bq24705 www.ti.com SLUS779 – DECEMBER 2007 Host-Controlled Multi-Chemistry Battery Charger With Low Input Power Detect FEATURES APPLICATIONS • • • • • • • REGN LODRV PGND 21 20 19 PVCC 1 18 DPMDET CE 2 17 CELLS ACN 3 16 SRP ACP 4 15 SRN ACDET 5 14 BAT ACSET 6 13 SRSET 7 8 9 10 11 12 IADAPT • • • 22 ISYNSET • 23 ACGOOD • 24 PH • • • The bq24705 charges two, three, or four series Li+ cells, supporting up to 8 A of charge current, and is available in a 24-pin, 4x4-mm thin QFN package. VADJ • The bq24705 is a high-efficiency, synchronous battery charger with integrated compensation and system power selector logic, offering low component count for space-constrained multi-chemistry battery charging applications. Charge current and voltage programming allows high regulation accuracies, and can be either hardwired with resistors, or programmed by the system power- management microcontroller using a DAC or GPIOs. HIDRV • DESCRIPTION VREF • Notebook and Ultra-Mobile Computers Portable Data-Capture Terminals Portable Printers Medical Diagnostics Equipment Battery Bay Chargers Battery Back-Up Systems BTST • NMOS-NMOS Synchronous Buck Converter with 600 kHz Frequency and >95% Efficiency 30-ns Minimum Driver Dead-time and 99.5% Maximum Effective Duty Cycle High-Accuracy Voltage and Current Regulation – ±0.5% Charge Voltage Accuracy – ±3% Charge Current Accuracy – ±3% Adapter Current Accuracy – ±2% Input Current Sense Amp Accuracy Integration – Internal Loop Compensation – Internal Soft-Start Safety – Input Overvoltage Protection (OVP) – Dynamic Power Management (DPM) with Status Indicator – Reverse-Conduction Protection Input FET Supports Two, Three, or Four Li+ Cells 5 – 24 V AC/DC-Adapter Operating Range Analog Inputs with Ratiometric Programming via Resistors or DAC/GPIO Host Control – Charge Voltage (4-4.512 V/cell) – Charge Current (up to 8 A, with 10-mΩ Sense Resistor) – Adapter Current Limit (DPM) Status and Monitoring Outputs – AC/DC Adapter Present with Programmable Voltage Threshold – DPM Loop Active – Current Drawn from Input Source Supports Any Battery Chemistry: Li+, NiCd, NiMH, Lead Acid, etc. Charge Enable 10-µA Off-State Battery Current 24-pin, 4x4-mm QFN Package AGND 1 Figure 1. bq24705, 24 LD QFN, Top View 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 © 2007, Texas Instruments Incorporated bq24705 www.ti.com SLUS779 – DECEMBER 2007 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. DESCRIPTION (CONTINUED) The bq24705 features Dynamic Power Management (DPM) and input power limiting. These features reduce battery charge current when the input power limit is reached to avoid overloading the AC adapter when supplying the load and the battery charger simultaneously. A highly-accurate current-sense amplifier enables precise measurement of input current from the AC adapter to monitor the overall system power. SYSTEM ADAPTER+ ADAPTER- R5 4W C1 1 mF RAC P P Q1 (ACFET) Q2 (ACFET) SI4435 SI4435 Controlled by C2 HOST R1 0.1 mF 432 kW 1% C6 C7 10 mF 10 mF 0.010 W C3 0.1 mF ACN PVCC C8 0.1 mF ACP ACDET bq24705 R3 10 kW PH BTST ACGOOD ACGOOD D1 BAT54 C9 L1 0.1 mF 4.7 mH REGN C10 1 mF SRSET DAC ACSET LODRV VREF HOST N R4 10 kW C4 1 mF P Q4 FDS6680A HIDRV AGND VREF N R2 66.5 kW 1% Q3(BATFET) SI4435 Controlled by HOST R SR 0.010 W PACK+ C11 10 mF C13 C13 0.1 mF Q5 FDS6680A C12 10 mF PACK- C14 0.1 mF PGND SRP DPMDET SRN CELLS BAT C15 0.1 mF CHGEN DAC ISYNSET VADJ ADC R6 68 kW IADAPT C5 PowerPad 100 pF (1) Pull-up rail could be either VREF or other system rail . (2) SRSET/ACSET could come from either DAC or resistor dividers . VIN = 20 V, VBAT = 3-cell Li-Ion, ICHARGE = 3 A, IADAPTER_LIMIT = 4 A Figure 2. Typical System Schematic, Voltage and Current Programmed by DAC 2 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 SYSTEM ADAPTER+ ADAPTER- RAC R5 4W P P Q1 (ACFET) Q2 (ACFET) SI4435 SI4435 Controlled by C2 HOST R1 0.1 mF 432 kW 1% C1 1 mF C6 C7 10 mF 10 mF 0.010 W C3 0.1 mF ACN PVCC C8 0.1 mF ACP Q3(BATFET) SI4435 Controlled by HOST ACDET bq24705 R3 10 kW PH BTST ACGOOD ACGOOD D1 R11 66.5 kW R12 100 kW 4.7 mH LODRV R SR 0.010 W PACK+ C11 10 mF C13 C13 0.1 mF Q5 FDS6680A C12 10 mF PACK- C14 0.1 mF PGND C4 1 mF R4 10 kW 0.1 mF C10 1 mF VREF HOST L1 REGN SRSET R10 100 kW ACSET C9 N R9 42 kW BAT54 P Q4 FDS6680A HIDRV AGND VREF N R2 66.5 kW 1% SRP GPIO DPMDET SRN LPMD BAT CELLS C15 0.1 mF ISYNSET CHGEN R6 68 kW VADJ ADC IADAPT C5 100 pF PowerPad (1) Pull-up rail could be either VREF or other system rail . (2) SRSET/ACSET could come from either DAC or resistor dividers. A. VIN = 20 V, VBAT = 3-cell Li-Ion, ICHARGE = 3 A, IADAPTER_LIMIT = 4 A Figure 3. Typical System Schematic, Voltage and Current Programmed by Resistor ORDERING INFORMATION Part Number Package bq24705 24-PIN 4 x 4 mm QFN Ordering Number (Tape and Reel) Quantity bq24705RGER 3000 bq24705RGET 250 PACKAGE THERMAL DATA (1) (2) PACKAGE θJA TA = 70°C POWER RATING DERATING FACTOR ABOVE TA = 25°C QFN – RGE (1) (2) 39°C/W 2.36 W 0.028 W/°C For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI Web site at www.ti.com. This data is based on using the JEDEC High-K board and the exposed die pad is connected to a Cu pad on the board. This is connected to the ground plane by a 2x3 via matrix. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 3 bq24705 www.ti.com SLUS779 – DECEMBER 2007 Table 1. TERMINAL FUNCTIONS – 24-PIN QFN TERMINAL DESCRIPTION NAME NO. PVCC 1 IC power positive supply. Connect to the common-source (diode-OR) point: source of high-side P-channel MOSFET and source of reverse-blocking power P-channel MOSFET. Place a 1-µF ceramic capacitor from PVCC to PGND pin close to the IC. CHGEN 2 Charge enable active-low logic input. LO enables charge. HI disables charge. ACN 3 Adapter current sense resistor, negative input. An optional 0.1-µF ceramic capacitor is placed from ACN pin to AGND for common-mode filtering. An optional 0.1-µF ceramic capacitor is placed from ACN to ACP to provide differential-mode filtering. ACP 4 Adapter current sense resistor, positive input. (See comments with ACN description) ACDET 5 Adapter detected voltage set input. Program the adapter detect threshold by connecting a resistor divider from adapter input to ACDET pin to AGND pin. Adapter voltage is detected if ACDET-pin voltage is greater than 2.4 V. The IADAPT current sense amplifier is active when the ACDET pin voltage is greater than 0.6 V. Input overvoltage, ACOV, disables charge and ACDRV when ACDET > 3.1 V. ACOV does not latch ACSET 6 Adapter current set input. The voltage ratio of ACSET voltage versus VREF voltage programs the input current regulation set-point during Dynamic Power Management (DPM). Program by connecting a resistor divider from VREF to ACSET to AGND; or by connecting the output of an external DAC to the ACSET pin. AGND 7 Analog ground. On PCB layout, connect to the analog ground plane, and only connect to PGND through the power pad underneath the IC. VREF 8 3.3-V regulated voltage output. Place a 1-µF ceramic capacitor from VREF to AGND pin close to the IC. This voltage could be used for ratiometric programming of voltage and current regulation. VADJ 9 Charge voltage set input. The voltage ratio of VADJ voltage versus VREF voltage programs the battery voltage regulation set-point. Program by connecting a resistor divider from VREF to VADJ, to AGND; or, by connecting the output of an external DAC to VADJ. VADJ connected to REGN programs the default of 4.2 V per cell. ACGOOD 10 Valid adapter active-low detect logic open-drain output. Pulled low when input voltage is above ACDET programmed threshold, OR input current is greater than 1.25 A with 10-mΩ sense resistor. Connect a 10-kΩ pullup resistor from ACGOOD pin to pullup supply rail. ISYNSET 11 Synchronous mode voltage set input. Place a resistor from ISYNSET to AGND to program the charge undercurrent threshold to force non-synchronous converter operation at low output current, and to prevent negative inductor current. Threshold should be set at greater than half of the maximum inductor ripple current (50% duty cycle). IADAPT 12 Adapter current sense amplifier output. IADAPT voltage is 20 times the differential voltage across ACP-ACN. Place a 100-pF or less ceramic decoupling capacitor from IADAPT to AGND. SRSET 13 Charge current set input. The voltage ratio of SRSET voltage versus VREF voltage programs the charge current regulation set-point. Program by connecting a resistor divider from VREF to SRSET to AGND; or by connecting the output of an external DAC to SRSET pin. BAT 14 Battery voltage remote sense. Directly connect a kelvin sense trace from the battery pack positive terminal to the BAT pin to accurately sense the battery pack voltage. Place a 0.1-µF capacitor from BAT to AGND close to the IC to filter high-frequency noise. SRN 15 Charge current sense resistor, negative input. An optional 0.1-µF ceramic capacitor is placed from SRN pin to AGND for common-mode filtering. An optional 0.1-µF ceramic capacitor is placed from SRN to SRP to provide differential-mode filtering. SRP 16 Charge current sense resistor, positive input. (See comments for SRN.) CELLS 17 2, 3 or 4 cells selection logic input. Logic low programs 3 cell. Logic high programs 4 cell. Floating programs 2 cell. DPMDET 18 Dynamic power management (DPM) input current loop active, open-drain output status. Logic low indicates input current is being limited by reducing the charge current. Connect 10-kΩ pullup resistor from DPMDET to VREF or a different pullup-supply rail. PGND 19 Power ground. On PCB layout, connect directly to source of low-side power MOSFET, to ground connection of input and output capacitors of the charger. Only connect to AGND through the power pad underneath the IC. LODRV 20 PWM low side driver output. Connect to the gate of the low-side power MOSFET with a short trace. REGN 21 PWM low side driver positive 6-V supply output. Connect a 1-µF ceramic capacitor from REGN to PGND, close to the IC. Use for high-side driver bootstrap voltage by connecting a small-signal Schottky diode from REGN to BTST. PH 22 PWM high side driver negative supply. Connect to the phase switching node (junction of the low-side power MOSFET drain, high-side power MOSFET source, and output inductor). Connect the 0.1-µF bootstrap capacitor from from PH to BTST. HIDRV 23 PWM high side driver output. Connect to the gate of the high-side power MOSFET with a short trace. BTST 24 PWM high side driver positive supply. Connect a 0.1-µF bootstrap ceramic capacitor from BTST to PH. Connect a small bootstrap Schottky diode from REGN to BTST. 4 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (unless otherwise noted) (1) (2) VALUE PVCC, ACP, ACN, SRP, SRN, BAT Voltage range PH –1 to 30 REGN, LODRV, VADJ, ACSET, SRSET, ACDET, ISYNSET, CHGEN, CELLS, ACGOOD, DPMDET, IADAPT –0.3 to 7 VREF Maximum difference voltage UNIT –0.3 to 30 V –0.3 to 3.6 BTST, HIDRV with respect to AGND and PGND –0.3 to 36 AGND–PGND –0.5 to 0.5 ACP–ACN, SRP–SRN 7 V Junction temperature range –40 to 155 Storage temperature range –55 to 155 (1) (2) °C 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 voltages are with respect to GND if not specified. Currents are positive into, negative out of the specified terminal. Consult Packaging Section of the data book for thermal limitations and considerations of packages. RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range (unless otherwise noted) MIN PH Voltage range –1 NOM MAX PVCC, ACP, ACN, SRP, SRN, BAT 0 24 REGN, LODRV, VADJ 0 6.5 VREF 0 3.3 ACSET, SRSET, ACDET, ISYNSET, CHGEN, CELLS, ACGOOD, DPMDET, IADAPT 0 5.5 BTST, HIDRV with respect to AGND and PGND 0 30 –0.3 0.3 Junction temperature range –40 125 Storage temperature range –55 150 AGND, PGND Maximum difference voltage: ACP–ACN, SRP–SRN UNIT 24 V 5.5 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 °C 5 bq24705 www.ti.com SLUS779 – DECEMBER 2007 ELECTRICAL CHARACTERISTICS 7.0 V ≤ VPVCC ≤ 24 V, 0°C < TJ < +125°C, typical values are at TA = 25°C, with respect to AGND (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT OPERATING CONDITIONS VPVCC_OP PVCC Input voltage operating range 5 24 V 8 18 V 0 REGN V 8 V, 8.4 V, 9.024 V –0.5% 0.5% 12 V, 12.6 V, 13.536 V –0.5% 0.5% 16 V, 16.8 V, 18.048 V –0.5% 0.5% VADJ connected to REGN, 8.4 V, 12.6 V, 16.8 V –0.5% 0.5% 0 100 0 VDAC –3% 3% CHARGE VOLTAGE REGULATION VBAT_REG_RNG BAT voltage regulation range VADJ_OP VADJ voltage range 4V-4.512V per cell, times 2,3,4 cell Charge voltage regulation accuracy Charge voltage regulation set to default to 4.2 V per cell CHARGE CURRENT REGULATION VIREG_CHG Charge current regulation differential voltage range VSRSET_OP SRSET voltage range VIREG_CHG = VSRP – VSRN VIREG_CHG = 40–100 mV Charge current regulation accuracy VIREG_CHG = 20 mV –5% 5% VIREG_CHG = 5 mV –25% 25% VIREG_CHG = 1.5 mV –33% 33% 0 200 0 2 VIREG_DPM = 40–100 mV –3% 3% VIREG_DPM = 20 mV –5% 5% VIREG_DPM = 5 mV –25% 25% VIREG_DPM = 1.5 mV –33% 33% 3.267 mV V INPUT CURRENT REGULATION VIREG_DPM Adapter current regulation differential voltage range VACSET_OP ACSET voltage range Input current regulation accuracy VIREG_DPM = VACP – VACN mV V VREF REGULATOR VVREF_REG VREF regulator voltage VACDET > 0.6 V, 0-30 mA IVREF_LIM VREF current limit VVREF = 0 V, VACDET > 0.6 V 35 3.3 3.333 V 75 mA 6.2 V REGN REGULATOR VREGN_REG REGN regulator voltage VACDET > 0.6 V, 0-75 mA, PVCC > 10 V 5.6 IREGN_LIM REGN current limit VREGN = 0 V, VACDET > 0.6 V 90 135 mA 0 24 V 0 2 V 5.9 ADAPTER CURRENT SENSE AMPLIFIER VACP/N_OP Input common mode range VIADAPT IADAPT output voltage range Voltage on ACP/SRN IIADAPT IADAPT output current AIADAPT Current sense amplifier voltage gain 0 AIADAPT = VIADAPT / VIREG_DPM VIREG_DPM = 40–100 mV Adapter current sense accuracy –2% 2% –3%% 3% VIREG_DPM = 5 mV –25% 25% VIREG_DPM = 1.5 mV –30% 30% Output current limit VIADAPT = 0 V CIADAPT_MAX Maximum output load capacitance For stability with 0 mA to 1 mA load Submit Documentation Feedback mA V/V VIREG_DPM = 20 mV IIADAPT_LIM 6 1 20 1 mA 100 pF Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 ELECTRICAL CHARACTERISTICS (continued) 7.0 V ≤ VPVCC ≤ 24 V, 0°C < TJ < +125°C, typical values are at TA = 25°C, with respect to AGND (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT ACDET COMPARATOR VPVCC-BAT_OP VACDET_CHG Differential Voltage from PVCC to BAT ACDET adapter-detect rising threshold –20 Min voltage to enable charging, VACDET rising VACDET_CHG_HYS ACDET falling hysteresis VACDET falling ACDET rising deglitch (1) VACDET rising 2.376 ACDET falling deglitch VACDET falling ACDET enable-bias rising threshold Min voltage to enable all bias, VACDET rising VACDET_BIAS_HYS Adapter present falling hysteresis ACDET rising deglitch (1) ACDET falling deglitch V 2.424 V 40 Charge Enable after ACDET rising VACDET_BIAS 2.40 24 mV 6.4 8 9.6 ms 518 700 908 ms µs 10 0.56 0.62 VACDET falling 20 VACDET rising 10 VACDET falling 10 0.68 V mV µs OPEN-DRAIN LOGIC OUTPUT PIN CHARACTERISTICS (ACGOOD) VOUT_LO Output low saturation voltage Sink Current = 4 mA Delay, ACGOOD falling 6.4 Delay, ACGOOD rising 8 0.5 V 9.6 ms µs 10 INPUT OVERVOLTAGE COMPARATOR (ACOV) VACOV AC Overvoltage rising threshold on ACDET (See ACDET in Terminal Functions) VACOV_HYS AC Overvoltage rising deglitch 1.3 AC Overvoltage falling deglitch 1.3 3.007 3.1 3.193 V ms AC CURRENT DETECT COMPARATOR (INPUT UNDER_CURRENT) VACIDET Adapter current detect rising threshold VACI = IAC × RAC × 20, falling edge VACIDET_HYS Adapter current detect hysteresis Rising edge 200 250 300 50 mV mV PVCC / BAT COMPARATOR (REVERSE DISCHARGING PROTECTION) VPVCC-BAT_FALL PVCC to BAT falling threshold VPVCC-BAT__HYS PVCC to BAT hysteresis VPVCC – VBAT to turn off ACFET 140 185 240 50 PVCC to BAT Rising Deglitch VPVCC – VBAT > VPVCC-BAT_RISE 10 PVCC to BAT Falling Deglitch VPVCC – VBAT < VPVCC-BAT_FALL 6 mV mV µs INPUT UNDERVOLTAGE LOCK-OUT COMPARATOR (UVLO) UVLO AC Undervoltage rising threshold VUVLO_HYS AC Undervoltage hysteresis, falling Measure on PVCC 3.5 4 4.5 260 V mV BAT OVERVOLTAGE COMPARATOR VOV_RISE Overvoltage rising threshold (1) VOV_FALL Overvoltage falling threshold (1) 104% As percentage of VBAT_REG 102% CHARGE OVERCURRENT COMPARATOR VOC Charge overcurrent falling threshold As percentage of IREG_CHG 145% Minimum Current Limit (SRP-SRN) 50 mV THERMAL SHUTDOWN COMPARATOR TSHUT Thermal shutdown rising temperature TSHUT_HYS Thermal shutdown hysteresis, falling Temperature Increasing 155 °C 20 PWM HIGH SIDE DRIVER (HIDRV) RDS_HI_ON High side driver turn-on resistance VBTST – VPH = 5.5 V, tested at 100 mA 3 6 RDS_HI_OFF High side driver turn-off resistance VBTST – VPH = 5.5 V, tested at 100 mA 0.7 1.4 (1) Ω Specified by design. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 7 bq24705 www.ti.com SLUS779 – DECEMBER 2007 ELECTRICAL CHARACTERISTICS (continued) 7.0 V ≤ VPVCC ≤ 24 V, 0°C < TJ < +125°C, typical values are at TA = 25°C, with respect to AGND (unless otherwise noted) PARAMETER VBTST_REFRESH TEST CONDITIONS Bootstrap refresh comparator threshold voltage MIN VBTST – VPH when low side refresh pulse is requested TYP MAX 4 UNIT V PWM LOW SIDE DRIVER (LODRV) RDS_LO_ON Low side driver turn-on resistance REGN = 6 V, tested at 100 mA 3 6 RDS_LO_OFF Low side driver turn-off resistance REGN = 6 V, tested at 100 mA 0.6 1.2 Ω PWM DRIVERS TIMING Driver Dead Time — Dead time when switching between LODRV and HIDRV. No load at LODRV and HIDRV 30 ns PWM OSCILLATOR FSW PWM switching frequency VRAMP_HEIGHT PWM ramp height 480 As percentage of PVCC 600 720 6.6 kHz %PVCC QUIESCENT CURRENT IOFF_STATE IAC IAC_SWITCH VBAT = 16.8 V, VACDET < 0.6 V, VPVCC > 5 V, TJ = 85°C 7 10 VBAT = 16.8 V, VACDET < 0.6 V, VPVCC > 5 V, TJ = 125°C 7 11 Adapter quiescent current VPVCC = 20 V, charge disabled 2.8 4 Adapter switching quiescent current VPVCC = 20 V, Charge enabled, converter running, total gate charge = 2 × 10 nC 25 mA 8 step 1.7 ms Total off-state battery current from SRP, SRN, BAT, VCC, BTST, PH, etc. µA mA INTERNAL SOFT START (8 steps to regulation current) Soft start steps Soft start step time CHARGER SECTION POWER-UP SEQUENCING Charge-enable delay after power-up Delay from when adapter is detected to when the charger is allowed to turn on 518 700 908 ms ISYNSET AMPLIFIER AND COMPARATOR (SYNCHRONOUS TO NON-SYNCHRONOUS TRANSITION) AISYNSET Accuracy 5 mV Gain ISYNSET amplifier gain –20% ISYNSET pin voltage VISYNSET 20% 250 V/I 1 V ISYNSET rising deglitch 20 µs ISYNSET falling deglitch 640 µs LOGIC IO PIN CHARACTERISTICS (CHGEN) VIN_LO Input low threshold voltage VIN_HI Input high threshold voltage VBIAS Input bias current 0.8 V 1 µA 2.1 VCHGEN = 0 to VREGN LOGIC INPUT PIN CHARACTERISTICS (CELLS) VIN_LO Input low threshold voltage, 3 cells CELLS voltage falling edge VIN_MID Input mid threshold voltage, 2 cells CELLS voltage rising for MIN, CELLS voltage falling for MAX 0.5 0.8 VIN_HI Input high threshold voltage, 4 cells CELLS voltage rising 2.5 IBIAS_FLOAT Input bias float current for 2-cell selection V = 0 to VREGN –1 1.8 V 1 µA OPEN-DRAIN LOGIC OUTPUT PIN CHARACTERISTICS (DPMDET) VOUT_LO Output low saturation voltage Sink Current = 5 mA Delay, rising/falling 8 0.5 10 Submit Documentation Feedback V ms Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 TYPICAL CHARACTERISTICS Table of Graphs (1) Y X Figure VREF Load and Line Regulation vs Load Current Figure 4 REGN Load and Line Regulation vs Load Current Figure 5 BAT Voltage vs VADJ/VREF Ratio Figure 6 Charge Current vs SRSET/VREF Ratio Figure 7 Input Current vs ACSET/VREF Ratio Figure 8 BAT Voltage Regulation Accuracy vs Charge Current Figure 9 BAT Voltage Regulation Accuracy Figure 10 Charge Current Regulation Accuracy Figure 11 Input Current Regulation (DPM) Accuracy Figure 12 VIADAPT Input Current Sense Amplifier Accuracy Figure 13 Input Regulation Current (DPM), and Charge Current vs System Current Figure 14 Transient System Load (DPM) Response Figure 15 Charge Current Regulation vs BAT Voltage Figure 16 Efficiency vs Battery Charge Current Figure 17 Battery Removal (from Constant Current Mode) Figure 18 REF and REGN Startup Figure 19 Charger on Adapter Removal Figure 20 Charge Enable / Disable and Current Soft-Start Figure 21 Nonsynchronous to Synchronous Transition Figure 22 Synchronous to Nonsynchronous Transition Figure 23 Near 100% Duty Cycle Bootstrap Recharge Pulse Figure 24 Battery Shorted Charger Response, Over Current Protection (OCP) and Charge Current Regulation Figure 25 Continuous Conduction Mode (CCM) Switching Waveforms Figure 26 Discontinuous Conduction Mode (DCM) Switching Waveforms Figure 27 DPMDET Response with Transient System Load Figure 28 (1) Test results based on Figure 3 application schematic. VIN = 20 V, VBAT = 3-cell Li-Ion, ICHG = 3 A, IADAPTER_LIMIT = 4 A, TA = 25°C, unless otherwise specified. VREF LOAD AND LINE REGULATION vs Load Current REGN LOAD AND LINE REGULATION vs LOAD CURRENT 0 0.50 -0.50 Regulation Error - % Regulation Error - % 0.40 0.30 PVCC = 10 V 0.20 0.10 0 -1 -1.50 PVCC = 10 V -2 PVCC = 20 V -0.10 -2.50 -0.20 -3 PVCC = 20 V 0 10 20 30 VREF - Load Current - mA 40 50 0 Figure 4. 10 20 30 40 50 60 REGN - Load Current - mA 70 80 Figure 5. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 9 bq24705 www.ti.com SLUS779 – DECEMBER 2007 BAT VOLTAGE vs VADJ/VREF RATIO CHARGE CURRENT vs SRSET/VREF RATIO 10 18.2 VADJ = 0 -VREF, 4-Cell, No Load Voltage Regulation - V 17.8 17.6 17.4 17.2 17 16.8 16.6 16.4 8 7 6 5 4 3 2 1 16.2 0 16 0 0.1 0.2 VADJ/VREF Ratio 0.4 0.5 0.6 SRSET/VREF Ratio Figure 6. Figure 7. INPUT CURRENT vs ACSET/VREF RATIO BAT VOLTAGE REGULATION ACCURACY vs CHARGE CURRENT 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1 0.1 0.2 0.3 0.7 0.8 0.9 1 0.2 10 ACSET Varied, 4-Cell, Vbat = 16 V 9 8 Vreg = 16.8 V 0.1 Regulation Error - % Input Current Regulation - A SRSET Varied, 4-Cell, Vbat = 16 V 9 Charge Current Regulation - A 18 7 6 5 4 3 0 -0.1 2 1 -0.2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 ACSET/VREF Ratio 0.8 0.9 0 1 2000 Figure 8. BAT VOLTAGE REGULATION ACCURACY CHARGE CURRENT REGULATION ACCURACY 4-Cell, VBAT = 16 V 1 VADJ = 0 -VREF SRSET Varied 0 -1 0.04 Regulation Error - % Regulation Error - % 8000 2 0.06 4-Cell, no load 0.02 0 -0.02 -0.04 -0.06 -0.10 16.5 -2 -3 -4 -5 -6 -7 -8 -0.08 -9 -10 17 17.5 18 18.5 19 0 V(BAT) - Setpoint - V Figure 10. 10 6000 Figure 9. 0.10 0.08 4000 Charge Current - mA 2 4 I(CHRG) - Setpoint - A 6 8 Figure 11. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 INPUT CURRENT REGULATION (DPM) ACCURACY VIADAPT INPUT CURRENT SENSE AMPLIFIER ACCURACY 5 10 ACSET Varied 9 0 7 4-Cell, VBAT = 16 V 6 Percent Error Regulation Error - % 8 5 4 3 2 VI = 20 V, CHG = EN -5 VI = 20 V, CHG = DIS -10 -15 1 0 -20 -1 -2 -25 Iadapt Amplifier Gain 0 1 2 3 4 Input Current Regulation Setpoint - A 5 0 6 1 2 3 4 5 6 I(ACPWR) - A 7 8 9 10 Figure 12. Figure 13. INPUT REGULATION CURRENT (DPM), AND CHARGE CURRENT vs SYSTEM CURRENT TRANSIENT SYSTEM LOAD (DPM) RESPONSE 5 VI = 20 V, 4-Cell, Vbat = 16 V 4 Ichrg and Iin - A Input Current 3 Charge Current 2 1 0 0 1 2 System Current - A 3 4 Figure 14. Figure 15. CHARGE CURRENT REGULATION vs BAT VOLTAGE EFFICIENCY vs BATTERY CHARGE CURRENT 5 100 Efficiency - % Charge Current - A 4 3 2 90 VI = 21 V V(BAT) = 16.8 V VI = 20 V V(BAT) = 12.6 V VI = 20 V V(BAT) = 8.4 V 80 1 o TA =20 C Ichrg_set = 4 A 0 70 0 2 4 6 8 10 12 Battery Voltage - V 14 16 18 0 Figure 16. 2000 6000 4000 Battery Charge Current - mA 8000 Figure 17. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 11 bq24705 www.ti.com SLUS779 – DECEMBER 2007 REF AND REGN STARTUP Ch4 12.3 V Ch4 1 V/div BATTERY REMOVAL VBAT Ch2 Ch3 5 A/div 20 V/div VPH IBAT CHARGER ON ADAPTER REMOVAL CHARGE ENABLE / DISABLE AND CURRENT SOFT-START VCHGEN Ch4 1 V/div VIN Ch1 12.6 V Ch3 2 A/div VBAT VBAT VPH Ch3 2 A/div IL Ch1 1.8 V Figure 19. Ch1 10 V/div Figure 18. Ch2 20 V/div Ch1 Ch4 5 V/div 5 V/div t − Time = 5 ms/div IBAT t − Time = 200 ms/div t − Time = 4 ms/div Figure 20. Figure 21. NONSYNCHRONOUS TO SYNCHRONOUS TRANSITION SYNCHRONOUS TO NONSYNCHRONOUS TRANSITION PH Ch2 10 V/div Ch2 10 V/div PH LDRV Ch4 5 V/div IL Ch3 2 A/div Ch3 2 A/div Ch4 5 V/div LDRV t − Time = 1 ms/div t − Time = 1 ms/div Figure 22. 12 IL Figure 23. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 Figure 25. CONTINUOUS CONDUCTION MODE (CCM) SWITCHING WAVEFORMS DISCONTINUOUS CONDUCTION MODE (DCM) SWITCHING WAVEFORMS HIDRV PH Ch3 5 V/div Ch2 20 V/div Ch3 5 V/div LODRV Ch4 2 A/div Ch4 5 A/div PH Ch1 20 V/div Figure 24. Ch2 20 V/div BATTERY SHORTED CHARGER RESPONSE, OVERCURRENT PROTECTION (OCP) AND CHARGE CURRENT REGULATION Ch1 20 V/div NEAR 100% DUTY CYCLE BOOTSTRAP RECHARGE PULSE IL t − Time = 400 ns/div HIDRV LODRV IL t − Time = 400 ns/div Figure 26. Figure 27. Ch4 5 A/div Ch3 5 A/div Ch2 5 A/div Ch1 2 V/div DPMDET RESPONSE WITH TRANSIENT SYSTEM LOAD DPMDET IBAT Isys IIN t - Time = 20 ms/div Figure 28. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 13 bq24705 www.ti.com SLUS779 – DECEMBER 2007 FUNCTIONAL BLOCK DIAGRAM 8 ms - 0.6V AC VGOOD - 2.4V + ACDET + 3.3V LDO VREF ENA_BIAS EAI ACGOOD Delay Rising EAO PVCC CHGEN 700 ms Delay Rising ACP PVCC FBO + V(ACP-ACN) - - IIN_REG IIN_ER COMP ERROR AMPLIFIER + ACN BTST CHGEN + 1V BAT VBAT_REG 10mA LEVEL SHIFTER BAT_ER + BAT_SHORT 20 mA CHRG_ON HIDRV ACOP SRP + 20X - V(SRP-SRN) IBAT_ REG + SRN PH DC-DC CONVERTER PWM LOGIC ICH_ER PVCC 6V LDO 20 mA REGN SYNCH V(SRP - SRN) + SYNCH ENA_BIAS ISYNSET BTST - REFRESH C BTST LODRV + BAT ACSET – 4V + _ BAT_SHORT PH + 2.9 V/Cell +- IC Tj 155°C + PGND TSHUT – ACP SRSET VBATSET IBATSET IINSET VADJ VBAT_REG IBAT_REG RATIO IIN_REG PROGRAM VREF CELLS 2, 3, 4 BAT + 104% X VBAT_REG – V(SRP-SRN) + 145% X IBAT_REG – ACDET + 3.1V +PVCC BAT_OVP ACN + 20x - V(IADAPT) IADAPT CHG_OCP ACOV DPM_LOOP_ON DPMDET – – UVLO + AGND 4 V +- 14 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 DETAILED DESCRIPTION BATTERY VOLTAGE REGULATION The bq24705 uses a high-accuracy voltage regulator for charging voltage. The internal default battery voltage setting VBATT= 4.2 V × cell count. The regulation voltage is ratio-metric with respect to VREF. The ratio of VADJ and VREF provides extra 12.5% adjust range on VBATT regulation voltage. By limiting the adjust range to 12.5% of the regulation voltage, the external resistor mismatch error is reduced from ±1% to ±0.1%. Therefore, an overall voltage accuracy as good as 0.5% is maintained, while using 1% mis-match resistors. Ratio-metric conversion also allows compatibility with D/As or microcontrollers (µC). The battery voltage is programmed through VADJ and VREF using Equation 1. V BATT + cell count ƪ ǒ 4V ) 0.5 V VADJ VREF Ǔƫ (1) VADJ is set between 0 and VREF. VBATT defaults to 4.2 V × cell count when VADJ is connected to REGN. CELLS pin is the logic input for selecting cell count. Connect CELLS to charge 2,3, or 4 Li+ cells. When charging other cell chemistries, use CELLS to select an output voltage range for the charger. CELLS CELL COUNT Float 2 AGND 3 VREF 4 The per-cell battery termination voltage is function of the battery chemistry. Consult the battery manufacturer to determine this voltage. The BAT pin is used to sense the battery voltage for voltage regulation and should be connected as close to the battery as possible, or directly on the output capacitor. A 0.1-µF ceramic capacitor from BAT to AGND is recommended to be as close to the BAT pin as possible to decouple high frequency noise. BATTERY CURRENT REGULATION The SRSET input sets the maximum charging current. Battery current is sensed by resistor RSR connected between SRP and SRN. The full-scale differential voltage between SRP and SRN is 100 mV. Thus, for a 0.010 Ω sense resistor, the maximum charging current is 10 A. SRSET is ratio-metric with respect to VREF using Equation 2: V I CHARGE + SRSET 0.10 VREF R SR (2) The input voltage range of SRSET is between 0 and VREF, up to 3.3 V. The SRP and SRN pins are used to sense across RSR with default value of 10 mΩ. However, resistors of other values can also be used. A larger the sense resistor, gives a larger sense voltage, and a higher regulation accuracy, but at the expense of higher conduction loss. INPUT ADAPTER CURRENT REGULATION The total input from an AC adapter or other DC sources is a function of the system supply current and the battery charging current. System current normally fluctuates as portions of the systems are powered up or down. Without Dynamic Power Management (DPM), the source must be able to supply the maximum system current and the maximum charger input current simultaneously. By using DPM, the input current regulator reduces the charging current when the input current exceeds the input current limit set by ACSET. The current capability of the AC adapter can be lowered, which may reduce the system cost. Similar to setting battery regulation current, adapter current is sensed by resistor RAC connected between ACP and ACN. The maximum value is set by ACSET, which is a ratio-metric with respect to VREF, using Equation 3. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 15 bq24705 www.ti.com SLUS779 – DECEMBER 2007 V I ADAPTER + ACSET VVREF 0.10 R AC (3) The input voltage range of ACSET is between 0 and VREF, up to 3.3 V. The ACP and ACN pins are used to sense RAC with default value of 10mΩ. However, resistors of other values can also be used. A larger the sense resistor, gives a larger sense voltage, and a higher regulation accuracy; but, at the expense of higher conduction loss. ADAPTER DETECT AND POWER UP An external resistor voltage divider attenuates the adapter voltage before it goes to ACDET. The adapter detect threshold should typically be programmed to a value greater than the maximum battery voltage, and lower than the minimum allowed adapter voltage. The ACDET divider should be placed before the ACFET in order to sense the true adapter input voltage whether the ACFET is on or off. Before the adapter is detected, BATFET stays on and ACFET turns off. If PVCC is below 5 V, the device is disabled, and both ACFET and BATFET turn off. If ACDET is below 0.6 V but PVCC is above 5 V, part of the bias is enabled, including a crude bandgap reference, ACFET drive and BATFET drive. IADAPT is disabled and pulled down to GND. The total quiescent current is less than 10 µA. Once ACDET rises above 0.6 V and PVCC is above 5 V, all the bias circuits are enabled and REGN output goes to 6 V and VREF goes to 3.3 V. IADAPT becomes valid to proportionally reflect the adapter current. When ACDET rises and passes 2.4 V, a valid AC adapter is present. 500 ms later, the following occurs: • ACGOOD becomes high through external pull-up resistor to the host digital voltage rail; • Charger turns on if all the conditions are satisfied and STAT becomes valid. (see Enable and Disable Charging) ENABLE AND DISABLE CHARGING The following conditions must be valid before a charge is enabled: • CHGEN is LOW; • Adapter is detected; • Adapter is higher than PVCC-BAT threshold; • Adapter is not over voltage; • 500 ms delay is complete after adapter detected; • REGNGOOD and VREFGOOD are valid; • Thermal Shut (TSHUT) is not valid; One of the following conditions will stop on-going charging: • CHGEN is HIGH; • Adapter is removed; • Adapter is less than 250 mV above battery; • Adapter is over voltage; • Adapter is over current; • TSHUT IC temperature threshold is reached (145°C on rising-edge with 15°C hysteresis). AUTOMATIC INTERNAL SOFT-START CHARGER CURRENT The charger automatically soft-starts the charger regulation current every time the charger is enabled to ensure there is no overshoot or stress on the output capacitors or the power converter. The soft-start consists of stepping-up the charge regulation current into 8 evenly divided steps up to the programmed charge current. Each step lasts around 1ms, for a typical rise time of 8 ms. No external components are needed for this function. 16 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 CONVERTER OPERATION The synchronous buck PWM converter uses a fixed frequency (600 kHz) voltage mode with feed-forward control scheme. A type III compensation network allows using ceramic capacitors at the output of the converter. The compensation input stage is connected internally between the feedback output (FBO) and the error amplifier input (EAI). The feedback compensation stage is connected between the error amplifier input (EAI) and error amplifier output (EAO). The LC output filter is selected to give a resonant frequency of 8–12.5 kHz nominal. fo + Where resonant frequency, fo, is given by: • CO = C11 + C12 • LO = L1 1 2p ǸLoC o where (from Figure 2 schematic) An internal saw-tooth ramp is compared to the internal EAO error control signal to vary the duty-cycle of the converter. The ramp height is one-fifteenth of the input adapter voltage making it always directly proportional to the input adapter voltage. This cancels out any loop gain variation due to a change in input voltage, and simplifies the loop compensation. The ramp is offset by 250 mV in order to allow zero percent duty-cycle, when the EAO signal is below the ramp. The EAO signal is also allowed to exceed the saw-tooth ramp signal in order to get a 100% duty-cycle PWM request. Internal gate drive logic allows achieving 99.98% duty-cycle while ensuring the N-channel upper device always has enough voltage to stay fully on. If the BTST pin to PH pin voltage falls below 4 V for more than 3 cycles, then the high-side n-channel power MOSFET is turned off and the low-side n-channel power MOSFET is turned on to pull the PH node down and recharge the BTST capacitor. Then the high-side driver returns to 100% duty-cycle operation until the (BTST-PH) voltage is detected to fall low again due to leakage current discharging the BTST capacitor below the 4 V, and the reset pulse is reissued. The 600 kHz fixed frequency oscillator keeps tight control of the switching frequency under all conditions of input voltage, battery voltage, charge current, and temperature, simplifying output filter design and keeping it out of the audible noise region. The charge current sense resistor RSR should be placed with at least half or more of the total output capacitance placed before the sense resistor contacting both sense resistor and the output inductor; and the other half or remaining capacitance placed after the sense resistor. The output capacitance should be divided and placed onto both sides of the charge current sense resistor. A ratio of 50:50 percent gives the best performance; but the node in which the output inductor and sense resistor connect should have a minimum of 50% of the total capacitance. This capacitance provides sufficient filtering to remove the switching noise and give better current sense accuracy. The type III compensation provides phase boost near the cross-over frequency, giving sufficient phase margin. SYNCHRONOUS AND NON-SYNCHRONOUS OPERATION The charger operates in non-synchronous mode when the sensed charge current is below the ISYNSET value. Otherwise, the charger operates in synchronous mode. During synchronous mode, the low-side n-channel power MOSFET is on, when the high-side n-channel power MOSFET is off. The internal gate drive logic ensures there is break-before-make switching to prevent shoot-through currents. During the 30ns dead time where both FETs are off, the back-diode of the low-side power MOSFET conducts the inductor current. Having the low-side FET turn-on keeps the power dissipation low, and allows safely charging at high currents. During synchronous mode the inductor current is always flowing and operates in Continuous Conduction Mode (CCM), creating a fixed two-pole system. During non-synchronous operation, after the high-side n-channel power MOSFET turns off, and after the break-before-make dead-time, the low-side n-channel power MOSFET will turn-on for around 80ns, then the low-side power MOSFET will turn-off and stay off until the beginning of the next cycle, where the high-side power MOSFET is turned on again. The 80ns low-side MOSFET on-time is required to ensure the bootstrap capacitor is always recharged and able to keep the high-side power MOSFET on during the next cycle. This is important for battery chargers, where unlike regular dc-dc converters, there is a battery load that maintains a voltage and can both source and sink current. The 80-ns low-side pulse pulls the PH node (connection between high and low-side MOSFET) down, allowing the bootstrap capacitor to recharge up to the REGN LDO value. After the 80 ns, the low-side MOSFET is kept off to prevent negative inductor current from occurring. The inductor current is blocked by the off low-side MOSFET, and the inductor current will become discontinuous. This mode is called Discontinuous Conduction Mode (DCM). Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 17 bq24705 www.ti.com SLUS779 – DECEMBER 2007 During the DCM mode the loop response automatically changes and has a single pole system at which the pole is proportional to the load current, because the converter does not sink current, and only the load provides a current sink. This means at low currents the loop response is slower, as there is less sinking current available to discharge the output voltage. At low currents during non-synchronous operation, there may be a small amount of negative inductor current during the 80 ns recharge pulse. The charge should be low enough to be absorbed by the input capacitance. When the converter goes into 0% duty-cycle mode, and BTST – PH < 4 V, the 80-ns recharge pulse occurs on LODRV, the high-side MOSFET does not turn on. The low-side MOSFET does not turn on (no 80-ns recharge pulse), and there is no discharge from the battery. ISYNSET CONTROL (CHARGE UNDERCURRENT) In bq24705, ISYN is internally set as the charge current threshold at which the charger changes from non-synchronous operation into synchronous operation. The low side driver turns on for only 80 ns to charge the boost cap. This is important to prevent negative inductor current, which may cause a boost effect in which the input voltage increases as power is transferred from the battery to the input capacitors. This can lead to an overvoltage on the PVCC node and potentially cause some damage to the system. This programmable value allows setting the current threshold for any inductor current ripple, and avoiding negative inductor current. The minimum synchronous threshold should be set from 1/2 the inductor current ripple to the full ripple current, where the inductor current ripple is given by: I RIPPLE_MAX v I SYN v I RIPPLE_MAX 2 ǒVIN_MAX * VBAT_MINǓ and I RIPPLE_MAX + ǒ Ǔ ǒǓ VBAT_MIN VIN_MAX 1 fs LMIN (4) where: VIN_MAX: maximum adapter voltage VBAT_MIN: minimum BAT voltage fS: switching frequency LMIN: minimum output inductor The ISYNSET comparator, or charge undercurrent comparator, compares the voltage between SRP-BAT and internal threshold on the cycle-to-cycle base. The threshold is set to 13 mV on the falling edge with 8 mV hysteresis on the rising edge with 10% variation. HIGH ACCURACY IADAPT USING CURRENT SENSE AMPLIFIER (CSA) An industry standard, high accuracy current sense amplifier (CSA) is used to monitor the input current by the host or some discrete logic through the analog voltage output of the IADAPT pin. The CSA amplifies the input sensed voltage of ACP – ACN by 20x through the IADAPT pin. The IADAPT output is a voltage source 20 times the input differential voltage. Once PVCC is above 5 V and ACDET is above 0.6V, IADAPT no longer stays at ground, but becomes active. If the user wants to lower the voltage, they could use a resistor divider from IOUT to AGND, and still achieve accuracy over temperature as the resistors can be matched their thermal coefficients. A 200-pF capacitor connected on the output is recommended for decoupling high-frequency noise. An additional RC filter is optional, after the 200-pF capacitor, if additional filtering is desired. Note that adding filtering also adds additional response delay. INPUT OVERVOLTAGE PROTECTION (ACOV) ACOV provides protection to prevent system damage due to high input voltage. The controller enters ACOV when ACDET > 3.1 V. Charge is disabled, the adapter is disconnected from the system by turning off ACDRV, and the battery is connected to the system by turning on BATDRV. ACOV is not latched—normal operation resumes when the ACDET voltage returns below 3.1 V. ACOV threshold is 130% of the adapter-detect threshold. 18 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 INPUT UNDERVOLTAGE LOCK OUT (UVLO) The system must have a minimum 5V PVCC voltage to allow proper operation. This PVCC voltage could come from either input adapter or battery, using a diode-OR input. When the PVCC voltage is below 5 V the bias circuits REGN and VREF stay inactive, even with ACDET above 0.6 V. BATTERY OVERVOLTAGE PROTECTION The converter stops switching when BAT voltage goes above 104% of the regulation voltage. The converter will not allow the high-side FET to turn on until the BAT voltage goes below 102% of the regulation voltage. This allows one-cycle response to an overvoltage condition, such as when the load is removed or the battery is disconnected. A 10-mA current sink from BAT to PGND is on only during charge, and allows discharging the stored output-inductor energy into the output capacitors. CHARGE OVERCURRENT PROTECTION The charger has a secondary overcurrent protection. It monitors the charge current, and prevents the current from exceeding 145% of regulated charge current. The high-side gate drive turns off when the overcurrent is detected, and automatically resumes when the current falls below the overcurrent threshold. THERMAL SHUTDOWN PROTECTION The QFN package has low thermal impedance, which provides good thermal conduction from the silicon to the ambient, to keep junctions temperatures low. As added level of protection, the charger converter turns off and self-protects whenever the junction temperature exceeds the TSHUT threshold of 145°C. The charger stays off until the junction temperature falls below 130°C. Status Outputs (ACGOOD, DPMDET) Two status outputs are available, and they all require external pull up resistors to pull the pins to system digital rail for a high level. ACGOOD open-drain output goes low under either of the two conditions: 1. ACDET is above 2.4 V 2. Adapter current is above 1.25 A using a 10-mΩ sense resistor (IADAPT voltage above 250 mV). Internally, the AC current detect comparator looks between IADAPT and an internal 250-mV threshold. It indicates a good adapter is connected because of valid voltage or current. STAT open-drain output goes low when charging. A high level on STAT indicates the charger is not charging; therefore, either, CHGEN pin is not low, or the charger is not able to charge because input voltage is still powering up and the 700-ms delay has not finished, or because of a fault condition such as overcurrent, input over voltage, or TSHUT overtemperature. DPMDET open-drain output goes low when the DPM loop is active to reduce the battery charge current (after a 10-ms delay). Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 19 bq24705 www.ti.com SLUS779 – DECEMBER 2007 Table 2. Component List for Typical System Circuit of Figure 2 PART DESIGNATOR QTY DESCRIPTION Q1, Q2, Q3 3 P-channel MOSFET, –30V,-6A, SO-8, Vishay-Siliconix, Si4435 Q4, Q2 2 N-channel MOSFET, 30V, 12.5A, SO-8, Fairchild, FDS6680A D1 1 Diode, Dual Schottky, 30V, 200mA, SOT23, Fairchild, BAT54C RAC, RSR 2 Sense Resistor, 10 mΩ, 1%, 1W, 2010, Vishay-Dale, WSL2010R0100F L1 1 Inductor, 10µH, 7A, 31mΩ, Vishay-Dale, IHLP5050FD-01 C6, C7, C11, C12 5 Capacitor, Ceramic, 10µF, 35V, 20%, X5R, 1206, Panasonic, ECJ-3YB1E106M C1, C4, C10 3 Capacitor, Ceramic, 1µF, 25V, 10%, X7R, 2012, TDK, C2012X7R1E105K C2, C3, C8, C9, C13, C14, C15 7 Capacitor, Ceramic, 0.1µF, 50V, 10%, X7R, 0805, Kemet, C0805C104K5RACTU R3, R4 4 Resistor, Chip, 10 kΩ, 1/16W, 5%, 0402 R1 1 Resistor, Chip, 432 kΩ, 1/16W, 1%, 0402 R2 1 Resistor, Chip, 66.5 kΩ, 1/16W, 1%, 0402 R5 1 Resistor, Chip, 4 Ω, 1/2W, 1%, 1210 R6 1 Resistor, Chip, 33 kΩ, 1/16W, 1%, 0402 APPLICATION INFORMATION Input Capacitance Calculation During the adapter hot plug-in, the ACDRV has not been enabled. The AC switch is off and the simplified equivalent circuit of the input is shown in Figure 29. Ii Li Ri C1 Vi A. C8 8 Ci Vc Ri and Li are the equivalent input inductance and resistance. C1 and C8 are the input capacitance. Figure 29. Simplified Equivalent Circuit During Adapter Insertion The voltage on the input capacitor(s) is given by: VC ( t ) = VC (0) + Z0 = where: 20 Vi × w Z 0 × C i × w 20 Li w= Ci , + - Vi Z 0 × C i × w 02 æR 1 - çç i L i C i è 2L i e Ri t 2L i æ ö R çç - i sin wt - w × cos wt ÷÷ è 2L i ø (5) 2 ö ÷÷ w0 = ø , and 1 L iCi Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 For a typical notebook charger application, the total stray inductance of the adapter output wire and the PCB connections is normally 5–12 µH, and the total effective resistance of the input connections is 0.15–0.5 Ω. Figure 30(a) demonstrates that a higher Ci helps to damp the voltage spike. Figure 30(b) demonstrates the effect of the input stray inductance Li on the input voltage spike. The dashed curve in Figure 30(b) represents the worst case for Ci=40 µF. Figure 30(c) shows how the resistance helps to suppress the input voltage spike. 35 35 Ci = 20 mF 30 Ci = 40 mF Ri = 0.15 W, Ci = 40 mF 30 Input Capacitor Voltage - V Input Capacitor Voltage - V Li = 5 mF Ri = 0.21 W, Li = 9.3 mH 25 20 15 10 5 Li = 12 mF 25 20 15 10 5 0 0 0.5 1 1.5 2 2.5 3 3.5 Time - 100 ms/div (a) Vc with various Ci values 4 4.5 0 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Time - 100 ms/div (b) Vc with various Li values 35 Li = 9.3 mH, Ci = 40 mF Ri = 0.15 W Input Capacitor Voltage - V 30 Ri = 0.50 W 25 20 15 10 5 0 0 0.5 1 1.5 2 2.5 3 Time - 100 ms/div 3.5 4 4.5 5 (c) Vc with various Ri values Figure 30. Parametric Study Of The Input Voltage Minimizing the input stray inductance, increasing the input capacitance and using high-ESR input capacitors helps to suppress the input voltage spike. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 21 bq24705 www.ti.com SLUS779 – DECEMBER 2007 Figure 31 shows the measured input voltages and currents with different input capacitances. The voltage spike drops by about 5 V after increasing Ci from 20 µF to 40 µF. The input voltage spike has been dramatically damped by using a 47 F electrolytic capacitor. Figure 31. Adapter DC Side Hot Plug-In With Various Input Capacitances Since the input voltage to the IC is PVCC which is 0.7 V (diode voltage drop) lower than Vc during the adapter insertion, a 40-µF input capacitance is normally adequate to keep the PVCC voltage well below the maximum voltage rating under normal conditions. In case of a higher input stray inductance, the input capacitance may be increased accordingly. An electrolytic capacitor will help reduce the input voltage spike due to its high ESR. 22 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 bq24705 www.ti.com SLUS779 – DECEMBER 2007 PCB Layout Design Guideline 1. It is critical that the exposed power pad on the backside of the IC package be soldered to the PCB ground. Ensure that there are sufficient thermal vias directly under the IC, connecting to the ground plane on the other layers. 2. The control stage and the power stage should be routed separately. At each layer, the signal ground and the power ground are connected only at the power pad. 3. The AC current-sense resistor must be connected to ACP (pin 4) and ACN (pin 3) with a Kelvin contact. The area of this loop must be minimized. The decoupling capacitors for these pins should be placed as close to the IC as possible. 4. The charge-current sense resistor must be connected to SRP (pin 16), SRN (pin 15) with a Kelvin contact. The area of this loop must be minimized. The decoupling capacitors for these pins should be placed as close to the IC as possible. 5. Decoupling capacitors for PVCC (pin 1), VREF (pin 8), REGN (pin 21) should be placed underneath the IC (on the bottom layer) with the interconnections to the IC as short as possible. 6. Decoupling capacitors for BAT (pin 14), IADAPT (pin 12) must be placed close to the corresponding IC pins with the interconnections to the IC as short as possible. 7. Decoupling capacitor CX for the charger input must be placed close to the Q4 drain and Q5 source. Figure 32 shows the recommended component placement with trace and via locations. (a) Top Layer (b) Bottom Layer Figure 32. Layout Example Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :bq24705 23 PACKAGE OPTION ADDENDUM www.ti.com 21-Dec-2007 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty BQ24705RGER ACTIVE QFN RGE 24 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR BQ24705RGET ACTIVE QFN RGE 24 250 CU NIPDAU Level-2-260C-1 YEAR Green (RoHS & no Sb/Br) Lead/Ball Finish MSL Peak Temp (3) (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. 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Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 19-Dec-2007 TAPE AND REEL BOX INFORMATION Device BQ24705RGER Package Pins RGE 24 Site Reel Diameter (mm) Reel Width (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) SITE 41 330 12 4.3 4.3 1.5 8 Pack Materials-Page 1 W Pin1 (mm) Quadrant 12 Q2 PACKAGE MATERIALS INFORMATION www.ti.com 19-Dec-2007 Device Package Pins Site Length (mm) Width (mm) Height (mm) BQ24705RGER RGE 24 SITE 41 346.0 346.0 29.0 Pack Materials-Page 2 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. 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