bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 1.5A USB-Friendly Li-Ion Battery Charger and Power-Path Management IC Check for Samples: bq24075T, bq24079T FEATURES Current Status Indication – Charging/Done, Power Good Small 3 mm × 3 mm 16 Lead QFN Package 1 • • • • • • • • • • • • Fully Compliant USB Charger Selectable 100mA and 500mA Maximum Input Current 100mA Maximum Current Limit Ensures Compliance to USB-IF Standard Input based Dynamic Power Management (VIN-DPM) for Protection Against Poor USB Sources 28V Input Rating with Overvoltage Protection Integrated Dynamic Power Path Management (DPPM) Function Simultaneously and Independently Powers the System and Charges the Battery Supports up to 1.5A Charge Current with Current Monitoring Output (ISET) Programmable Input Current Limit up to 1.5A for Wall Adapters Battery Disconnect Function with SYSOFF Input Reverse Current, Short-Circuit and Thermal Protection Flexible Voltage Based NTC Thermistor Input Proprietary Start Up Sequence Limits Inrush • • APPLICATIONS • • • • Smart Phones PDAs MP3 Players Low-Power Handheld Devices DESCRIPTION The bq2407xT series of devices are integrated Li-ion linear chargers and system power path management devices targeted at space-limited portable applications. The devices operate from either a USB port or AC adapter and support charge currents up to 1.5A. The input voltage range with input overvoltage protection supports unregulated adapters. The USB input current limit accuracy and start up sequence allow the bq2407xT to meet USB-IF inrush current specification. Additionally, the input dynamic power management (VIN-DPM) prevents the charger from crashing incorrectly configure USB sources. (Description continued on next page) 1 kW Adaptor IN DC GND CHG 9 PGOOD 7 1 kW SYSTEM OUT 10 13 11 1mF 4.7 mF bq24075T bq24079T 8 VSS EN2 5 BAT 2 3 14 TMR 16 I SET 4.7 mF 12 I LIM 4 CE 15 SYSOFF 6 EN1 System ON /OFF Control TS 1 TEMP PACK+ PACK- 1.18 kW 1.13 kW 13 kW 10 kW V IN 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 © 2009, Texas Instruments Incorporated bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. DESCRIPTION (CONTINUED) The bq2407xT features dynamic power path management (DPPM) that powers the system while simultaneously and independently charging the battery. The DPPM circuit reduces the charge current when the input current limit causes the system output to fall to the DPPM threshold; thus, supplying the system load at all times while monitoring the charge current separately. This feature reduces the number of charge and discharge cycles on the battery, allows for proper charge termination and enables the system to run with a defective or absent battery pack. Additionally, the regulated system input enables instant system turn-on when plugged in even with a totally discharged battery. The power-path management architecture also permits the battery to supplement the system current requirements when the adapter cannot deliver the peak system currents, enabling the use of a smaller adapter. The battery is charged in three phases: conditioning, constant current, and constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if the 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, charge status display, and charge termination. The input current limit and charge current are programmable using external resistors. ORDERING INFORMATION (2) VOVP VBAT(REG) VOUT(REG) VDPPM OPTIONAL FUNCTION MARKING bq24075TRGTR 6.6 V 4.2 V 5.5 V 4.3 V SYSOFF OEC bq24075TRGTT 6.6 V 4.2 V 5.5 V 4.3 V SYSOFF OEC bq24079TRGTR 6.6 V 4.1 V 5.5 V 4.3 V SYSOFF OED bq24079TRGTT 6.6 V 4.1 V 5.5 V 4.3 V SYSOFF OED PART NO. (1) (1) (2) 2 The RGT package is available in the following options: R – taped and reeled in quantities of 3,000 devices per reel. T – taped and reeled in quantities of 250 devices per reel. This product is RoHS compatible, including a lead concentration that does not exceed 0.1% of total product weight and is suitable for use in specified lead-free soldering processes. In addition, this product uses package materials that do not contain halogens, including bromine (BR) or antimony (Sb) above 0.1% of total product weight. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 ABSOLUTE MAXIMUM RATINGS (1) (2) over operating free-air temperature range (unless otherwise noted) VALUE / UNIT Input voltage Input current IN (with respect to VSS) –0.3 to 28 V BAT (with respect to VSS) –0.3V to 5V OUT, EN1, EN2, CE, TS, ISET, PGOOD, CHG, ILIM, VREF, ITERM, SYSOFF, TD (with respect to VSS) –0.3 TO 7 V IN 1.6 A OUT Output current (Continuous) Output sink current 5A BAT (Discharge mode) 5A BAT (Charging mode) 1.5A CHG, PGOOD 15 mA Junction temperature, TJ –40°C to 150°C Storage temperature, TSTG –65°C to 150°C (1) (2) 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. The IC operational charging life is reduced to 20,000 hours, when charging at 1.5A and 125°C. The thermal regulation feature reduces charge current if the IC’s junction temperature reaches 125°C; thus without a good thermal design the maximum programmed charge current may not be reached. DISSIPATION RATINGS PACKAGE RθJA RθJC TA < 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C QFN-16 RGT 39.47 °C/W 2.4°C/W 2.3 W 225 mW RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range (unless otherwise noted) MIN VIN MAX UNITS IN voltage range 4.35 26 V IN operating voltage range 4.35 6.4 V IIN Input current, IN pin 1.5 A IOUT Current, OUT pin 4.5 A IBAT Current, BAT pin (Discharging) 4.5 A ICHG Current, BAT pin (Charging) TJ Junction Temperature RILIM Maximum input current programming resistor RISET Fast-charge current programming resistor (2) RITERM Termination current programming resistor RTMR Timer programming resistor (1) (2) 1.5 (1) A 125 °C 1.07 7.5 kΩ 590 3000 Ω 0 15 kΩ 18 72 kΩ 0 The IC operational charging life is reduced to 20,000 hours, when charging at 1.5A and 125°C. The thermal regulation feature reduces charge current if the IC’s junction temperature reaches 125°C; thus without a good thermal design the maximum programmed charge current may not be reached. Use a 1% tolerance resistor RISET to avoid issues with the RISET short test when using the maximum charge current setting. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 3 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com ELECTRICAL CHARACTERISTICS Over junction temperature range (0°C < TJ < 125°C) and the recommended supply voltage range (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP 3.3 MAX UNIT INPUT VUVLO Under-voltage lock-out VIN: 0V → 4V 3.2 VHYS-UVLO Hysteresis on UVLO VIN: 4V → 0V 200 VIN-DT Input power detection threshold (Input power detected if VIN > VBAT + VIN-DT) VBAT = 3.6V, VIN: 3.5V → 4V 55 VHYS-INDT Hysteresis on VIN-DT VBAT = 3.6V, VIN: 4V → 3.5V 20 tDGL(PGOOD) Deglitch time, input power detected status Time measured from VIN: 0V → 5V, 1μs rise-time to PGOOD = LO VOVP Input over-voltage protection threshold VIN: 5V → 7V VHYS-OVP Hysteresis on OVP VIN: 7V → 5V tBLK(OVP) Input over-voltage blanking time tREC(OVP) V mV 140 mV mV 1.2 6.4 Time measured from VIN: 11V → 5V 1μs fall-time to PGOOD = LO Input over-voltage recovery time 80 3.4 300 6.6 ms 6.8 V 240 mV 50 μs 1.2 ms 1.3 mA 520 mV ILIM, ISET SHORT CIRCUIT TEST ISC Current source VSC QUIESCENT CURRENT IBAT(PDWN) Sleep current into BAT pin IIN(STDBY) Standby current into IN pin ICC Active supply current, IN pin CE = LO or HI, input power not detected, no load on OUT pin 6.5 μA EN1= HI, EN2=HI, VIN ≤ 6V 50 EN1= HI, EN2=HI, VIN > 6V 200 CE = LO, VIN = 6V, no load on OUT pin, VBAT > VBAT(REG), (EN1,EN2)≠(HI,HI) 1.5 mA 300 475 mV 50 100 mV μA POWER PATH VDO(IN-OUT) VIN – VOUT VIN = 4.3V, IIN = 1A, VBAT = 4.2V VDO(BAT-OUT) VBAT – VOUT IOUT = 1A, VIN = 0V, VBAT > 3V VO(REG) OUT pin voltage regulation VIN > VOUT + VDO(IN-OUT) 5.4 5.5 5.6 V EN1 = LO, EN2 = LO 90 95 100 mA EN1 = HI, EN2 = LO 450 475 500 mA IIN-MAX Maximum input current EN2 = HI, EN1 = LO KILIM/RIL A IM ILIM ≥ 500mA 1500 1600 1700 200mA < ILIM < 500mA 1330 1512 1700 KILIM Maximum input current factor AΩ IIN-MAX Programmable input current limit range EN2 = HI, EN1 = LO, RILIM = 8kΩ to 1.1kΩ 200 VIN-LOW Input voltage threshold when input current is reduced EN2 = LO, EN1 = X 4.35 VDPM Output voltage threshold when charging current is reduced 4.2 VBSUP1 Enter battery supplement mode VOUT falling, Supplement mode entered when VOUT < VBSUP1 VBAT – 40mV V VBSUP2 Exit battery supplement mode VOUT rising, Supplement mode exited when VOUT > VBSUP2 VBAT – 20mV V VO(SC1) Output short-circuit detection threshold, power-on 0.8 0.9 1.0 V VO(SC2) Output short-circuit detection threshold, supplement mode VBAT – VOUT > VO(SC2) indicates short-circuit 200 250 300 mV tDGL(SC2) Deglitch time, supplement mode short circuit tREC(SC2) Recovery time, supplement mode short circuit 1500 mA 4.5 4.63 V 4.3 4.4 V 250 μs 60 ms BATTERY CHARGER IBAT(SC) Source current for BAT pin short-circuit detection VBAT(SC) BAT pin short-circuit detection threshold VBAT(REG) Battery charge voltage VLOWV Pre-charge to fast-charge transition threshold 4 4 7.5 11 mA 1.6 1.8 2.0 V bq24075T 4.16 4.20 4.24 bq24079T 4.059 4.100 4.141 2.9 3 3.1 Submit Documentation Feedback V V Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 ELECTRICAL CHARACTERISTICS (continued) Over junction temperature range (0°C < TJ < 125°C) and the recommended supply voltage range (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 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 ICHG Battery fast charge current range VBAT(REG) > VBAT > VLOWV, VIN = 5V, CE = LO, EN1= LO, EN2 = HI ICHG Battery fast charge current CE = LO, EN1= LO, EN2 = HI, VBAT > VLOWV, VIN = 5V, IIN-MAX > ICHG, no load on OUT pin, thermal loop not active, DPM loop not active KISET Fast charge current factor IPRECHG Pre-charge current kPRECHG Pre-charge current factor ITERM 300 1500 KISET/RISET 797 A 890 975 KPRECHG /RISET Charge current value for termination detection threshold tDGL(TERM) Deglitch time, termination detected VRCH Recharge detection threshold tDGL(RCH) Deglitch time, recharge threshold detected 88 106 CE = LO, (EN1,EN2)≠(LO,LO), VBAT > VRCH, t < tMAXCH, VIN = 5V, DPM loop not active, thermal loop not active 0.09×ICHG 0.1×ICHG 0.11×ICHG CE = LO, (EN1,EN2)=(LO,LO), VBAT > VRCH, t < tMAXCH, VIN = 5V, DPM loop not active, thermal loop not active 0.027×ICHG G 0.040×ICHG 25 VO(REG) –140mV tDGL(NO-IN) Delay time, input power loss to charger turn-off IBAT(DET) Sink current for battery detection tDET Battery detection timer VBAT = 3.6V. Time measured from VIN: 5V → 3.3V 1μs fall-time 5 AΩ A 70 .033×ICH mA VO(REG) –100mV ms VO(REG) –60mV V 62.5 ms 20 ms 7.5 10 250 mA ms BATTERY CHARGING TIMERS tPRECHG Pre-charge safety timer value TMR = floating 1440 1800 2160 s tMAXCH Charge safety timer value TMR = floating 14400 18000 21600 s tPRECHG Pre-charge safety timer value(externally set) 18kΩ < RTMR < 72kΩ RTMR x KTMR tMAXCH Charge safety timer value (externally set) 18kΩ < RTMR < 72kΩ 10 x RTMR x KTMR KTMR Timer factor s s 35 45 55 s / kΩ 12 12.5 13 % of VIN BATTERY – PACK NTC MONITOR VHOT High temperature trip point Battery charging VHYS(HOT) Hysteresis on high trip point Battery charging VCOLD Low temperature trip point Battery charging VHYS(COLD) Hysteresis on low trip point Battery charging 1 % of VIN tDGL(TS) Deglitch time, pack temperature fault detection Battery charging 50 ms % of VIN 1 24.5 25 25.5 % of VIN THERMAL REGULATION TJ(REG) Temperature Regulation Limit 125 °C TJ(OFF) Thermal shutdown temperature 155 °C TJ(OFF-HYS) Thermal shutdown hysteresis 20 °C LOGIC LEVELS ON EN1, EN2, CE, SYSOFF, TD VIL Logic LOW input voltage 0 0.4 VIH Logic HIGH input voltage 1.4 6.0 V V IIL 1 μA IIH 10 μA 0.4 V LOGIC LEVELS ON PGOOD, CHG VOL Output LOW voltage ISINK = 5 mA Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 5 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com DEVICE INFORMATION PIN DIAGRAM CE 4 14 VREF 13 IN 10 OUT 9 CHG 8 3 VSS BAT 11 OUT bq24075T bq24079T 7 2 PGOOD BAT 12 ILIM EN1 6 1 EN2 5 TS 15 SYSO 16 ISET Pin out designations are not final. Subject to change. TERMINAL FUNCTIONS NAME NO. I/O DESCRIPTION 1 I/O External NTC Thermistor Input. Connect the TS input to the center tap of a resistor divider from VIN to GND with the NTC in parallel with the bottom resistor to monitor the NTC in the battery pack. For applications that do not utilize the TS function, set the resistor divider to be a 20% ratio. See the Battery Pack Temperature Monitoring section for details on calculating the resistor values. BAT 2,3 I/O Charger Power Stage Output and Battery Voltage Sense Input. Connect BAT to the positive terminal of the battery. Bypass BAT to VSS with a 4.7μF to 47μF ceramic capacitor. CE 4 I Charge Enable Active-Low Input. Connect CE to a high logic level to place the battery charger in standby mode. In standby mode, OUT is active and battery supplement mode is available. Connect /CE to a low logic level to enable the battery charger. CE is internally pulled down with ~285kΩ. Do not leave CE unconnected to ensure proper operation. EN2 5 I EN1 6 I Input Current Limit Configuration Inputs. Use EN1 and En2 to control the maximum input current and enable USB compliance. See Table 1 for the description of the operation states. EN1 and EN2 are internally pulled down with ~285kΩ. Do not leave EN1 or EN2 unconnected to ensure proper operation. PGOOD 7 O Open-Drain Power Good Status Indication Output. PGOOD pulls to VSS when a valid input source is detected. PGOOD is high-impedance when the input power is not within specified limits. Connect PGOOD to the desired logic voltage rail using a 1kΩ to 100kΩ resistor, or use with an LED for visual indication. VSS 8 – Ground. Connect to the thermal pad and to the ground rail of the circuit. CHG 9 O Open-Drain Charging Status Indication Output. CHG pulls to VSS when the battery is charging. CHG is high-impedance when charging is complete or when the charger is disabled. CHG flashes to indicate a timer fault. Connect CHG to the desired logic voltage rail using a 1kΩ to 100kΩ resistor, or use with an LED for visual indication. OUT 10,11 O System Supply Output. OUT provides a regulated output when the input is below the OVP threshold and above the regulation voltage. When the input is out of the operation range, OUT is connected to VBAT except when SYSOFF is high. Connect OUT to the system load. Bypass OUT to VSS with a 4.7μF to 47μF ceramic capacitor. ILIM 12 O Adjustable Current Limit Programming Input. Connect a 1.07kΩ to 7.5kΩ resistor from ILIM to VSS to program the maximum input current (EN2=1, EN1=0). The input current includes the system load and the battery charge current. Leaving ILIM unconnected disables all charging. IN 13 I Input Power Connection. Connect IN to the external DC supply (AC adapter or USB port). The input operating range is 4.35V to 6.6V. The input accepts voltages up to 26V without damage, but operation is suspended. Bypass IN to VS with a 1μF to 10μF ceramic capacitor. TMR 14 O Timer Programming Input. TMR controls the pre-charge and fast-charge safety timers. Connect TMR to VSS to disable all safety timers. Connect a 18kΩ to 72kΩ resistor between TMR and VSS to program the timers to a desired length. Leave TMR unconnected to set the timers to the default values. TS 6 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 TERMINAL FUNCTIONS (continued) NAME NO. I/O DESCRIPTION SYSOFF 15 I System Enable Input. Connect SYSOFF high to turn off the FET connecting the battery to the system output. When an adapter is connected, charge is also disabled. Connect SYSOFF low for normal operation. SYSOFF is internally pulled up to VBAT through a large resistor (~5MΩ). Do not leave SYSOFF unconnected to ensure proper operation. ISET 16 I/O Fast Charge Current Programming Input. Connect a 590 Ω to 3 kΩ resistor from ISET to VSS to program the fast charge current level. Charging is disabled if ISET is left unconnected. While charging, the voltage ISET reflects the actual charging current and can be used to monitor charge current. See the Charge Current Translator section of this datasheet for more details. Thermal Pad -- – There is an internal electrical connection between the exposed thermal pad and the VSS pin of the device. The thermal pad must be connected to the same potential as the VSS pin on the printed circuit board. Do not use the thermal pad as the primary ground input for the device. VSS must be connected to ground at all times. Table 1. EN1/EN2 Settings EN2 EN1 0 0 100 mA. USB100 mode MAXIMUM INPUT CURRENT INTO IN 0 1 500 mA. USB500 mode 1 0 Set by external resistor from ILIM to VSS 1 1 Standby (USB suspend mode) Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 7 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com SIMPLIFIED BLOCK DIAGRAM 250mV VO(SC1) V BAT OUT-SC1 t DGL(SC2) OUT- SC2 Q1 IN OUT EN2 Short Detect 225mV Precharge VIN-LOW USB100 USB5 00 ISET 2.25V Fastcharge TJ ILIM VREF- ILIM USB-susp TJ(REG) Short Detect V DPPM V O(REG) Q2 VOUT EN2 EN1 V BAT (REG) BAT VBAT V OUT CHARGEPUMP SYSOFF 40mV Supplement V LOWV 225mV) V BAT(SC) tDGL(RCH) tDGL2(LOWV) VIN tDGL1(LOWV) tDGL(TE RM) V RCH VIN BAT-SC V BAT + VIN-DT tDGL(NO-IN) tDGL(PGOOD) V UVLO VCOLD TS t DGL(TS) Charge Control V HOT V OVP tBLK(OVP) EN1 EN2 USB Suspend CE Halt timers CHG V IPRECHG VICHG V ISET Reset timers PGOOD Dynamically Controlled Oscillator TMR Fast- Charge Timer Timer fault Pre- Charge Timer 8 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 TYPICAL CHARACTERISTICS VIN = 6V, EN1 = 1, EN2 = 0, TA = 25°C, unless otherwise noted. ADAPTER PLUG-IN BATTERY CONNECTED RLOAD = 10Ω VIN BATTERY DETECTION BATTERY INSERTED 5 V/div BATTERY DETECTION BATTERY REMOVED VCHG 5 V/div VCHG 5 V/div Charging Initiated 1 A/div 500 mV/div VBAT 3.6 V VPGOOD 5 V/div 500 mA/div IBAT IBAT IBAT 2 V/div VBAT 4 ms/div 1 A/div Battery Inserted 2 V/div Battery Removed VBAT Battery Detection Mode Battery Detection Mode 400 ms/div 400 ms/div Figure 1. Figure 2. Figure 3. ENTERING AND EXITING DPPM MODE ILOAD = 25 mA TO 250 mA, ICHARGE = 300 mA ENTERING AND EXITING BATTERY SUPPLEMENT MODE ILOAD = 25mA TO 750mA bq2407x CHARGER ON/OFF USING CE 200 mA/div IOUT 500 mA/div VCE 5 V/div IOUT VCHG VOUT 5.5 V 500 mV/div IBAT 200 mA/div IOUT 5.5 V Supplement Mode 5 V/div 500 mA/div 1 V/div VBAT 3.6 V 500 mV/div IBAT IBAT VBAT 4.1 V Mandatory Precharge 2 ms/div 500 mA/div 10 ms/div 2 ms/div Figure 4. Figure 5. Figure 6. OVP FAULT VIN = 5.5V TO 8.5V SYSTEM ON/OFF WITH INPUT CONNECTED VIN = 6V SYSTEM ON/OFF WITH INPUT NOT CONNECTED VIN = 0V VIN VSYSOFF 5 V/div VSYSOFF 2 V/div VBAT 4V 5 V/div 2 V/div VOUT 4.3 V VBAT 4.2 V 200 mV/div VOUT 5.5 V VBAT 4V 2 V/div VOUT Battery Powering System 500 mA/div IBAT 500 mA/div 40 ms/div Figure 7. System Power Off IBAT IBAT 400 ms/div Figure 8. 500 mA/div 4 ms/div Figure 9. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 9 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com TYPICAL CHARACTERISTICS (continued) VIN = 6V, EN1 = 1, EN2 = 0, TA = 25°C, unless otherwise noted. DROPOUT VOLTAGE vs TEMPERATURE NO INPUT SUPPLY DROPOUT VOLTAGE vs TEMPERATURE THERMAL REGULATION 600 0.7 120 IL = 1 A 300 200 100 0.5 0.4 0.3 0.2 0.1 120 125 130 135 Temperature - oC 140 0 145 80 VBAT = 3 V 60 VBAT = 3.9 V 40 20 0 0 25 100 50 75 TJ - Junction Temperature - °C 125 0 50 75 100 25 TJ - Junction Temperature - °C 125 Figure 10. Figure 11. Figure 12. OUTPUT REGULATION VOLTAGE vs TEMPERATURE BAT REGULATION VOLTAGE vs TEMPERATURE bq24075T BATTERY REGULATION VOLTAGE vs TEMPERATURE bq24079T VIN = 6 V, IL = 1 A 5.70 VBAT - Regulation Voltage - V 5.65 5.60 5.55 5.50 5.45 5.40 5.35 4.210 4.11 4.205 4.105 VBAT - Regulation Voltage - V 5.75 VO - Output Voltage - V 100 Dropout Voltage - VBAT-VOUT Dropout Voltage - VIN-VOUT IBAT - mA 400 0 IL = 1 A 0.6 500 4.200 4.195 4.190 4.185 4.1 4.095 4.09 4.085 5.30 5.25 0 25 50 75 100 TJ - Junction Temperature - °C Figure 13. 10 125 4.180 0 4.08 5 10 15 20 25 30 TJ - Junction Temperature - °C Figure 14. Submit Documentation Feedback 0 5 10 15 20 25 TJ - Junction Temperature - °C 30 Figure 15. Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 TYPICAL CHARACTERISTICS (continued) VIN = 6V, EN1 = 1, EN2 = 0, TA = 25°C, unless otherwise noted. OVERVOLTAGE PROTECTION THRESHOLD vs TEMPERATURE INPUT CURRENT LIMIT vs INPUT VOLTAGE RISET = 900 W RILIM IBAT - Fast Charge Current - A 700 6.65 VI Rising 6.60 6.55 VI Falling 6.50 600 500 USB500 400 300 200 USB100 1.03 1.01 0.99 0.97 100 6.45 0 0 25 50 75 100 TJ - Junction Temperature - °C 0.95 5 125 6 7 8 9 VI - Input Voltage - V 10 3 3.2 3.6 3.8 4 3.4 VBAT - Battery Voltage - V Figure 16. Figure 17. Figure 18. FASTCHARGE CURRENT vs BATTERY VOLTAGE FASTCHARGE CURRENT vs BATTERY VOLTAGE PRECHARGE CURRENT vs BATTERY VOLTAGE RISET = 3 kW RISET = 900 W 104 RISET = 3 kW 295 290 285 31 103 IBAT - Precharge Current - A IBAT - Precharge Current - A 305 300 4.2 31.5 105 310 IBAT - Fast Charge Current - A 1.05 800 6.6 V ILIM - Input Current - mA VOVP - Output Voltage Threshold - V 6.70 FASTCHARGE CURRENT vs BATTERY VOLTAGE 102 101 100 99 98 97 30.5 30 29.5 29 96 280 28.5 95 3 3.2 3.4 3.6 3.8 4 VBAT - Battery Voltage - V 4.2 Figure 19. 2 2.2 2.4 2.6 2.8 3 VBAT - Battery Voltage - V Figure 20. 2 2.2 2.4 2.6 2.8 VBAT - Battery Voltage - V Figure 21. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 3 11 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com APPLICATION CIRCUITS R4 1.5 kW R5 1.5 kW SYSTEM IN C1 1µF GND CHG DC+ PGOOD Adaptor OUT C2 4.7µF VSS HOST bq24075T bq24079T R8 100 kW TS EN2 EN1 SYSOFF CE BAT T MR TEMP ISET PACK + C3 4.7 µF ILIM R6 10 kW R7 13.2 kW PACK - R1 46.8 kW R2 1.18 kW R3 1.13 kW NOTE: VIN = UVLO to VOVP, IFASTCHG = 800mA, IIN(MAX) = 1.35A, Battery Temperature Charge Range = 0°C to 50°C, 6.25 hour Fastcharge Safety Timer Figure 22. Using the bq24075T/bq24079T to Disconnect the Battery from the System DETAILED FUNCTIONAL DESCRIPTION The bq2407x devices are integrated Li-Ion linear chargers and system power path management devices targeted at space-limited portable applications. The device powers the system while simultaneously and independently charging the battery. This feature reduces the number of charge and discharge cycles on the battery, allows for proper charge termination and enables the system to run with a defective or absent battery pack. It also allows instant system turn-on even with a totally discharged battery. The input power source for charging the battery and running the system can be an AC adapter or a USB port. The devices feature Dynamic Power Path Management (DPPM), which shares the source current between the system and battery charging, and automatically reduces the charging current if the system load increases. When charging from a USB port, the input dynamic power management (VIN-DPM) circuit reduces the input current if the input voltage falls below a threshold, preventing the USB port from crashing. The power-path architecture also permits the battery to supplement the system current requirements when the adapter cannot deliver the peak system currents. UNDERVOLTAGE LOCKOUT (UVLO) The bq2407X family remains in power down mode when the input voltage at the IN pin is below the undervoltage threshold (UVLO). During the power down mode the host commands at the control inputs (CE, EN1 and EN2) are ignored. The Q1 FET connected between IN and OUT pins is off, and the status outputs, CHG and PGOOD, are high impedance. The Q2 FET that connects BAT to OUT is ON. (If SYSOFF is high, Q2 is off). During power down mode, the VOUT(SC2) circuitry is active and monitors for overload conditions on OUT. 12 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 POWER ON When VIN exceeds the UVLO threshold, the bq2407xT powers up. While VIN is below VBAT + VIN(DT), the host commands at the control inputs (CE, EN1 and EN2) are ignored. The Q1 FET connected between IN and OUT pins is off, and the status outputs CHG and PGOOD are high impedance. The Q2 FET that connects BAT to OUT is ON. (If SYSOFF is high, Q2 is off). During this mode, the VOUT(SC2) circuitry is active and monitors for overload conditions on OUT. Once VIN rises above VBAT + VIN(DT), PGOOD is driven low to indicate the valid power status and the CE, EN1, and EN2 inputs are read. The device enters standby mode if (EN1 = EN2 = HI) or if an input overvoltage condition occurs. In standby mode, Q1 is OFF and Q2 is ON so OUT is connected to the battery input. (If SYSOFF is high, FET Q2 is off). During this mode, the VOUT(SC2) circuitry is active and monitors for overload conditions on OUT. When the input voltage at IN is within the valid range: VIN > UVLO AND VIN > VBAT + VIN(DT) AND VIN < VOVP, and the EN1 and EN2 pins indicate that the USB suspend mode is not enabled [(EN1, EN2) ≠ (HI, HI)] all internal timers and other circuit blocks are activated. The device then checks for short-circuits at the ISET and ILIM pins. If no short conditions exists, the device switches on the input FET Q1 with a 100mA current limit to checks for a short circuit at OUT. When VOUT is above VSC, the FET Q1 switches to the current limit threshold set by EN1, EN2 and RILIM and the device enters into the normal operation. During normal operation, the system is powered by the input source (Q1 is regulating), and the device continuously monitors the status of CE, EN1 and EN2 as well as the input voltage conditions. / PGOOD= Hi-Z /CHG = Hi-Z BATTFET ON VUVLO <VIN <VOVP and VIN >V BAT +VIN (DT) No Yes / PGOOD= Low Yes EN1=EN2=1 No Yes ILIM or ISET short ? No Begin Startup IIN (MAX ) 100mA VOUT short? Yes No Input Current Limit set by EN1 and EN2 No /CE = Low Yes Begin Charging Figure 23. Startup Flow Diagram Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 13 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com OVERVOLTAGE PROTECTION (OVP) The bq2407xT accepts inputs up to 28V without damage. Additionally, an overvoltage protection (OVP) circuit is implemented that shuts off the internal LDO and discontinues charging when VIN > VOVP for a period longer than tDGL(OVP). When in OVP, the system output (OUT) is connected to the battery and PGOOD is high impedance. Once the OVP condition is removed, a new power on sequence starts (See the POWER ON section). The safety timers are reset and a new charge cycle will be indicated by the CHG output. DYNAMIC POWER-PATH MANAGEMENT The bq2407xT features an OUT output that powers the external load connected to the battery. This output is active whenever a source is connected to IN or BAT. The following sections discuss the behavior of OUT with a source connected to IN to charge the battery and a battery source only. INPUT SOURCE CONNECTED (ADAPTER or USB) With a source connected, the dynamic power-path management (DPPM) circuitry of the bq2407xT monitors the input current continuously. The OUT output for the bq24075T/ 79T is regulated to a fixed voltage (VO(REG)). The current into IN is shared between charging the battery and powering the system load at OUT. The bq2407xT has internal selectable current limits of 100mA (USB100) and 500mA (USB500) for charging from USB ports, as well as a resistor-programmable input current limit. The bq2407xT is USB IF compliant for the inrush current testing. The USB spec allows up to 10μF to be hard started, which establishes 50μC as the maximum inrush charge value when exceeding 100mA. The input current limit for the bq2407xT prevents the input current from exceeding this limit, even with system capacitances greater than 10μF. Note that the input capacitance to the device must be selected small enough to prevent a violation (<10μF), as this current is not limited. Figure 24 demonstrates the startup of the bq2407xT and compares it to the USB-IF specification. Figure 24. USB-IF Inrush Current Test The input current limit selection is controlled by the state of the EN1 and EN2 pins as shown in Table 1. When using the resistor-programmable current limit, the input current limit is set by the value of the resistor connected from the ILIM pin to VSS, and is given by the equation: IIN-MAX = KILIM / RILIM The input current limit is adjustable up to 1.5A. The valid resistor range is 1.07 kΩ to 7.5kΩ. 14 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 When the IN source is connected, priority is given to the system load. The DPPM and Battery Supplement modes are used to maintain the system load. Figure 26 illustrates an example of the DPPM and supplement modes. These modes are explained in detail in the following sections. Input DPM Mode (VIN-DPM) The bq2407xT utilizes the VIN-DPM mode for operation from current-limited USB ports. When EN1 and EN2 are configured for USB100 (EN2=0, EN1=0) or USB500 (EN2=0, EN2=1) modes, the input voltage is monitored. If VIN falls to VIN-DPM, the input current limit is reduced to prevent the input voltage from falling further. This prevents the bq2407xT from crashing poorly designed or incorrectly configured USB sources. Figure 25 shows the VIN-DPM behavior to a current limited source. In this figure, the input source has a 400mA current limit and the device is in USB500 mode (EN1=1, EN2=0). Figure 25. VIN-DPM Mode DPPM Mode When the sum of the charging and system load currents exceeds the maximum input current (programmed with EN1, EN2 and ILIM pins), the voltage at OUT decreases. Once the voltage on the OUT pin falls to VDPPM, the bq2407xT enters DPPM mode. In this mode, the charging current is reduced as the OUT current increases in order to maintain the system output. Battery termination is disabled while in DPPM mode. Battery Supplement Mode While in DPPM mode, if the charging current falls to zero and the system load current increases beyond the programmed input current limit, the voltage at OUT reduces further. When the OUT voltage drops below the VBSUP1 threshold, the battery supplements the system load. The battery stops supplementing the system load when the voltage at OUT rises above the VBSUP2 threshold. During supplement mode, the battery supplement current is not regulated (BAT-FET is fully on), however there is a short circuit protection circuit built in. demonstrate supplement mode. If during battery supplement mode, the voltage at OUT drops VO(SC2) below the BAT voltage, the OUT output is turned off if the overload exists after tDGL(SC2). The short circuit recovery timer then starts counting. After tREC(SC2), OUT turns on and attempts to restart. If the short circuit remains, OUT is turned off and the counter restarts. Battery termination is disabled while in supplement mode. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 15 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com 5.5 V Figure 26. DPPM and Battery Supplement Modes (VOREG = 5.5V, VBAT = 3.6V) INPUT SOURCE NOT CONNECTED When no source is connected to the IN input, OUT is powered strictly from the battery. During this mode the current into OUT is not regulated, similar to Battery Supplement Mode, however the short circuit circuitry is active. If the OUT voltage falls below the BAT voltage by 250mV for longer than tDGL(SC2), OUT is turned off. The short circuit recovery timer then starts counting. After tREC(SC2), OUT turns on and attempts to restart. If the short circuit remains, OUT is turned off and the counter restarts. This ON/OFF cycle continues until the overload condition is removed. BATTERY CHARGING Set CE low to initiate battery charging. First, the device checks for a short-circuit on the BAT pin by sourcing IBAT(SC) to the battery and monitoring the voltage. When the BAT voltage exceeds VBAT(SC), the battery charging continues. The battery is charged in three phases: conditioning pre-charge, constant current fast charge (current regulation) and a constant voltage tapering (voltage regulation). In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is exceeded. 16 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 Figure 27. Typical Charging Cycle Figure 27 illustrates a normal Li-Ion charge cycle using the bq2407xT. In the pre-charge phase, the battery is charged at with the pre-charge current (IPRECHG). Once the battery voltage crosses the VLOWV threshold, the battery is charged with the fast-charge current (ICHG). As the battery voltage reaches VBAT(REG), the battery is held at a constant voltage of VBAT(REG) and the charge current tapers off as the battery approaches full charge. When the battery current reaches ITERM, the CHG pin indicates charging done by going high-impedance. Note that termination detection is disabled whenever the charge rate is reduced because of the actions of the thermal loop, the DPPM loop or the VIN-DPM loop. The value of the fast-charge current is set by the resistor connected from the ISET pin to VSS, and is given by the equation ICHG = KISET / RISET The charge current limit is adjustable up to 1.5A. The valid resistor range is 590Ω to 3 kΩ. Note that if ICHG is programmed as greater than the input current limit, the battery will not charge at the rate of ICHG, but at the slower rate of IIN(MAX) (minus the load current on the OUT pin, if any). In this case, the charger timers will be proportionately slowed down. CHARGE CURRENT TRANSLATOR When the charger is enabled, internal circuits generate a current proportional to the charge current at the ISET input. The current out of ISET is 1/400 (±10%) of the charge current. This current, when applied to the external charge current programming resistor, RISET, generates an analog voltage that can be monitored by an external host to calculate the current sourced from BAT. VISET = ICHARGE / 400 × RISET Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 17 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com Begin Charging Battery short detected ? Yes No Start Precharge /CHG= Low No No V BAT > VLOWV tPRECHARGE Elapsed? Yes End Charge Flash/CHG Start Fastcharge ICHARGE set by ISET No No IBAT < ITERM tFASTCHARGE Elapsed? Yes End Charge Flash/CHG Charge Done /CHG= Hi-Z TD= Low (’72, ’73 Only) (’74, ’75= YES) No Yes Termination Reached BATTFET Off Wait for VBAT < V RCH No VBAT < V RCH Yes Run Battery Detection No Battery Detected ? Yes Figure 28. Battery Charging Flow Diagram 18 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 BATTERY DETECTION AND RECHARGE The bq2407xT automatically detects if a battery is connected or removed. Once a charge cycle is complete, the battery voltage is monitored. When the battery voltage falls below VRCH, the battery detection routine is run. During battery detection, current (IBAT(DET)) is pulled from the battery for a duration tDET to see if the voltage on BAT falls below VLOWV. If not, charging begins. If it does, then it indicates that the battery is missing or the protector is open. Next, the precharge current is applied for tDET to close the protector if possible. If VBAT < VRCH, then the protector is closed and charging is initiated. If VBAT > VRCH, then the battery is determined to be missing and the detection routine continues. BATTERY DISCONNECT (SYSOFF Input) The bq24075T and bq24079T feature a SYSOFF input that allows the user to turn the FET Q2 off and disconnect the battery from the OUT pin. This is useful for disconnecting the system load from the battery, factory programming where the battery is not installed or for host side impedance track fuel gauging, such as bq27500, where the battery open circuit voltage level must be detected before the battery charges or discharges. The CHG output remains low when SYSOFF is high. Connect SYSOFF to VSS, to turn Q2 on for normal operation. SYSOFF is internally pulled to VBAT through ~5 MΩ resistor. DYNAMIC CHARGE TIMERS (TMR Input) The bq2407xT devices contain internal safety timers for the pre-charge and fast-charge phases to prevent potential damage to the battery and the system. The timers begin at the start of the respective charge cycles. The timer values are programmed by connecting a resistor from TMR to VSS. The resistor value is calculated using the following equation: tPRECHG = KTMR × RTMR tMAXCHG = 10 × KTMR × RTMR Leave TMR unconnected to select the internal default timers. Disable the timers by connecting TMR to VSS. Note that timers are suspended when the device is in thermal shutdown, and the timers are slowed proportionally to the charge current when the device enters thermal regulation. 1. During the fast charge phase, several events increase the timer durations. 2. The system load current activates the DPPM loop which reduces the available charging current 3. The input current is reduced because the input voltage has fallen to VIN-DPM 4. The device has entered thermal regulation because the IC junction temperature has exceeded TJ(REG) During each of these events, the internal timers are slowed down proportionately to the reduction in charging current. For example, if the charging current is reduced by half for two minutes, the timer clock is reduced to half the frequency and the counter counts half as fast resulting in only one minute of "counting" time. If the precharge timer expires before the battery voltage reaches VLOWV, the bq2407xT indicates a fault condition. Additionally, if the battery current does not fall to ITERM before the fast charge timer expires, a fault is indicated. The CHG output flashes at approximately 2 Hz to indicate a fault condition. The fault condition is cleared by toggling CE or the input power, entering/ exiting USB suspend mode, or an OVP event. STATUS INDICATORS (PGOOD, CHG) The bq2407xT contains two open-drain outputs that signal its status. The PGOOD output signals when a valid input source is connected. PGOOD is low when (VBAT + VIN(DT)) < VIN < VOVP. When the input voltage is outside of this range, PGOOD is high impedance. The charge cycle after power-up, CE going low, or exiting OVP is indicated with the CHG output on (low - LED on), whereas all refresh (subsequent) charges will result in the CHG output off (open – LED off). In addition, the CHG signals timer faults by flashing at approximately 2Hz. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 19 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com Table 2. PGOOD Status Indicator INPUT STATE PGOOD OUTPUT VIN < VUVLO Hi impedance VUVLO < VIN < VIN(DT) Hi impedance VIN(DT) < VIN < VOVF Low VIN < VOVP Hi impedance Table 3. CHG Status Indicator CHARGE STATE Charging Charging suspended by thermal loop, or DPPM loop CHG OUTPUT Low (for first charge cycle) Safety timers expired Flashing at 2 Hz Charging done Recharging after termination IC disabled or no valid input power Hi impedance Battery absent THERMAL REGULATION AND THERMAL SHUTDOWN The bq2407xT contain a thermal regulation loop that monitors the die temperature. 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 and heavy OUT system load conditions. Under these conditions, if the die temperature increases to TJ(OFF), the input FET Q1 is turned OFF. FET Q2 is turned ON to ensure that the battery still powers the load on OUT. Once the device die temperature cools by TJ(OFF-HYS), the input FET Q1 is turned on and the device returns to thermal regulation. Continuous overtemperature conditions result in a "hiccup" mode. During thermal regulation, the safety timers are slowed down proportionately to the reduction in current limit. Note that this feature monitors the die temperature of the bq2407xT. 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 and the LDO associated with OUT. A modified charge cycle with the thermal loop active is shown in Figure 29. Battery termination is disabled during thermal regulation. 20 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 PRECHARGE THERMAL REGULATION CC FAST CHARGE CV TAPER DONE VO(REG) IO(CHG) Battery Voltage Battery Current V(LOWV) HI-z I(PRECHG) I(TERM) TJ(REG) IC Junction Temperature, TJ Figure 29. Charge Cycle Modified by Thermal Loop BATTERY PACK TEMPERATURE MONITORING The bq2407xT features an 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. The timers maintain their values but suspend counting. When the voltage measured at TS returns to within the operation window, charging is resumed and the timers continue counting. When charging is suspended due to a battery pack temperature fault, the CHG output remains low and continues to indicate charging. VIN R6 = -1 VCOLD 1 1 + R 7 RCOLD (1) Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 21 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com é 1 1 ù VIN ´ RCOLD ´ RHOT ´ ê ú V V HOT û ë COLD R7 = é V ù é V ù RHOT ´ ê IN - 1ú - RCOLD ´ ê IN - 1ú ëVHOT û ëVCOLD û (2) Where: VCOLD = 0.25 X VIN VHOT = 0.125 X VIN RHOT is the expected thermistor resistance at the programmed hot threshold, RCOLD is the expected thermistor resistance at the programmed cold threshold. If the value of R6 is less than 100kΩ, R3 must be added to protect the IC from 28V inputs. If R6 is greater than 100kΩ, R8 does not need to be used. Adapter IN R6 1 V COLD + TS R8 PACK+ TEMP Not necessary in all applications VHOT R7 PACK- + bq240xT Figure 30. NTC Monitoring Function For applications that do not require the TS monitoring function, set R6 = 200kΩ and R7 = 49.9kΩ to set the TS voltage at a valid level and maintain charging. APPLICATION INFORMATION bq2407xT CHARGER DESIGN EXAMPLE Refer to Typical Application Circuits for Schematics of the Design Example. Supply voltage = 5V Fast charge current of approximately 800 mA; ISET – pin 16 Input Current Limit =1.35A; ILIM – pin 12 Safety timer duration, Fast-Charge = 6.25 hours; TMR – pin 14 Battery Temperature Sense = 10kΩ; NTC (103AT-2), 0°C to 50°C Operation Program the Fast Charge Current (ISET): 22 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 RISET = KISET / ICHG KISET = 890 AΩ; from the electrical characteristics table RISET = 890AΩ / 0.8A = 1.1125 kΩ Select the closest standard value, which for this case is 1.13kΩ. Connect this resistor between ISET (pin 16) and VSS. Program the Input Current Limit (ILIM) RILIM = KILIM / IIN(MAX) KILIM = 1600 AΩ; from the electrical characteristics table. RISET = 1600AΩ / 1.35A = 1.19 kΩ Select the closest standard value, which for this case is 1.18 kΩ. Connect this resistor between ILIM (pin 12) and VSS. Program 6.25-hour Fast-Charge Safety Timer (TMR) RTMR = tMAXCHG / (10 × KTMR) KTMR = 45 s/kΩ from the electrical characteristics table. RTMR = (6.25 hr × 3600 s/hr) / (10 x 45 s/kΩ) = 46.8kΩ; Select the closest standard value, which for this case is 46.4 kΩ. Connect this resistor between TMR (pin 2) and VSS. TS Function Using a 10kΩ NTC thermistor in the battery pack (103AT-2). Connect a resistor divider from VIN to VSS with the thermistor and TS connected to the center tap (R6 and R7 in typical application circuits). RHOT = 4.086kΩ; 50°C threshold from NTC data sheet RCOLD = 28.16 kΩ; 0°C threshold from NTC data sheet VCOLD = 0.25 X VIN = 0.25 X 5V = 1.25V VHOT = 0.125 X VIN = 0.125 X 5V = 0.625V é 1 1 ù 1 ù é 1 VIN ´ RCOLD ´ RHOT ´ ê 5 ´ 28160 ´ 4086 ´ ê ú V V 1.25 0.625 úû COLD HOT û ë ë R7 = = = 8.236k W é VIN ù é VIN ù é 5 ù é 5 ù 4086 1 28160 1 ´ ´ RHOT ´ ê - 1ú - RCOLD ´ ê - 1ú ê 0.625 ú ê 1.25 ú ë û ë û ëVHOT û ëVCOLD û (3) VIN 5 -1 -1 VCOLD 1.25 R6 = = = 19.14k W 1 1 1 1 + + 8250 28160 R 7 RCOLD (4) Since the calculated values for R6 is less than 100kΩ, a 100kΩ resistor for R8 must be used. Choose the closest standard values, which for this case are R6=8.25kΩ and R7 = 19.1kΩ. For applications that do not require the TS monitoring function, set R6 = 200kΩ and R7 = 49.9kΩ to set the TS voltage at a valid level and maintain charging. CHG and PGOOD LED Status: connect a 1.5kΩ resistor in series with a LED between OUT and CHG to indicate charging status. Connect a 1.5kΩ resistor in series with a LED between OUT and PGOOD to indicate when a valid input source is connected. Processor Monitoring Status: connect a pullup resistor (on the order of 100 kΩ) between the processor power rail and CHG and PGOOD System ON/OFF (SYSOFF): Connect SYSOFF high to disconnect the battery from the system load. Connect SYSOFF low for normal operation. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 23 bq24075T bq24079T SLUS937 – DECEMBER 2009 www.ti.com SELECTING IN, OUT AND BAT CAPACITORS In most applications, all that is needed is a high-frequency decoupling capacitor (ceramic) on the power pin, input, output and battery pins. Using the values shown on the application diagram, is recommended. After evaluation of these voltage signals with real system operational conditions, one can determine if capacitance values can be adjusted toward the minimum recommended values (DC load application) or higher values for fast high amplitude pulsed load applications. Note if designed high input voltage sources (bad adapters or wrong adapters), the capacitor needs to be rated appropriately. Ceramic capacitors are tested to 2x their rated values so a 16V capacitor may be adequate for a 30V transient (verify tested rating with capacitor manufacturer). THERMAL PACKAGE The bq2407xT family is packaged in a thermally enhanced MLP package. The package includes a thermal pad to provide an effective thermal contact between the IC and the printed circuit board (PCB). The power pad should be directly connected to VSS. Full PCB design guidelines for this package are provided in the application note entitled: QFN/SON PCB Attachment Application Note. 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: = (TJ – T) / P Where: TJ = chip junction temperature T = ambient temperature P = device power dissipation Factors that can 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 Due to the charge profile of Li-Ion batteries the maximum power dissipation is typically seen at the beginning of the charge cycle when the battery voltage is at its lowest. Typically after fast charge begins the pack voltage increases to 3.4V within the first 2 minutes. The thermal time constant of the assembly typically takes a few minutes to heat up so when doing maximum power dissipation calculations, 3.4V is a good minimum voltage to use. This is verified, with the system and a fully discharged battery, by plotting temperature on the bottom of the PCB under the IC (pad should have multiple vias), the charge current and the battery voltage as a function of time. The fast charge current will start to taper off if the part goes into thermal regulation. The device power dissipation, P, is a function of the charge rate and the voltage drop across the internal PowerFET. It can be calculated from Equation 5 when a battery pack is being charged : P = [VIN – VOUT] × IOUT + [VOUT – VBAT] × IBAT (5) The thermal loop feature reduces the charge current to limit excessive IC junction temperature. It is recommended that the design not run in thermal regulation for typical operating conditions (nominal input voltage and nominal ambient temperatures) and use the feature for non typical situations such as hot environments or higher than normal input source voltage. With that said, the IC will still perform as described, if the thermal loop is always active. Half-Wave Adapters Some adapters implement a half rectifier topology, which causes the adapter output voltage to fall below the battery voltage during part of the cycle. To enable operation with adapters under those conditions, the bq2407xT family keeps the charger on for at least 20 msec (typical) after the input power puts the part in sleep mode. This feature enables use of external adapters using 50 Hz networks. The input must not drop below the UVLO voltage for the charger to work properly. Thus, the battery voltage should be above the UVLO to help prevent the input from dropping out. Additional input capacitance may be needed. 24 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T bq24075T bq24079T www.ti.com SLUS937 – DECEMBER 2009 When the input is between VUVLO and VIN(DT), the device enters sleep mode. After entering sleep mode for 20ms the internal FET connection between the IN and OUT pin is disabled and pulling the input to ground will not discharge the battery, other than the leakage on the BAT pin. If one has a full 1000mAHr battery and the leakage is 10μA, then it would take 1000mAHr/10μA = 100000 hours (11.4 years) to discharge the battery. The battery ‘s self discharge is typically 5 times higher than this Layout Tips 1. 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 bq2407xT, with short trace runs to both IN, OUT and GND (thermal pad). 2. 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. 3. 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 bq2407xT family is packaged in a thermally enhanced MLP 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. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): bq24075T bq24079T 25 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. 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