Brazil Tech Day 2008 - Portal Texas Instruments - Brasil

Battery Charging Design Considerations 

Brazil Tech Day 2008 

Jinrong (John) Qian, Ph. D. 

Distinguished Member of Technical Staff 

Battery Management Applications Manager 

Texas Instruments 

1


Longer 

Battery Life 

Smaller Size 

& Weight 

Battery Power Management 

Safety (bq26100) 

Longer cycle life and runtime 

Faster and cooler charging 

Smaller size and lighter weight 

2


Agenda 

• Li-Ion Battery Characteristics and Charging Requirements 

• Battery Charging Front-End (CFE) Protector 

• Power Path Management Battery Charger 

• 3MHz switching mode USB battery charger 

• Low EMI 1-2A Synchronous Switching Li-Ion Battery Charger 

• 1-4 Cell Li-Ion battery switching charge controller 

• Summary 

3


Battery Chemistries 

• Primary battery: Non-rechargeable (Alkaline) 

• Secondary battery: Rechargeable 

• NiCd: 1.0V to 1.5V 

• NiMH: 1.0V to 1.5V 

• Li-Ion 

LiCoO2 - Coke: 3.0V to 4.1V 

LiCoO2 - Graphite: 3.0V to 4.2V 

LiMnO4 - Graphite: 3.0V to 4.4V 

LiFePO4 - Graphite: 2.0V to 3.6V 

4


NiMH Battery Charge Characteristics 

dT 

dt 

-∆V 

1 C 

0.5 C 

• Constant current 

• Cell voltage drop 

• Cell temperature Increase 

• Charge termination: -∆V, dT/dt, safety timer 

0.1 C 

1 C 

0.5 C 0.1 C 

C BAT R BAT 

5

1200 

1000 

800 

600 

400 

200 

0 


NiMH Self-Discharge Characteristics 

Capacity mAh 

45 0 C 

0 10 20 30 40 50 60 70 

Time: Days 

• Self-Discharge 2.5%/day at 25C 

• Higher T, Higher Self-discharge 

15 0 C 

25 0 C 

35 0 C 

6


Advantages and Limitations: NiMH Battery 

Advantages: 

• Fast and simple charge: constant current charge 

• 50-100% more capacity/energy than NiCd 

• No transportation regulation 

• Lower cost than Li-Ion, but 20% more expensive than NiCd 

Disadvantages 

• High self-discharge at high temperature (30% per month) 

• Voltage depression. Cathode material changes into inactive crystalline 

form when stored in charged state. 

• Prevention – discharge regularly. 

• Repair: Charge/discharge several times to 0.7V. For cases of severe 

capacity loss, keep at 0.7V for prolonged time (24 hrs) 

7

Performance 

bq2002 


NiMH/NiCd Battery Charger 

bq24400 

bq2000 

bq2005 

bq2004 

• Simple switching charge controller 

• Termination: PVD, ∆T/ ∆t 

• Integrated closed loop current control 

• Low-cost charger termination controller 

• Termination: PVD, -∆V, ∆T/ ∆t 

• Controls current-limited or constant current supply 

Cost 

• Sequential fast charge of 2 

battery packs 

• Discharge-before-charge option 

• Termination: PVD, -∆V, ∆T/ ∆t 

• Dual LED status display 

• Charges NiCd/NiMH and Li-Ion 

• Termination: PVD, ∆T/ ∆t for NiCd/NiMH, 

minimum current for Li-Ion 

Switching 

Current- 

Limited 

8


Li-Ion Battery Characteristics and 

Charging Requirements 

9

Cell Capacity mAh 

3500 

3000 

2500 

2000 

1500 

1000 

500 

0 

• Source: TIAX LLC, Portable Power 2005 Li-Ion Battery Tutorial, and Boston Power, Florida battery seminar, 2007 


18650 Li-Ion Cell Capacity Development Trend 

1992 1994 1996 1998 2000 2002 2004 2006 

• 18650: Cylindrical, 65mm length, 18mm diameter 

• 8% yearly capacity increase over last 15 years 

• NB makers are using 2400mA, 2600mAh 

18650 Cell 

18mm 

65mm 

10

500 

450 

400 

350 

300 

250 

200 

150 

Wh/kg 


Energy Density Development for Li-Ion Cells 

Gravimetric Density 

100 

1994 1996 1998 2000 2002 2004 2006 

7% 

80 

6% 

Ali Madani, “An overview of the European Li-Ion battery R&D” Florida Battery seminar 2007 

200 

160 

120 

• 6-7% annual energy density increase 

40 

0 

Wh/L 

Volumetric Density 

1994 1996 1998 2000 2002 2004 2006 

11

Cathode 

+ 

Positive 

electrode 

LiCoO 2 


Battery Electrical Equivalent Circuit 

Electrolyte 

Separator 

Battery AC model 

Anode 

- 

Negative 

electrode 

Graphite 

Constant current discharge, 

transient effect 

ON 

I . R BAT 

OFF 

Capacitor 

Capacitor + resistor 

Battery 

Battery DC model 

C BAT R BAT 

12

Voltage, V 

4.5 

4.0 

3.5 

3.0 

0 

Load current: 0.2C 


Battery Chemical Capacity 

3.6V (Battery rated voltage) 

EDV=3.0V/cell 

1 2 3 4 5 6 

Capacity, Ah Qmax Battery Capacity: 1C 

Discharge rate 1C: 

Current to completely discharge a 

battery in one hour 

Example: 

2200mAh battery, 

1C discharge rate: 2200mA, 1 hr 

0.5C rate: 1100mA, 2hrs 

C BAT R BAT 

• Battery capacity (Qmax) : Amount of charge can be extracted from the fully charged 

cell to the end of discharge voltage (EDV). 

• EDV is mini. voltage acceptable for the application or for battery chemistry 

13

Battery Voltage (V) 

4.2 

3.6 

3.0 

2.4 

EDV 


I•R BAT 

+ - I 

OCV RBAT + - 

Useable Capacity Quse 

V=OCV - I*R BAT 

Open Circuit Voltage 

(OCV) 

Quse 

Qmax 

• EDV will be reached earlier for higher discharge current. 

• Useable capacity Quse < Qmax Q use 

Q max 

14


Li-Ion 18650 Discharge Characteristics 

EDV 

ΔV1 

1/5C 

2C 

What’s battery DC impedance at SOC=50%? 

(3.8V-3.4V)/3A=130mΩ 

1C 

ΔV2 

ΔV = ΔI R BAT 

15

Li-Ion 18650 Temperature Discharge Profile 

Self-heat Effect (Internal impedance decrease when T increase) 


16

100 

80 

60 

40 

20 

0 


Li-Ion Storage Characteristics 

Capacity % 

40 0 C 200 C 

60 0 C 

0 0 C 

0 2 4 6 8 10 12 

Storage Time: Month 

• 2-3% Self-discharge per month at 20 0 C 

• Self-discharge rate doubles for every 10 0 C 

17


Safety and Thermal Stability 

OCV=4.3V 

Thermal 

Runaway 

• Active metallic lithium is deposited on anode @ overcharged. 

• Rapid temperature increase can happen @ overcharged or shorted 

• Increased temperature can accelerate degradation, cause thermal run-away, and 

battery explosion 

18

4.2 

3.9 


0.2C 

3.6 I • R 

3.3 

3.0 

2.7 

2.4 

5C 

EDV 


High Discharge Rate and Safety Battery 

Battery Capacity 

• High internal resistance causes large I • R drop 

• EDV is reached too early, reducing useable capacity 

• 5 to 20 min full discharge (12C to 3C rate) 

• Low Internal Impedance 

• Main Applications 

– Power tools 

– E-bike 

1C 

ΔQ 

+ 

C BAT RBAT 

+ - I 

VOCV V=V 0CV - I*R BAT 

- 

19


High Safety Battery 

• Fine-tune the cell for either high discharge rate or high capacity. 

10C rate discharge are available with Ni/Co/Mn hybrid cathodes) 

• Example: A123 Systems company: 26650A LiFePO4, 

– Safety: 350°C Thermal Runaway 

– 10 mΩ at 1 Hz 

4.0 

3.0 

2.0 

1.0 

0.0 

T = 25 o C 

Discharge Capacity % 

25 o C, 2.3-A charge/discharge 

45 o C, 3-A charge/5-A discharge 

60 o C, 3-A charge/5-A discharge 

0 0.5 1.0 1.5 2.0 2.5 

0 

0 200 400 600 800 1000 

Capacity (Ah) 

http://www.a123systems.com 

Cycle 

100 

80 

60 

40 

20 

20

Pack+ 

SMD 

SMC 

Pack- 


Basic Battery Pack Electronics 

RT 

SMBus 

Gas Gauge IC 

Over Voltage 

Under Voltage 

Temp Sensing 

Voltage ADC 

Discharge 

MOSFET 

Chemical Fuse Q1 Q2 

bq20z90 

Current ADC 

LDO 

I 2 C 

AFE 

OCP 

Cell 

Balancing 

bq29330 

Charge 

MOSFET 

Second 

Safety 

OVP IC 

bq29412A 

Sense 

Resistor 

• Measurement: Current, Voltage, and Temperature 

• Fuel Gauge bq20zxx: Remaining Capacity, Run-Time, Health condition 

• Analog Front End (AFE) 

R s 

21

Pre-charge 

4.2V/Cell 


I CHARGE 

3.0V/Cell 

I PRECHARGE 

Li-Ion Charge CC-CV Profile 

Fast-charge 

Pre-charge Timer Safety Timer 

Pre-charge Timer Safety Timer 

Constant Voltage 

Battery Voltage 

Taper Current 

I TERMINATION 

• Constant Current: 20-30% charging time, 70-80% capacity 

• Constant Voltage: 70-80% charging time, 20-30% capacity 

22


Charge Voltage Affects Battery Service Life 

4.35V 

4.3V 

• 10-20% more capacity with 4.35V than 4.2V 

• Over charging shortens battery cycle life 

4.2V 

4.25V 

23


Battery Capacity at Different Charge Voltage 


4.2 

4.0 

3.8 

3.6 

3.4 

3.2 

3.0 

2.8 

2.6 

Discharge Current: 500mA 

0 30 60 90 120 

Time (Minute) 

• 800mAh @4.1V, 10% less than @4.2V 

• 875mAh @ 4.2V 

4.2V 

4.1V 

24

Charge Current 

Current should be limited to 1C rate to prevent overheating 

and resulting accelerated degradation. 

“Factors that affect cycle-life and possible degradation mechanisms of 

a Li-ion cell based on LiCoO2”, Journal of Power Sources 111 (2002) 130-136 


Charge Current vs Battery Degradation 

1.1C 

1.0C 

1.3C 

1.5C 

2.0C 

25

Charge Voltage 

• 4.1V for Coke Based Anode (1990’s) 

• 4.2V for Graphite Anode 

• 4.4V for LiNiMnCoO2 cathode. 

• 3.6V for LiFePO4 cathode 

• Charging lower voltage improves cycle life and safety 

Charge Current 

• ≤ 1C rate; preferred 0.7C to prevent overheating and resulting 


Li-Ion Battery Charging Requirements 

accelerated degradation 

26

Battery charging Temperature Qualification 

0°C to 45°C. Charging at higher temperature results in accelerated 

aging 

Low-Voltage Battery Pack Charge 

Pre-charge current: < 0.1C for VCELL < 3.0V 

Charging Termination 

In Constant Voltage Mode, Charge current < 0.1C 

Charge Timer 

3-5 hrs. 


Li-Ion Charging Requirements (Cont.) 

27

1C 

0.5C 


New Charging Requirements for Portable EEs 

MAX. Charging Current 

#1 

#2 

T1 T2 T3 T4 T5 

100 0 C 

0C 450C500C600C 4.25V 

4.15V 

4.10V 

Note: LiCoO 2 Type Battery Cell 

• Low charge current or voltage @ low temperature 

• Low charge voltage @ high temperature 

MAX. Charging Voltage 

#2 

#1 

T1 T2 T3 T4 T5 

100 0 C 

0C 450C500C600C 28

Battery Charging Front-End (CFE) Protector 


29 

29


Battery Charging System Requirements 

• Safety and Reliability 

• Adapter Hot Plug-in 

• Adapter Reverse Input to the charger 

• Short Circuit and Overcharging Protection 

30


Cellular Phone Charger Interface 

AC 100-240 V 50/60 Hz 

DC 5 V, 0.31 A 

• USB type A connector from adapter output 

• Terminal to the portable device could be different 

USB 

5V 

Data 

Clock 

GND 

Adapter 

V+ 

D+ 

D- 

GND 

31

Causes of System Failure Due to Input Power 

Input Over Voltage 

• Wrong Adapter or After-Market Adapter 

• Transformer–Rectifier Adapters (un-regulated) 

• Hot Plug Event 


ADAPTER 

V INCIN 

Battery 

Charger 

SYSTEM 

8.0 

6.0 

4.0 

2.0 

Adapter Voltage (V) 

5-V/500-mA UNREGULATED 

5-V/500-mA REG 

0 

0 0.5 1.0 1.5 2.0 

Adapter Current (A) 

32

120 AC 

220 AC 


Hot Plug In Test Setup and Equivalent Circuit 

V i 

Oscillation conditions: 

R + ESR < 2 

i 

L 

C 

i 

IN 

+ 

Vi - 

1-m Cable 

Ri 

I IN 

Li 

C IN 

ESR 

C IN 

V IN 

V IN 

CHARGER 

Charge 

Controller 

CHARGER 

Charge 

Controller 

Battery 

Battery 

33

7.5 V 


Reducing Overshoot by Increasing ESR 

R C 

C IN 

C IN = 2×1 μF (0805, X7R) 

Overshoot: 50 % to 7.5 V 

V IN 

I IN 

5V 

2.95 A 

5 V 

V IN 

bq2406x 

Battery 

Charger 

System 

C IN = 2×1 μF (0805,X7R) + 1 Ω 

overshoot: 20%, 6.08 V 

6.0 V 5 V 

• High ESR or external resistor can help reduce voltage overshoot. 

I IN 

R + 

ESR > 

V IN 

2 A 

i 

2 

L 

C 

i 

34 

IN

120V 

220V 

AC 


Solution: Charge Front End (CFE) Improves Safety 

AC 

Adapter 

C IN 

V IN 

bq243xx 

Charge 

Front 

End 

(CFE) 

CFE Provide System Level Protections 

• Input Transient Over-Voltage 

• Steady state over voltage 

• Over-Current Protection, Latch or Hiccup 

• Adapter Reverse Polarity 

• Battery Over-voltage 

bq2408x 

Low 

Voltage 

Charger 

Low 

Voltage 

System 

35

• Input over-voltage 

• User-programmable input over-current 

• Battery over-voltage (EEPROM versions) 

• 30V maximum input voltage 

• Supports up to 1.5A input current limit 

•

q24316 

bq24380 


Summary of bqCFE Protection Features 

2x2 mm 

4x3 mm 

2x2 mm 

6.3 5.5 

INPUT OVP OCP Battery OVP 

Part # Package V OVP V O(REG) t BLANK(OVP) I OCP t BLANK(OCP) BV OVP Counter 

bq24300 2x2 mm 10.5 5.5 64 μs 300 mA 5 ms 4.35 HICCUP 



bq24314 

2x2 mm 

4x3 mm 

5.8 0 PROG 176 μs 4.35 LATCH 

6.8 

0 

0 

PROG 

No 

176 μs 

4.35 

4.35 

LATCH 

Hiccup 

bq24381 2x2 mm 7.1 5.0 0 No 4.35 Hiccup 

• Latch: After 15 times OCP or OVP, then latch 

37


Power Path Management Battery Charger 

38


Charging with an Active System Load: Issues 

+ 

Adapter 

or USB 

Charger 

I CHG 

Charger output current is shared: 

I CHG = I BAT + I SYS 

Issues: 

Safety Timer False Expiration 

Termination Detection 

I SYS 

I BAT 

System 

39

+ 

Adapter 

or USB 


Issue 1: Pre-charge and Safety Timer Fault 

Pre-Charge Mode: 

Battery voltage may not reach the fast charge voltage threshold 

Pre-charge timer may expire 

Solution: keep system off or in low-power mode in pre-charge mode 

Drawback: Can not operate the system while charging a deeply 

discharged battery simultaneously 

I CHG 

I SYS 

100 mA 80 mA 

IBAT Charger 20 mA 

System 

40

+ 

Adapter 

or USB 


Issue 2: Charge Termination NOT Detected 

Charger 

I CHG 

I BAT 

I SYS 

Voltage Regulation Mode: 

System 

If I SYS > I TAPER , Termination is never detected 

Solution: current supplement circuit 

Current (A) 

1 

0.8 

0.6 

0.4 

0.2 

0 

I CHG 

I BAT 

I SYS 

20 40 60 80 

Time 

I TAPER 

41


Power Path Management Battery Charger 

Adapter 

+ 

- 

Q1 

Controller 

Powering System 

Q2 

• System power supplied from adapter through Q1 

• Charge current controlled by Q2 

• Ideal topology when powering system and charging battery 

simultaneously is a requirement 

• Separates charge current path from system current path 

• No interaction between charge current and system current 

C1 

Charging 

Battery 

System 

42

Adapter 

+ 

- 

I ADP 

Q1 

Controller 


Power Path Management: Potential Issues 

Q2 

V OUT 

I BAT 

System Current 

C1 

Charging 

Battery 

Input current : I ADP = I BAT + I SYS 

Issues: 

• Input voltage collapses 

I SYS 

System 

I SYS 

V OUT 

I CHG 

I SYS + I CHG 

Adapter current limit 

Solution 1: 

Design the AC adapter at maximum I SYS + I CHG , HIGH COST 

Adapter 

voltage 

collapses 

I ADP 

Time 

43

+ 

Adapter - 

+ 

or USB 

1.15 VDPPM - 


Voltage Based Dynamic Power Path Management (DPPM) 

I ADP 

Q2 

V OUT 

I CHG 

I SYS 

C1 

System 

Bus voltage drop causes system reset 

DPPM function : 

Reduces the charge current when 

the system voltage is VDPPM “Finds” maximum adapter power 

Battery Supplement Mode 

I SYS 

I ADP AC adapter current limit 

I CHG 

V OUT 

VDPPM 

DPPM 

Mode 

System Voltage 

V BAT 

Time 

44

103AT 

TS 

2.5V 


- 

+ 

- 

+ 

0.5V Hot 

Temperature Qualification 

0 0 C – 45 0 C 

Cold Temp Fault 

100uA 

bq2403x 

Hot Temp Fault 

RT1 

RT2 

RT1 and RT2 calculation from the Temp sense software 

TS 

X 0 C – Y 0 C 

Cold Temp Fault 

2.5V 

- 

+ 

- 

+ 

0.5V Hot 

http://focus.ti.com/docs/toolsw/folders/print/tempsense-sw.html 

100uA 

bq2403x 

Hot Temp Fault 

45


Thermal Fold-back Function 

This internal thermal limit (~125°C) can be reached 

Increased Input voltage – Higher Power Dissipation 

Large System Load - Higher Power Dissipation VIN Low Battery Voltage at High Charge Level - Higher Power Dissipation 

High Ambient Temperatures – Reduces PWR DISS needed to Reach Thermal Limit 

The thermal foldback loop reduces the charge current , in order to 

keep the IC junction temperature under control and avoid damage 

Safety timer duration is increased. 

Charge termination is disabled 

ICHG 

T j = 125 0 C 

Time 

I CHG_THRM 

46

USB 

Voltage Based Dynamic Power-Path Management Charger 

Adapter 

C1 C2 

• OUT: 4.4 V for bq24032A; 6.0 V for bq24030 

• Dynamically reduces the charge rate to maximize adapter to system current 

• Regulate junction temperature at 125°C by reducing charge current 

• Dynamically increase the safety timer based on real charge current 


Vcc 

R4 

R5 

R6 

R7 

High: 500 mA 

Low: 100 mA 

D1 

D2 

D3 

D4 

R1 

R2 

AC 

USB 

STAT1 

STAT2 

USBPG 

ACPG 

ISET2 

ISET1 

TMR 

VSS 

Q1 

Q3 

Q2 

bq2403x 

OUT 

OUT 

OUT 

CE 

BAT 

BAT 

TS 

LDO 

PSEL 

DPPM 

High 

Enable 

3.3 V/20 mA 

High: AC 

Low: USB 

R3 

System Load 

C3 

10 µF 

103AT 

C4 

RT1 

RT2 

47

Dual Input 

Adapter 

/USB 

Single 

Input 

bqTINY TM -II 

$0.80 bq24020 

7V IN –1A 

2 Status Pins 

Temp Sensor 

3x3 QFN 


Li-Ion Linear Charger Portfolio 

bqHYBRID 

7V IN –1A 

2 Status Pins 

Temp Sensor 

Integrated DC/DC 

Converter (300mA) 

3.5x4.5 QFN 

bq24080/1 $0.80 

bq24010 bq24060 

7V IN –1A 

2 Status Pins 

3x3 QFN 

bq2501x 

bqTINY TM -I 

18V IN –1A 

2 Status Pins 

3x3 QFN 

bqTINY TM -III 

bq2403x 

18V IN –1.5A 

2 Status Pins 

DPPM 

Thermal Regulation 

3.5x4.5 QFN 

bqTPOD 

26V IN –1A 

2 Status Pins 

LDO Mode 


Input OVP 

3x3 QFN 

bqMicro-Lite 

bq24085/6/7 

26V IN –0.75A 

2 Status Pins 

LDO Mode 


Input OVP 

3x3 QFN 

bqTINY TM -III 

Bq24070/1 

18V IN –1.5A 

2 Status Pins 

DPPM 


3.5x4.5 QFN 

48

Fully Integrated Switch-Mode Li-Ion Battery Charger with Full 


USB Compliance and USB-OTG Support 

49

Voltage budget: 

• Low power mode: 4.4V to 5.25V 

• High power mode: 4.75V to 5.25V 

• Bus-powered hub: < 350mV drop 


USB Voltage and Current Budget 

Current budget: 

• Suspend mode: < 0.5mA/2.5mA 

• Low power mode: < 100mA 

• High power mode: < 500mA 

All USB devices must follow these electrical specification. 

50

+ 

V IN 

Adapter 

LOSS 


Power Loss in Linear Battery Charger 

Linear 

Charger 

V BAT 

( V ) IN −VBAT 

ICHG 

P = 

• 

• Simple and low cost. 

• Highest power dissipation from pre-charge to fast charge mode transition. 

• Ideal for low charge current < 800mA. 

• Thermal issue for ≥ 800mA charge current. 

• For high charge current applications (Portable DVD, PMP) 

I CHG 

4 

3 

2 

1 

0 

PLOSS (Watt) VIN=5.5V 1.24A 

(1800mAh Li-Ion) 

700mA 

(1000mAh battery) 

2.4 2.7 3 3.3 3.6 3.9 4.2 

VBAT (V) 

51

500 mA 

+ USB 

500 mA 

+ USB 

V IN 

V IN 


Linear 

Charger 

Charge 

Controller 

Switching Charger 

Fast USB Battery Charging 

I CHG = 500 mA 

L 

Battery 

C 

I CHG =? 

Charge Current (A) 

V BAT 

1.0 

0.9 

0.8 

0.7 

0.6 

0.5 


Linear Charger 

0.4 

2.4 2.8 3.2 3.6 4.0 


• 500-mA Current Limit 

• 40% more charge current 

• Full use of USB Power 

• Short battery charging time 

V IN 

I CHG = • η • 500mA 

V BAT 

52

Efficiency (%) 

95 

90 

85 

80 

75 

70 

65 

60 

55 

50 

Switch Mode Charger 

45 

2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 


Charger Comparison: Efficiency 

Vin=5V, Iin=0.5A 

Linear Mode Charger 


Switch Mode Charger 

Fs=3Meg Hz 

L=1uH 

DCR=0.1 ohm 

Rsns=0.068 ohm 


V 

EffLinear 

= 

V 

100% 

Switch mode charger: 

• Higher efficiency 

• More suitable for power limited source application, e.g. USB battery charging 

BAT 

IN 

53

Temperature (°C) 

130 

120 

110 

100 

90 

80 

70 

60 

50 

40 

30 

2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 


Charger Comparison: Temperature 

Vin=5V, Iin=0.5A 


Switch-Mode Charger 


Switch-mode charger: 

• Lower temperature 

• Higher safety and reliability 

Assume ambient temperature 

25°C 

Thermal impedance is 75°C/W 

for 2x2 size QFN package 

T ⋅ P + T 

j 

= RθJA 

loss 

am 

54

SCL 

SDA 

10k 

STAT 

OTG 

USB 

VAUX 

HOST 

10k 

10k 

10k 


BQ2415x Typical Application Circuit 

C1 

1uF 

C2 

4.7uF 

VBUS 

PMID 

SCL 

SDA 

STAT 

OTG 

Q1 

Q2 

bq2415x 

Q3 

SW 

BOOT 

PGND 

SGND 

CSIN 

CSOUT 

AUXPWR 

VREF 

L1 1uH 

C4 

10nF 

C7 

1uF 

R1 0.068 C3 10uF 

C6 

1uF 

C5 

0.1uF 

• Internal input current sensing 

• Input current limiting: current loop 

• Charge in constant current and constant voltage mode 

• Automatic termination with internal safety timer 

• Boost mode operation for USB OTG 

55


bq24150 Specifications and Features 

• Input voltage ABS Max 20 V 

• Switching frequency: 3 MHz with 0% to 99.5% duty cycle 

• Programmable charge parameters by I 2 C interface 

• Boost 

• Charge current up to 1.25A 

• Charge voltage: 3.5—4.42V, step 20mV 

• Termination current 

• Support USB OTG 

• PWM and PFM mode boost operation for high efficiency 

• Complete protection 

• Package: 20 Pins 2.0X2.0 mm WCSP 

56

USB 

Q1 

I IN 

Temp 


Battery Charge Control Loop 

Q2 

PWM 

Q3 

L1 1uH 

I BAT 

V BAT 

• Charge voltage regulation: 0.5% (25ºC), 1% (0-125ºC) 

• Charge current regulation: 5% 

• Input current regulation: 5% 

• Temperature regulation: 125ºC, 165ºC shut down 

R1 0.068 C3 10uF 

57


USB-OTG Support 

58

Host (Master) 


USB On-The-Go Defines a New Connection Paradigm 

OTG is for this applications 

Device (Slave) 

USB 2.0 has 

no definition 

between 

slave to slave 

• USB OTG provides a STANDARD USB connection for mobile devices. 

59

USB OTG Voltage range: 


USB OTG Voltage and Current Budget 

• 4.4V to 5.25V for 0-100mA range, same as USB 2.0 low power mode 

USB OTG Current range: 

• 8mA ≤ Current supplied ≤ 100mA 

USB OTG Application Power: 

• DSC: typically 0-10mA (self powered) 

• Keyboard: typically 30-45mA with all LEDs turned on (bus powered) 

• Flash memory reader: typically 40-50mA (bus powered) 

60

+ 

V IN 

+ 

V IN 

USB 

USB 

Linear 

Charger 


How to Support OTG for Providing 5V Bus? 

Boost 

Charge 

Controller 

Charge 


Battery 

L 

C 

V BAT 

• Can not provide 5V VBUS 

• Have to add boost IC 

• Buck mode for charging 

• Boost mode for OTG 

• No additional cost 

61


OTG: Boost Converter Protection and Fault Detection 

• VBUS OVP: VBUS > 6V 

• Cycle by cycle current limit: 1A 

• Battery OVP: VBAT > 4.9V 

• Battery voltage too low: VBAT < 3V (before boost) 

VBAT < 2.6V (during boost) 

• Thermal shut down: 165ºC 

• 32sec timer expires: stop boosting and report timer fault 

62


EVM Software Interface 

63


EVM Hardware 

64


Low EMI 1-2A Switching Charger 

65

EMI Definition 


EMI Considerations 

The interference of one piece of electronic equipment on the operation of 

another by means of electromagnetic energy transfer. 

• A generator of electromagnetic energy: (a source) 

• Transmission of that energy between equipments: (a coupling means) 

• A receptor circuit whose operation is negatively impacted by the 

transmitted energy: (a victim circuit) 

EMI Principles: 

Inductive Coupling Capacitive Coupling 

di 

e = M 

i = 

dt 

C 

dv 

dt 

66


Solutions to Reduce EMI 

• Adding filter (cost! may not work for radiated EMI) 

• Adding snubber (cost!) 

• Excellent layout (design difficulty) 

• Slower switching speed 

- No extra cost 

- Reduce both conducted and radiated EMI 

- May impact efficiency 

67

V IN 

V IN 


Major EMI Source of a Converter 

I Q1 I OUT 

V PH 

V PH Waveform 

D·T 

T 

High dv/dt and di/dt switching on 

the phase node is the major EMI 

source in a Buck converter 

D·T 

I Q1 Waveform 

T 

IQ1 

I OUT 

68

1V 

1V 

trise=5ns 

1us 

trise=100ns 

1us 


Why Slower Switching Helps 

Magnitude (dB) 



-100 

-150 

-200 

-250 

-100 

-150 

-200 

-250 

Fourier 

Analysis 

100kHz 1MHz 10MHz 100MHz 1GHz 

Fourier 

Analysis 

About 25dB Less! 

5 6 7 8 9 

100kHz 1MHz 10MHz 1GHz 

Frequency 

100MHz 

-175dB 

-200dB 

69


ADAPTER (9V or 12V) 

V IN 

bq24120: 1 Cell 

bq24123: 1-2 Cell 

bq24125: 1-3 Cell 

Typical Applications Circuit 

VIN=9V, Battery: 2-cell in series, ICHG=1.25A, Safety timer: 5 hours, 

I PRECHG = 125mA, Temperature range: 0-45C 

R 1 :1.5kΩ 

C IN 

10μF 

C 3 

0.1μF 

D3: Charge 

R 2 : 1.5kΩ D2: Done 

R 3 : 1.5kΩ 

D1: Adapter 

C TTC : 0.1μF 

3 IN 

4 

13 

6 

10 

2 

19 

5 

7 

16 

IN 

CELL 

VCC 

VSS 

PWM 

Controller 

STAT1 

STAT2 

PG 

TTC 

CE 

Q1 

Q2 

bq24123 

OUT 

OUT 

1 

20 

SNS 15 

BAT 

ISET1 

ISET2 

VTSB 

PGND 

PGND 

14 

8 

9 

TS 12 

11 

17 

18 

L 

10μH 

C OUT 

10μF 

R SET1 : 7.5k 

R SET2 : 7.5k 

C 2 : 0.1μF 

R SNS 

0.1Ω 

C 1 

0.1μF 

R T1 

9.31k 

1% 

R T2 

442k 

1% 

VTSB 

V BAT 

PACK+ 

PACK- 

R T 

103AT 

70

VPH: 


Switching Waveforms and EMI Spectrum @ Vin=9V Ichrg=1A 

Phase node voltage 

≈7ns 

VPH: Phase node voltage 

≈20ns 

(dBuV) 

60 

50 

40 

30 

20 

10 

0 

-10 

After increasing the turn-on 

(dBuV) 

time by 3 times (bq24120/123) 

60 

50 

40 

30 

20 

10 

0 

-10 

FCC 

FCC 

46dB 

31dB 

CISPR (Europe) 

50M 100M 200M 500M 1G(Hz) 

CISPR (Europe) 

50M 100M 200M 500M 1G(Hz) 

• 15dB reduction around 150MHz 

71


Switching Charger controller 

72

ADAPTER 

R SNS2 

Regulation Loops 

1. Input Current 

2. Charge Current 

3. Battery Voltage 


Input Current Based DPM Battery Charger 

I ADP 

Q1 

Q2 

• Input Current Regulation 

SYSTEM LOAD 

L 

I SYS 

R SNS1 

I CHG 

ISYS DPPM 

ISYS1 I ADP 

I CHG 

Mode 

Adapter Current 

Limit 

t0 t1 t2 

Charge 

Current 

Regulation 

• Current sharing between system and battery charger 

• Minimize the AC adapter size and power rating 

I CHG1 

I SYS2 

I CHG2 

Adapter 

Regulation 

73 

Time

ADAPTER 


Input Current Regulation Based DPM Battery Charger Example 

R SNS2 

bq24750/51 

bq24745 

Regulation Loops 

1. Input Current 

2. Charge Current 

3. Battery Voltage 

I ADP 

Q1 

Q2 

SYSTEM LOAD 

L 

I SYS 

R SNS1 

I CHG 

Test Conditions: 

n System step load 0- 4.0A 

n Constant charge current = 4A 

n AC adapter current limit = 5A 

LOAD CURRENT: 5A/div 

ADAPTER CURRENT: 5A/div 

CHARGE CURRENT: 5A/div 

BATTERY VOLTAGE 10V/div 

• Constant System Bus Voltage 

• Maximizing use of AC adapter power to minimize the charge time 

74

Adapter 

AC Adapter 

Detection 

ACGOOD 

C1 

10µF 

VREF 

C4:1µF 

Pack Temperature 

Monitoring 

HOST 

Brazil Tech ADC Day 2008 

Input Current Based DPM Battery Charger Application Circuit 

DAC 

DAC 

DAC 

DAC 

R8 

430.8k 

R9 

66.4k 

Q1 

R4 

5.6k 

R5 

118k 

Q2 

R3 

10k 

R1: 10mΩ 

C11 

0.1µF 

ACN 

ACP 

ACDRV 

ACDET 

ACGOOD 

TS 

AGND 

CELLS 

SRSET 

ACSET 

VREF 

DPMDET 

CHGEN 

VDAC 

VADJ 

IADAPT 

PVCC 

bq24750 

BATDRV 

REGN 

BTST 

HIDRV 

PH 

LODRV 

PGND 

SRP 

SRN 

BAT 

ACOP 

C6 

10uF 

C8:1µF 

Q3 

C17 

0.47µF 

Q4 

C7 

0.1µF 

C2 

2x10µF 

C6 

10uF 

L: 10µH 

C4 

10µF 

R2 

10mΩ 

SYSTEM LOAD 

Q5 

C5 

10µF 

Power 

Source 

Selector 

Battery Pack 

C3 

10µF 

75


Li-Ion Switch-Mode Charger Portfolio 

EMI improvement 

(increase gate resistance 

to slow down switching) 

Standalone only 

2-cell for UMPC 

bq24103/5 

bq24113/5 

18V IN -2A 

1.1MHz Sync PWM 

Integrated FETs 

1 - 3 Cells in Series 

3.5x4.5 QFN 

Standalone & Host 

Controlled 

Very small 

solution size 

Stand-alone Host-controlled 

bq24123/5 

bq24721C 

bq24705 

(4x4) 

30V IN –8A 

300/500kHz Sync PWM 

High V/I Accuracy 

Dynamic Power Mgt 

3-4 Cells in Series 

5x5 QFN-28 

SMBus Interface 

Power source selector 

bq24740 

(5x5) 

No power source selector 

bq24750/51A 

bq24745 

(5x5) 

SMBus, 1-4 cell 

No power source selector 

30V IN –8A 

300kHz Sync PWM 

High V/I Accuracy 

Dynamic Power Mgt 

2-4 Cells in Series 

5x5 QFN-28 

Power source selector 

76


Summary: Battery Charging 

• Charge voltage and charge current 

• Internal or external power FET 

• Linear or switching topology 

• Standalone or host controlled 

• Charge cycle management 

– Pre-charge voltage, pre-charge current 

– Termination current, status reporting 

– Safety timer 

• Thermal management: 

– Battery temperature qualification 

– Thermal regulation 

– Thermal shutdown 

• Power path management 

77


Thanks you! 

Q & A 

78

Brazil Tech Day 2008 - Portal Texas Instruments - Brasil

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