Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - battery management Charge management, Surge/undervoltage protection Li-Ion VQFN 20

6 7 8 9 10

20 19 18 17 16

ACN

ACP

CMSRC

ACDRV

ACOK

ACDET

IOUT

SDA

SCL

ILIM

BATDRV

SRN

SRP

GND

LODRV

REGN

BTST

HIDRV

PHASE

VCC

bq24725A

www.ti.com

SLUSAL0 –SEPTEMBER 2011

1-4 Cell Li+ Battery SMBus Charge Controller with N-Channel Power MOSFET Selector

and Advanced Circuit Protection

Check for Samples: bq24725A

FEATURES

DESCRIPTION

The bq24725A is a high-efficiency, synchronous

• SMBus Host-Controlled NMOS-NMOS

battery charger, offering low component count for

Synchronous Buck Converter with

space-constraint, multi-chemistry battery charging

Programmable 615kHz, 750kHz, and 885kHz

applications.

Switching Frequencies

The bq24725A utilizes two charge pumps to

• Automatic N-channel MOSFET Selection of

separately drive n-channel MOSFETs (ACFET,

System Power Source from Adapter or Battery

RBFET and BATFET) for automatic system power

Driven by Internal Charge Pumps

source selection.

• Enhanced Safety Features for Over Voltage

SMBus controlled input current, charge current, and

Protection, Over Current Protection, Battery,

charge voltage DACs allow for very high regulation

Inductor and MOSFET Short Circuit Protection

accuracies that can be easily programmed by the

• Programmable Input Current, Charge Voltage,

system power management micro-controller.

Charge Current Limits

The bq24725A uses internal input current register or

– ±0.5% Charge Voltage Accuracy up to 19.2V

external ILIM pin to throttle down PWM modulation to

– ±3% Charge Current Accuracy up to 8.128A

reduce the charge current.

– ±3% Input Current Accuracy up to 8.064A

The bq24725A charges one, two, three or four series

– ±2% 20x Adapter Current or Charge Current

Li+ cells, and is available in a 20-pin, 3.5x3.5 mm

QFN package.

Amplifier Output Accuracy

• Programmable Battery Depletion Threshold,

and Battery LEARN Function PIN CONFIGURATION

• Programmable Adapter Detection and

Indicator

• Integrated Soft Start

• Integrated Loop Compensation

• Real Time System Control on ILIM pin to Limit

Charge Current

• AC Adapter Operating Range 4.5V-24V

• 5µA Off-State Battery Discharge Current

• 0.65mA (0.8mA max) Adapter Standby

Quiescent Current

• 20-pin 3.5 x 3.5 mm

QFN Package

APPLICATIONS

• Portable Notebook Computers, UMPC,

Ultra-Thin Notebook, and Netbook

• Handheld Terminal

• Industrial and Medical Equipment

• Portable Equipment

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.

Summary of content (42 pages)

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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com 1-4 Cell Li+ Battery SMBus Charge Controller with N-Channel Power MOSFET Selector and Advanced Circuit Protection Check for Samples: bq24725A FEATURES DESCRIPTION • The bq24725A is a high-efficiency, synchronous battery charger, offering low component count for space-constraint, multi-chemistry battery charging applications.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. DEVICE INFORMATION Reverse Input Protection Adapter + Adapter - Q6 BSS138W R12 1M R13 3.01M Q1 (ACFET) FDS6680A * Ri 2? Ci 2.2µF C17 2200pF D2 BAT54C Q2 (RBFET) FDS6680A RAC 10m? C16 0.1µF C1 0.1µF * SYSTEM Total Csys 220µF R9 10 Ω C3 0.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com D3 PDS1040 Adapter + Adapter - * Q1 (ACFET) FDS6680A C17 2200 pF Ri 2? Ci 2.2µF RAC 10 mW SYSTEM C16 0.1µF C1 0.1µF * R10 4.02 kW C3 0.1µF * C5 1µF ACN C2 0.1µF Total Csys 220µF R9 10 Ω VCC R6 4.02 kW BATDRV ACP R11 4.02 kW CMSRC Q5 (BATFET) FDS6680A C15 0.01µF C6 1µF REGN ACDRV R1 430 kW BTST D1 BAT54 C8 10uF ACDET R2 66.5 kW HIDRV R8 100 kW ILIM R7 549 kW +3.3V HOST R3 10 kW R4 10 kW U1 bq24725A R5 10 kW C7 0.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Q1 (ACFET) FDS6680A Adapter + C17 2200pF Q2 (RBFET) FDS6680A RAC 10 mW C16 0.047µF C1 0.1 µF Adapter - SYSTEM C3 0.1µF * Din BAT54A C2 0.1µF R10 4.02 kW Total Csys 220 µF R9 4.7 W C5 1µF ACN VCC ACP BATDRV * Q5 (BATFET) Si4435DDY R6 4.02 kW R11 4.02 kW R12 100 kW C6 1µF CMSRC D2 SL42 REGN D1 BAT54 ACDRV R1 430 kW BTST C8 10uF ACDET R2 487 kW HIDRV R8 100 kW ILIM R7 549 kW +3.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com THERMAL INFORMATION bq24725A THERMAL METRIC (1) (2) θJA Junction-to-ambient thermal resistance θJCtop Junction-to-case (top) thermal resistance (3) 46.8 56.9 (4) θJB Junction-to-board thermal resistance ψJT Junction-to-top characterization parameter ψJB Junction-to-board characterization parameter θJCbot (1) (2) (3) (4) (5) (6) (7) UNITS RGR (20 PIN) 46.6 (5) Junction-to-case (bottom) thermal resistance °C/W 0.6 (6) 15.3 (7) 4.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS 4.5 V ≤ VVCC ≤ 24 V, 0°C ≤ TJ ≤ 125°C, typical values are at TA = 25°C, with respect to GND (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT OPERATING CONDITIONS VVCC_OP VCC Input voltage operating range 4.5 24 V 19.2 V 16.884 V CHARGE VOLTAGE REGULATION VBAT_REG_RNG Battery voltage range 1.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 4.5 V ≤ VVCC ≤ 24 V, 0°C ≤ TJ ≤ 125°C, typical values are at TA = 25°C, with respect to GND (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 6.5 UNIT REGN REGULATOR VREGN_REG IREGN_LIM REGN regulator voltage REGN current limit 5.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 4.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 4.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 4.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com TYPICAL CHARACTERISTICS Table 1. Table of Graphs FIGURE NO.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Figure 7. Current Soft-Start Figure 8. Charge Disable by ILIM CH1: PHASE, 10V/div, CH2: LODRV, 5V/div, CH3: HIDRV, 10V/div, CH4: inductor current, 2A/div, 400ns/div Figure 9. Continuous Conduction Mode Switching Waveforms CH1: PHASE, 10V/div, CH2: LODRV, 5V/div, CH4: inductor current, 2A/div, 4us/div Figure 11. 100% Duty and Refresh Pulse 12 CH1: PHASE, 10V/div, CH2: LODRV, 5V/div, CH3: HIDRV, 10V/div, CH4: inductor current, 1A/div, 400ns/div Figure 10.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com 98 97 96 Efficiency - % 95 94 3-cell 12.6 V 93 2-cell 8.4 V 4-cell 16.8 V 92 91 VIN = 20 V, F = 750 kHz, L = 4.7 mH 90 89 88 0 0.5 CH1: PHASE, 20V/div, CH2: battery voltage, 5V/div, CH3: LODRV, 10V/div, CH4: inductor current, 2A/div, 400us/div Figure 13. Battery Insertion 1 1.5 2 2.5 3 Charge Current 3.5 4 4.5 Figure 14. Efficiency vs Output Current Pin Functions – 20-Pin QFN PIN NO.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Pin Functions – 20-Pin QFN (continued) PIN NO. 12 SRN Charge current sense resistor negative input. SRN pin is for battery voltage sensing as well. Connect SRN pin to a 7.5 Ω resistor first then from resistor another terminal connect a 0.1µF ceramic capacitor to GND for common-mode filtering and connect to current sensing resistor. Connect a 0.1µF ceramic capacitor between current sensing resistor to provide differential mode filtering.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com FUNCTIONAL BLOCK DIAGRAM bq24725A 135mV 1.07 Figure 15.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com DETAILED DESCRIPTION SMBus Interface The bq24725A operates as a slave, receiving control inputs from the embedded controller host through the SMBus interface. The bq24725A uses a simplified subset of the commands documented in System Management Bus Specification V1.1, which can be downloaded from www.smbus.org. The bq24725A uses the SMBus Read-Word and Write-Word protocols (see Figure 16) to communicate with the smart battery.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Figure 17. SMBus Write Timing A B tLOW C D E F G H I J K t HIGH SMBCLK SMBDATA A = START CONDITION E = SLAVE PULLS SMBDATA LINE LOW I = ACKNOWLEDGE CLOCK PULSE B = MSB OF ADDRESS CLOCKED INTO SLAVE F = ACKNOWLEDGE BIT CLOCKED INTO MASTER J = STOP CONDITION C = LSB OF ADDRESS CLOCKED INTO SLA VE G = MSB OF DATA CLOCKED INTO MASTER K = NEW START CONDITION D = R/W BIT CLOCKED INTO SLAVE H = LSB OF DATA CLOCKED INTO MASTER Figure 18.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Setting Charger Options By writing ChargeOption() command (0x12H or 0b00010010), bq24725A allows users to change several charger options after POR (Power On Reset) as shown in Table 3. Table 3. Charge Options Register (0x12H) BIT BIT NAME DESCRIPTION [15] ACOK Deglitch Time Adjust Adjust ACOK deglitch time. After POR, the first time the adapter plug in occurs, deglitch time is always 150ms no matter if this bit is 0 or 1.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Setting the Charge Current To set the charge current, write a 16bit ChargeCurrent() command (0x14H or 0b00010100) using the data format listed in Table 4. With 10mΩ sense resistor, the bq24725A provides a charge current range of 128mA to 8.128A, with 64mA step resolution. Sending ChargeCurrent() below 128mA or above 8.128A clears the register and terminates charging. Upon POR, charge current is 0A. A 0.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com The SRN pin is used to sense the battery voltage for voltage regulation and should be connected as close to the battery as possible, and place a decoupling capacitor (0.1µF recommended) as close to the IC as possible to decouple high frequency noise. Table 5. Charge Voltage Register (0x15H) BIT BIT NAME 0 - DESCRIPTION Not used. 1 - Not used. 2 - Not used. 3 - Not used. 4 Charge Voltage, DACV 0 0 = Adds 0mV of charger voltage.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com The ACP and ACN pins are used to sense RAC with default value of 10mΩ. However, resistors of other values can also be used. For a larger sense resistor, larger sense voltage is given, and a higher regulation accuracy; but, at the expense of higher conduction loss. If input current rises above FAST_DPM threshold, the charger will reduce charging current to allow the input current drop.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com change this option, the VCC pin voltage must above UVLO, and the ACDET pin voltage must be above 0.6V which enables the IC SMBus communication and sets ChargeOption() bit[15] to 0 which sets the next ACOK rising deglitch time to be 150ms. The purpose of the default 1.3s rising edge deglitch time is to turn off the ACFET long enough when the ACDET pin is pulled below 2.4V by excessive system current, such as over current or short circuit.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com external capacitor of ACFET must be carefully selected. The larger the Cgs and Cgd capacitance, the slower turn on of ACFET will be and less inrush current of adapter. However, if Cgs or Cgd is too large, the ACDRV-CMSRC voltage may still go low after the 20ms turn on time window is expired. To make sure ACFET will not be turned on when adapter is hot plugged in, the Cgs value should be 20 times or higher than Cgd.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Converter Operation The synchronous buck PWM converter uses a fixed frequency voltage mode control scheme and internal type III compensation network. The LC output filter gives a characteristic resonant frequency 1 ¦o = 2p Lo Co (3) The resonant frequency fo is used to determine the compensation to ensure there is sufficient phase margin and gain margin for the target bandwidth.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Both CCM and DCM are synchronous operation with LSFET turn-on every clock cycle. If the average charge current goes below 125mA on 10mΩ current sensing resistor or the battery voltage falls below 2.5V, the LSFET keeps turn-off. The battery charger operates in non-synchronous mode and the current flows through the LSFET body diode. During non-synchronous operation, the LSFET turns on only for a refreshing pulse to charge the BTST capacitor.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com If frequency is reduced, for a fixed inductor the current ripple is increased. Inductor value must be carefully selected so that it will not trig cycle-by-cycle peak over current protection even for the worst condition such as higher input voltage, 50% duty cycle, lower inductance and lower switching frequency. Inductor Short, MOSFET Short Protection The bq24725A has a unique short circuit protection feature.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Table 8. Component List for Typical System Circuit of Figure 1 (continued) PART DESIGNATOR QTY DESCRIPTION R15 1 Resistor, Chip, 7.5Ω, 1/10W, 5%, 0603 RAC, RSR 2 Resistor, Chip, 0.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com APPLICATION INFORMATION Negative Output Voltage Protection Reversely insert the battery pack into the charger output during production or hard shorts on battery to ground will generate negative output voltage on SRP and SRN pin.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com The bq24725A has charge under current protection (UCP) by monitoring charging current sensing resistor cycle-by-cycle. The typical cycle-by-cycle UCP threshold is 5mV falling edge corresponding to 0.5A falling edge for a 10mΩ charging current sensing resistor. When the average charging current is less than 125mA for a 10mΩ charging current sensing resistor, the low side MOSFET is off until BTST capacitor voltage needs to refresh the charge.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Ptop = D ´ ICHG2 ´ RDS(on) + 1 ´ VIN ´ ICHG ´ (t on + t off ) ´ f s 2 (9) The first item represents the conduction loss. Usually MOSFET RDS(ON) increases by 50% with 100°C junction temperature rise. The second term represents the switching loss. The MOSFET turn-on and turn-off times are given by: Q Q t on = SW , t off = SW Ion Ioff (10) where Qsw is the switching charge, Ion is the turn-on gate driving current and Ioff is the turn-off gate driving current.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com D1 Adapter connector R2(1206) 10-20 Ω R1(2010) 2Ω VCC pin C1 2.2μF C2 0.47-1μF Figure 19. Input Filter bq24725A Design Guideline The bq24725A has a unique short circuit protection feature. Its cycle-by-cycle current monitoring feature is achieved through monitoring the voltage drop across RDS(on) of the MOSFETs after a certain amount of blanking time.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com To prevent unintentional charger shut down in normal operation, MOSFET RDS(on) selection and PCB layout is very important. Figure 21 shows a improvement PCB layout example and its equivalent circuit. In this layout, the system current path and charger input current path is not separated, as a result, the system current causes voltage drop in the PCB copper and is sensed by the IC.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com PCB Layout The switching node rise and fall times should be minimized for minimum switching loss. Proper layout of the components to minimize high frequency current path loop (see Figure 23) is important to prevent electrical and magnetic field radiation and high frequency resonant problems. Here is a PCB layout priority list for proper layout. Layout PCB according to this specific order is essential. 1.
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bq24725A SLUSAL0 – SEPTEMBER 2011 www.ti.com Charge Current Direction R SNS To Inductor To Capacitor and battery Current Sensing Direction To SRP and SRN pin Figure 24. Sensing resistor PCB layout.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 25-Feb-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant BQ24725ARGRR VQFN RGR 20 3000 330.0 12.4 3.75 3.75 1.15 8.0 12.0 Q1 BQ24725ARGRT VQFN RGR 20 250 180.0 12.4 3.75 3.75 1.15 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 25-Feb-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) BQ24725ARGRR VQFN RGR 20 3000 552.0 367.0 36.0 BQ24725ARGRT VQFN RGR 20 250 552.0 185.0 36.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.