Sample & Buy Product Folder Support & Community Tools & Software Technical Documents bq25071 SLUSBK6 – JULY 2014 bq25071 1-A, Single-Input, Single-Cell LiFePO4 Linear Battery Charger with 50 mA LDO 1 Features 3 Description • • The bq25071 is a highly integrated, linear, LiFePO4 battery charger targeted at space-limited portable applications. It accepts power from either a USB port or AC adapter and charges a single-cell LiFePO4 battery with up to 1 A of charge current. The 30 V input rating with 10.5 V input overvoltage protection supports low-cost unregulated adapters. 1 • • • • • • • Single Cell LiFePO4 Charging Algorithm 30V Input Rating, With 10.5 V Overvoltage Protection (OVP) 50mA Integrated Low Dropout Linear Regulator (LDO) Programmable Charge Current Through ISET and EN Terminals 7% Charge Current Regulation Accuracy Thermal Regulation and Protection Soft-Start Feature to Reduce Inrush Current Battery NTC Monitoring Charging Status Indication The bq25071 has a single power output that simultaneously charges the battery and powers the system. The input current is programmable from 100 mA up to 1 A using the ISET input or configurable for USB500. There is also a 4.9 V ±10% 50 mA LDO integrated into the IC for supplying low power external circuitry. The LiFePO4 charging algorithm removes the current taper typically seen as part of the constant voltage mode control used in Li-Ion battery charge cycles which reduces charge time significantly. Instead, the battery is fast charged to the overcharge voltage and then allowed to relax to a lower float charge voltage threshold. The charger integrates the power stage with the charge current and voltage sense to achieve a high level of accuracy in the current and voltage regulation loops. An internal control loop monitors the IC junction temperature through the charge cycle and reduces the charge current if an internal temperature threshold is exceeded. 2 Applications • • • • Smart Phones Mobile Phones Portable Media Players Low Power Handheld Devices Device Information(1) PART NUMBER PACKAGE BODY SIZE (NOM) bq25071 WSON (10) 2.00mm x 3.00mm (1) For all available packages, see the orderable addendum at the end of the datasheet. 4 Application Schematic Pull-Up bq25071 STATUS USB or TA CHG VBUS GND IN VDD OUT D+ D- ABB EN BAT PACK+ TS TEMP ISET PACK- GND LDO PWRPD VCHG DET USB DET VUSBIN ACDET GPIO 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. bq25071 SLUSBK6 – JULY 2014 www.ti.com Table of Contents 1 2 3 4 5 6 7 8 9 Features .................................................................. Applications ........................................................... Description ............................................................. Application Schematic .......................................... Revision History..................................................... Device Comparison Table..................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 1 2 3 3 4 8.1 8.2 8.3 8.4 8.5 8.6 8.7 4 4 4 4 5 6 7 Absolute Maximum Ratings ..................................... Handling Ratings....................................................... Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Timing Requirements ................................................ Typical Characteristics .............................................. 9.1 9.2 9.3 9.4 Overview ................................................................... 8 Functional Block Diagram ......................................... 9 Feature Description................................................. 10 Device Functional Modes........................................ 12 10 Application and Implementation........................ 14 10.1 Application Information.......................................... 14 10.2 Typical Application ............................................... 14 11 Power Supply Recommendations ..................... 17 12 Layout................................................................... 17 12.1 Layout Guidelines ................................................. 17 12.2 Layout Example .................................................... 17 13 Device and Documentation Support ................. 19 13.1 Trademarks ........................................................... 19 13.2 Electrostatic Discharge Caution ............................ 19 13.3 Glossary ................................................................ 19 14 Mechanical, Packaging, and Orderable Information ........................................................... 19 Detailed Description .............................................. 8 5 Revision History 2 DATE REVISION NOTES July 2014 * Initial release. Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 6 Device Comparison Table PART NUMBER VBAT(OVCH) VBAT(FLOAT) V(OVP) V(LDO) bq25071DQCR 3.7 V 3.5 V 10.5 V 4.9 V bq25071DQCT 3.7 V 3.5 V 10.5 V 4.9 V 7 Pin Configuration and Functions bq25071 (TOP VIEW) IN 1 10 OUT 2 9 GND GND 3 8 CHG LDO 4 7 EN TS 5 6 BAT ISET 10 -pin 2mm x 3mm DFN Pin Functions PIN NAME NO. I/O DESCRIPTION IN 1 I Input power supply. IN is connected to the external DC supply (AC adapter or USB port). Bypass IN to GND with at least a 0.1 μF ceramic capacitor. ISET 2 O Input current programming bias pin. Connect a resistor from ISET to GND to program the input current limit when the user programmable mode is selected by grounding the EN pin. The resistor range is between 1 kΩ and 10 kΩ to set the current between 100 mA and 1 A. GND 3, 9 – Ground pin. Connect to the thermal pad and the ground plane of the circuit. LDO 4 O LDO output. LDO is regulated to 4.9V and drives up to 50 mA. Bypass LDO to GND with a 0.1 μF ceramic capacitor. LDO is enabled when V(UVLO) < VIN < V(OVP). TS 5 I Battery pack NTC monitoring input. Connect a resistor divider from LDO to GND with TS connected to the center tap to set the charge temperature window. The battery pack NTC is connected in parallel with the bottom resistor of the divider. See the Detailed Design Procedure section for details on the selecting the proper component values. BAT 6 I BAT is the sense input for the battery voltage. Connect BAT and OUT to the battery. EN 7 I Enable input. Drive EN high to disable the IC. Connect EN to GND to place the bq25071 in the user programmable mode using the ISET input where the input current is programmed. Leave EN floating to place the bq25071 in USB500 mode. See the Input Current Limit Control (EN) section for details on using the EN interface. CHG 8 O Charge status indicator open-drain output. CHG is pulled low while the device is charging the battery. CHG goes high impedance when the battery is fully charged. OUT 10 O System output connection. Bypass the OUT to GND with a 1 μF ceramic capacitor. Connect OUT and BAT together. – There is an internal electrical connection between the exposed thermal pad and the GND pin of the device. The thermal pad must be connected to the same potential as the GND pin on the printed circuit board. Do not use the thermal pad as the primary ground input for the device. GND pin must be connected to ground at all times. Thermal Pad Pad Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 3 bq25071 SLUSBK6 – JULY 2014 www.ti.com 8 Specifications 8.1 Absolute Maximum Ratings (1) over operating free-air temperature range (unless otherwise noted) Input Voltage MIN MAX UNIT IN (with respect to GND) –0.3 30 V EN, TS (with respect to GND) –0.3 7 V Output Voltage BAT, OUT, LDO, CHG, ISET (with respect to GND) –0.3 7 V Input Current (Continuous) IN 1.2 A Output Current (Continuous) BAT 1.2 A Output Current (Continuous) LDO 100 mA Output Sink Current CHG 5 mA 150 °C Junction temperature, TJ (1) –40 Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. All voltage values are with respect to the network ground pin unless otherwise noted. 8.2 Handling Ratings TSTG VESD (1) (2) MIN MAX UNIT –65 150 °C Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins (1) 0 3000 Charged device model (CDM), per JEDEC specification JESD22-C101, all pins (2) 0 1000 Storage temperature Electrostatic discharge V V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 8.3 Recommended Operating Conditions MIN VIN IN voltage 3.75 28 IN operating voltage 3.75 (1) 10.2 IIN Input current, IN IOUT Output Current in charge mode, OUT TJ Junction Temperature (1) MAX (1) UNITS V 1 0 A 1 A 125 °C Charge current may be limited at low input voltages due to the dropout of the device. 8.4 Thermal Information THERMAL METRIC (1) bq25071 DQC (10 PINS) RθJA Junction-to-ambient thermal resistance 61.6 RθJC(top) Junction-to-case (top) thermal resistance 65.5 RθJB Junction-to-board thermal resistance 22.8 ψJT Junction-to-top characterization parameter 1.5 ψJB Junction-to-board characterization parameter 22.7 RθJC(bot) Junction-to-case (bottom) thermal resistance 5.5 (1) 4 UNIT °C/W For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953. Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 8.5 Electrical Characteristics Over junction temperature range 0°C ≤ TJ ≤ 125°C and recommended supply voltage (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 3.15 3.30 3.55 UNITS INPUT V(UVLO) Under-voltage lock-out VIN: 0 V → 4 V VHYS(UVLO) Hysteresis on V(UVLO) VIN: 4 V → 0 V VIN(SLP) Valid input source threshold VIN(SLP) above VBAT Input power good if VIN > VBAT + VIN(SLP) V(BAT) = 3.6 V, VIN: 3.5 V → 4 V 30 75 150 mV VHYS(INSLP) Hysteresis on VIN(SLP) V(BAT) = 3.6 V, VIN: 4 V → 3.5 V 18 32 54 mV tDGL(NO-IN) Delay time, input power loss to charger turnoff Time measured from VIN: 5 V → 2.5 V 1 μs fall-time VOVP Input over-voltage protection threshold VIN: 5 V → 11 V VHYS(OVP) Hysteresis on OVP VIN: 11 V → 5 V 250 32 10.2 10.5 V mV ms 10.8 100 V mV QUIESCENT CURRENT IBAT(PDWN) Battery current into BAT, No input connected VIN = 0 V (1), V(CHG) = Low, TJ = 85°C 6 EN = HI, VIN = 5.5V IIN(STDBY) Standby current into IN pin μA 0.25 EN = HI, VIN ≤ V(OVP) 0.5 EN = HI, VIN > V(OVP) 2 mA BATTERY CHARGER FAST-CHARGE TA = 0°C to 125°C, IOUT = 50 mA 3.455 3.5 3.545 TA = 25°C 3.455 3.5 3.539 3.62 3.7 VBAT(REG) Battery charge regulation voltage VBAT(OVCH) Battery overcharge voltage threshold IIN(RANGE) User programmable input current limit range IIN(LIM) Input current limit, or fast-charge current KISET Fast charge current factor R(ISET) = 1 kΩ to 10 kΩ, EN = VSS VDO(IN-OUT) VIN – VOUT VIN = 3.55 V, IOUT = 0.75 A R(ISET) = 1 kΩ to 1 0kΩ, EN = VSS 100 EN = FLOAT 435 EN = VSS 467 3.78 V 1000 mA 500 KISET/RISET 900 V mA 1000 1100 AΩ 500 900 mV 430 700 Ω 1.07 2 A ISET SHORT CIRCUIT PROTECTION RISET(MAX) Highest resistor value considered a short fault IOUT(CL) Maximum OUT current limit regulation (Clamp) R(ISET): 900 Ω → 300 Ω, IOUT latches off, Cycle power to reset, Fault range > 1.10 A PRE-CHARGE AND CHARGE DONE V(LOWV) Pre-charge to fast-charge transition threshold I(PRECHARGE) Precharge current to BAT during precharge mode V(BAT) = 0 V to 0.7 V 0.5 0.7 0.9 V 41.5 45 48.5 mA RECHARGE OR REFRESH V(RCH) Recharge detection threshold V(BAT) falling 3.1 3.3 3.5 V V(LDO) LDO Output Voltage VIN = 5 V to 10.5 V, I(LDO) = 0 mA to 50 mA 4.7 4.9 5.1 V I(LDO) Maximum LDO Output Current V(DO) Dropout Voltage 200 350 LDO (1) 60 VIN = 4.5V, I(LDO) = 50 mA mA mV Force V(CHG) Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 5 bq25071 SLUSBK6 – JULY 2014 www.ti.com Electrical Characteristics (continued) Over junction temperature range 0°C ≤ TJ ≤ 125°C and recommended supply voltage (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNITS LOGIC LEVELS ON EN VIL Logic low input voltage VIH Logic high input voltage 1.4 0.4 V(FLT) Logic FLOAT input voltage 600 I(FLTlkg) Maximum leakage sink or source current to keep in FLOAT IEN(DRIVE) Minimal drive current from an external device for Low or High V V 850 1100 mV 1 µA 8 µA BATTERY-PACK NTC MONITOR (TS) V(COLD) TS Cold Threshold V(TS) Rising V(CUTOFF) TS Cold Cutoff Threshold V(TS) Falling V(HOT) TS Hot Threshold V(TS) Falling VHOT(HYS) TS Hot Cutoff Threshold V(TS) Rising VOL Output LOW voltage I(SINK) = 1 mA IIH Leakage current CHG = 5 V 24.5 25 12 12.5 25.5 1 %VLDO %VLDO 13 1 %VLDO %VLDO CHG OUTPUT 0.45 V 1 μA THERMAL REGULATION TJ(REG) Temperature Regulation Limit TJ rising 125 °C TJ(OFF) Thermal shutdown temperature TJ rising 155 °C TJ(OFF-HYS) Thermal shutdown hysteresis TJ falling 20 °C 8.6 Timing Requirements MIN TYP MAX UNIT INPUT tBLK(OVP) tREC(OVP) 100 μs Time measured from VIN: 11 V → 5 V 1 μs fall-time to LDO = HI, V(BAT) = 3.5 V 100 μs Clear fault by cycling V(BUS) or EN 1.5 ms Input overvoltage blanking time Input overvoltage recovery time ISET SHORT CIRCUIT PROTECTION tDGL(SHORT) Deglitch time transition from I(SET) short to IOUT disable PRE-CHARGE AND CHARGE DONE tDGL1(LOWV) Deglitch time on pre-charge to fastcharge transition 25 ms tDGL2(LOWV) Deglitch time on fast-charge to precharge transition 25 ms V(BAT) falling to New Charge Cycle 25 ms Fault detected on TS to stop charge 25 ms RECHARGE OR REFRESH tDGL(RCH) Deglitch time, recharge threshold detected BATTERY-PACK NTC MONITOR (TS) tdgl(TS) 6 Deglitch for TS Fault Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 8.7 Typical Characteristics 4 1.6 3.5 1.4 V(BAT) V(CHG) I(BAT) 1.2 1 2.5 2 0.8 1.5 0.6 1 0.4 0.5 0.2 0 0:00:00 Current (A) Voltage (V) 3 Dropout Voltage (V) VIN = 5 V, VBAT = 3.2 V, I(CHG) = 280 mA, Typical Application Circuit 0 4:48:00 1:12:00 2:24:00 3:36:00 Elapsed Time (hh:mm:ss) 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 25 50 75 Temperature (°C) VIN = 4.5 V 10.6 3.54 10.58 3.53 10.56 3.52 3.51 3.5 3.49 3.48 10.52 10.5 10.48 10.46 10.44 3.46 10.42 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Charge Current (A) 0.8 0.9 10.4 1 0 50 75 Temperature (°C) 100 125 G009 Figure 4. OVP Threshold vs Temperature 0.7 100mA Current Limit 500mA Current Limit 0.6 Input Current Limit (A) Charge Current (A) 25 G008 Figure 3. Battery Regulation Voltage vs Charge Current 1.1 1.05 1 0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 G007 IOUT = 1 A 10.54 3.47 3.45 125 Figure 2. Dropout Voltage vs Temperature 3.55 OVP Threshold (V) Battery Regulation Voltage (V) Figure 1. Voltage and Current vs Elapsed Time 100 Thermal Regulation 0.5 0.4 0.3 0.2 0.1 5 6 7 8 Input Voltage (V) 9 10 0 2.5 G010 2.75 3 Battery Voltage (V) 3.25 3.5 G011 VIN = 5 V Figure 5. Charge Current vs Input Voltage Figure 6. Input Current Limit vs Battery Voltage Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 7 bq25071 SLUSBK6 – JULY 2014 www.ti.com 9 Detailed Description 9.1 Overview The bq25071 is a highly integrated, linear, LiFePO4 battery charger targeted at space-limited portable applications. It accepts power from either a USB port or AC adapter and charges a single-cell LiFePO4 battery with up to 1 A of charge current. The 30 V input rating with 10.5 V input overvoltage protection supports low-cost unregulated adapters. The bq25071 has a single power output that simultaneously charges the battery and powers the system. The input current is programmable from 100 mA up to 1 A using the ISET input or configurable for USB500. There is also a 4.9 V ±10% 50 mA LDO is integrated into the IC for supplying low power external circuitry. The LiFePO4 charging algorithm removes the constant voltage mode control typically used in Li-Ion battery charge cycles which reduces charge time significantly. Instead, the battery is fast charged to the overcharge voltage and then allowed to relax to a lower float charge voltage threshold. The charger power stage and charge current sense functions are fully integrated. The charger function has high accuracy current and voltage regulation loops, and charge status display. During the charge cycle, an internal control loop monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is exceeded. 8 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 9.2 Functional Block Diagram LDO + Q2 Q1 OUT IN + TJ(REG) TJ Charge Pump IIN(REG) BAT + 1.5V VBAT(REG) + ISET VIN(SLP) ILIM + + Sleep Comparator + + VBAT VBAT(REG) OVP Comparator EN VBAT VIN UVLO Comparator VOVP VIN + ± VIN VUVLO Overcharge Comparator Charge Control CHG TS VLDO Status Output TS Cold + Disable + TS Hot Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 9 bq25071 SLUSBK6 – JULY 2014 www.ti.com 9.3 Feature Description 9.3.1 Input Overvoltage Protection The bq25071 contains an input overvoltage protection circuit that disables the LDO output and charging when the input voltage rises above V(OVP). This prevents damage from faulty adapters. The OVP circuitry contains an 100 μs blanking period that prevents ringing on the input from line transients from tripping the OVP circuitry falsely. If an adapter with an output greater than V(OVP) is plugged in, the IC completes soft-start power up and then shuts down if the voltage remains above V(OVP) after 100 μs. The LDO remains off and charging remains disabled until the input voltage falls below V(OVP). 9.3.2 Undervoltage Lockout (UVLO) The bq25071 remains in power down mode when the input voltage is below the undervoltage lockout threshold (V(UVLO)). During this mode, the control input (EN) is ignored. The LDO, the charge FET connected between IN and OUT are off and the status output (CHG) is high impedance. Once the input voltage rises above V(UVLO), the internal circuitry is turned on and the normal operating procedures are followed. 9.3.3 External NTC Monitoring (TS) The bq25071 features a flexible, voltage based external battery pack temperature monitoring input. The TS input connects to the NTC thermistor in the battery pack to monitor battery temperature and prevent dangerous overtemperature conditions. During charging, the voltage at TS is continuously monitored. If the voltage at the TS pin is outside of the operating range (V(HOT) to V(COLD) for longer than the built in 25 ms deglitch time, charging is suspended. When the voltage measured at TS returns to within the operation window, charging resumes. When a battery pack temperature fault occurs charging is suspended, but the CHG output remains low and continues to indicate charging. The temperature thresholds are programmed using a resistor divider from LDO to GND with the NTC thermistor connected to the center tap from TS to GND. See Figure 7 for the circuit example. The value of R1 and R2 are calculated using the following equations: -R2 ´ RHOT ´ (0.125 - 1) R1 = 0.125 ´ (R2 + RHOT) (1) R2 = -RHOT ´ RCOLD ´ (0.125 - 0.250) RHOT ´ 0.250 ´ (0.125 - 1) + RCOLD ´ 0.125 ´ (1 - 0.250) (2) RHOT is the expected thermistor resistance at the programmed hot threshold; RCOLD is the expected thermistor resistance at the programmed cold threshold. 10 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 Feature Description (continued) LDO R1 VCOLD TS PACK+ TEMP + VHOT R2 PACK- + bq25071 For applications that do not require the TS monitoring function, set R1 = 490 kΩ and R2 = 100 kΩ to set the TS voltage at a valid level and maintain charging. Figure 7. NTC Monitoring Function 9.3.4 50 mA LDO (LDO) The LDO output of the bq25071 is a low dropout linear regulator (LDO) that supplies up to 50 mA while regulating to V(LDO). The LDO is active whenever the input voltage is above V(UVLO) and below V(OVP). It is not affected by the EN input. The LDO output is used to power and protect circuitry such as USB transceivers from transients on the input supply. 9.3.5 Charge Status Indicator (CHG) The bq25071 contains an open drain CHG output that indicates charging state and faults. When charging a battery in precharge or fastcharge mode, the CHG output is pulled to GND. Once the BAT output reaches the overcharge voltage threshold, CHG goes high impedance to signal the battery is fully charged. When the battery voltage drops below the recharge voltage threshold the CHG output is pulled low to signal the host of a new charge cycle. Connect CHG to the required logic level voltage through a 1 kΩ to 100 kΩ resistor to use the signal with a microprocessor. I(CHG) must be below 5 mA. The IC monitors the CHG pin when no input is connected to verify if the system circuitry is active. If the voltage at CHG is logic being drive low when no input is connected, the TS circuit is turned off for a low quiescent current state. Once the voltage at CHG increases above logic high, the TS circuit is turned on. 9.3.6 Input Current Limit Control (EN) The bq25071 contains a 3-state that controls the input current limit. Drive EN low to program the input current limit to the user defined value programmed using ISET. Drive EN high to place the bq25071 in USB suspend mode. In USB suspend mode, the input current into bq25071 is reduced. Leaving EN unconnected or connected to a high impedance source programs the USB500 input current limit. Table 1. EN Input Definition EN MODE Low ISET Hi-Z USB500 Hi USB Suspend Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 11 bq25071 SLUSBK6 – JULY 2014 www.ti.com 9.4 Device Functional Modes 9.4.1 Charging Operation The bq25071 uses a charge algorithm that is unique to LiFePO4 chemistry cells. The current taper typically seen as part of the constant voltage mode control usually present in Li-Ion battery charge cycles is replaced with a floating regulation voltage with minimal charging current. This dramatically decreases the charge time. When the bq25071 is enabled by EN, the battery voltage is monitored to verify which stage of charging must be used. When V(BAT) < V(LOWV), the bq25071 charges in precharge mode; when V(BAT) > V(LOWV), the normal charge cycle is used. 9.4.1.1 Charger Operation with Minimum System Voltage Mode Enabled PRECHARGE Constant Current Fast Charge Float-Voltage Regulation VOUT(OVCH) VOUT(REG) IFASTCHG CHG = Hi -Z VLOWV IPRECHG Battery and Output Voltage Battery Current Figure 8. Typical Charging Cycle with Minimum System Voltage Enabled 9.4.1.2 Precharge Mode (V(BAT) ≤ V(LOWV)) The bq25071 enters precharge mode when VBAT ≤ V(LOWV). Upon entering precharge mode, the battery is charged with a 47.5 mA current and CHG goes low. 9.4.1.3 Fast Charge Mode Once V(BAT) > V(LOWV), the bq25071 enters constant current (CC) mode where charge current is regulated using the internal MOSFETs between IN and OUT. The total current is shared between the output load and the battery. Once the battery voltage charges up to VBAT(OVCH), the CHG output goes high indicating the charge cycle is complete and the bq25071 switches the battery regulation voltage to VBAT(REG). The battery voltage is allowed to relax down to VBAT(REG). The charger remains enabled and regulates the output to VBAT(REG). If at any time the battery falls below V(RCH), the charge cycle restarts. 12 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 Device Functional Modes (continued) 9.4.2 Programmable Input Current Limit (ISET) When the charger is enabled, and the user programmable current limit is selected by the EN input, internal circuits generate a current proportional to the input current at the ISET input. The current out of ISET is 1/1000 (±10%) of the charge current. This current, when applied to the external charge current programming resistor, R1 (Figure 9), generates an analog voltage that is regulated to program the fast charge current. Connect a resistor from ISET to GND to program the input current limit using the following equation: K (ISET) 1000A ´ W = I(IN_LIM) = R(ISET) R(ISET) (3) I(IN_LIM) is programmable from 100 mA to 1 A. The voltage at ISET can be monitored by an external host to calculate the charging current to the battery. The input current is related to the ISET voltage using the following equation: 1000 IIN = V(ISET) ´ R(ISET) (4) Monitoring the ISET voltage allows for the host to calculate the actual charging current and therefore perform more accurate termination. The input current to the system must be monitored and subtracted from the current into the bq25071 which is show by V(ISET). 9.4.3 Thermal Regulation and Thermal Shutdown The bq25071 contains a thermal regulation loop that monitors the die temperature continuously. If the temperature exceeds TJ(REG), the device automatically reduces the charging current to prevent the die temperature from increasing further. In some cases, the die temperature continues to rise despite the operation of the thermal loop, particularly under high VIN conditions. If the die temperature increases to TJ(OFF), the IC is turned off. Once the device die temperature cools by TJ(OFF-HYS), the device turns on and returns to thermal regulation. Continuous overtemperature conditions result in the pulsing of the load current. If the junction temperature of the device exceeds TJ(OFF), the charge FET is turned off. The FET is turned back on when the junction temperature falls below TJ(OFF) – TJ(OFF-HYS). Note that these features monitor the die temperature of the bq25071. This is not synonymous with ambient temperature. Self heating exists due to the power dissipated in the IC because of the linear nature of the battery charging algorithm. Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 13 bq25071 SLUSBK6 – JULY 2014 www.ti.com 10 Application and Implementation 10.1 Application Information The typical application circuit uses a single output which charges the battery and powers the system. Additionally a 50-mA LDO can supply a low power external circuit. The bq25071EVM-658 evaluation module (EVM) is a complete charger module for evaluating the bq25071. Refer to SLUUB49. 10.2 Typical Application VGPIO R2 100 kW bq25071 USB or TA STATUS CHG IN VBUS GND VDD OUT C1 0.1 mF D+ C2 1 mF D- EN ABB BAT PACK+ TEMP TS ISET R1 1 kW PACK- GND VCHG DET LDO PWRPD C2 0.1 mF R5 1.5 kW USB DET R3 1.5 kW VUSBIN ACDET R4 1.5 kW GPIO Figure 9. bq25071 Typical Application Circuit 10.2.1 Design Requirements Table 2. Design Parameters 14 PARAMETER EXAMPLE VALUE Input supply range 5 V ±5% Output voltage range 3.5 V Output current rating 1000 mA Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 10.2.2 Detailed Design Procedure 10.2.2.1 Selection of Input and Output Capacitors In most applications, all that is needed is a high-frequency decoupling capacitor on the input power pin. For normal charging applications, a 0.1 μF ceramic capacitor, placed in close proximity to the IN pin and GND pad works best. In some applications, depending on the power supply characteristics and cable length, it may be necessary to increase the input filter capacitor to avoid exceeding the OVP voltage threshold during adapter hot plug events where the ringing exceeds the deglitch time. The charger in the bq25071 requires a capacitor from OUT to GND for loop stability. Connect a 1 μF ceramic capacitor from OUT to GND close to the pins for best results. More output capacitance may be required to minimize the output drop during large load transients. The LDO also requires an output capacitor for loop stability. Connect a 0.1 μF ceramic capacitor from LDO to GND close to the pins. For improved transient response, this capacitor may be increased. 10.2.2.2 Thermal Considerations The bq25071 is packaged in a thermally enhanced QFN package. The package includes a thermal pad to provide an effective thermal contact between the IC and the printed circuit board (PCB). Full PCB design guidelines for this package are provided in the application note entitled: QFN/SON PCB Attachment Application Note (SLUA271). The most common measure of package thermal performance is thermal impedance (θJA) measured (or modeled) from the chip junction to the air surrounding the package surface (ambient). The mathematical expression for θJA is: Where: q JA = TJ - TA PD (5) TJ = chip junction temperature TA = ambient temperature PD = device power dissipation Factors that can greatly influence the measurement and calculation of θJA include: • Whether or not the device is board mounted • Trace size, composition, thickness, and geometry • Orientation of the device (horizontal or vertical) • Volume of the ambient air surrounding the device under test and airflow • Whether other surfaces are in close proximity to the device being tested The device power dissipation, PD, is a function of the charge rate and the voltage drop across the internal PowerFET. It can be calculated from the following equation when a battery pack is being charged: PD = (VIN – VOUT) × IOUT Due to the charge profile of LiFePO4 batteries the maximum power dissipation is typically seen at the beginning of the charge cycle when the battery voltage is at its lowest. See the charging profile, Figure 8. If the board thermal design is not adequate the programmed fast charge rate current may not be achieved under maximum input voltage and minimum battery voltage, as the thermal loop can be active, effectively reducing the charge current to avoid excessive IC junction temperature. Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 15 bq25071 SLUSBK6 – JULY 2014 www.ti.com 10.2.3 Application Curves 5V/div VIN 5V/div V(LDO) 200mA/div IOUT 2V/div V(CHG) 5V/div V(CTRL) 5V/div V(LDO) 200mA/div IOUT 2V/div V(CHG) 10ms/div 20ms/div V(CTRL) = 0 V Figure 11. Charger Enable Using EN Figure 10. Adapter Plug-In With Battery Connected 5V/div V(CTRL) 5V/div 5V/div V(LDO) 200mA/div VIN 5V/div V(LDO) IOUT 2V/div V(CHG) 1A/div IOUT 2V/div V(CHG) 400μs/div 40μs/div VIN = 5 V to 12 V Figure 12. Charger Disable Using EN 16 Submit Documentation Feedback Figure 13. OVP Fault Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 11 Power Supply Recommendations In a typical application, the system is powered by a USB port or USB wall adapter. The wide input voltage range supports low cost and unregulated adapters. The minimum input voltage - where the charging process starts with a reduced charging current - could be 3.75 V. The maximum supported input voltage is up to 10 V; the overvoltage protection kicks in at 10.5 V and the maximum input voltage rating is 30 V Input Rating. 12 Layout 12.1 Layout Guidelines It is important to pay special attention to the PCB layout. The following provides some guidelines: • To obtain optimal performance, the decoupling capacitor from IN to GND (thermal pad) and the output filter capacitors from OUT to GND (thermal pad) should be placed as close as possible to the bq25071, with short trace runs to both IN, OUT and GND (thermal pad). • All low-current GND connections should be kept separate from the high-current charge or discharge paths from the battery. Use a single-point ground technique incorporating both the small signal ground path and the power ground path. • The high current charge paths into IN pin and from the OUT pin must be sized appropriately for the maximum charge current in order to avoid voltage drops in these traces. • The bq25071 is packaged in a thermally enhanced SON package. The package includes a thermal pad to provide an effective thermal contact between the IC and the printed circuit board (PCB); this thermal pad is also the main ground connection for the device. Connect the thermal pad to the PCB ground connection. Full PCB design guidelines for this package are provided in the application note entitled: QFN/SON PCB Attachment Application Note (SLUA271). 12.2 Layout Example The bottom plane is a ground plane that is connected to the top through vias. Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 17 bq25071 SLUSBK6 – JULY 2014 www.ti.com Layout Example (continued) R1 0.1mF D1 USB or Adapter CHG VBUS GND D+ IN C3 1 mF OUT C4 C2 1 mF 0.1mF C2 22 mF D- bq25071 U1 EN BAT PACK+ TEMP TS R3 24.3kW R2 1 kW ISET R4 11.3kW PACK- GND LDO PWRPD C5 0.1mF Figure 14. Schematic 18 Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 bq25071 www.ti.com SLUSBK6 – JULY 2014 13 Device and Documentation Support 13.1 Trademarks All trademarks are the property of their respective owners. 13.2 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 13.3 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 14 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated Product Folder Links: bq25071 19 PACKAGE OPTION ADDENDUM www.ti.com 31-Jul-2014 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) BQ25071DQCR ACTIVE WSON DQC 10 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 85 25071 BQ25071DQCT ACTIVE WSON DQC 10 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR -40 to 85 25071 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 31-Jul-2014 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 18-Aug-2014 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant BQ25071DQCR WSON DQC 10 3000 180.0 8.4 2.25 3.25 1.05 4.0 8.0 Q1 BQ25071DQCT WSON DQC 10 250 180.0 8.4 2.25 3.25 1.05 4.0 8.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 18-Aug-2014 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) BQ25071DQCR WSON DQC 10 3000 210.0 185.0 35.0 BQ25071DQCT WSON DQC 10 250 210.0 185.0 35.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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