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

bq24725

Not Recommended for New Designs

bq24725

www.ti.com

SLUS702A –JULY 2010–REVISED NOVEMBER 2010

2-4 Cell Li+ Battery SMBus Charge Controller with N-Channel Power MOSFET Selector

and Advanced Circuit Protection

Check for Samples: bq24725

FEATURES

DESCRIPTION

• SMBus Host-Controlled NMOS-NMOS

The bq24725 is a high-efficiency, synchronous

Synchronous Buck Converter with

battery charger, offering low component count for

Programmable 615kHz, 750kHz, and 885kHz

space-constraint, multi-chemistry battery charging

Switching Frequencies

applications.

• Automatic N-channel MOSFET Selection of

The bq24725 uses two charge pumps to separately

System Power Source from Adapter or Battery

drive n-channel MOSFETs (ACFET, RBFET and

Driven by Internal Charge Pumps

BATFET) for automatic system power source

• Enhanced Safety Features for Over Voltage

selection.

Protection, Over Current Protection, Battery,

SMBus controlled input current, charge current, and

Inductor and MOSFET Short Circuit Protection

charge voltage DACs allow for high regulation

• Programmable Input Current, Charge Voltage,

accuracies that can be programmed by the system

Charge Current Limits

power management micro-controller.

– ±0.5% Charge Voltage Accuracy up to 19.2V

The bq24725 uses internal input current register or

– ±3% Charge Current Accuracy up to 8.128A

external ILIM pin to throttle down PWM modulation to

reduce the charge current.

– ±3% Input Current Accuracy up to 8.064A

– ±2% 20x Adapter Current or Charge Current

The bq24725 charges two, three or four series Li+

Amplifier Output Accuracy

cells, and is available in a 20-pin, 3.5 x 3.5 mm

QFN

package.

• Programmable Battery Depletion Threshold,

and Battery LERAN Function

• 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 9V-24V

• 5µA Off-State Battery Discharge Current

• 20-pin 3.5 x 3.5 mm

QFN Package

APPLICATIONS

• Portable Notebook Computers, UMPC, Ultra-

Thin Notebook, and Netbook

• Personal Digital Assistant

• 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.

2PowerPAD is a trademark of Texas Instruments.

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 (40 pages)

PAGE 1
Not Recommended for New Designs bq24725 www.ti.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 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 C17 2200pF Ri 2? Ci 2.2µF D2 BAT54C Q2 (RBFET) FDS6680A RAC 10m? C16 0.1µF C1 0.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 D3 PDS1040 Adapter + Adapter - Q1 (ACFET) FDS6680A C17 2200pF Ri 2? Ci 2.2µF RAC 10m? SYSTEM C16 0.1µF C1 0.1µF C3 0.1µF C2 0.1µF R10 4.02k Total Csys 220µF R9 10Ω C5 1µF ACN VCC ACP BATDRV R6 4.02k R11 4.02k CMSRC Q5 (BATFET) FDS6680A C15 0.01µF C6 1µF REGN D1 BAT54 ACDRV R1 430k BTST R2 66.5k HIDRV R8 100k ILIM R7 549k +3.3V HOST R3 10k R4 10k U1 bq24725 R5 10k C7 0.
PAGE 4
Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (unless otherwise noted) (1) (2) VALUE SRN, SRP, ACN, ACP, CMSRC, VCC Voltage range Maximum difference voltage UNIT –0.3 to 30 PHASE –2 to 30 ACDET, SDA, SCL, LODRV, REGN, IOUT, ILIM, ACOK –0.3 to 7 BTST, HIDRV, ACDRV, BATDRV –0.3 to 36 SRP–SRN, ACP–ACN –0.5 to 0.
PAGE 5
Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 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 UNIT 81.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 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 UNIT QUIESCENT CURRENT IBAT_BATFET_OFF Battery BATFET OFF STATE Current, BATFET off, ISRP + ISRN + IPHASE + IACP + IACN VVBAT = 16.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 ELECTRICAL CHARACTERISTICS (continued) 4.
PAGE 8
Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 4.
PAGE 9
Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 Figure 3.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS Table 1. Table of Graphs FIGURE NO.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 CH1: HIDRV, 10V/div, CH2: LODRV, 5V/div, CH3: PHASE, 10V/div, CH4: inductor current, 2A/div, 400ns/div Figure 8. Continuous Conduction Mode Switching Waveforms CH1: HIDRV, 10V/div, CH2: LODRV, 5V/div, CH3: PHASE, 10V/div, CH4: inductor current, 1A/div, 400ns/div Figure 9. Cycle-by-Cycle Synchronous to Non-synchronous CH1: PHASE, 10V/div, CH2: LODRV, 5V/div, CH4: inductor current, 2A/div, 4us/div Figure 10.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com 98 4-cell 16.8 V 97 96 Efficiency - % 95 3-cell 12.6 V 94 93 2-cell 8.4 V 92 91 VI = 20 V, f = 750 kHz, L = 4.7 mH 90 89 88 0 0.5 CH1: PHASE, 20V/div, CH2: LODRV, 10V/div, CH3: battery voltage, 5V/div, CH4: inductor current, 2A/div, 4us/div Figure 14. Battery to Ground Short Transition 1 1.5 2 2.5 Charge Current 3 3.5 4 4.5 Figure 15.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 PIN FUNCTIONS – 20-PIN QFN (continued) PIN NO. FUNCTION DESCRIPTION NAME 13 SRP Charge current sense resistor positive input. Connect the SRP pin to a 10Ω resistor first then from resistor another terminal connect to current sensing resistor. Connect a 0.1µF ceramic capacitor between current sensing resistor to provide differential mode filtering.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com FUNCTIONAL BLOCK DIAGRAM ** Threshold or deglitch time is adjustable by ChargeOption () 3.75V UVLO VCC 20 EN_REGN ACOK_DRV ACN WAKEUP ACDET 6 CMSRC+6V ACN-SRN ACDRV CHARGE PUMP SRN+200mV 0.6V 4 ACDRV ACDRV-CMSRC ACDRV ACOVP CMSRC+5.9V 3.15V ACGOOD ACOC 3 CMSRC Selector Logic SRN+6V Latch off VCC_SRN ** 2.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 DETAILED DESCRIPTION SMBus Interface The bq24725 operates as a slave, receiving control inputs from the embedded controller host through the SMBus interface. The bq24725 uses a simplified subset of the commands documented in System Management Bus Specification V1.1, which can be downloaded from www.smbus.org.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com Figure 18.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 Setting Charger Options By writing ChargeOption() command (0x12H or 0b00010010), bq24725 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 [15] ACOK Deglitch Time Adjust ACOK deglitch time. Adjust To change this option, VCC pin voltage must above UVLO and ACDET pin voltage must above 0.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 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 bq24725 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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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 Setting the Charge Voltage To set the output charge regulation voltage, write a 16bit ChargeVoltage() command (0x15H or 0b00010101) using the data format listed in Table 5. The bq24725 provides charge voltage range from 1.024V to 19.200V, with 16mV step resolution. Sending ChargeVoltage() below 1.024V or above 19.2V clears the register and terminates charging. Upon POR, charge voltage limit is 0V.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com To set the input current limit, write a 16-bit InputCurrent() command (0x3FH or 0b00111111) using the data format listed in Table 6. When using a 10mΩ sense resistor, the bq24725 provides an input-current limit range of 128mA to 8.064A, with 128mA resolution. The suggested input current limit is set to no less than 512mA. Sending InputCurrent() below 128mA or above 8.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 The rising edge delay default is 150ms after ACDET has a valid voltage to make ACOK pull high. The first time after IC POR always gives a 150ms ACOK rising edge delay no matter what the ChargeOption register value. To change this option, the VCC pin voltage must above UVLO, and the ACDET pin voltage must above 0.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com To limit the adapter inrush current when ACFET is turned on to power system from adapter, the Cgs and Cgd 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.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 High Accuracy Current Sense Amplifier As an industry standard, high accuracy current sense amplifier (CSA) is used to monitor the input current or the charge current, selectable via SMBUS (ChargeOption() bit[5]=0 select the input current, bit[5]=1 select the charge current) by host. The CSA senses voltage across the sense resistor by a factor of 20 through the IOUT pin.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com Continuous Conduction Mode (CCM) With sufficient charge current the bq24725’s inductor current never crosses zero, which is defined as continuous conduction mode. The controller starts a new cycle with ramp coming up from 200mV. As long as EAO voltage is above the ramp voltage, the high-side MOSFET (HSFET) stays on.
PAGE 25
Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 Battery Shorted to Ground (BATLOWV) The bq24725 will disable charge for 1ms if the battery voltage on SRN falls below 2.5V. After 1ms reset, the charge is resumed with soft-start if all the enable conditions in the Enable and Disable Charging sections are satisfied. This prevents any overshoot current in inductor which can saturate inductor and may damage the MOSFET. The charge current is limited to 0.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com Table 8. Component List for Typical System Circuit of Figure 1 (continued) PART DESIGNATOR QTY DESCRIPTION Csys 1 Capacitor, Electrolytic, 220µF, 25V D1 1 Diode, Schottky, 30V, 200mA, SOT-23, Fairchild, BAT54 D2 1 Diode, Dual Schottky, 30V, 200mA, SOT-23, Fairchild, BAT54C Q1, Q2, Q5 3 N-channel MOSFET, 30V, 12.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 working life. When the system is totally shutdown, it is not necessary to let the internal BATFET charge pump work. The host controller can use a digital signal EN to disconnect the battery power path to the VCC pin by U2 in Figure 1. As a result, battery quiescent current can be minimized.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com The bq24725 has internal loop compensator. To get good loop stability, the resonant frequency of the output inductor and output capacitor should be designed between 10 kHz and 20 kHz. The preferred ceramic capacitor is 25V X7R or X5R for output capacitor. 10-20μF capacitance is suggested for a typical of 3-4A charging current.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 The maximum charging current in non-synchronous mode can be up to 0.25A for a 10mΩ charging current sensing resistor or 0.5A if battery voltage is below 2.5V. The minimum duty cycle happens at lowest battery voltage. Choose the bottom-side MOSFET with either an internal Schottky or body diode capable of carrying the maximum non-synchronous mode charging current.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 www.ti.com Adapter ACP RAC ACN R PCB BTST High-Side MOSFET SCP1 PHASE L REGN COMP1 Adapter Plug in COMP2 Count to 7 CLR RDC Low-Side MOSFET SCP2 Battery C Latch off Charger Figure 21.
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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 R AC System Path PCB Trace I DPM System current Single point connection at RAC I SYS R AC R PCB Charger input current ACP To ACP To ACN ACN I CHRGIN Charger I BAT Charger Input PCB Trace (a) PCB Layout (b) Equivalent Circuit Figure 23. Optimized PCB layout example. The total voltage drop sensed by IC can be express as the following equation.
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Not Recommended for New Designs bq24725 SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 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 24) 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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Not Recommended for New Designs bq24725 www.ti.com SLUS702A – JULY 2010 – REVISED NOVEMBER 2010 Charge Current Direction R SNS To Inductor To Capacitor and battery Current Sensing Direction To SRP and SRN pin Figure 25. Sensing resistor PCB layout. SPACRE REVISION HISTORY Changes from Original (July 2010) to Revision A Page • Changed the Functional Block Diagrams, Figure 1 and Figure 2 .........................................................................................
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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 BQ24725RGRR VQFN RGR 20 3000 330.0 12.4 3.75 3.75 1.15 8.0 12.0 Q1 BQ24725RGRR VQFN RGR 20 3000 330.0 12.4 3.75 3.75 1.15 8.0 12.0 Q1 BQ24725RGRT 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) BQ24725RGRR VQFN RGR 20 3000 367.0 367.0 35.0 BQ24725RGRR VQFN RGR 20 3000 552.0 367.0 36.0 BQ24725RGRT VQFN RGR 20 250 552.0 185.0 36.0 BQ24725RGRT VQFN RGR 20 250 210.0 185.0 35.
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