bq25070 SLUSA66 – JULY 2011 www.ti.com 1A, Single-Input, Single-Cell LiFePO4 Linear Battery Charger with 50mA LDO Check for Samples: bq25070 FEATURES • • • 1 • • • • • • • Single Cell LiFePO4 Charging Algorithm 30V Input Rating, With 10.5V Over-Voltage Protection (OVP) 50mA Integrated Low Dropout Linear Regulator (LDO) Programmable Charge Current Through Single Input Interface (CTRL) 7% Charge Current Regulation Accuracy Thermal Regulation and Protection Soft-Start Feature to Reduce Inrush Current Battery NTC Monitoring Charging Status Indication Available in Small 2mm × 3mm 10 Pin SON Package APPLICATIONS • • • • Smart Phones Mobile Phones Portable Media Players Low Power Handheld Devices DESCRIPTION The bq25070 is a highly integrated LiFePO4 linear battery charger targeted at space-limited portable applications. It operates from either a USB port or AC Adapter and charges a single-cell LiFePO4 battery with up to 1A of charge current. The 30V input voltage range with input over-voltage protections supports low-cost unregulated adapters. The bq25070 has a single power output that charges the battery and powers the system. The charge current is programmable up to 1A using the CTRL input. Additionally, a 4.9V ±10% 50mA LDO is integrated into the IC for supplying low power external circuitry. The LiFePO4 charging algorithm removes the constant voltage mode control usually present in Li-Ion battery charge cycles. Instead, the battery is fastcharged to the overcharge voltage and then allowed to relax to a lower float charge voltage threshold. The removal of the constant voltage control reduces charge time significantly. 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. 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. APPLICATION SCHEMATIC bq25070 USB or TA CHG VBUS GND D+ VGPIO R2 100 kW STATUS IN VDD OUT C1 0.1 mF C2 1 mF D- ABB CTRL BAT PACK+ TEMP TS IMON R1 1 kW PACK- GND VCHG DET LDO PWRPD C3 0.1 mF R5 1.5 kW R3 1.5 kW R4 1.5 kW USB DET VUSBIN ACDET GPIO 1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com 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. ORDERING INFORMATION (1) (1) PART NUMBER ILIM(DEF) VBAT(OVCH) VBAT(FLOAT) VOVP VLDO MARKING bq25070DQCR 300 mA 3.7 V 3.5 V 10.5 V 4.9 V QUS bq25070DQCT 300 mA 3.7 V 3.5 V 10.5 V 4.9 V QUS For the most current package and ordering information, see the Package Option Addendum at the end of this document, or visit the device product folder on ti.com (www.ti.com), ABSOLUTE MAXIMUM RATINGS (1) over operating free-air temperature range (unless otherwise noted) VALUE UNIT IN (with respect to GND) –0.3 to 30 V CTRL, TS (with respect to GND) –0.3 to 7 V Output Voltage BAT, OUT, LDO, CHG, IMON (with respect to GND) –0.3 to 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 Junction temperature, TJ –40 to 150 °C Storage temperature, TSTG –65 to 150 °C Input Voltage (1) 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 terminal unless otherwise noted. THERMAL INFORMATION bq25070 THERMAL METRIC (1) SON UNITS 10 PINS θJA Junction-to-ambient thermal resistance (2) 58.7 θJCtop Junction-to-case (top) thermal resistance (3) 3.9 (1) (2) (3) °C/W For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953. The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as specified in JESD51-7, in an environment described in JESD51-2a. The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific JEDEC-standard test exists, but a close description can be found in the ANSI SEMI standard G30-88. RECOMMENDED OPERATING CONDITIONS MIN VIN IN voltage range 3.75 28 IN operating voltage range 3.75 (1) 10.2 IIN Input current, IN IOUT Output Current in charge mode, OUT TJ Junction Temperature (1) 2 MAX (1) 1 0 UNITS V A 1 A 125 °C Charge current may be limited at low input voltages due to the dropout of the device. Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com 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 VUVLO Under-voltage lock-out VIN: 0 V → 4 V VHYS-UVLO Hysteresis on UVLO VIN: 4 V → 0 V VBATUVLO Battery UVLO VBAT rising VHYS-BUVLO Hysteresis on BAT UVLO VBAT falling VIN-SLP Valid input source threshold VIN-SLP above VBAT Input power good if VIN > VBAT + VIN-SLP VBAT = 3.6 V, VIN: 3.5 V → 4 V 30 75 150 mV VHYS-INSLP Hysteresis on VIN-SLP VBAT = 3.6 V, VIN: 4 V → 3.5 V 18 32 54 mV tDGL(NO-IN) Delay time, input power loss to charger turn-off Time measured from VIN: 5 V → 2.5 V 1μs fall-time VOVP Input over-voltage protection threshold VIN: 5 V → 11 V VHYS-OVP Hysteresis on OVP VIN: 11 V → 5 V tBLK(OVP) Input over-voltage blanking time tREC(OVP) Input over-voltage recovery time 250 1.95 2.05 2.15 125 10.5 V mV 32 10.2 V mV ms 10.8 V 100 mV 100 μs Time measured from VIN: 11 V → 5 V 1μs fall-time to LDO = HI, VBAT = 3.5 V 100 μs VIN = 0 V, VCHG = High, TS Enabled 120 QUIESCENT CURRENT IBAT(PDWN) IIN(STDBY) ICC Battery current into BAT, No input connected Standby current into IN pin Active supply current, IN pin VIN = 0 V, VCHG = Low, TS Disabled, TJ = 85°C 150 μA 6 μA CTRL = HI, VIN = 5.5V 0.25 CTRL = HI, VIN ≤ VOVP 0.5 CTRL = HI, VIN > VOVP 2 VIN = 6 V, No load on OUT pin, VBAT> VBAT(REG), IC enabled 3 mA mA BATTERY CHARGER FAST-CHARGE VBAT(REG) Battery float charge voltage VBAT(OVCH) Battery overcharge voltage threshold IIN(LIM) Input Current Limit (selected by CTRL interface) TA = 0°C to 125°C 3.465 3.5 3.535 TA = 25°C 3.465 3.5 3.529 3.62 3.7 3.78 4 pulses on CTRL 87 93 100 5 pulses on CTRL 174 187 200 6 pulses on CTRL 261 280 300 7 pulses on CTRL 348 374 400 8 pulses on CTRL 435 467 500 9 pulses on CTRL 608 654 700 10 pulses on CTRL 739 794 850 11 pulses on CTRL 869 935 1000 500 1400 VDO(IN-OUT) VIN – VOUT VIN = 3.5 V, IOUT = 0.75 A KIMON Input current monitor ratio KIMON = IIMON / ICHG, RIMON = 1kΩ, Current programmed using CTRL VIMON(MAX) Maximum IMON voltage IMON open IMON Accuracy 1 1.2 V V mA mV mA / A 1.25 IIN < 100 mA –25% 25% IIN = 100 mA to 1 A –10% 10% V PRE-CHARGE AND CHARGE DONE VLOWV Pre-charge to fast-charge transition threshold tDGL1(LOWV) Deglitch time on pre-charge to fast-charge transition 25 ms tDGL2(LOWV) Deglitch time on fast-charge to pre-charge transition 25 ms Copyright © 2011, Texas Instruments Incorporated 2.4 2.5 2.6 V 3 bq25070 SLUSA66 – JULY 2011 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Over junction temperature range 0°C ≤ TJ ≤ 125°C and recommended supply voltage (unless otherwise noted) PARAMETER IPRECHARGE Precharge current to BAT during precharge mode TEST CONDITIONS VBAT = 0 V to 0.7 V MIN TYP MAX UNITS 41.5 45 48.5 mA 3.1 3.3 3.5 V RECHARGE OR REFRESH VRCH Recharge detection threshold VBAT falling tDGL(RCH) Deglitch time, recharge threshold detected VBAT falling to New Charge Cycle VLDO LDO Output Voltage VIN = 5 V to 10.5 V, ILDO = 0 mA to 50 mA ILDO Maximum LDO Output Current VDO Dropout Voltage 25 ms LDO 4.7 4.9 5.1 200 350 60 VIN = 4.5V, ILDO = 50mA V mA mV CTRL INTERFACE tCTRL_DGL CTRL Deglitch timer 5 tCTRL_LATCH CTRL Latch timer 2 tHI_MIN High Duration on CTRL 50 tLO_MIN Low Time Duration on CTRL 50 RPULLDOWN CTRL Pulldown Resistor ms ms 1000 1000 260 μs μs kΩ LOGIC LEVELS ON CTRL VIL Logic LOW input voltage VIH Logic HIGH input voltage 0.4 1.4 V V BATTERY-PACK NTC MONITOR (TS) VCOLD TS Cold Threshold VTS Rising 24.5 25 12 12.5 25.5 VCUTOFF TS Cold Cutoff Threshold VTS Falling VHOT TS Hot Threshold VTS Falling VHOT_HYS TS Hot Cutoff Threshold VTS Rising tdgl(TS) Deglitch for TS Fault Fault detected on TS to stop charge VOL Output LOW voltage ISINK = 1 mA IIH Leakage current CHG = 5 V tFLSH(TS) TS fault flash period 50% Duty Cycle, TS out of valid range 100 ms 1 %VLDO %VLDO 13 %VLDO 1 %VLDO 25 ms CHG OUTPUT 0.45 1 V 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 4 Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com TYPICAL CHARACTERISTICS VIN = 5 V, VBAT = 3.2 V, ICHG = 280 mA, Typical Application Circuit 5V/div VCTRL 5V/div VIN 5V/div VLDO 5V/div VLDO 200mA/div 200mA/div IOUT IOUT 2V/div 2V/div VCHG VCHG VCTRL = 0V 10ms/div 20ms/div G002 G001 Figure 1. Adapter Plug-In With Battery Connected Figure 2. Charger Enable Using CTRL 5V/div VCTRL 2V/div 5V/div VLDO VCTRL 200mA/div IOUT 500mA/div 2V/div VCHG IOUT 400μs/div 4ms/div G003 Figure 3. Charger Disable Using CTRL G004 Figure 4. Default to 1A Transition Using CTRL VIN = 5V to 12V 5V/div VIN 5V/div VLDO 1A/div IOUT 2V/div VCHG 40μs/div G005 Figure 5. OVP Fault Copyright © 2011, Texas Instruments Incorporated 5 bq25070 SLUSA66 – JULY 2011 www.ti.com TYPICAL CHARACTERISTICS (continued) VIN = 5 V, VBAT = 3.2 V, ICHG = 280 mA, Typical Application Circuit VOLTAGE and CURRENT vs ELAPSED TIME 4 1.6 3.5 1.4 1.2 1 2.5 2 0.8 1.5 0.6 1 0.4 0.5 0.2 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 25 50 75 Temperature (°C) Figure 7. BATTERY REGULATION VOLTAGE vs CHARGE CURRENT OVP THRESHOLD vs TEMPERATURE 3.54 10.58 3.53 10.56 3.52 3.51 3.5 3.49 3.48 10.5 10.46 10.42 0.3 0.4 0.5 0.6 0.7 Charge Current (A) 0.8 0.9 10.4 1 G007 10.48 10.44 0.2 125 10.52 3.46 0.1 100 10.54 3.47 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 0 Figure 6. Complete Charge Cycle 10.6 0 VIN = 4.5V IOUT = 1A G006 3.55 3.45 Charge Current (A) 0 4:48:00 1:12:00 2:24:00 3:36:00 Elapsed Time (hh:mm:ss) OVP Threshold (V) Battery Regulation Voltage (V) 0 0:00:00 Dropout Voltage (V) IBAT 0 25 50 75 Temperature (°C) G008 100 125 G009 Figure 8. Figure 9. CHARGE CURRENT vs INPUT VOLTAGE INPUT CURRENT LIMIT vs BATTERY VOLTAGE 0.7 0.6 Input Current Limit (A) Voltage (V) VCHG Current (A) VBAT 3 Thermal Regulation VIN = 5V 100mA Current Limit 500mA Current Limit 0.5 0.4 0.3 0.2 0.1 5 6 7 8 Input Voltage (V) Figure 10. 6 DROPOUT VOLTAGE vs TEMPERATURE 9 10 G010 0 2.5 2.75 3 Battery Voltage (V) 3.25 3.5 G011 Figure 11. Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com SIMPLIFIED BLOCK DIAGRAM LDO + – Q1 Q2 IN OUT + Charge Pump IMON – 125°C TJ IIN(REG) 1.5V BAT – + VBAT(REG) – + VREF Charge Pump ILIM Overcharge Comparator VBAT – 3.7V + Sleep Comparator CTRL 260kΩ VLDO OVP Comparator + VOVP – VIN Charge Control – 75mV VBAT + Digital Decode VIN CHG Status Output Disable + TS Cold – + TS Hot – TS GND Copyright © 2011, Texas Instruments Incorporated 7 bq25070 SLUSA66 – JULY 2011 www.ti.com PIN CONFIGURATION (Top View) IN 1 10 OUT IMON 2 9 GND GND 3 8 CHG bq25070 LDO 4 7 CTRL TS 5 6 BAT 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 0.1μF ceramic capacitor. IMON 2 O Current monitoring output. Connect a 1kΩ resistor from IMON to GND to monitor the input current. The voltage at IMON ranges from 0V to 1V which corresponds to an input current from 0A to 1A. GND 3, 9 – Ground terminal. 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 50mA. Bypass LDO to GND with a 0.1μF ceramic capacitor. LDO is enabled when VUVLO < VIN < VOVP. 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 Applications Design section for details on the selecting the proper component values. BAT 6 O Battery connection output. BAT is the sense input for the battery. Connect BAT and OUT to the battery and bypass to GND with a 1μF ceramic capacitor. CTRL 7 I Single-input interface Input. Drive CTRL with pulses to enable/disable the device, enable/disable VIN-DPM, and select current limits. See the interface section for details on using the CTRL 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. Connect OUT and BAT together. Bypass the OUT and BAT connection to GND with a 1μF ceramic capacitor. Pad – 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 8 Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com APPLICATIONS CIRCUITS VGPIO R2 100 kW USB or TA STATUS CHG IN VBUS GND OUT C1 0.1 mF D+ D- VDD C2 1 mF ABB bq25070 CTRL BAT PACK+ TEMP TS IMON R1 1 kW PACK- GND VCHG DET LDO PWRPD C3 0.1 mF R5 1.5 kW USB DET R3 1.5 kW R4 1.5 kW VUSBIN ACDET GPIO Figure 12. bq25070 Typical Application Circuit Copyright © 2011, Texas Instruments Incorporated 9 bq25070 SLUSA66 – JULY 2011 www.ti.com DETAILED FUNCTIONAL DESCRIPTION The bq25070 is a highly integrated LiFePO4 linear battery charger targeted at space-limited portable applications. It operates from either a USB port or AC Adapter and charges a single-cell LiFePO4 battery with up to 1A of charge current. The 30V input voltage range with input over-voltage protections supports low-cost unregulated adapters. The LiFePO4 charging algorithm removes the constant voltage mode control usually present in Li-Ion battery charge cycles. Instead, the battery is charged with the fastcharge current to the overcharge voltage and then allowed to relax to a lower float charge voltage threshold. The removal of the constant voltage control reduces charge time significantly. 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. The charger power stage and charge current sense functions are fully integrated. The charger function has high accuracy voltage and current regulation loops, and charge status display. CHARGING OPERATION The bq25070 uses a charge algorithm that is unique to LiFePO4 chemistry cells. The constant voltage mode control usually present in Li-Ion battery charge cycles is eliminated. This dramatically decreases the charge time. When the bq25070 is enabled by CTRL, the battery voltage is monitored to verify which stage of charging must be used. When VBAT < VLOWV, the bq25070 charges in precharge mode; when VBAT > VLOWV, the normal charge cycle is used. 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 13. Typical Charging Cycle with Minimum System Voltage Enabled Precharge Mode (VBAT ≤ VLOWV) The bq25070 enters precharge mode when VBAT ≤ VLOWV. Upon entering precharge mode, the battery is charged with a 47.5mA current and CHG goes low. 10 Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com Fast Charge Mode Once VBAT > VLOWV, the bq25070 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 bq25070 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 VREC, the charge cycle restarts. CHARGE CURRENT TRANSLATOR (IMON) When the charger is enabled, internal circuits generate a current proportional to the charge current at the IMON input. The current out of IMON is 1/1000 (±10%) of the charge current. This current, when applied to the external charge current programming resistor, R1 (Figure 12), generates an analog voltage that can be monitored by an external host to calculate the current sourced from BAT. Connect a 1kΩ resistor from IMON to GND. The voltage at IMON is calculated as: VIMON = IIN ´ 1 V A (1) INPUT OVER VOLTAGE PROTECTION The bq25070 contains an input over voltage protection circuit that disables the LDO output and charging when the input voltage rises above VOVP. This prevents damage from faulty adapters. The OVP circuitry contains an 115μs deglitch that prevents ringing on the input from line transients from tripping the OVP circuitry falsely. If an adapter with an output greater than VOVP is plugged in, the IC completes soft-start power up and then shuts down if the voltage remains above VOVP after 115μs. The LDO remains off and charging remains disabled until the input voltage falls below VOVP. UNDER-VOLTAGE LOCKOUT (UVLO) The bq25070 remains in power down mode when the input voltage is below the under-voltage lockout threshold (VUVLO). During this mode, the control input (CTRL) 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 VUVLO, the internal circuitry is turned on and the normal operating procedures are followed. EXTERNAL NTC MONITORING (TS) The bq25070 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 over-temperature conditions. During charging, the voltage at TS is continuously monitored. If, at any time, the voltage at TS is outside of the operating range (VCOLD to VHOT), charging is suspended. When the voltage measured at TS returns to within the operation window, charging is resumed. When charging is suspended due to a battery pack temperature fault, 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 14 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) (2) R2 = -RHOT ´ RCOLD ´ (0.125 - 0.250) RHOT ´ 0.250 ´ (0.125 - 1) + RCOLD ´ 0.125 ´ (1 - 0.250) (3) RHOT is the expected thermistor resistance at the programmed hot threshold; RCOLD is the expected thermistor resistance at the programmed cold threshold. Copyright © 2011, Texas Instruments Incorporated 11 bq25070 SLUSA66 – JULY 2011 www.ti.com LDO R1 VCOLD TS PACK+ TEMP + VHOT R2 PACK- + bq25070 For applications that do not require the TS monitoring function, set R1 = 490kΩ and R2 = 100kΩ to set the TS voltage at a valid level and maintain charging. Figure 14. NTC Monitoring Function 50 mA LDO (LDO) The LDO output of the bq25070 is a low dropout linear regulator (LDO) that supplies up to 50mA while regulating to VLDO. The LDO is active whenever the input voltage is above VUVLO and below VOVP. It is not affected by the CTRL input. The LDO output is used to power and protect circuitry such as USB transceivers from transients on the input supply. CHARGE STATUS INDICATOR (CHG) The bq25070 contains an open drain CHG output that indicates when charge cycles 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. The CHG output goes low during battery recharge cycles to signal the host. Additionally, CHG notifies the host if a NTC temperature fault has occurred. CHG pulses with a period of 100ms and a 50% duty cycle if a TS faults occurs. Connect CHG to the required logic level voltage through a 1kΩ to 100kΩ resistor to use the signal with a microprocessor. ICHG must be below 5mA. 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. SINGLE INPUT INTERFACE (CTRL) CTRL is used to enable/disable the device as well as select the input current limit, enable/disable charge, extend the TS operation range and disable VIN-DPM mode. CTRL is pulled low to enable the device. After the 50μs deglitch expires, the IC enters the 32ms WAIT state. CTRL may be used to program the bq25070 during this time. Once tWAIT expires, the IC starts up. If no command is sent to CTRL during tWAIT, the IC starts up with a default 285mA current limit. Programming the different modes is done by pulsing the CTRL input. See Table 1 for a map of the different modes. The width of the CTRL pulses is unimportant as long as they are between 50μs and 1000μs long. The time between pulses must be between 50μs and 1000μs to be properly read. Once CTRL is held low for 2ms, the number of pulses is passed to the control logic and decoded and then the mode changes. To ensure proper operation, do not send more than 16 pulses in one programming cycle. 12 Copyright © 2011, Texas Instruments Incorporated bq25070 SLUSA66 – JULY 2011 www.ti.com Table 1. Pulse Counting Map for CTRL Interface # of Pulses Current Limit 1 No Change 2 No Change 3 No Change 4 93 mA 5 187 mA 6 280 mA 7 374 mA 8 467 mA 9 654 mA 10 794 mA 11 935 mA >11 No Change If, at any time, the CTRL input is held high for more than 2ms, the IC is disabled. When disabled, charging is suspended and the bq25070 input quiescent current is reduced. IC disabled if CTRL pulled high for >2.0ms # of pulses decoded once CTRL pulled low for 2.0ms IC can be programmed during tWAIT tHI 2.0ms 2.0ms CTRL tCTRL_DGL tCTRL_LATCH 2.0ms tCTRL_LATCH tCTRL_LATCH tLO Power up with default 285mA current limit 475mA current limit programmed 190mA current limit programmed IIN Figure 15. CTRL Timing Diagram THERMAL REGULATION AND THERMAL SHUTDOWN The bq25070 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 over-temperature 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 bq25070. 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. Copyright © 2011, Texas Instruments Incorporated 13 bq25070 SLUSA66 – JULY 2011 www.ti.com APPLICATION INFORMATION SELECTION OF INPUT/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 0.1μF 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 bq25070 requires a capacitor from OUT to GND for loop stability. Connect a 1μF ceramic capacitor from BAT to GND close to the pins for best results. More output capacitance may be required to minimize the output droop during large load transients. The LDO also requires an output capacitor for loop stability. Connect a 0.1μF ceramic capacitor from LDO to GND close to the pins. For improved transient response, this capacitor may be increased. THERMAL CONSIDERATIONS The bq25070 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 (4) 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 13. 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. PCB LAYOUT CONSIDERATIONS 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 bq25070, with short trace runs to both IN, OUT and GND (thermal pad). 14 Copyright © 2011, Texas Instruments Incorporated bq25070 www.ti.com • • • SLUSA66 – JULY 2011 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 bq25070 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). Copyright © 2011, Texas Instruments Incorporated 15 PACKAGE OPTION ADDENDUM www.ti.com 15-Jul-2011 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Qty Eco Plan (2) Lead/ Ball Finish MSL Peak Temp (3) BQ25070DQCR ACTIVE WSON DQC 10 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR BQ25070DQCT ACTIVE WSON DQC 10 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Samples (Requires Login) (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. 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. 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Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 20-Aug-2012 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 BQ25070DQCR WSON DQC 10 3000 330.0 12.4 2.3 3.3 0.85 4.0 12.0 Q1 BQ25070DQCT WSON DQC 10 250 180.0 12.4 2.3 3.3 0.85 4.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 20-Aug-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) BQ25070DQCR WSON DQC 10 3000 367.0 367.0 35.0 BQ25070DQCT 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 JESD46C and to discontinue any product or service per JESD48B. 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