BQ24125_技术文档

bq24120

bq24123

Actual Size

3,5 mm x 4,5 mm

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

SINGLE-CHIP SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT

IC WITH ENHANCED EMI PERFORMANCE(bqSWITCHER™)

1

FEATURES

DESCRIPTION

2

•

Enhanced EMI Performance

•

Integrated Power FETs For Up To 2-A Charge

Rate

The bqSWITCHER™ series are highly integrated

Li-ion

and

Li-polymer

switch-mode

charge

management devices targeted at a wide range of

portable applications. The bqSWITCHER™ series

offers integrated synchronous PWM controller and

power FETs, high-accuracy current and voltage

regulation, charge preconditioning, charge status, and

charge termination, in a small, thermally enhanced

QFN package.

Suitable For 1-, 2-, or 3-Cell Li-Ion and

Li-Polymer Battery Packs

Synchronous Fixed-Frequency PWM

Controller Operating at 1.1 MHz With 0% to

100% Duty Cycle

•

High-Accuracy Voltage and Current Regulation

The bqSWITCHER charges the battery in three

phases: conditioning, constant current, and constant

voltage. Charge is terminated based on user-

selectable minimum current level. A programmable

charge timer provides a safety backup for charge

termination. The bqSWITCHER automatically restarts

the charge cycle if the battery voltage falls below an

internal threshold. The bqSWITCHER automatically

enters sleep mode when V_CCsupply is removed.

Status Outputs For LED or Host Processor

Interface Indicates Charge-In-Progress, Charge

Completion, Fault, and AC-Adapter Present

Conditions

•

20-V Absolute Maximum Voltage Rating on IN

and OUT Pins

•

Accurate High-Side Battery Current Sensing

Battery Temperature Monitoring

Automatic Sleep Mode for Low Power

Consumption

RHL PACKAGE

(TOP VIEW BQ24123)

•

Reverse Leakage Protection Prevents Battery

Drainage

•

Thermal Shutdown and Protection

Built-In Battery Detection

1

20

19

18

17

16

15

14

13

12

STAT2

PGND

CE

2

3

4

5

6

7

8

9

STAT1

IN

Available in 20 pin 3,5 mm x 4,5 mm QFN

Package

IN

PG

SNS

VCC

TTC

ISET1

ISET2

APPLICATIONS

BAT

•

Handheld Products

CELLS

TS

Portable Media Players

Industrial and Medical Equipment

Portable Equipment

11

10

Portable DVD Players

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.

2

bqSWITCHER, PowerPAD are trademarks of Texas Instruments.

UNLESS OTHERWISE NOTED this document contains

PRODUCTION DATA information current as of publication date.

Products conform to specifications per the terms of Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED 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.

ORDERING INFORMATION⁽¹⁾

CHARGE REGULATION

VOLTAGE (V)

INTENDED

APPLICATION

T_J

PART NUMBER⁽²⁾⁽³⁾

MARKINGS

BQ24120RHLR / BQ24120RHLT

BQ24123RHLR / BQ24123RHLT

BQU

BQV

CDZ

4.2 V

Stand-alone

–40°C to 125°C

4.2 V/8.4 V

2.1 V to 15.5 V

Externally Programmable BQ24125RHLR / BQ24125RHLT

(1) 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.

(2) The RHL package is available in the following options:

R - taped and reeled in quantities of 3,000 devices per reel

T - taped and reeled in quantities of 250 devices per reel

(3) This product is RoHS compatible, including a lead concentration that does not exceed 0.1% of total product weight, and is suitable for

use in specified lead-free soldering processes.

PACKAGE DISSIPATION RATINGS

T_A< 40°C

POWER RATING

DERATING FACTOR

ABOVE T_A= 40°C

PACKAGE

Θ_JA

Θ_JC

RHL⁽¹⁾

46.87°C/W

2.15°C/W

1.81 W

0.021 W/°C

(1) This data is based on using the JEDEC High-K board, and the exposed die pad is connected to a copper pad on the board. This is

connected to the ground plane by a 2x3 via matrix.

ABSOLUTE MAXIMUM RATINGS⁽¹⁾

over operating free-air temperature range (unless otherwise noted)

UNIT

Supply voltage range (with respect to V_SS

)

IN, VCC

20 V

–0.3 V to 20 V

–0.7 V to 20 V

7 V

STAT1, STAT2, PG, CE, CELLS, SNS, BAT

OUT

Input voltage range (with respect to V_SSand PGND)

TS, TTC

VTSB

3.6 V

ISET1, ISET2

3.3 V

Voltage difference between SNS and BAT inputs (V_SNS- V_BAT

)

±1 V

Output sink

STAT1, STAT2, PG

OUT

10 mA

Output current (average)

Operating free-air temperature range

Junction temperature range

Storage temperature

2.2 A

T_A

–40°C to 85°C

–40°C to 125°C

–65°C to 150°C

300°C

T_J

T_stg

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds

(1) Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings

only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating

conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

RECOMMENDED OPERATING CONDITIONS

MIN

4.35⁽¹⁾

–40

NOM

MAX UNIT

Supply voltage, V_CCand IN (Tie together)

Operating junction temperature range, T_J

16.0⁽²⁾

V

125

°C

(1) The IC continues to operate below V_min, to 3.5 V, but these conditions are not tested, and are not specified.

(2) The inherent switching noise voltage spikes should not exceed the absolute maximum rating on either the IN or OUT pins. A tight layout

minimizes switching noise.

2

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bq24120

bq24123

bq24125

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SLUS688E–MARCH 2006–REVISED DECEMBER 2007

ELECTRICAL CHARACTERISTICS

T_J= 0°C to 125°C and recommended supply voltage range (unless otherwise stated)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

INPUT CURRENTS

V_CC> V_CC(min), PWM switching

V_CC> V_CC(min), PWM NOT switching

V_CC> V_CC(min), CE = HIGH

10

mA

I_VCC(VCC)

V_CCsupply current

5

315

µA

0°C ≤ T_J≤ 65°C, V_I(BAT)= 4.2 V,

V_CC< V_(SLP)or V_CC> V_(SLP)but not in charge

3.5

5.5

7.7

Battery discharge sleep current, (SNS,

BAT, OUT pins)

0°C ≤ T_J≤ 65°C, V_I(BAT)= 8.4 V,

V_CC< V_(SLP)or V_CC> V_(SLP)but not in charge

I_(SLP)

µA

0°C ≤ T_J≤ 65°C, V_I(BAT)= 12.6 V,

V_CC< V_(SLP)or V_CC> V_(SLP)but not in charge

VOLTAGE REGULATION

Output voltage, bq24123

CELLS = Low, in voltage regulation

CELLS = High, in voltage regulation

Operating in voltage regulation

4.2

8.4

4.2

V_OREG

V

Output voltage, bq24120

Feedback regulation REF for bq24125 only

(W/FB)

V_IBAT

I_IBAT= 25 nA typical into pin

2.1

T_A= 25°C

–0.5%

–1%

0.5%

1%

Voltage regulation accuracy

CURRENT REGULATION - FAST CHARGE

V

_LOWV≤ V_I(BAT)< V_OREG,

I_OCHARGE

Output current range of converter

150

2000

mA

V_(VCC)- V_I(BAT)> V_(DO-MAX)

(1)

100 mV ≤ V_IREG≤ 200 mV,

1V

RSET1

V

+

1000,

IREG

V_IREG

Voltage regulated across R_(SNS)Accuracy

–10%

10%

Programmed Where

5 kΩ ≤ RSET1 ≤ 10 kΩ, Select RSET1 to

program V_IREG

,

V_{IREG(measured)}= I_OCHARGE×R_SNS

(–10% to 10% excludes errors due to RSET1

and R_(SNS)tolerances)

V

_(LOWV)≤ V_I(BAT)≤ V_O(REG)

,

V_(ISET1)

K_(ISET1)

Output current set voltage

Output current set factor

1

V

V_(VCC)≥ V_I(BAT)+ V _(DO-MAX)

V_LOWV≤ V_I(BAT)< V_O(REG)

,

1000

V/A

V_(VCC)≥ V_I(BAT)+ V_(DO-MAX)

PRECHARGE AND SHORT-CIRCUIT CURRENT REGULATION

Precharge to fast-charge transition voltage

threshold, BAT

V_LOWV

68

71.4

30

75

%V_O(REG)

ms

Deglitch time for precharge to fast charge

transition

Rising voltage;

t_RISE, t_FALL= 100 ns, 2-mV overdrive

t

20

15

40

I_OPRECHG

V_(ISET2)

K_(ISET2)

Precharge range

V_I(BAT)< V_LOWV, t < t_PRECHG

200

mA

mV

V/A

Precharge set voltage, ISET2

Precharge current set factor

V_I(BAT)< V_LOWV, t < t_PRECHG

100

1000

(1)

10 mV ≤ V_IREG-PRE≤ 100 mV,

0.1V

RSET2

V

+

1000,

IREG*PRE

V_IREG-PRE

Voltage regulated across R_SNS-Accuracy

–20%

20%

Where

1.0 kΩ ≤ RSET2 ≤ 10 kΩ, Select RSET2

to program V_IREG-PRE,

V_IREG-PRE(Measured) = I_OPRE-CHG× R_SNS

(–20% to 20% excludes errors due to RSET2

and R_SNStolerances)

CHARGE TERMINATION (CURRENT TAPER) DETECTION

I_TERMCharge current termination detection range V_I(BAT)> V_OREG- V_RCH

15

200

mA

(1) Inductor peak current should be less than 2.6 A. Use equations 12, 13, 15, 18, and 19 to make sure the peak inductor current is less

than 2.6 A.

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3

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bq24120

bq24123

bq24125

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SLUS688E–MARCH 2006–REVISED DECEMBER 2007

ELECTRICAL CHARACTERISTICS (continued)

T_J= 0°C to 125°C and recommended supply voltage range (unless otherwise stated)

PARAMETER

TEST CONDITIONS

MIN

TYP

100

MAX

UNIT

mV

Charge termination detection set voltage,

ISET2

V_TERM

V_I(BAT)> V_OREG- V_RCH

K_(ISET2)

Termination current set factor

Charger termination accuracy

1000

V/A

V_I(BAT)> V_OREG- V_RCH

–20%

20

20%

40

Both rising and falling,

2-mV overdrive t_RISE, t_FALL= 100 ns

t_dg-TERM

Deglitch time for charge termination

30

ms

TEMPERATURE COMPARATOR AND VTSB BIAS REGULATOR

V_LTF

V_HTF

V_TCO

Cold temperature threshold, TS

Hot temperature threshold, TS

Cutoff temperature threshold, TS

LTF hysteresis

72.8

33.7

28.7

0.5

73.5

34.4

29.3

1.0

74.2

35.1

29.9

1.5

Initiate Charge

During Charge

%V_O(VTSB)

Both rising and falling,

2-mV overdrive t_RISE, t_FALL= 100 ns

t_dg-TS

Deglitch time for temperature fault, TS

TS bias output voltage

20

30

40

ms

V

V_CC> V_IN(min)

,

V_O(VTSB)

3.15

I_(VTSB)= 10 mA 0.1 µF ≤ C_O(VTSB)≤ 1 µF

V_CC

>

,

IN(min)

TS bias voltage regulation accuracy

–10%

10%

I_(VTSB)= 10 mA 0.1 µF ≤ C_O(VTSB)≤ 1 µF

BATTERY RECHARGE THRESHOLD

V_RCH

Recharge threshold voltage

Deglitch time

Below V_OREG

75

20

100

30

125

40

mV/cell

ms

V_I(BAT)< decreasing below threshold,

t_FALL= 100 ns 10-mV overdrive

t_dg-RCH

STAT1, STAT2, AND PG OUTPUTS

V_OL(STATx)Low-level output saturation voltage, STATx I_O= 5 mA

0.5

0.1

V

V_OL(PG)

Low-level output saturation voltage, PG

I_O= 10 mA

CE , CELLS INPUTS

V_IL

Low-level input voltage

I_IL= 5 µA

0

0.4

V_IH

High-level input voltage

I_IH= 20 µA

1.3

V_CC

TTC INPUT

t_PRECHG

t_CHARGE

Precharge timer

1440

25

1800

2160

572

s

Programmable charge timer range

Charge timer accuracy

Timer multiplier

t_(CHG)= C_(TTC)× K_(TTC)

minutes

0.01 µF ≤ C_(TTC)≤ 0.18 µF

-10%

10%

K_TTC

2.6

min/nF

µF

C_TTC

Charge time capacitor range

TTC enable threshold voltage

0.01

0.22

V_{TTC_EN}

V_(TTC)rising

200

mV

SLEEP COMPARATOR

V

_CC≤ V_IBAT

+5 mV

V

_CC≤ V_IBAT

+75 mV

2.3 V ≤ V_I(OUT)≤ V_OREG,for 1 or 2 cells

V_SLP-ENT

Sleep-mode entry threshold

V

V_I(OUT)= 12.6 V, R_IN= 1kΩ,

V

_CC≤ V_IBAT

V

_CC≤ V_IBAT

+73 mV

bq24125⁽²⁾

–4 mV

V_SLP-EXIT

Sleep-mode exit hysteresis,

Deglitch time for sleep mode

2.3 V ≤ V_I(OUT)≤ V_OREG

40

160

mV

V_CCdecreasing below threshold,

t_FALL= 100 ns, 10-mV overdrive,

PMOS turns off

5

µs

t_dg-SLP

V_CCdecreasing below threshold,

t_FALL= 100 ns, 10-mV overdrive,

STATx pins turn off

20

30

40

ms

UVLO

V_UVLO-ON

IC active threshold voltage

IC active hysteresis

V_CCrising

V_CCfalling

3.15

120

3.30

150

3.50

V

mV

(2) For bq24125 only. R_INis connected between IN and PGND pins and needed to ensure sleep entry.

4

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SLUS688E–MARCH 2006–REVISED DECEMBER 2007

ELECTRICAL CHARACTERISTICS (continued)

T_J= 0°C to 125°C and recommended supply voltage range (unless otherwise stated)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

PWM

7 V ≤ V_CC≤ V_CC(max)

400

500

130

150

Internal P-channel MOSFET on-resistance

Internal N-channel MOSFET on-resistance

4.5 V ≤ V_CC≤ 7 V

7 V ≤ V_CC≤ V_CC(max)

4.5 V ≤ V_CC≤ 7 V

mΩ

f_OSC

Oscillator frequency

1.1

MHz

Frequency accuracy

–9%

0%

9%

D_MAX

D_MIN

Maximum duty cycle

100%

Minimum duty cycle

t_TOD

Switching delay time (dead time)

Minimum synchronous FET on time

Synchronous FET minimum current-off

20

60

ns

t_syncmin

50

400

mA

(3)

threshold

BATTERY DETECTION

Battery detection current during time-out

fault

I_DETECT

V_I(BAT)< V_OREG– V_RCH

2

mA

I_DISCHRG1

t_DISCHRG1

I_WAKE

Discharge current

Discharge time

Wake current

Wake time

V_SHORT< V_I(BAT)< V_OREG– V_RCH

Begins after termination detected,

400

1

µA

s

2

mA

s

t_WAKE

0.5

I_DISCHRG2

t_DISCHRG2

Termination discharge current

Termination time

400

262

µA

V_I(BAT)≤ V_OREG

ms

OUTPUT CAPACITOR

Required output ceramic capacitor range

C_OUT

from SNS to PGND, between inductor and

R_SNS

4.7

10

47

µF

Required SNS capacitor (ceramic) at SNS

C_SNS

PROTECTION

0.1

Threshold over V_OREGto turn off P-channel

MOSFET, STAT1, and STAT2 during charge

or termination states

V_OVP

OVP threshold voltage

110

117

121

%V_O(REG)

I_LIMIT

Cycle-by-cycle current limit

Short-circuit voltage threshold, BAT

Short-circuit current

2.6

1.95

35

3.6

2

4.5

2.05

65

A

V_SHORT

I_SHORT

T_SHTDWN

V_I(BAT)falling

V/cell

mA

V_I(BAT)≤ V_SHORT

Thermal trip

165

10

°C

Thermal hysteresis

(3) N-channel always turns on for ~60 ns and then turns off if current is too low.

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bq24120

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bq24125

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SLUS688E–MARCH 2006–REVISED DECEMBER 2007

TERMINAL FUNCTIONS

TERMINAL

I/O

DESCRIPTION

NAME

bq24120

bq24123

bq24125

Battery voltage sense input. Bypass it with a capacitor to VSS if there are long

inductive leads to battery.

BAT

14

I

Charger enable input. This active low input, if set high, suspends charge and

places the device in the low-power sleep mode. Do not pull up this input to VTSB.

CE

16

13

16

Available on parts with selectable output voltage. Ground or float for single-cell

operation (4.2 V). For two-cell operation (8.4 V) pull up this pin with a resistor to

CELLS

I

V_IN.

Output voltage analog feedback adjustment. Connect the output of a resistive

voltage divider powered from the battery terminals to this node to adjust the

output battery voltage regulation.

FB

13

IN

3, 4

8

3, 4

8

3, 4

8

I

Charger input voltage. Bypass it with a 10µF capacitor from IN to PGND.

Charger current set point 1 (fast charge). Use a resistor to ground to set this

value.

ISET1

I/O

Charge current set point 2 (precharge and termination), set by a resistor

connected to ground.

ISET2

N/C

9

I/O

13

1

–

No connection. This pin must be left floating in the application.

1

O

Charge current output inductor connection. Connect a zener TVS diode between

OUT pin and PGND to clamp the voltage spike to protect the power MOSFETs

during abnormal conditions.

OUT

20

O

Power-good status output (open drain). The transistor turns on when a valid V_CC

is detected. It is turned off in the sleep mode. PG can be used to drive a LED or

communicate with a host processor.

PG

5

O

PGND

SNS

17,18

15

17,18

15

17,18

15

Power ground input

Charge current-sense input. Battery current is sensed via the voltage drop

developed on this pin by an external sense resistor in series with the battery pack.

A 0.1µF capacitor to VSS is required.

I

Charge status 1 (open-drain output). When the transistor turns on indicates

charge in process. When it is off and with the condition of STAT2 indicates

various charger conditions (See Table 1)

STAT1

STAT2

TS

2

19

12

7

2

19

12

7

2

19

12

7

O

I

Charge status 2 (open-drain output). When the transistor turns on indicates

charge is done. When it is off and with the condition of STAT1 indicates various

charger conditions (See Table 1)

Temperature sense input. This input monitors its voltage against an internal

threshold to determine if charging is allowed. Use an NTC thermistor and a

voltage divider powered from VTSB to develop this voltage. (See Figure 13)

Timer and termination control. Connect a capacitor from this node to VSS to set

the bqSWITCHER timer. When this input is low, the timer and termination

detection are disabled.

TTC

I

VCC

VSS

6

Analog device input. A 0.1µF capacitor to VSS is required.

10

Analog ground input

TS internal bias regulator voltage. Connect capacitor (with a value between a

0.1µF and 1µF) between this output and VSS.

VTSB

11

O

There is an internal electrical connection between the exposed thermal pad and

VSS. The exposed thermal pad must be connected to the same potential as the

VSS pin on the printed circuit board. The power pad can be used as a star ground

connection between V_SSand PGND. A common ground plane may be used. VSS

pin must be connected to ground at all times.

Exposed

Thermal

Pad

6

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SLUS688E–MARCH 2006–REVISED DECEMBER 2007

TYPICAL APPLICATION CIRCUITS

I_CHARGE= 1.3A, I_PRECHARGE= 133mA, Charge Safety Timer = 5.0 hours, Battery Charging Qualification Temperature Range =

0°C to 45°C

Battery

Pack

L_O

BQ24120

R_SNS

V

IN

3

4

6

2

IN

OUT 1

Pack+

C

1.5 KW

Done

10mH

IN

0.1W

C_OUT

10mF

IN

OUT 20

10 mF

Adapter

Present

Charge

Pack-

103AT

MMBZ18VALT1

VCC

PGND 17

STAT1 PGND 18

19 STAT2

SNS 15

BAT 14

5

7

PG

7.5 KW

R

ISET1

VTSB

TTC

ISET1

ISET2

8

9

7.5 KW

16 CE

10 VSS

13 NC

R_T1

9.31 KW

C_TTC

0.1 mF

R

ISET2

TS 12

R_T2

VTSB 11

0.1 mF

442 KW

0.1 mF

Figure 1. Stand-Alone 1-Cell Application

Battery

Pack

L_O

BQ24123

R_SNS

V

IN

OUT

1

3

4

6

2

IN

Pack+

1.5 KW

Done

10 mH

0.1W

C_OUT

10mF

OUT 20

IN

C

Adapter

Present

Charge

IN

Pack-

103AT

10 mF

MMBZ18VALT1

VCC

STAT1

PGND 17

PGND 18

SNS 15

BAT 14

19 STAT2

5

7

PG

7.5 KW

R

VTSB

ISET1

TTC

ISET1

ISET2

8

9

R_T1

7.5 KW

9.31 KW

16 CE

C_TTC

0.1 mF

R

ISET2

10 VSS

13 CELLS

TS 12

0.1 mF

R_T2

VTSB 11

442 KW

0.1 mF

V

IN

10 KW

Figure 2. Stand-Alone 2-Cells Application

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bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

TYPICAL APPLICATION CIRCUITS (continued)

I_CHARGE= 1.3A, I_PRECHARGE= 133mA, Charge Safety Timer = 5.0 hours, Battery Charging Qualification Temperature Range =

0°C to 45°C

Battery

Pack

L_OUT

BQ24125

R_SNS

V_IN

3

4

6

2

IN

OUT 1

Pack+

1.5 KW

10 mF

1.5 KW

Adapter

Present

1.5 KW

Done

10 mH

D1

0.1W

C_IN

C_OUT

Charge

IN

OUT 20

10 mF

Pack-

VCC

MMBZ18VALT1

PGND 17

103AT

(See Note)

STAT1 PGND 18

19 STAT2

SNS 15

BAT 14

5

7

PG

7.5 KW

R

ISET1

VTSB

TTC

ISET1

ISET2

8

9

7.5 KW

ISET2

RT1

RT2

9.31 KW

16 CE

10 VSS

13 FB

C

TTC

R

0.1 mF

TS 12

0.1 mF

VTSB 11

442 KW

0.1 mF

301 KW

100 KW

0.1 mF

A. Zener diode not needed for bq24125.

Figure 3. Externally Programmable Application

8

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SLUS688E–MARCH 2006–REVISED DECEMBER 2007

TYPICAL OPERATING PERFORMANCE

See Figure 1 for a 1-cell application test circuit schematic and Figure 2 for the stand-alone cells application test

circuits schematic.

Level [dBµV]

BQ2412X Typical Radiated EMI Performance on EVM

60

V_IN= 16 V

50

I_CHARGE= 1 A

40

30

20

10

0

-10

30M

50M

70M

100M

Frequency [Hz]

200M

300M

500M

700M

1G

MES bq2412x_16v_1.0A

Figure 4. Typical Radiated EMI Performance Measured on EVM

100

90

100

V = 9 V

V

= 8.4 V

I

bat

V

= 4.2 V

bat

V = 5 V

I

90

80

70

V = 16 V

I

80

70

V = 16 V

I

60

50

60

50

0

1

2

0

1

2

Charge Current Ibat - A

Figure 5. Efficiency 1-Cell

Figure 6. Efficiency 2-Cells

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CH3

1.38 A

200 mA/div

CH3 = Inductor Current

CH1 = BAT

CH1

2 V/div

3.8 V

CH2 = OUT

CH2

9 V

5 V/div

t = Time = 400 ns/div

Figure 7. Switching Waveforms in Fast Charge Mode

CH3 = Inductor Current

CH3

500 mA

500 mA/div

CH1 = BAT

CH1

8.4 V

5 V/div

CH2 = OUT

CH2

16 V

CH2

10 V/div

t - Time = 400 ns/div

Figure 8. Switching Waveforms in Voltage Regulation Mode

10

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CH1 = BAT

CH1

2 V/div

4.2 V

CH3 = Inductor Current

CH3

200 mA/div

480 mA

CH2 = OUT

CH2

5 V

CH2

2 V/div

20 ns

35 ns

t = Time = 50 ns/div

Figure 9. Dead Time

CH1 = BAT

CH1

2 V/div

3.8 V

CH3 = Inductor Current

CH3

1.3 A

CH2 = OUT

CH2

5 V

CH3

500 mA/div

CH2

5 V/div

t = Time = 1 ms/div

Figure 10. Soft Start Waveforms

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FUNCTIONAL BLOCK DIAGRAM

-

+

12

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OPERATIONAL FLOW CHART

POR

Check for battery

Presence

Battery

No

Detected?

Indicate BATTERY

ABSENT

Yes

Suspend charge

TS pin

in LTF to HTF

range?

No

Indicate CHARGE

SUSPEND

Yes

Regulate

I

PRECHG

Reset and Start

T30min timer

V

<V

Yes

BAT

LOWV

Indicate Charge-

In-Progress

No

Suspend charge

TS pin

in LTF to TCO

range?

Reset and Start

FSTCHG timer

No

Indicate CHARGE

SUSPEND

No

Regulate

Yes

Current or Voltage

TS pin

in LTF to HTF

range?

Indicate Charge-

In-Progress

No

V

<V

BAT LOWV

Suspend charge

Yes

TS pin

in LTF to TCO

range?

Yes

No

Indicate CHARGE

SUSPEND

T30min

No

Yes

No

Expired?

TS pin

in LTF to HTF

range?

FSTCHG timer

Expired?

Yes

No

- Fault Condition

- Enable I

DETECT

No

Indicate Fault

Yes

No

Yes

V

<V

BAT LOWV

Yes

V

> V

-

BAT OREG -

V

?

RCH

Yes

No

V

> V

BAT OREG

-

V

?

RCH

No

I

detection?

TERM

- Disable I

DETECT

Indicate Fault

Yes

- Fault Condition

Indicate Fault

- Turn off charge

- Enable I

DISCHG2

for t

DISCHG2

No

Indicate Charge-

In-Progress

Battery

Replaced?

V

< V

BAT OREG -

V

?

RCH

Charge Complete

Indicate DONE

V

< V

BAT

OREG -

?

No

Yes

V

RCH

Battery Removed

Yes

Indicate BATTERY

ABSENT

Figure 11. Operational Flow Chart

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DETAIL DESCRIPTION

The bqSWITCHER™ supports a precision Li-ion or Li-polymer charging system for single cell or two cell

applications. See Figure 11 and Figure 12 for a typical charge profile.

The bq2412X has enhanced EMI performance that helps minimize the number of components needed to meet

the FCC-B Standard. The rise time of the OUT pin was slowed down to minimize the radiated EMI.

Precharge

Phase

Voltage Regulation and

Charge Termination Phase

Current Regulation Phase

Regulation V oltage

Regulation Current

Charge Voltage

V

LOW

V

SHORT

Charge Current

Precharge

and Termination

I

SHORT

Programmable

Safety Timer

Precharge

Timer

UDG-04037

Figure 12. Typical Charging Profile

PWM Controller

The bq2412X provides an integrated fixed 1MHz frequency voltage-mode controller with Feed-Forward function

to regulate charge current or voltage. This type of controller is used to help improve line transient response,

thereby simplifying the compensation network used for both continuous and discontinuous current conduction

operation. The voltage and current loops are internally compensated using a Type-III compensation scheme that

provides enough phase boost for stable operation, allowing the use of small ceramic capacitors with very low

ESR. There is a 0.5V offset on the bottom of the PWM ramp to allow the device to operate between 0% to 100%

duty cycle.

The internal PWM gate drive can directly control the internal PMOS and NMOS power MOSFETs. The high-side

gate voltage swings from V_CC(when off), to V_CC-6 (when on and V_CCis greater than 6V) to help reduce the

conduction losses of the converter by enhancing the gate an extra volt beyond the standard 5V. The low-side

gate voltage swings from 6V, to turn on the NMOS, down to PGND to turn it off. The bq2412X has two back to

back common-drain P-MOSFETs on the high side. An input P-MOSFET prevents battery discharge when IN is

lower than BAT. The second P-MOSFET behaves as the switching control FET, eliminating the need of a

bootstrap capacitor.

14

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Cycle-by-cycle current limit is sensed through the internal high-side sense FET. The threshold is set to a nominal

3.6A peak current. The low-side FET also has a current limit that decides if the PWM Controller will operate in

synchronous or non-synchronous mode. This threshold is set to 100mA and it turns off the low-side NMOS

before the current reverses, preventing the battery from discharging. Synchronous operation is used when the

current of the low-side FET is greater than 100mA to minimize power losses.

Temperature Qualification

The bqSWITCHER continuously monitors battery temperature by measuring the voltage between the TS pin and

VSS pin. A negative temperature coefficient thermistor (NTC) and an external voltage divider typically develop

this voltage. The bqSWITCHER compares this voltage against its internal thresholds to determine if charging is

allowed. To initiate a charge cycle, the battery temperature must be within the V_(LTF)-to-V_(HTF)thresholds. If

battery temperature is outside of this range, the bqSWITCHER suspends charge and waits until the battery

temperature is within the V_(LTF)-to-V_(HTF)range. During the charge cycle (both precharge and fast charge), the

battery temperature must be within the V_(LTF)-to-V_(TCO)thresholds. If battery temperature is outside of this range,

the bqSWITCHER suspends charge and waits until the battery temperature is within the V_(LTF)-to-V_(HTF)range.

The bqSWITCHER suspends charge by turning off the PWM and holding the timer value (i.e., timers are not

reset during a suspend condition). Note that the bias for the external resistor divider is provided from the VTSB

output. Applying a constant voltage between the V_(LTF)-to-V_(HTF)thresholds to the TS pin disables the

temperature-sensing feature.

1

V

RTH

HOT

ƪ

*

ƫ

O(VTSB)

COLD

V

LTF

HTF

RT2 +

V

O(VTSB)

RTH

V

* 1 * RTH

COLD

* 1

ǒ Ǔ ǒ Ǔ

HOT

V

HTF

LTF

O(VTSB)

* 1

V

LTF

RT1 +

1

)

RT2 RTH

COLD

(1)

V

CC

Charge Suspend

V

(LTF)

Temperature Range

to Initiate Charge

Temperature Range

During Charge Cycle

V

(HTF)

V

(TCO)

Charge Suspend

V

SS

Figure 13. TS Pin Thresholds

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Battery Preconditioning (Precharge)

On power up, if the battery voltage is below the V_LOWVthreshold, the bqSWITCHER applies a precharge current,

I_PRECHG, to the battery. This feature revives deeply discharged cells. The bqSWITCHER activates a safety timer,

t_PRECHG, during the conditioning phase. If the V_LOWVthreshold is not reached within the timer period, the

bqSWITCHER turns off the charger and enunciates FAULT on the STATx pins. In the case of a FAULT

condition, the bqSWITCHER reduces the current to I_DETECT. I_DETECTis used to detect a battery replacement

condition. Fault condition is cleared by POR or battery replacement.

The magnitude of the precharge current, I_O(PRECHG), is determined by the value of programming resistor, R_(ISET2)

,

connected to the ISET2 pin.

K_(ISET2) V_(ISET2)

I_O(PRECHG)

⁺ǒ_R

Ǔ

R_(SNS)

(ISET2)

(2)

where

R_SNSis the external current-sense resistor

V_(ISET2)is the output voltage of the ISET2 pin

K_(ISET2)is the V/A gain factor

V_(ISET2)and K_(ISET2)are specified in the Electrical Characteristics table.

Battery Charge Current

The battery charge current, I_O(CHARGE), is established by setting the external sense resistor, R_(SNS), and the

resistor, R_(ISET1), connected to the ISET1 pin.

In order to set the current, first choose R_(SNS)based on the regulation threshold V_IREGacross this resistor. The

best accuracy is achieved whe the V_IREGis between 100mV and 200mV.

V

IREG

R

+

(SNS)

I

OCHARGE

(3)

If the results is not a standard sense resistor value, choose the next larger value. Using the selected standard

value, solve for V_IREG. Once the sense resistor is selected, the ISET1 resistor can be calculated using the

following equation:

K

R

V

ISET1

CHARGE

R

+

ISET1

I

SNS

(4)

Battery Voltage Regulation

The voltage regulation feedback occurs through the BAT pin. This input is tied directly to the positive side of the

battery pack. The bqSWITCHER monitors the battery-pack voltage between the BAT and VSS pins. The

bqSWITCHER is offered in a fixed single-cell voltage version (4.2 V) and as a one-cell or two-cell version

selected by the CELLS input. A low or floating input on the CELLS selects single-cell mode (4.2 V) while a

high-input through a resistor selects two-cell mode (8.4 V).

Charge Termination and Recharge

The bqSWITCHER monitors the charging current during the voltage regulation phase. Once the termination

threshold, I_TERM, is detected, the bqSWITCHER terminates charge. The termination current level is selected by

the value of programming resistor, R_(ISET2), connected to the ISET2 pin.

K

⁺ǒ_R

V

(ISET2)

TERM

I

TERM

_(SNS)Ǔ

R

(ISET2)

(5)

16

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where

R_(SNS)is the external current-sense resistor

V_TERMis the output of the ISET2 pin

K_(ISET2)is the A/V gain factor

V_TERMand K_(ISET2)are specified in the Electrical Characteristics table

As a safety backup, the bqSWITCHER also provides a programmable charge timer. The charge time is

programmed by the value of a capacitor connected between the TTC pin and GND by the following formula:

t

_CHARGE+ C_(TTC) K_(TTC)

(6)

where

C_(TTC)is the capacitor connected to the TTC pin

K_(TTC)is the multiplier

A new charge cycle is initiated when one of the following conditions is detected:

•

The battery voltage falls below the V_RCHthreshold.

Power-on reset (POR), if battery voltage is below the V_RCHthreshold

CE toggle

TTC pin, described as follows.

In order to disable the charge termination and safety timer, the user can pull the TTC input below the V_{TTC_EN}

threshold. Going above this threshold enables the termination and safety timer features and also resets the timer.

Tying TTC high disables the safety timer only.

Sleep Mode

The bqSWITCHER enters the low-power sleep mode if the VCC pin is removed from the circuit. This feature

prevents draining the battery during the absence of VCC.

Charge Status Outputs

The open-drain STAT1 and STAT2 outputs indicate various charger operations as shown in Table 1. These

status pins can be used to drive LEDs or communicate to the host processor. Note that OFF indicates that the

open-drain transistor is turned off.

Table 1. Status Pins Summary

Charge State

STAT1

ON

STAT2

OFF

ON

Charge-in-progress

Charge complete

OFF

Charge suspend, timer fault, overvoltage, sleep mode, battery absent

OFF

PG Output

The open-drain PG (power good) indicates when the AC-to-DC adapter (i.e., V_CC) is present. The output turns on

when sleep-mode exit threshold, V_SLP-EXIT, is detected. This output is turned off in the sleep mode. The PG pin

can be used to drive an LED or communicate to the host processor.

CE Input (Charge Enable)

The CE digital input is used to disable or enable the charge process. A low-level signal on this pin enables the

charge and a high-level V_CCsignal disables the charge. A high-to-low transition on this pin also resets all timers

and fault conditions. Note that the CE pin should not be tied to VTSB. This may create power-up issues.

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Timer Fault Recovery

As shown in Figure 11, bqSWITCHER provides a recovery method to deal with timer fault conditions. The

following summarizes this method.

Condition 1 V_I(BAT)above recharge threshold (V_OREG- V_RCH) and timeout fault occurs.

Recovery method: bqSWITCHER waits for the battery voltage to fall below the recharge threshold. This could

happen as a result of a load on the battery, self-discharge or battery removal. Once the battery falls below the

recharge threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or

CE toggle also clears the fault.

Condition 2 Charge voltage below recharge threshold (V_OREG– V_RCH) and timeout fault occurs

Recovery method: Under this scenario, the bqSWITCHER applies the I_DETECTcurrent. This small current is used

to detect a battery removal condition and remains on as long as the battery voltage stays below the recharge

threshold. If the battery voltage goes above the recharge threshold, then the bqSWITCHER disables the I_DETECT

current and executes the recovery method described in Condition 1. Once the battery falls below the recharge

threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or CE toggle

also clears the fault.

Output Overvoltage Protection (Applies To All Versions)

The bqSWITCHER provides a built-in overvoltage protection to protect the device and other components against

damages if the battery voltage gets too high, as when the battery is suddenly removed. When an overvoltage

condition is detected, this feature turns off the PWM and STATx pins. The fault is cleared once V_IBATdrops to the

recharge threshold (V_OREG- V_RCH).

Inductor, Capacitor, and Sense Resistor Selection Guidelines

The bqSWITCHER provides internal loop compensation. With this scheme, best stability occurs when LC

resonant frequency, f_ois approximately 16 kHz (8 kHz to 32 kHz). Equation 7 can be used to calculate the value

of the output inductor and capacitor. Table 2 provides a summary of typical component values for various charge

rates.

1

f₀+

Ǹ

2p L_OUT C_OUT

(7)

Table 2. Output Components Summary

CHARGE CURRENT

0.5 A

22 µH

4.7 µF

0.2 Ω

1 A

2 A

4.7 µH

Output inductor, L_OUT

10 µH

10 µF

0.1 Ω

Output capacitor, C_OUT

Sense resistor, R_(SNS)

22 µF (or 2 × 10 µH) ceramic

0.05 Ω

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Battery Detection

For applications with removable battery packs, bqSWITCHER provides a battery absent detection scheme to

reliably detect insertion and/or removal of battery packs.

POR or V

RCH

Detection routine runs on power up

and if V drops below refresh

BAT

threshold due to removing battery

or discharging battery.

Yes

Enable

(DETECT)

I

for t

(DETECT)

BATTERY

PRESENT,

No

V

I(BAT)

<V

(SHORT)

Begin Charge

Yes

Apply I

(WAKE)

for t

BATTERY

PRESENT,

Begin Charge

V

>

I(BAT)

No

V

O(REG)

−V

RCH

Yes

BATTERY

ABSENT

Figure 14. Battery Detection for bq2412x ICs

The voltage at the BAT pin is held above the battery recharge threshold, V_OREG– V_RCH, by the charged battery

following fast charging. When the voltage at the BAT pin falls to the recharge threshold, either by a load on the

battery or due to battery removal, the bqSWITCHER begins a battery absent detection test. This test involves

enabling a detection current, I_DISCHARGE1, for a period of t_DISCHARGE1and checking to see if the battery voltage is

below the short circuit threshold, V_SHORT. Following this, the wake current, I_WAKEis applied for a period of t_WAKE

and the battery voltage is checked again to ensure that it is above the recharge threshold. The purpose of this

current is to attempt to close an open battery pack protector, if one is connected to the bqSWITCHER.

Passing both of the discharge and charge tests indicates a battery absent fault at the STAT pins. Failure of either

test starts a new charge cycle. For the absent battery condition, typically the voltage on the BAT pin rises and

falls between 0V and V_OVPthresholds indefinitely.

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VBAT

Battery

Connected

V

OREG

No

Battery

Detected

No

Battery

Detected

Yes

Battery

Detected

2V/cell

I

WAKE

IBAT

- I

DISCHRG1

t

WAKE

DISCHRG1

Figure 15. Battery Detect Timing Diagram

Battery Detection Example

In order to detect a no battery condition during the discharge and wake tests, the maximum output capacitance

should not exceed the following:

a. Discharge (I_DISCHRG1= 400 µA, t_DISCHRG1= 1s, V_SHORT= 2V)

I

t

DISCHRG1

SHORT

C

+

MAX_DIS

V

* V

OREG

400 mA 1s

4.2 V * 2 V

C

MAX_DIS

+ 182 mF

(8)

b. Wake (I_WAKE= 2 mA, t_WAKE= 0.5 s, V_OREG– V_RCH= 4.1V)

I

t

WAKE

C

⁺ǒ_V

_RCHǓ _{* 0 V}

MAX_WAKE

* V

OREG

2 mA 0.5s

(4.2 V * 0.1 V) * 0V

C

+

MAX_WAKE

C

+ 244 mF

(9)

Based on these calculations the recommended maximum output capacitance to ensure proper operation of the

battery detection scheme is 100 µF which will allow for process and temperature variations.

Figure 16 shows the battery detection scheme when a battery is inserted. Channel 3 is the output signal and

Channel 4 is the output current. The output signal switches between V_OREGand GND until a battery is inserted.

Once the battery is detected, the output current increases from 0A to 1.3A, which is the programmed charge

current for this application.

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Figure 16. Battery Detection Waveform When a Battery is Inserted

Figure 17 shows the Battery Detection scheme when a battery is removed. Channel 3 is the output signal and

Channel 4 is the output current. When the battery is removed, the output signal goes up due to the stored energy

in the inductor and it crosses the V_OREG– V_RCHthreshold. At this point the output current goes to 0A and the IC

terminates the charge process and turns on the I_DISCHG2for t_DISCHG2. This causes the output voltage to fall down

below the V_OREG– V_RCHGthreshold triggering a Battery Absent condition and starting the Battery Detection

scheme.

Figure 17. Battery Detection Waveform When a Battery is Removed

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Current Sense Amplifier

BQ2412X family offers a current sense amplifier feature that translates the charge current into a DC voltage.

Figure 18 is a block diagram of this feature.

OUT

SNS

R

SNS

+

K

ISET2

-

BAT

-

+

FASTCHG

-

Disable

ISET2

R

ISET2

Figure 18. Current Sense Amplifer

The voltage on the ISET2 pin can be used to calculate the charge current. Equation 10 shows the relationship

between the ISET2 voltage and the charge current:

V

K

ISET2

(ISET2)

ISET2

I

+

CHARGE

R

SNS

(10)

This feature can be used to monitor the charge current during the current regulation phase (Fastcharge only) and

the voltage regulation phase. The schematics for the application circuit for this waveform is shown in Figure 2

CH3 = Inductor Current

CH3

500 mA/div

CH1 = ISET2

CH3

0 A

CH1

200 mV/div

CH1

CH2 = OUT

0 V

CH2

16 V

CH2

10 V/div

t = Time = 200 ms/div

Figure 19. Current Sense Amplifier

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SYSTEM DESIGN EXAMPLE AND APPLICATIONS INFORMATION

The following section provides a detailed system design example for the bq24120.

System Design Specifications:

•

V_IN= 16V

V_BAT= 4.2V (1-Cell)

I_CHARGE= 1.33 A

I_PRECHARGE= I_TERM= 133 mA

Safety Timer = 5.0 hours

Inductor Ripple Current = 30% of Fast Charge Current

Initiate Charge Temperature = 0°C to 45°C

1. Determine the inductor value (L_OUT) for the specified charge current ripple:

DI + I

I

Ripple

L

CHARGE

ǒ_V

_BATǓ

V

* V

BAT

V

INMAX

L

+

OUT

ƒ DI

INMAX

L

4.2 (16 * 4.2)

L

+

16 (1.1 10⁶) (1.33 0.3)

OUT

L

+ 7.06 mH

OUT

(11)

Set the output inductor to standard 10 µH. Calculate the total ripple current with using the 10 µH inductor:

ǒ_V

_BATǓ

V

* V

BAT

V

INMAX

DI +

L

ƒ L

INMAX

OUT

4.2 (16 * 4.2)

16 (1.1 10⁶) (10 10^*6

DI +

L

)

DI + 0.282 A

L

(12)

Calculate the maximum output current (peak current):

DI

L

I

+ I

)

LPK

OUT

2

0.282

2

I

+ 1.33 )

LPK

I

+ 1.471 A

LPK

(13)

Use standard 10 µH inductor with a saturation current higher than 1.471A. (i.e., Sumida CDRH74-100)

2. Determine the output capacitor value (C_OUT) using 16 kHz as the resonant frequency:

1

ƒ +

o

_2pǸ_L

C

OUT

1

OUT

C

+

2

4p² ƒ L

OUT

o

OUT

1

+

4p² (16 10³)² (10 10^*6

)

OUT

C

+ 9.89 mF

OUT

Use standard value 10 µF, 25V, X5R, ±20% ceramic capacitor (i.e., Panasonic 1206 ECJ-3YB1E106M

(14)

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3. Determine the sense resistor using the following equation:

V

RSNS

R

+

SNS

I

CHARGE

(15)

In order to get better current regulation accuracy (±10%), let V_RSNSbe between 100 mV and 200 mV. Use

V_RSNS= 100 mV and calculate the value for the sense resistor.

100 mV

R

+

SNS

1.33 A

+ 0.075 W

(16)

This value is not standard in resistors. If this happens, then choose the next larger value which in this case is

0.1Ω. Using the same equation (15) the actual V_RSNSwill be 133mV. Calculate the power dissipation on the

sense resistor:

2

P

+ I

R

RSNS

CHARGE

SNS

P

+ 1.33² 0.1

+ 176.9 mW

RSNS

P

RSNS

(17)

Select standard value 100 mΩ, 0.25W 0805, 1206 or 2010 size, high precision sensing resistor. (i.e., Vishay

CRCW1210-0R10F)

4. Determine ISET 1 resistor using the following equation:

K

V

ISET1

CHARGE

R

+

ISET1

R

I

SNS

1000 1.0

0.1 1.33

R

ISET1

R

+ 7.5 kW

ISET1

(18)

(19)

(20)

Select standard value 7.5 kΩ, 1/16W ±1% resistor (i.e., Vishay CRCWD0603-7501-F)

5. Determine ISET 2 resistor using the following equation:

K

V

ISET2

PRECHARGE

R

+

ISET2

R

I

SNS

1000 0.1

0.1 0.133

R

ISET2

R

+ 7.5 kW

ISET2

Select standard value 7.5 kΩ, 1/16W ±1% resistor (i.e., Vishay CRCWD0603-7501-F)

6. Determine TTC capacitor (C_TTC) for the 5.0 hours safety timer using the following equation:

t

CHARGE

C

+

TTC

K

TTC

300 m

2.6 mńnF

C

+

TTC

C

+ 115.4 nF

TTC

Select standard value 100 nF, 16V, X7R, ±10% ceramic capacitor (i.e., Panasonic ECJ-1VB1C104K). Using

this capacitor the actual safety timer will be 4.3 hours.

7. Determine TS resistor network for an operating temperature range from 0°C to 45°C.

24

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Product Folder Link(s): bq24120 bq24123 bq24125

bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

VTSB

RT1

RT2

TS

RTH

103AT

Figure 20. TS Resistor Network

Assuming a 103AT NTC Thermistor on the battery pack, determine the values for RT1 and RT2 using the

following equations:

1

V

RTH

HOT

ƪ

*

ƫ

O(VTSB)

COLD

V

LTF

HTF

RT2 +

V

O(VTSB)

RTH

V

* 1 * RTH

COLD

* 1

ǒ Ǔ ǒ Ǔ

HOT

V

HTF

LTF

O(VTSB)

* 1

V

LTF

RT1 +

1

)

RT2 RTH

COLD

(21)

(22)

RTH

+ 27.28 kW

COLD

RTH

+ 4.912 kW

HOT

RT1 + 9.31 kW

RT2 + 442 kW

Submit Documentation Feedback

25

Product Folder Link(s): bq24120 bq24123 bq24125

bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

APPLICATION INFORMATION

Charging Battery and Powering System Without Affecting Battery Charge and Termination

R_SYS

Battery

Pack

L_O

BQ24120

R_SNS

V_IN

3

4

6

2

IN

OUT 1

Pack+

1.5 KW

10 mF

1.5 KW

Adapter

Present

1.5 KW

Done

10 mH

0.1W

C_IN

C_OUT

Charge

IN

OUT 20

10 mF

Pack-

103AT

VCC

PGND 17

MMBZ18VALT1

STAT1 PGND 18

19 STAT2

SNS 15

BAT 14

5

7

PG

7.5 KW

VTSB

TTC

ISET1

ISET2

8

9

9.31 KW

16 CE

10 VSS

13 NC

0.1 mF

TS 12

VTSB 11

442 KW

0.1 mF

Figure 21. Application circuit for charging a battery and powering a system without affecting termination

The bqSWITCHER was designed as a stand-alone battery charger but can be easily adapted to power a system

load, while considering a few minor issues.

Advantages:

1. The charger controller is based only on what current goes through the current-sense resistor (so precharge,

constant current, and termination all work well), and is not affected by the system load.

2. The input voltage has been converted to a usable system voltage with good efficiency from the input.

3. Extra external FETs are not needed to switch power source to the battery.

4. The TTC pin can be grounded to disable termination and keep the converter running and the battery fully

charged, or let the switcher terminate when the battery is full and then run off of the battery via the sense

resistor.

Other Issues:

1. If the system load current is large (≥ 1 A), the IR drop across the battery impedance causes the battery

voltage to drop below the refresh threshold and start a new charge. The charger would then terminate due to

low charge current. Therefore, the charger would cycle between charging and termination. If the load is

smaller, the battery would have to discharge down to the refresh threshold resulting in a much slower

cycling. Note that grounding the TTC pin keeps the converter on continuously.

2. If TTC is grounded, the battery is kept at 4.2 V (not much different than leaving a fully charged battery set

unloaded).

3. Efficiency declines 2-3% hit when discharging through the sense resistor to the system.

26

Submit Documentation Feedback

Product Folder Link(s): bq24120 bq24123 bq24125

bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

Using bq24125 to charge the LiFePO4 battery

The LiFePO4 battery has many unique features such as a very high thermal runaway temperature, high

discharge current capability, and high charge current. These special features make it attractive in many

applications such as power tools. The recommended charge voltage is 3.6 V and termination current is 50 mA.

Figure 22 shows an application circuit for charging one cell LiFePO4 using bq24105. The charge voltage is 3.6 V

and recharge voltage is 3.516 V. The fast charging current is set to 1.33 A while the termination current is

50 mA. This circuit can be easily changed to support two or three cell applications. However, only 84 mV

difference between regulation set point and rechargeable threshold makes it frequently enter into recharge mode

when small load current is applied. This can be solved by lower down the recharge voltage threshold to 200 mV

to discharge more energy from the battery before it enters recharge mode again. See the application report,

Using the bq24105/25 to Charge LiFePO4 Battery (SLUA443), for additional details. The recharge threshold

should be selected according to real application conditions.

Battery

Pack

L_OUT

BQ24125

R_SNS

V_IN

3

4

6

2

IN

OUT 1

Pack+

1.5 KW

10 mF

1.5 KW

Adapter

Present

1.5 KW

Done

10 mH

D1

0.1W

C_IN

C_OUT

Charge

IN

OUT 20

10 mF

Pack-

VCC

MMBZ18VALT1

PGND 17

103AT

(See Note)

STAT1 PGND 18

19 STAT2

SNS 15

BAT 14

5

7

PG

7.5 KW

R

ISET1

VTSB

TTC

ISET1

ISET2

8

9

20 KW

ISET2

RT1

RT2

9.31 KW

16 CE

10 VSS

13 FB

C

TTC

R

0.1 mF

TS 12

0.1 mF

VTSB 11

442 KW

0.1 mF

143 KW

200 KW

0.1 mF

A. Zener diode not needed for bq24125.

Figure 22. 1-Cell LiFePO4 Application

Submit Documentation Feedback

27

Product Folder Link(s): bq24120 bq24123 bq24125

bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

THERMAL CONSIDERATIONS

Thermal Considerations

The SWITCHER is packaged in a thermally enhanced MLP package. The package includes a thermal pad to

provide an effective thermal contact between the IC and the printed circuit board (PCB). Full PCB design

guidelines for this package are provided in the application report entitled: QFN/SON PCB Attachment

(SLUA271).

The most common measure of package thermal performance is thermal impedance (θ_JA) measured (or modeled)

from the chip junction to the air surrounding the package surface (ambient). The mathematical expression for θ_JA

is:

T_J* T_A

+

q_(JA)

P

(23)

Where:

T_J= chip junction temperature

T_A= ambient temperature

P = device power dissipation

Factors that can greatly influence the measurement and calculation of θ_JAinclude:

•

Whether or not the device is board mounted

Trace size, composition, thickness, and geometry

Orientation of the device (horizontal or vertical)

Volume of the ambient air surrounding the device under test and airflow

Whether or not other surfaces are in close proximity to the device being tested

The device power dissipation, P, is a function of the charge rate and the voltage drop across the internal power

FET. It can be calculated from the following equation:

P = [Vin × lin - Vbat × Ibat]

Due to the charge profile of Li-xx batteries, the maximum power dissipation is typically seen at the beginning of

the charge cycle when the battery voltage is at its lowest. (See Figure 12.)

28

Submit Documentation Feedback

Product Folder Link(s): bq24120 bq24123 bq24125

bq24120

bq24123

bq24125

www.ti.com

SLUS688E–MARCH 2006–REVISED DECEMBER 2007

PCB LAYOUT CONSIDERATION

It is important to pay special attention to the PCB layout. The following provides some guidelines:

•

To obtain optimal performance, the power input capacitors, connected from input to PGND, should be placed

as close as possible to the bqSWITCHER. The output inductor should be placed directly above the IC and the

output capacitor connected between the inductor and PGND of the IC. The intent is to minimize the current

path loop area from the OUT pin through the LC filter and back to the PGND pin. The sense resistor should

be adjacent to the junction of the inductor and output capacitor. Route the sense leads connected across the

R_SNSback to the IC, close to each other (minimize loop area) or on top of each other on adjacent layers. BAT

and SNS traces should be away from high di/dt traces such as the OUT pin. Use an optional capacitor

downstream from the sense resistor if long (inductive) battery leads are used.

•

Place all small-signal components (C_TTC, RSET1/2 and TS) close to their respective IC pin (do not place

components such that routing interrupts power stage currents). All small control signals should be routed

away from the high current paths.

The PCB should have a ground plane (return) connected directly to the return of all components through vias

(3 vias per capacitor for power-stage capacitors, 3 vias for the IC PGND, 1 via per capacitor for small-signal

components). A star ground design approach is typically used to keep circuit block currents isolated

(high-power/low-power small-signal) which reduces noise-coupling and ground-bounce issues. A single

ground plane for this design gives good results. With this small layout and a single ground plane, there is not

a ground-bounce issue, and having the components segregated minimizes coupling between signals.

•

The high-current charge paths into IN and from the OUT pins must be sized appropriately for the maximum

charge current in order to avoid voltage drops in these traces. The PGND pins should be connected to the

ground plane to return current through the internal low-side FET. The thermal vias in the IC PowerPAD™

provide the return-path connection.

The bqSWITCHER is packaged in a thermally enhanced MLP package. The package includes a thermal pad

to provide an effective thermal contact between the IC and the PCB. Full PCB design guidelines for this

package are provided in the application report entitled: QFN/SON PCB Attachment (SLUA271). Six 10-13 mil

vias are a minimum number of recommended vias, placed in the IC's power pad, connecting it to a ground

thermal plane on the opposite side of the PWB. This plane must be at the same potential as V_SSand PGND

of this IC.

•

See user guide SLUU200 for an example of good layout.

Submit Documentation Feedback

29

Product Folder Link(s): bq24120 bq24123 bq24125

PACKAGE OPTION ADDENDUM

www.ti.com

12-Dec-2007

PACKAGING INFORMATION

Orderable Device

BQ24120RHLR

BQ24120RHLRG4

BQ24120RHLT

BQ24120RHLTG4

BQ24123RHLR

BQ24123RHLRG4

BQ24123RHLT

BQ24123RHLTG4

BQ24125RHLR

BQ24125RHLT

Status ⁽¹⁾

ACTIVE

Package Package

Pins Package Eco Plan ⁽²⁾Lead/Ball Finish MSL Peak Temp ⁽³⁾

Qty

Type

Drawing

QFN

RHL

20

3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

QFN

RHL

3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR

no Sb/Br)

⁽¹⁾The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in

a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2)

Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check

http://www.ti.com/productcontent for the latest availability information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements

for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered

at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and

package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS

compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame

retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)

(3)

MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder

temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is

provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the

accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take

reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on

incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited

information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI

to Customer on an annual basis.

Addendum-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

12-Dec-2007

TAPE AND REEL BOX INFORMATION

Device

Package Pins

Site

Reel

A0 (mm)

B0 (mm)

K0 (mm)

P1

W

Pin1

Diameter Width

(mm) (mm) Quadrant

(mm)

330

180

330

180

330

180

(mm)

12

BQ24120RHLR

BQ24120RHLT

BQ24123RHLR

BQ24123RHLT

BQ24125RHLR

BQ24125RHLT

RHL

20

SITE 41

SITE 48

SITE 41

SITE 48

SITE 41

3.8

4.8

1.6

1.3

1.6

1.3

1.6

8

12

Q1

12

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

12-Dec-2007

Device

Package

Pins

Site

Length (mm) Width (mm) Height (mm)

BQ24120RHLR

BQ24120RHLT

BQ24123RHLR

BQ24123RHLT

BQ24125RHLR

BQ24125RHLT

RHL

20

SITE 41

SITE 48

SITE 41

SITE 48

SITE 41

346.0

190.0

346.0

190.0

370.0

346.0

195.0

190.0

346.0

212.7

346.0

212.7

355.0

346.0

200.0

212.7

29.0

31.75

29.0

31.75

55.0

29.0

45.0

31.75

Pack Materials-Page 2

IMPORTANT NOTICE

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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

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Following are URLs where you can obtain information on other Texas Instruments products and application solutions:

Products

Amplifiers

Data Converters

DSP

Applications

Audio

amplifier.ti.com

dataconverter.ti.com

dsp.ti.com

www.ti.com/audio

Automotive

Broadband

Digital Control

Military

www.ti.com/automotive

www.ti.com/broadband

www.ti.com/digitalcontrol

www.ti.com/military

Interface

interface.ti.com

logic.ti.com

Logic

Power Mgmt

Microcontrollers

RFID

power.ti.com

Optical Networking

Security

www.ti.com/opticalnetwork

www.ti.com/security

www.ti.com/telephony

www.ti.com/video

microcontroller.ti.com

www.ti-rfid.com

www.ti.com/lpw

Telephony

Low Power

Wireless

Video & Imaging

Wireless

www.ti.com/wireless

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265


型号：	BQ24125
厂家：	TEXAS INSTRUMENTS
描述：	SINGLE-CHIP SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH ENHANCED EMI PERFORMANCE(bqSWITCHER⑩) 单片开关模式，锂离子和锂聚合物充电管理具有增强的EMI性能的IC （ bqSWITCHER⑩ ）开关
文件：	总36页 (文件大小：1109K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

BQ24125 [TI]

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