 0 4 5 6 VIN (V) 7 8 9 10 VIN (V) Figure 5. VBAT vs VIN IBAT = 0mA, TA = 25°C Figure 8. Trickle Charge Current vs VIN VBAT = 2.0V, TA = 25°C 1.2 2400 1.0 2000 VISET (V) VIN Pin Supply Current ( µA) 10 Figure 7. Constant Charge Current vs VIN VBAT = 3.0V, TA = 25°C 4.3 3.5 4 9 1600 Charger Enabled 1200 800 0.6 0.4 400 0 0.8 0.2 Charger Disabled 3 4 5 6 7 8 9 10 VIN (V) Figure 6. VIN Pin Supply Current vs VIN IBAT = 0mA, TA = 25°C 11 0.0 5 6 7 8 9 10 VIN (V) Figure 9. VISET vs VIN VBAT = 3.9V, TA = 25°C 34671 8 Analog Integrated Circuit Device Data Freescale Semiconductor 1.2 VISET (V) 1.0 RISET=4.36 kΩ RISET=8.80 kΩ 0.8 0.6 0.4 0.2 0.0 0 100 200 300 400 500 600 Constant Charge Current (mA) ELECTRICAL CHARACTERISTICS ELECTRICAL PERFORMANCE CURVES 700 RISET=4.27 kΩ 600 500 400 RISET=8.51 kΩ 300 200 RISET=17.21 kΩ 100 0 -40 -20 Charge Current (mA) Trickle Charge Current (mA) Charge Current (mA) 250 200 150 RISET=17.80 kΩ 50 1 2 80 3 4 150 RISET=4.27 kΩ 125 100 75 RISET=8.51 kΩ 50 RISET=17.21 kΩ 25 0 -40 -20 0 20 40 60 80 o VBAT (V) Temperature ( C) Figure 14. Trickle Charge Current vs Temperature VIN = 5.0V, VBAT = 2.0V Figure 11. Charge Current vs VBAT VIN = 5.0V, TA = 25°C 1.2 4.30 1.0 4.25 0.8 4.20 VISET (V) VBAT (V) 60 Temperature ( C) RISET=8.80 kΩ 0 40 Figure 13. Constant Charge Current vs Temperature VIN = 5.0V, VBAT = 3.9V 350 100 20 o Figure 10. VISET vs Charge Current VIN = 5.0V, TA = 25°C 300 0 4.15 4.10 0.6 0.4 0.2 4.05 4.00 -40 -20 0 20 40 o Temperature ( C) Figure 12. VBAT vs Temperature VIN = 5.0V, IBAT = 0mA 60 80 0.0 -40 -20 0 20 40 60 80 o Temperature ( C) Figure 15. VISET vs Temperature VIN = 5.0V 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 9 ELECTRICAL CHARACTERISTICS ELECTRICAL PERFORMANCE CURVES RDS(ON) ( mΩ) 550 500 450 400 350 300 -40 -20 0 20 40 60 80 BAT Pin Supply Current ( µA) 600 1.0 0.8 0.6 0.4 0.2 0.0 -40 -20 40 60 80 Figure 18. BAT Pin Supply Current vs Temperature VBAT = 5.0V, VIN Not Powered or Charger Disabled 2000 4.20 4.15 4.10 4.05 4.00 3.95 -20 0 20 40 60 80 o Temperature ( C) Figure 17. Recharge Voltage Threshold vs Temperature RISET = 17.21kΩ, VIN = 5.0V VIN Pin Supply Current ( µA) Recharge Voltage Threshold (V) 20 Temperature ( C) Temperature ( C) Figure 16. RDS(ON) vs Temperature VBAT = 4.0V, ICHG=300mA, IBAT= 250mA 3.90 -40 0 o o 1750 Charger Enabled 1500 1250 1000 750 500 Charger Disabled 250 0 -40 -20 0 20 40 60 80 o Temperature ( C) Figure 19. VIN Pin Supply Current vs Temperature VIN = 5.0V 34671 10 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DESCRIPTION INTRODUCTION FUNCTIONAL DESCRIPTION INTRODUCTION The MC34671 is a fully-integrated Li-Ion and Li-Polymer battery charger in a tiny package. It uses current, voltage and temperature control loops to regulate the charge current. It has up to a 28V input voltage rating, which makes the handheld device safe even when connected to a wrong AC adapter. The MC34671 requires only two external capacitors and one resistor to build a fully functional charger for spacelimited applications such as cell phones, Bluetooth accessories and MP3 players. Its ultra high-accuracy (±0.7%) output voltage and temperature-limited charging current offer additional battery safety during charging. The CC-mode current can be programmed with an external resistor (RISET). The voltage across this resistor is proportional to the charge current, so the system can monitor the charge current during the whole charge cycle. The EOC current threshold is preset to 10% of the CC-mode current. For a deeply discharged battery with a voltage lower than 2.7V, the MC34671 charges the battery with a trickle-mode current, which is 20% of the CC-mode current. Three indication outputs make it easy to report the input power status and the charge status to MCUs, or users via LEDs. FUNCTIONAL PIN DESCRIPTION INPUT SUPPLY (VIN) The supply input. This pin should be bypassed to ground with a 1.0µF capacitor. POWER PRESENT INDICATOR (PPR) Open-drain logic output to indicate the input-power status. The PPR pin output is only determined by the input voltage, not other conditions such as the EN pin input. The output is low if VIN is higher than VPOR. This pin is capable to sink at least 12.0mA of current to drive an LED indicator. CHARGE INDICATOR (CHG) Open-drain logic output to indicate the charge status. The output is low when the MC34671 is charging, until the EOC conditions are reached. This pin is capable to sink at least 12.0mA of current to drive an LED indicator. ENABLE (EN) Active low enable logic Input. This pin is internally pulled to ground by a weak current source. When left floating, the charger is enabled. Pulling this pin to a high voltage, externally disables the charger. GROUND (GND) mode threshold. This pin is capable to sink more than 0.3mA of current. When the charger is on, this pin outputs a logic low signal if the battery voltage is higher than the trickle-mode threshold. When the charger is in the shutdown mode or in any fault conditions, this pin outputs a high-impedance. CC-MODE CURRENT SETTING AND CHARGE CURRENT MONITOR (ISET) The CC-mode current, ICHG, is programmed by connecting a resistor, RISET, between this pin and the ground. When charging in the CC-mode, the voltage at this pin is 1.0V. The voltage reduces proportionally as the charge current reduces in the CV-mode. During the whole charge cycle, the voltage at this pin can be used to monitor the charge current using the following equation: V ISET I BAT = --------------- ⋅ I CHG 1.0V equ. 1 where IBAT is the actual charge current, ICHG is the programmed CC-mode current, and VISET is the voltage of the ISET pin during the whole charge cycle. CHARGER OUTPUT (BAT) Charger output pin. Connect this pin to the battery being charged. Bypass to ground with a 2.2µF or higher capacitor. Ground. FAST CHARGE INDICATOR (FAST) When charging, this open-drain logic output indicates whether or not the battery voltage is higher than the trickle- EXPOSED PAD (EPAD) Exposed pad. It must be soldered on the large ground plane of the PCB to enhance the thermal conductivity. The pad must be connected to GND electrically. 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 11 FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION MC34671 - Functional Block Diagram Integrated Supply Internal Supply & Reference Sensing & Control VIN Monitor Charge Control Current Setting End of Charge Current Monitor VIN - BAT Compare Power MOSFET Die Temperature Feedback Logic Logic Control Status Indication Integrated Supply Sensing & Control Logic MOSFET Figure 20. 34671 Functional Internal Block Diagram INTEGRATED SUPPLY CURRENT SETTING AND MONITOR INTERNAL SUPPLY AND REFERENCE This block programs the charge current in the constantcurrent mode and monitors the actual charge current during the whole charge cycle. This block steps down the high input voltage to a lower voltage to power all the internal blocks. In addition, this block generates the reference voltage for the charge control block. SENSING AND CONTROL VIN MONITOR The input voltage monitor block monitors the input voltage for two thresholds, power-on-reset (POR) and over-voltage protection (OVP). If the input is lower than the POR or higher than the OVP threshold, this block outputs a logic signal to disable the charger. CHARGE CONTROL The charge-control block controls the gate voltage of the power MOSFET to regulate the charge current, the battery voltage, or the die temperature. It can also completely turn off the power MOSFET to stop the current flow between the input and the battery. Also, monitoring of the charge current and the charger output voltage determines the trickle-charge mode and the recharge cycle. EOC (END OF CHARGE) The EOC block monitors the charge current and the battery voltage for the EOC conditions. Once the EOC conditions are reached, this block outputs a logic signal to indicate the end of the charge. VIN-BAT COMPARATOR The VIN-BAT comparator monitors the voltage difference between the input voltage and the battery voltage. The input voltage has to be higher than the battery voltage for the charger to be enabled. If the input voltage falls below the battery voltage, this block outputs a signal to disable the charger to prevent the leakage current from the battery to the input. DIE TEMPERATURE FEEDBACK The die temperature feedback block monitors the die temperature. Once the die temperature reaches the threshold temperature, the charge control block can reduce the charge current to prevent further die temperature rise. 34671 12 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION LOGIC LOGIC CONTROL AND STATUS INDICATION The logic control block determines the on and off of the charger. It takes the signals from the VIN Monitor, VIN-BAT Comparator, EOC, and the external enable signal, and determines the on and off states as well as the charge status indication outputs of the charger (CHG, PPR, and FAST). POWER MOSFET The power MOSFET passes the charging current from the input to the output. 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 13 FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES CHARGE CYCLE outputs logic high voltage at the CHG pin to indicate that the charging is completed. The MC34671 uses the standard charge profile with trickle, constant-current (CC), and constant-voltage (CV) charge modes, as shown in Figure 21. Both the CC and the CV charge modes are also called fast-charge mode. When the input voltage rises above an internal power-on-reset threshold, the PPR pin outputs a low voltage to indicate the power supply presence. The charger starts with the tricklecharge mode until the battery voltage is above 2.7V. The CHG pin outputs logic low voltage at the beginning of the trickle-charge mode. If the battery voltage is unable to rise due to a battery failure, charging will remain in the tricklecharge mode. When the battery voltage reaches the 2.7V threshold, the MC34671 softly changes to the CC-mode. The soft transition minimizes the input voltage drop and reduces the requirement of the input decoupling capacitance. In the fast-charge mode, the FAST pin outputs a low voltage. When the battery voltage reaches 4.2V, the MC34671 enters the CV-mode and regulates the output voltage at 4.2V. The charge current decreases gradually in the CV-mode. When the current drops to the EOC current threshold, the MC34671 Trickle Constant Current ITRKL 1. VIN > VOVP 2. VIN - VBAT < VOS 3. EN pin is high where VOS is the offset voltage for the comparator that monitors the input and the battery voltages. Figure 22 shows the complete charge-cycle state diagram. ILOAD >ICHG Constant Voltage 4.2V ICHG 2.7V After the charging is completed, the MC34671 continues to regulate the output to 4.2V, and monitors the output voltage. If a load is in parallel with the battery, the charger continues to output the current to the load even the charge is completed. If the load current exceeds the programmed CCmode current, the battery will supply the additional current to the load and the battery voltage will decline. Once the battery voltage drops below the recharge voltage threshold, the MC34671 returns to the fast-charge mode and indicates a low voltage at the CHG pin. When one of the following three conditions happens, the MC34671 is disabled. Charge Voltage 100mV Charge Current IEOC TIME CHG TIME FAST TIME Figure 21. Charge Profile CHARGE CURRENT SETTING An external resistor between the ISET pin and the ground programmes the CC-mode current with the following equation: 2667 I CHG = --------------------------R ISET + 96 equ. 2 where RISET is the resistor between the ISET pin and ground in Ω. In addition, the current out of the ISET pin is proportional to the charge current. The system may measure the ISET pin 34671 14 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES voltage to monitor the actual charge current as given in equ. 1 during the whole charging cycle. EN pin is driven to a high logic voltage, the charger is disabled. CHARGE CURRENT LIMITATION INPUT POWER PRESENCE INDICATOR The charge current is limited by multiple factors. When the voltage difference between the input and the battery (VIN - VBAT) is low, (VIN - VBAT) / RDS(ON), where RDS(ON) is the on resistance of the power MOSFET, may be less than the programmed CC-mode current ICHG. The charge current is limited by (VIN - VBAT) / RDS(ON) in this case. When the voltage difference between the input and the battery is too high, the large power dissipation may lead to the charge current thermal foldback operation, due to the die temperature regulation. The charge current is reduced to prevent further temperature rise (See Charge Current Thermal Foldback for more information). When VIN is applied and the voltage is above the poweron-reset voltage threshold (VPOR), the PPR pin outputs a low voltage to indicate the input power presence. The PPR output is only controlled by the input voltage. All other functions, such as the EN pin, the over-voltage protection, and the VINBAT comparator, do not affect the PPR output. The PPR pin is capable to sink at least 12.0mA of current when outputting a low voltage to drive an external LED. DC INPUT VOLTAGE The MC34671 accepts up to 28V DC input. When all of the following conditions are satisfied, the input is in a power-good range for the charger to start charging. The conditions include: 1. VIN > VPOR 2. VIN - VBAT > VOS 3. VIN < VOVP where VOS is the offset voltage for the comparator that monitors the input and the battery voltages. The VOS is for preventing the reverse leakage current from the battery when the power supply is off. VOVP is the over-voltage protection threshold. When the DC input voltage is above the overvoltage protection threshold, the charger is disabled internally. The 28V input voltage rating eliminates the need of any additional input over-voltage protection circuitry. CHARGE-ENABLE INPUT The charge-enable input, EN, has a weak internal pulldown current. Driving it to a low logic voltage, leaving it floating, or shorting it to the ground, will enable the charger if the input voltage is in the power-good range. Whenever the CHARGE STATUS INDICATORS The MC34671 has two charge status indicators, CHG and FAST. CHG outputs a low voltage when the charger is enabled and the charging is in progress. When the charge cycle completes, CHG outputs high-impedance. If the charger is disabled or the input voltage is out of the powergood range, the CHG pin outputs high-impedance as well. The CHG pin has at least 12.0mA of current-sinking capability to drive an external LED, same as the PPR pin. FAST indicates whether the MC34671 is in the fast-charge mode or not. When the charger is on and the battery voltage is higher than the trickle-mode threshold, the charger enters the fast-charge mode and FAST outputs a low voltage. The open-drain FAST pin requires a pull-up resistor to output the logic signal. If the charger is in the trickle-charge mode or is disabled, or when the input voltage is out of the power-good range, the FAST pin outputs high-impedance. CHARGE CURRENT THERMAL FOLDBACK An internal thermal feedback loop begins to reduce the charge current when the die temperature reaches 110°C to prevent further temperature rise. This feature protects the MC34671 from over-temperature failures and allows the user to push the limits of the power handling capability of a given circuit board without the risk of damaging the MC34671. The charge current can be programmed according to the typical (not the worst-case) ambient temperature with the assurance that the charger will automatically reduce the current in worstcase conditions. 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 15 FUNCTIONAL DEVICE OPERATION STATE DIAGRAM STATE DIAGRAM PWR OFF VIN<VPOR Charger: OFF VIN>VPOR EN=high or VIN>VOVP or VIN<VBAT+VOS SHUTDOWN Charger: OFF EN=low and VIN<VOVP and VIN>VBAT+VOS VBAT < 2.7V TRICKLE CHARGE VBAT > 2.7V Charger: ON VBAT < 2.7V FAST CHARGE Charger: ON VBAT=4.2V and IBAT < IEOC VBAT<4.10V CHARGE COMPLETE Charger: ON Figure 22. Charge Cycle State Diagram 34671 16 Analog Integrated Circuit Device Data Freescale Semiconductor TYPICAL APPLICATIONS INTRODUCTION TYPICAL APPLICATIONS INTRODUCTION INPUT CAPACITOR DROPOUT VOLTAGE The input capacitor is used to reduce the input voltage transient that may cause instability. A 1.0µF, X5R, 16V-rated ceramic capacitor is recommended for most applications. If the DC input voltage is too low, it may not maintain the programmed CC-mode charge current due to the voltage dropout over the power MOSFET. The worst-case of the RDS(ON) is 700mΩ. The input voltage should be at least higher than VBAT + ICHG x 700mΩ to guarantee the programmed CC-mode current. OUTPUT CAPACITOR For stable operation, an X5R ceramic capacitor with a minimum 2.2µF nominal value is recommended at the output. Depending on the load transient current, larger capacitance may be required. CC-MODE CURRENT SETTING The CC-mode current can be programmed by the external resistor, RISET. A 1% accuracy resistor is recommended to guarantee 5% a current accuracy. THERMAL CONSIDERATIONS The MC34671 is available in a tiny 2x3 thermallyenhanced UDFN package. A careful thermal design must be considered. The exposed pad needs to be well soldered to a large copper ground plane on the component layer. If the component layer is space limited and does not allow for a large copper plane, the thermal pad must be connected to other ground layers through a via array. This allows MC34671 to charge the battery with the maximum current, while minimizing the die temperature. APPLICATIONS STAND-ALONE CHARGER The MC34671 can be used in a stand-alone charger without MCUs. Figure 23 shows such an application. The Input 1µF GREEN 470 RED green LED indicates the power presence and the red LED indicates the charge status. In total, only 7 external components are required. BAT VIN GND 2.2µF MC34671 ISET 470 Li+ 5.23k CHG PPR FAST EN Figure 23. Standalone Li+ Battery Charger 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 17 TYPICAL APPLICATIONS APPLICATIONS MCU INTERFACED CHARGER When the charger is used in handheld systems with MCU control, the MC34671 uses PPR to report the DC input status to the MCU. After the MCU pulls the EN pin to a logic low Input VIN voltage to start charging, the MC34671 reports the charge status through CHG and FAST pins to the MCU. The MCU can also monitor the charge current by measuring the voltage at the ISET pin. Figure 24 is the typical application circuit. BAT 1µF 2.2µF Li+ VIO GND 100kx3 ISET CHG 5.23k MCU PPR FAST EN OFF ON Figure 24. MCU Interfaced Charger 34671 18 Analog Integrated Circuit Device Data Freescale Semiconductor TYPICAL APPLICATIONS PACKAGE DIMENSIONS PACKAGE DIMENSIONS For the most current package revision, visit www.freescale.com and perform a keyword search using the “98A” listed below. EP SUFFIX 8-PIN 98ASA10774D REVISION 0 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 19 TYPICAL APPLICATIONS PACKAGE DIMENSIONS EP SUFFIX 8-PIN 98ASA10774D REVISION 0 34671 20 Analog Integrated Circuit Device Data Freescale Semiconductor REVISION HISTORY REVISION HISTORY REVISION 1.0 DATE 1/2008 DESCRIPTION OF CHANGES • Initial Release 34671 Analog Integrated Circuit Device Data Freescale Semiconductor 21 How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. Technical Information Center, EL516 2100 East Elliot Road Tempe, Arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.com/support 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) www.freescale.com/support Japan: Freescale Semiconductor Japan Ltd. Headquarters ARCO Tower 15F 1-8-1, Shimo-Meguro, Meguro-ku, Tokyo 153-0064 Japan 0120 191014 or +81 3 5437 9125 firstname.lastname@example.org Asia/Pacific: Freescale Semiconductor Hong Kong Ltd. Technical Information Center 2 Dai King Street Tai Po Industrial Estate Tai Po, N.T., Hong Kong +800 2666 8080 email@example.com For Literature Requests Only: Freescale Semiconductor Literature Distribution Center P.O. Box 5405 Denver, Colorado 80217 1-800-441-2447 or 303-675-2140 Fax: 303-675-2150 LDCForFreescaleSemiconductor@hibbertgroup.com MC34671 Rev. 1.0 01/2008 Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductor products. There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. Freescale Semiconductor reserves the right to make changes without further notice to any products herein. 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