LTC4120EUD-4.2#PBF_技术文档

LTC4120/LTC4120-4.2

Wireless Power Receiver and

400mA Buck Battery Charger

FEATURES

DESCRIPTION

The LTC^®4120 is a constant-current/constant-voltage wire-

less receiver and battery charger. An external program-

ming resistor sets the charge current up to 400mA. The

LTC4120-4.2 is suitable for charging Li-Ion/Polymer bat-

teries,whiletheprogrammablefloatvoltageoftheLTC4120

accommodates several battery chemistries. The LTC4120

usesaDynamicHarmonizationControl(DHC)techniquethat

allowshighefficiencycontactlesschargingacrossanairgap.

n

Dynamic Harmonization Control Optimizes

Wireless Charging Over a Wide Coupling Range

n

Wide Input Voltage Range (12.5V to 40V)

n

Adjustable Float Voltage (3.5V to 11V)

n

Fixed 4.2V Float Voltage Option (LTC4120-4.2)

50mA to 400mA Charge Current Programmed with a

Single Resistor

n

1% Feedback Voltage Accuracy

Programmable 5% Accurate Charge Current

No Microprocessor Required

The LTC4120 regulates its input voltage via the DHC pin.

This technique modulates the resonant frequency of a

receiver tank to automatically adjust the power received

as well as the power transmitted to provide an efficient

solution for wirelessly charging battery-powered devices.

No Transformer Core

Thermally Enhanced, Low Profile 16-Lead

(3mm × 3mm × 0.75mm) QFN Package

Wireless charging with the LTC4120 provides a method

to power devices in harsh environments without requiring

expensive failure-prone connectors. This allows products

to be charged while locked within sealed enclosures, or

in moving or rotating equipment, or where cleanliness or

sanitation is critical.

APPLICATIONS

n

Handheld Instruments

n

Industrial/Military Sensors and Devices

n

Harsh Environments

n

Portable Medical Devices

n

This full featured battery charger includes accurate RUN

pinthreshold,lowvoltagebatterypreconditioningandbad

battery fault detection, timer termination, auto-recharge,

and NTC temperature qualified charging. The FAULT pin

providesanindicationofbadbatteryortemperaturefaults.

Physically Small Devices

n

Electrically Isolated Devices

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks

and AutoResonant is a trademark of Linear Technology Corporation. All other trademarks are

the property of their respective owners.

Once charging is terminated, the LTC4120 signals end-of-

charge via the CHRG pin, and enters a low current sleep

mode. An auto-restart feature starts a new charging cycle

if the battery voltage drops by 2.2%.

TYPICAL APPLICATION

Wireless Rx Voltage/Charge Current vs Spacing

26.7nF

400

333

267

200

133

67

40

35

30

25

IN

RUN

INTV

CC

FREQ

BOOST

I

CHARGE

MAX

2.2µF

22nF 33µH

10µF

V

IN

LTC4120

6.5nF

47µH

SW

NOT

Tx CIRCUITRY

5µH

DHC

CHGSNS

NTC

CHARGING

FAULT

CHRG

BAT

20

15

10

1.01M

1.35M

+

Li-Ion

4.2V

T

CHARGING

FB

GND PROG FBG

3.01k

22µF

0

0.4 0.6

0.8 1.0 1.2

SPACING (cm)

1.4

1.6 1.8

4120 TA01a

4120 TA01b

4120ff

1

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

ABSOLUTE MAXIMUM RATINGS ^{(Note 1)}

IN, RUN, CHRG, FAULT, DHC...................... –0.3V to 43V

BOOST ................................... V – 0.3V to (V + 6V)

I

............................................................... 350mA

DHC RMS

I

, I

, I .................................................. 5mA

SW

CHRG FAULT FBG

FB

SW (DC)........................................ –0.3V to (V + 0.3V)

......................................................................... 5mA

IN

SW (Pulsed <100ns) ......................–1.5V to (V + 1.5V)

I

.................................................................. –5mA

IN

INTVCC

CHGSNS, BAT, FBG, FB ...............................–0.3V to 12V

Operating Junction Temperature Range

(Note 2).................................................. –40°C to 125°C

Storage Temperature Range .................. –65°C to 150°C

FREQ, NTC, PROG, INTV .......................... –0.3V to 6V

CC

I

, I ..................................................... 600mA

CHGSNS BAT

PIN CONFIGURATION

LTC4120

LTC4120-4.2

TOP VIEW

16 15 14 13

INTV

1

2

3

4

12 NTC

11 FBG

INTV

1

2

3

4

12 NTC

11 NC

CC

BOOST

IN

BOOST

IN

17

GND

17

GND

FB

BATSNS

10

9

10

9

SW

BAT

SW

BAT

5

6

7

8

5

6

7

8

UD PACKAGE

16-LEAD (3mm × 3mm) PLASTIC QFN

= 125°C, θ = 54°C/W

UD PACKAGE

16-LEAD (3mm × 3mm) PLASTIC QFN

= 125°C, θ = 54°C/W

T

JMAX

JA

EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB TO OBTAIN θ

JA

ORDER INFORMATION

(http://www.linear.com/product/LTC4120#orderinfo)

LEAD FREE FINISH

LTC4120EUD#PBF

LTC4120IUD#PBF

TAPE AND REEL

PART MARKING*

LGHB

PACKAGE DESCRIPTION

TEMPERATURE RANGE

–40°C to 125°C

LTC4120EUD#TRPBF

LTC4120IUD#TRPBF

16-Lead (3mm × 3mm) Plastic QFN

LGHB

LTC4120EUD-4.2#PBF

LTC4120IUD-4.2#PBF

LTC4120EUD-4.2#TRPBF LGMT

LTC4120IUD-4.2#TRPBF LGMT

Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through

designated sales channels with #TRMPBF suffix.

LTC4120 OPTIONS

LTC4120

FLOAT VOLTAGE

Programmable

4.2V Fixed

LTC4120-4.2

4120ff

2

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

ELECTRICAL CHARACTERISTICS ^Thel denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T_A= 25°C (Note 2). V_IN= V_RUN= 15V, V_CHGSNS= V_BAT= 4V, R_PROG= 3.01k,

V_FB= 2.29V (LTC4120), V_BATSNS= 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative.

SYMBOL

PARAMETER

CONDITIONS

MIN

12.5

0

TYP

MAX

40

UNITS

V

l

Operating Input Supply Range

Battery Voltage Range

DC Supply Current

11

V

I

Switching, FREQ = GND

Standby Mode (Note 3)

Sleep Mode (Note 3)

3.5

mA

µA

IN

l

130

220

100

LTC4120: V = 2.51V (Note 5),

LTC4120-4.2: V

60

µA

FB

= 4.4V

BATSNS

l

Disabled Mode (Note 3)

Shutdown Mode (Note 3)

37

20

80

70

40

µA

Differential Undervoltage Lockout

Hysteresis

V -V Falling, V = 5V (LTC4120),

20

160

mV

∆V

IN BAT

IN BATSNS

IN

DUVLO

INTVCC

V -V

Falling, V = 5V (LTC4120-4.2)

IN

V -V Rising, V = 5V (LTC4120),

115

mV

IN BAT

IN BATSNS

IN

V -V

Rising, V = 5V (LTC4120-4.2)

IN

l

UV

INTV Undervoltage Lockout

INTV Rising, V = INTV + 100mV, V = NC

4.00

4.15

220

4.26

V

CC

IN

CC

BAT

Hysteresis

INTV Falling (Note 4)

mV

CC

Battery Charger

l

I

BAT Standby Current

Standby Mode (LTC4120) (Notes 3, 7, 8)

Standby Mode (LTC4120-4.2) (Notes 3, 7, 8)

2.5

50

4.5

1000

µA

nA

BAT

l

BAT Shutdown Current

Shutdown Mode (LTC4120) (Notes 3, 7, 8)

Shutdown Mode (LTC4120-4.2) (Notes 3, 7, 8)

1100 2000

nA

10

1000

l

I

BATSNS Standby Current (LTC4120-4.2)

BATSNS Shutdown Current (LTC4120-4.2)

Feedback Pin Bias Current (LTC4120)

Standby Mode (Notes 3, 7, 8)

Shutdown Mode (Notes 3, 7, 8)

5.4

10

µA

nA

µA

Ω

BATSNS

1100 2000

I

V

= 2.5V (Notes 5, 7)

FB

25

60

1

FB

Feedback Ground Leakage Current (LTC4120) Shutdown Mode (Notes 3, 7)

Feedback Ground Return Resistance (LTC4120)

FBG(LEAK)

R

1000 2000

2.393 2.400 2.407

2.370 2.418

FBG

V

Feedback Regulation Voltage (LTC4120)

Regulated Float Voltage (LTC4120-4.2)

Battery Charge Current

(Note 5)

V

FB(REG)

l

V

4.188 4.200 4.212

V

FLOAT

CHG

4.148

4.227

l

I

R

PROG

R

PROG

= 3.01k

= 24.3k

383

45

402

50

421

55

mA

V

Undervoltage Current Limit

V

Falling

12.0

–50

–92

988

V

mV

UVCL

IN

l

Battery Recharge Threshold

Ratio of BAT Current to PROG Current

Falling Relative to V (LTC4120) (Note 5)

FB_REG

–38

–70

–62

RCHG

FB

Falling Relative to V (LTC4120-4.2)

FLOAT

–114

mV

RCHG_4.2

PROG

BATSNS

h

V

< V < V (LTC4120) (Note 5)

FB(REG)

TRKL_4.2

mA/mA

TRKL

FB

< V

(LTC4120-4.2)

BATSNS

FLOAT

l

V

PROG Pin Servo Voltage

1.206 1.227 1.248

300

V

PROG

R

CHGSNS-BAT Sense Resistor

I

= –100mA

BAT

mΩ

SNS

4120ff

3

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

ELECTRICAL CHARACTERISTICS ^Thel denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T_A= 25°C (Note 2). V_IN= V_RUN= 15V, V_CHGSNS= V_BAT= 4V, R_PROG= 3.01k,

V_FB= 2.29V (LTC4120), V_BATSNS= 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

I

Low Battery Linear Charge Current

0V < V < V

, V = 2.6V (LTC4120),

6

9

16

mA

LOWBAT

FB

TRKL BAT

V

< V

, V = 2.6V (LTC4120-4.2)

BATSNS

TRKL_4.2 BAT

l

V

Low Battery Threshold Voltage

V

Rising (LTC4120),

BATSNS

2.15

2.21

2.28

V

LOWBAT

BAT

Rising (LTC4120-4.2)

Hysteresis

147

mV

mA

I

Switch Mode Trickle Charge Current

V

< V , V < V

< V

(LTC4120) (Note 5),

TRKL_4.2

I

/10

CHG

TRKL

LOWBAT

BAT FB

BATSNS

TRKL

< V

(LTC4120-4.2)

PROG Pin Servo Voltage in Switch Mode

Trickle Charge

V

< V , V < V

(LTC4120) (Note 5),

122

mV

LOWBAT

BAT FB

TRKL

< V

(LTC4120-4.2)

BATSNS

TRKL_4.2

l

V

Trickle Charge Threshold

Hysteresis

V

Rising (LTC4120) (Note 5)

Falling (LTC4120) (Note 5)

1.64

2.86

1.68

50

1.71

2.98

V

mV

TRKL

FB

Trickle Charge Threshold

Hysteresis

Rising (LTC4120-4.2)

Falling (LTC4120-4.2)

2.91

88

V

TRKL_4.2

BATSNS

mV

h

End of Charge Indication Current Ratio

Safety Timer Termination Period

Bad Battery Termination Timeout

(Note 6)

0.1

2.0

30

mA/mA

Hours

Minutes

C/10

1.3

19

2.8

42

Switcher

l

f

Switching Frequency

FREQ = INTV

FREQ = GND

1.0

0.5

1.5

0.75

2.0

1.0

MHz

OSC

CC

t

Minimum Controllable On-Time

Duty Cycle Maximum

(Note 9)

120

ns

%

MIN(ON)

94

Top Switch R

I

= –100mA

0.8

0.5

750

Ω

DS(ON)

SW

Bottom Switch R

= 100mA

Ω

DS(ON)

I

Peak Current Limit

Measured Across R

Series with R

with a 15µH Inductor in

585

1250

mA

PEAK

SNS

(Note 9)

SNS

l

Switch Pin Current (Note 8)

V

= Open-Circuit, V

= 0V, V = 8.4V (LTC4120)

15

7

30

15

µA

SW

IN

RUN

SW

= 0V, V = 4.2V

SW

(LTC4120-4.2)

Status Pins FAULT, CHRG

Pin Output Voltage Low

Pin Leakage Current

I = 2mA

500

1

mV

µA

V = 43V, Pin High Impedance

0

NTC

l

Cold Temperature V /V

Fault

Rising V

Falling V

Threshold

73

35.5

1

74

72

75

%INTV

NTC INTVCC

NTC

CC

Hot Temperature V /V

Falling V

Rising V

Threshold

36.5

37.5

37.5 %INTV

%INTV

NTC INTVCC

NTC

CC

NTC Disable Voltage

Falling V

Rising V

Threshold

2

3

%INTV

NTC

CC

NTC Input Leakage Current

V

= V

–50

50

nA

NTC

INTVCC

4120ff

4

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

ELECTRICAL CHARACTERISTICS ^Thel denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T_A= 25°C (Note 2). V_IN= V_RUN= 15V, V_CHGSNS= V_BAT= 4V, R_PROG= 3.01k,

V_FB= 2.29V (LTC4120), V_BATSNS= 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative.

SYMBOL

RUN

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

Enable threshold

Hysteresis

V

Rising

Falling

= 40V

Falling

2.35

2.45

200

2.55

V

mV

µA

V

EN

RUN

Run Pin Input Current

Shutdown Threshold (Note 3)

Hysteresis

0.01

0.1

1.2

0.4

SD

220

mV

FREQ

l

FREQ Pin Input Low

FREQ Pin Input High

FREQ Pin Input Current

V

-V

0.6

1

INTVCC FREQ

0V < V

< V

µA

FREQ

INTVCC

Dynamic Harmonization Control

V

Input Regulation Voltage

DHC Pin Current

14

V

IN(DHC)

V

= 1V, V < V

330

mA

RMS

DHC

IN

IN(DHC)

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 4: The internal supply INTV should only be used for the NTC

CC

divider, it should not be used for any other loads.

Note 5: The FB pin is measured with a resistance of 588k in series with

the pin.

Note 2: The LTC4120 is tested under pulsed load conditions such that

Note 6: h

is expressed as a fraction of measured full charge current as

C/10

T ≈ T . The LTC4120E is guaranteed to meet performance specifications

J

A

measured at the PROG pin voltage when the CHRG pin de-asserts.

for junction temperatures from 0°C to 85°C. Specifications over the

–40°C to 125°C operating junction temperature range are assured by

design, characterization and correlation with statistical process controls.

The LTC4120I is guaranteed over the full –40°C to 125°C operating

junction temperature range. Note that the maximum ambient temperature

consistent with these specifications is determined by specific operating

conditions in conjunction with board layout, the rated package thermal

impedance, and other environmental factors.

Note 7: In an application circuit with an inductor connected from SW to

CHGSNS, the total battery leakage current when disabled is the sum of

I

, I

and I (LTC4120), or I

and I and I (LTC4120-

BATSNS BAT SW

BAT FBG(LEAK)

4.2).

SW

Note 8: When no supply is present at IN, the SW powers IN through

the body diode of the topside switch. This may cause additional SW pin

current depending on the load present at IN.

Note 9: Guaranteed by design and/or correlation to static test.

Note 3: Standby mode occurs when the LTC4120 stops switching due

to an NTC fault condition, or when the charge current has dropped low

enough to enter Burst Mode operation. Disabled mode occurs when V

RUN

is between V and V . Shutdown mode occurs when V

is below V

SD

EN

RUN

SD

or when the differential undervoltage lockout is engaged. SLEEP mode

occurs after a timeout while the battery voltage remains above the V

RCHG

or V

threshold.

RCHG_42

4120ff

5

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

TYPICAL PERFORMANCE CHARACTERISTICS

Typical V_FB(REG)vs Temperature

T_A= 25°C, unless otherwise noted.

Typical V_FLOATvs Temperature

LTC4120-4.2

2.43

4.25

4.24

4.23

4.22

4.21

4.20

4.19

4.18

4.17

4.16

4.15

4 UNITS TESTED

2.42

2.41

HIGH LIMIT

DUT1 V

HIGH LIMIT

(V)

DUT1 V

FB(REG)

FLOAT

2.40

2.39

2.38

2.37

DUT2 V

DUT3 V

DUT4 V

DUT2 V

FLOAT

FB(REG)

DUT3 V

FLOAT

DUT4 V

FLOAT

LOW LIMIT

DUT = DEVICE

UNDER TEST

2.36

–40

5

35 50 65 80 95 110 125

–25 –10

20

50 110 125

65 80 95

–40 –25 –10

5

20 35

TEMPERATURE (°C)

4120 G01

4120 G20

IN Pin Standby/Sleep Current vs

Temperature

IN Pin Disabled/Shutdown Current

vs Temperature

60

50

40

30

180

160

2 UNITS TESTED

V

IN

= 15V

V

IN

= 15V

140

120

100

80

I

IN

I

IN

I

IN

I

IN

I

IN

I

IN

STANDBY FREQ = INTV

STANDBY FREQ = GND

SLEEP

CC

IIN DISABLED

SLEEP

20

10

0

IIN SD

60

40

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

4120 G03

4120 G02

BAT Pin Sleep/Shutdown Current

vs Temperature

Typical Battery Charge Current

vs Temperature

Typical R_SNSCurrent Limit

vs Temperature

8

402

401

1120

1100

1080

1060

1040

1020

1000

980

DUT1

DUT2

DUT3

2 UNITS TESTED

V

R

= 4.2V

= 1.01M

= 1.35M

BAT

FB2

FB1

7

6

I

SLEEP

400

399

398

397

396

BAT

5

4

3

2

1

R

PROG

= 3.01k

2 UNITS TESTED

FREQ = GND

FREQ = INTV

I

SHUTDOWN

BAT

960

CC

940

3 UNITS TESTED

0

395

920

–25

0

50

75 100 125

–50

25

50

TEMPERATURE (°C)

100 125

50

75

–50 –25

0

25

75

–50 –25

0

25

100 125

TEMPERATURE (°C)

4120 G06

4120 G04

4120 G05

4120ff

6

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

T_A= 25°C, unless otherwise noted.

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Frequency

BAT Pin Leakage Current/V_BAT-V_IN

vs Temperature

Buck Efficiency vs Battery Current

16

400

95

90

85

80

75

70

65

60

55

50

V

= OPEN-CIRCUIT

BAT

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

IN

= 4.2V

14

12

350

300

FREQ = INTV

CC

10

8

250

200

150

100

50

V

IN

V

IN

V

IN

V

IN

= 12.5V

= 14V

= 20V

= 30V

FREQ = GND

6

2 UNITS TESTED

4

I

BAT

BAT IN

I

L

= 68µH, SLF12555T-680M1R3

SW

2

V

-V

FREQ = GND

= 4.2V

-V

V

2 UNITS TESTED

BAT IN

BAT

0

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

–25

0

50

75 100 125

–50

25

200 250

0

50 100 150

I

300 350 400

TEMPERATURE (°C)

(mA)

BAT

4120 G07

4120 G09

4120 G08

Wireless Power Transfer Efficiency,

V_{IN_RX}vs Battery Current

Typical t_MIN(ON)vs Temperature

130

125

120

115

110

105

100

95

70

60

24

V

SW

R

= 8.3V

2 UNITS TESTED

FLOAT

L

= SLF6028-470MR59

22

= 4.64k

PROG

50

40

30

20

10

0

20

18

16

14

12

10

9mm EFFICIENCY

10mm EFFICIENCY

11mm EFFICIENCY

9mm V_RX

10mm V_RX

11mm V_RX

90

85

80

50

100

150

(mA)

250

0

200

–50

0

25

50

75 100 125

–22

TEMPERATURE (°C)

I

BAT

4120 G11

4120 G10

Typical Burst Mode Waveforms,

I_BAT= 38mA

Typical Wireless Charging Cycle

Burst Mode Trigger Current

450

400

350

300

250

200

150

100

50

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

90

80

70

60

50

40

30

20

10

V

BAT

R

PROG

= 3k

V

SW

5V/DIV

V

CHRG

I

BAT

R

= 6.2k

PROG

0V

V

PROG

500mV/DIV

0V

I

LSW

BAT = 940mAhr

200mA/DIV

0mA

L

R

= TDK SLF4075 15µH

SW

FB1

= 732k, R = 976k

FB2

4120 G14

= 3.01k

PROG

4µs/DIV

APPLICATION CCT OF FIGURE 10

SPACING = 14mm

0

1

2

3

10

15

20

25

(V)

40

30

35

TIME (HOURS)

V

IN

4120 G12

4120 G13

4120ff

7

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

T_A= 25°C, unless otherwise noted.

TYPICAL PERFORMANCE CHARACTERISTICS

IN Pin Shutdown Current

IN Pin Standby Current vs V_IN

vs Input Voltage

220

80

V

RUN

= 0.4V

V

= 4.21V

BAT

NTC = GND

70

60

50

40

30

20

10

0

200

180

I

IN

I

IN

I

IN

I

IN

I

IN

I

IN

STBY FREQ HIGH 130°C

STBY FREQ LOW 130°C

STBY FREQ HIGH 25°C

STBY FREQ LOW 25°C

STBY FREQ HIGH –45°C

STBY FREQ LOW –45°C

160

140

120

100

I

IN

I

IN

I

IN

SD TEMP = 125°C

SD TEMP = 35°C

SD TEMP = –40°C

80

5

10

40

0

15 20 25 30 35

(V)

20

(V)

0

10

30

40

V

IN

4120 G15

4120 G16

IN Pin Disabled Current

vs Input Voltage

IN Pin Switching Current vs Input

Voltage

UVCL: I_CHARGEvs Input Voltage

100

90

80

70

60

50

40

30

20

10

0

7

6

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0

V

RUN

= 1.6V

I

TEMP=125°C

TEMP=35°C

TEMP=–40°C

130°C

25°C

–45°C

BAT

I

FREQ HIGH

CC

ICCQ(SWITCHING)

5

4

3

2

1

FREQ = INTV

I

FREQ LOW

ICCQ(SWITCHING)

FREQ = GND

I

SD TEMP = 125°C

SD TEMP = 35°C

SD TEMP = –40°C

IN

UVCL

15

I

= 0

BAT

0

10

20

(V)

30

40

12.00 12.05 12.10 12.15

12.20

25

(V)

35

40

11.90 11.95

10

20

30

V

IN

(V)

V

IN

4120 G18

4120 G17

4120 G19

4120ff

8

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

PIN FUNCTIONS

current sense resistor. In low battery conditions a small

INTV (Pin 1): Internal Regulator Output Pin. This pin is

CC

linear charge current, I

, is sourced from this pin to

the output of an internal linear regulator that generates the

LOWBAT

precondition the battery. Decouple the BAT pin with a low

ESR 22µF or greater ceramic capacitor to GND.

internal INTV supply from IN. It also supplies power to

CC

the switch gate drivers and the low battery linear charge

current I

. Connect a 2.2µF low ESR capacitor from

LOWBAT

BATSNS (Pin 10, LTC4120-4.2 Only): Battery Voltage

Sense Pin. For proper operation, this pin must always be

connectedphysicallyclosetothepositivebatteryterminal.

INTV to GND. Do not place any external load on INTV

CC

other than the NTC bias network. Overloading this pin can

disrupt internal operation. When the RUN pin is above

FB(Pin10, LTC4120Only):BatteryVoltageFeedbackPin.

Thechargefunctionoperatestoachieveafinalfloatvoltage

of 2.4V at this pin. Battery float voltage is programmed

using a resistive divider from BAT to FB to FBG, and can be

programmed up to 11V. The feedback pin input bias cur-

V , and INTV rises above the UVLO threshold, and

EN

CC

IN rises above BAT by ∆V

and its hysteresis, the

DUVLO

charger is enabled.

BOOST(Pin2):BoostedSupplyPin.Connecta22nFboost

capacitor from this pin to the SW pin.

rent, I , is 25nA. Using a resistive divider with a Thevenin

FB

IN (Pin 3): Positive Input Power Supply. Decouple to GND

with a 10µF or larger low ESR capacitor.

equivalent resistance of 588k compensates for input bias

current error (see curve of FB Pin Bias Current versus

Temperature in the Typical Performance Characteristics).

SW (Pin 4): Switch Pin. The SW pin delivers power from

IN to BAT via the step-down switching regulator. An in-

ductor should be connected from SW to CHGSNS. See

the Applications Information section for a discussion of

inductor selection.

FBG (Pin 11, LTC4120 Only): Feedback Ground Pin. This

pindisconnectstheexternalFBdividerloadfromthebattery

when it is not needed. When sensing the battery voltage

this pin presents a low resistance, R , to GND. When in

FBG

disabled or shutdown modes this pin is high impedance.

GND (Pin 5, Exposed Pad Pin 17): Ground Pin. Connect

toexposedpad. TheexposedpadmustbesolderedtoPCB

GND to provide a low electrical and thermal impedance

connection to ground.

NTC(Pin12):InputtotheNegativeTemperatureCoefficient

Thermistor Monitoring Circuit. The NTC pin connects to

a negative temperature coefficient thermistor which is

typically co-packaged with the battery to determine if the

battery is too hot or too cold to charge. If the battery’s

temperature is out of range, the LTC4120 enters standby

mode and charging is paused until the battery tempera-

ture re-enters the valid range. A low drift bias resistor is

DHC(Pin6):DynamicHarmonizationControlPin.Connect

a Schottky diode from the DHC pin to the IN pin, and a

capacitor from the DHC pin as shown in the Typical Ap-

plication or the Block Diagram. When V is greater than

IN

V

, this pin is high impedance. When V is below

IN(DHC)

IN

this pin is low impedance allowing the LTC4120

required from INTV to NTC and a thermistor is required

CC

to modulate the resonance of the tuned receiver network.

See Applications Information for more information on the

tuned receiver network.

from NTC to GND. Tie the NTC pin to GND to disable NTC

qualified charging if NTC functionality is not required.

PROG(Pin13):ChargeCurrentProgramandChargeCurrent

MonitorPin.Connecta1%resistorbetween3.01k(400mA)

and 24.3k (50mA) from PROG to ground to program the

charge current. While in constant-current mode, this pin

regulates to 1.227V. The voltage at this pin represents the

averagebatterychargecurrentusingthefollowingformula:

FREQ (Pin 7): Buck Switching Frequency Select Input Pin.

ConnecttoINTV toselecta1.5MHzswitchingfrequency

CC

orGNDtoselecta750kHzswitchingfrequency.Donotfloat.

CHGSNS (Pin 8): Battery Charge Current Sense Pin. An

internal current sense resistor between CHGSNS and BAT

pins monitors battery charge current. An inductor should

be connected from SW to CHGSNS.

V_PROG

I_BAT= h_PROG

•

R_PROG

BAT (Pin 9): Battery Output Pin. Battery charge current

is delivered from this pin through the internal charge

4120ff

9

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

PIN FUNCTIONS

where h

is typically 988. Keep parasitic capacitance

when disabled, and can sink currents up to 5mA when

enabled. An NTC temperature fault causes this pin to be

pulled low. A bad battery fault also causes this pin to

be pulled low. If no fault conditions exist, the FAULT pin

remains high impedance.

PROG

on the PROG pin to a minimum.

CHRG (Pin 14): Open-Drain Charge Status Output Pin.

Typically pulled up through a resistor to a reference

voltage, the CHRG pin indicates the status of the battery

charger. The pin can be pulled up to voltages as high as

IN when disabled, and can sink currents up to 5mA when

enabled. When the battery is being charged, the CHRG

pin is pulled low. When the termination timer expires or

the charge current drops below 10% of the programmed

value, the CHRG pin is forced to a high impedance state.

RUN (Pin 16): Run Pin. When RUN is pulled below V

EN

and its hysteresis, the device is disabled. In disabled

mode, battery charge current is zero and the CHRG and

FAULT pins assume high impedance states. If the voltage

at RUN is pulled below V , the device is in shutdown

SD

mode. When the voltage at the RUN pin rises above V ,

EN

the INTV LDO turns on. When the INTV LDO rises

CC

FAULT (Pin 15): Open-Drain Fault Status Output Pin. Typi-

cally pulled up through a resistor to a reference voltage,

this status pin indicates fault conditions during a charge

cycle. The pin can be pulled up to voltages as high as IN

above its UVLO threshold the charger is enabled. The

RUN pin should be tied to a resistive divider from V to

IN

program the input voltage at which charging is enabled.

Do not float the RUN pin.

BLOCK DIAGRAM

C2S

ENABLE

INTV

LTC4120

IN

CC

LDO

3

1

2

C

INTVCC

2.2µF

RUN

INTV

CC

+

–

16

ENABLE

BOOST

C

IN

10µF

2.45V

C

22nF

BST

+

–

C2P

SW

PWM

4

INTV

CC

0.9V

BAT

SHUTDOWN

•

+

–

L

R

SW

33µH

DUVLO

GND

CHGSNS

BAT

5

8

9

IN – 80mV

INTV

CC

+

–

V

IN(DHC)

DHC

6

R

SNS

0.3Ω

IN

I

C-EA

INTV

FREQ

TH

R

7

NOM

C

BAT

22µF

10k

IN

INTV

CC

INTV

+

CC

FAULT

R

FB1

15

FB

1.2V

10

11

–

+

ENABLE

LOWBAT

+

588k

V

FB(REG)

–

FB2

T

10k

FBG

CNTRL

UVCL

V-EA

CHRG

14

12

ENABLE

Li-Ion

INTV

CC

PROG

13

NTC

D

R

Z

PROG

HOT

COLD

DISABLE

–

+

BAT

2.21V

LOWBAT

4120 F01

Figure 1. Block Diagram

4120ff

10

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

BLOCK DIAGRAM

LTC4120-4.2

INTV

C-EA

CC

+

–

CHGSNS

8

R

SNS

I

TH

0.3Ω

BAT

9

BATSNS

+

–

DUVLO

IN – 80mV

BATSNS

10

C

+

BAT

IN

INTV

+

INTV

CC

Li-Ion

22µF

1.2V

–

+

588k

V

–

FB(REG)

UVCL

V-EA

ENABLE

–

+

BATSNS

2.21V

PROG

13

LOWBAT

D

R

Z

PROG

4120 F02

Figure 2. LTC4120-4.2 BATSNS Connections

TEST CIRCUIT

20V

2k

680nF

665Ω

49.9Ω

IRLML5103TR

V

IN(DHC)

IN

NTC

LTC4120

RUN

INTV

CC

665Ω

10Ω

10µF

2.2µF

DHC

GND

4120 F03

Figure 3. V_IN(DHC)Test Circuit

4120ff

11

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

Wireless Power System Overview

application. The LTC4120 serves as a constant-current/

constant-voltagebatterychargerwiththefollowingbuilt-in

chargerfunctions:programmablechargecurrent,program-

mable float voltage (LTC4120), battery precondition with

half-hour timeout, precision shutdown/run control, NTC

thermal protection, a 2-hour safety termination timer, and

automatic recharge. The LTC4120 also provides output

pins to indicate state of charge and fault status.

The LTC4120 is one component in a complete wireless

power system. A complete system is composed of trans-

mit circuitry, a transmit coil, a receive coil and receive

circuitry—including the LTC4120. Please refer to the

Applications Information section for more information

on transmit circuitry and coils. In particular, the Resonant

Transmitter and Receiver and the Alternative Transmit-

ter Options sections include information necessary to

complete the design of a wireless power system. Further

information can be found in the Applications Information

section of this document under the heading Resonant

Transmitter and Receiver, as well as in AN138: Wireless

Power Users Guide, as well as the DC1969A: wireless

power transmit and receiver demo kit and manual. The

Gerber layout files for both the Transmitter and Receiver

boards are available at the following link:

The circuit in Figure 4 is a fully functional system using a

basic current-fed resonant converter for the transmitter

and a series resonant converter for the receiver with the

1

LTC4120.AdvancedtransmittersbyPower-By-Proxi may

also be used with the LTC4120. For more information on

transmitter design refer to Application Note 138: Wireless

Power Users Guide.

Wireless Power Transfer

A wireless coupled power transfer system consists of a

transmitter that generates an alternating magnetic field,

and a receiver that collects power from that field. The

ideal transmitter efficiently generates a large alternating

http://www.linear.com/product/LTC4120#demoboards

LTC4120 Overview

The LTC4120 is a synchronous step-down (buck) wire-

less battery charger with dynamic harmonization control

(DHC). DHC is a highly efficient method of regulating the

receivedinputvoltageinaresonantcoupledpowertransfer

current in the transmitter coil, L . The push-pull current-

X

fed resonant converter, shown in Figure 4, is an example

1

www.PowerByProxi.com

V

DC

5V

TRANSMITTER

C2S

D9

L1

C4

L2

D6

39V

C

IN

C

X

L

X

L

R

D8

D5

DFLZ39

C2P

IN

DHC BOOST

C5

C

BST

SW

LTC4120

R1

D2

R2

D3

L

SW

D5, D8, D9: DFLS240L

CHGSNS

BAT

M1

M2

+

Li-Ion

C

BAT

D1

D4

GND

4120 F04

Figure 4. DC-AC Converter, Transmit/Receive Coils, Tuned Series Resonant Receiver and AC-DC Rectifier

4120ff

12

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

of a basic power transmitter that may be used with the

LTC4120.Thistransmittertypicallyoperatesatafrequency

of approximately 130kHz; though the operating frequency

varies depending on the load at the receiver and the cou-

pling to the receiver coil. For L = 5µH, and C = 300nF,

the transmitter frequency is:

power to appear at the receiver by tuning the receiver

resonance closer to the transmitter resonance. If the input

voltage exceeds V

, the LTC4120 tunes the receiver

IN(DHC)

resonance away from the transmitter, which reduces the

power available at the receiver. The amount that the input

powerincreasesordecreasesisafunctionofthecoupling,

X

the tuning capacitor, C2P, the receiver coil, L , and the

R

1

f_O≈

= 130kHz

operating frequency.

2 • π • L_X•C_X

Figure 5 illustrates the components that implement the

DHC function to automatically tune the resonance of the

This transmitter typically generates an AC coil current of

receiver. Capacitor C2S and inductor L serve as a series

about 2.5A . For more information on this transmitter,

R

RMS

resonator. Capacitor C2P and the DHC pin of the LTC4120

form a parallel resonance when the DHC pin is low imped-

ance,anddisconnectwhentheDHCpinishighimpedance.

C2P adjusts the receiver resonance to control the amount

of power available at the input of the LTC4120. C2P also

affects power dissipation in the LTC4120 due to the AC

current being shunted by the DHC pin. For this reason it

is not recommended to apply total capacitance in excess

of 30nF at this pin.

refer to AN138: Wireless Power Users Guide.

Thereceiverconsistsofacoil,L ,configuredinaresonant

R

circuitfollowedbyarectifierandtheLTC4120.Thereceiver

coilpresentsaloadreflectedbacktothetransmitterthrough

the mutual inductance between L and L . The reflected

R

X

impedance of the receiver may influence the operating

frequency of the transmitter. Likewise, the power output

by the transmitter depends on the load at the receiver. The

resonant coupled charging system, consisting of both the

transmitter and LTC4120 charger, provides an efficient

method for wireless battery charging as the power output

bythetransmittervariesautomaticallybasedonthepower

used to charge a battery.

Using DHC, the LTC4120 automatically adjusts the power

received depending on load requirements; typically the

load is battery charge current. This technique results in

significant power savings, as the power required by the

C2S

D9

Dynamic Harmonization Control

1:n

C

IN

D5

C

L

R

D8

X

Dynamic harmonization control (DHC) is a technique for

regulating the received input power in a wireless power

transfer system. DHC modulates the impedance of the

resonant receiver to regulate the voltage at the input to

the LTC4120. When the input voltage to the LTC4120 is

C2P

IN

LTC4120

DHC

4120 F05

Figure 5. Resonant Receiver Tank

below the V

set point, the LTC4120 allows more

IN(DHC)

4120ff

13

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

transmitter automatically adjusts to the requirements

at the receiver. Furthermore, DHC reduces the rectified

voltage seen at the input of the LTC4120 under light load

conditions when the battery is fully charged.

Programming The Battery Float Voltage

For the LTC4120, the battery float voltage is programmed

by placing a resistive divider from the battery to FB and

FBG as shown in Figure 6. The programmable battery float

The design of the resonant receiver circuit (L , C2S and

voltage,V

,isthengovernedbythefollowingequation:

FLOAT

R

C2P), the transmitter circuit, and the mutual inductance

R

_FB1+R_FB2

R_FB2

(

•

FB(REG)

)

betweenL andL determinesboththemaximumunloaded

X

R

V

= V

FLOAT

voltageattheinputtotheLTC4120aswellasthemaximum

power available at the input to the LTC4120. The value and

tolerancesofthesecomponentsmustbeselectedwithcare

for stable operation, for this reason it is recommended to

only use components with tight tolerances.

where V

is typically 2.4V.

FB(REG)

Due to the input bias current (I ) of the voltage error amp

FB

(V-EA), care must also be taken to select the Thevenin

equivalent resistance of R ||R close to 588k. Start by

FB1 FB2

To understand the operating principle behind dynamic

harmonization control (DHC), consider the following sim-

plification.Here,afixed-frequencytransmitterisoperating

calculating R to satisfy the following relations:

FB1

V_FLOAT• 588k

R_FB1

=

at a frequency f = 130kHz. DHC automatically adjusts the

O

V_FB(REG)

impedanceofthereceivertunednetworksoastomodulate

the resonant frequency of the receiver between f and f .

T

D

Find the closest 0.1% or 1% resistor to the calculated

value. With R calculate:

1

FB1

f_T≅

f_D≅

2 • π • L • C2P +C2S

(

)

V_FB(REG)•R_FB1

R

R_FB2

=

– 1000Ω

1

V

– V_FB(REG)

FLOAT

2 • π • L_R•C2S

where 1000Ω represent the typical value of R . This is

the resistance of the FBG pin which serves as the ground

return for the battery float voltage divider.

FBG

When the input voltage is above V

(typically 14V),

IN(DHC)

the LTC4120 opens the DHC pin, detuning the receiver

resonance away from the transmitter frequency f , so that

O

less power is received. When the input voltage is below

V

FLOAT

V

, the LTC4120 shunts the DHC pin to ground,

IN(DHC)

BAT

FB

LTC4120

I

tuning the receiver resonance closer to the transmitter

frequency so that more power is available.

Li-Ion

R

22µF

FB1

4120 F06

FB

FB2

FBG

FortheresonantconvertershowninFigure4,theoperating

frequencyofthetransmitterisnotfixed,butvariesdepend-

ing on the load impedance. However the basic operating

principle of DHC remains valid. For more information on

the design of the wireless power receiver resonant circuit

refer to the applications section.

ENABLE

Figure 6. Programming the Float Voltage with the LTC4120

4120ff

14

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

Once R and R are selected, recalculate the value of

where h

is typically 988, V

is either 1.227V or

PROG

FB1

FB2

PROG

V

obtained with the resistors available. If the error

122mV during trickle charge, and R

is the resistance

FLOAT

PROG

is too large substitute another standard resistor value for

of the grounded resistor applied to the PROG pin. The

PROG resistor sets the maximum charge current, or the

currentdeliveredwhilethechargerisoperatinginconstant-

current (CC) mode.

R

and recalculate R . Repeat until the float voltage

FB1

FB2

error is acceptable.

Table 1 and Table 2 list recommended standard 0.1% and

1% resistor values for common battery float voltages.

Analog Charge Current Monitor

Table 1: Recommended 0.1% Resistors for Common V_FLOAT

The PROG pin provides a voltage signal proportional to

the actual charge current. Care must be exercised in mea-

suring this voltage as any capacitance at the PROG pin

forms a pole that may cause loop instability. If observing

the PROG pin voltage, add a series resistor of at least 2k

and limit stray capacitance at this node to less than 50pF.

V

R

FB2

TYPICAL ERROR

–0.13%

0.15%

FLOAT

FB1

3.6V

4.1V

4.2V

7.2V

8.2V

8.4V

887k

1.01M

1.8M

1780k

1.42M

1.35M

898k

–0.13%

0.08%

2.00M

2.05M

825k

0.14%

816k

0.27%

In the event that the input voltage cannot support the

demanded charge current, the PROG pin voltage may not

represent the actual charge current. In cases such as this,

the PWM switch frequency drops as the charger enters

drop-out operation where the top switch remains on for

morethanoneclockcycleastheinductorcurrentattempts

torampuptothedesiredcurrent. Ifthetopswitchremains

on in drop-out for 8 clock cycles a dropout detector forces

the bottom switch on for the remainder of the 8th cycle.

In such a case, the PROG pin voltage remains at 1.227V,

but the charge current may not reach the desired level.

Table 2: Recommended 1% Resistors for Common V_FLOAT

V

R

FB2

TYPICAL ERROR

–0.13%

0.26%

FLOAT

FB1

3.6V

4.1V

4.2V

7.2V

8.2V

8.4V

887k

1.02M

1.78M

2.00M

2.1M

1780k

1.43M

1.37M

887k

–0.34%

0.16%

825k

0.14%

845k

–0.50%

Programming the Charge Current

The current-error amp (C-EA) measures the current

through an internal 0.3Ω current sense resistor between

the CHGSNS and BAT pins. The C-EA outputs a fraction

Undervoltage Current Limit

The undervoltage current limit (UVCL) feature reduces

charge current as the input voltage drops below V

UVCL

of the charge current, 1/h

, to the PROG pin. The

PROG

(typically 12V). This low gain amplifier typically keeps V

IN

voltage-error amp (V-EA) and PWM control circuitry can

limit the PROG pin voltage to control charge current. An

within 100mV of V

, but if insufficient power is avail-

UVCL

able the input voltage may drop below this value; and the

charge current will be reduced to zero.

internal clamp (D ) limits the PROG pin voltage to V

,

Z

PROG

which in turn limits the charge current to:

h_PROG• V

1212V

R_PROG

PROG

I_CHG

=

R_PROG

_PROG• V

h

120V

R_PROG

PROG_ TRKL

I_{CHG_ TRKL}

=

R_PROG

4120ff

15

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

NTC Thermal Battery Protection

of the R

resistor. For the same Vishay Curve 2 therm-

BIAS

istor, this corresponds to approximately 40°C. With a

Vishay Curve 2 thermistor, the hot and cold comparators

both have about 2°C of hysteresis to prevent oscillations

about the trip points.

TheLTC4120monitorsbatterytemperatureusingatherm-

istor during the charging cycle. If the battery temperature

moves outside a safe charging range, the IC suspends

charging and signals a fault condition until the tempera-

ture returns to the safe charging range. The safe charging

range is determined by two comparators that monitor the

voltage at the NTC pin. NTC qualified charging is disabled

Thehotandcoldtrippointsmaybeadjustedusingadiffer-

ent type of thermistor, or a different R

resistor, or by

BIAS

adding a desensitizing resistor, R , or by a combination

ADJ

if the NTC pin is pulled below about 85mV (V ).

of these measures as shown in Figure 7. For example, by

DIS

increasing R

to 12.4k, with the same thermistor as

BIAS

Thermistor manufacturers usually include either a tem-

perature lookup table identified with a characteristic curve

number, or a formula relating temperature to the resistor

value. Each thermistor is also typically designated by a

before, the cold trip point moves down to –5°C, and the

hot trip point moves down to 34°C. If a Vishay Curve 1

thermistor with B

= 3950 and resistance of 100k at

25/85

25°C is used, a 1% R

resistor of 118k and a 1% R

BIAS

ADJ

thermistor gain value B

.

25/85

resistor of 12.1k results in a cold trip point of 0°C, and a

hot trip point of 39°C.

The NTC pin should be connected to a voltage divider

from INTV to GND as shown in Figure 7. In the simple

CC

application (R

= 0) a 1% resistor, R

, with a value

End-Of-Charge Indication and Safety Timeout

ADJ

BIAS

equal to the resistance of the thermistor at 25°C is

The LTC4120 uses a safety timer to terminate charging.

Whenever the LTC4120 is in constant current mode the

connected from INTV to NTC, and a thermistor is con-

CC

nected from NTC to GND. With this setup, the LTC4120

timer is paused, and if FB transitions through the V

RCHG

pauses charging when the resistance of the thermistor

threshold the timer is reset. When the battery voltage

reaches the float voltage, a safety timer begins count-

ing down a 2-hour timeout. If charge current falls below

one-tenth of the programmed maximum charge current

increases to 285% of the R

resistor as the tempera-

BIAS

ture drops. For a Vishay Curve 2 thermistor with B

25/85

= 3490 and 25°C resistance of 10k, this corresponds to

a temperature of about 0°C. The LTC4120 also pauses

charging if the thermistor resistance decreases to 57.5%

(h ), the CHRG status pin rises, but top-off charge

C/10

current continues to flow until the timer finishes. After

the timeout, the LTC4120 enters a low power sleep mode.

BAT

LTC4120

INTV

CC

Automatic Recharge

R

BIAS

NTC

+

–

In sleep mode, the IC continues to monitor battery volt-

TOO COLD

TOO HOT

R

ADJ

74% INTV

age. If the battery falls 2.2% (V

or V

) from

CC

OPT

RCHG

RCHG_42

the full-charge float voltage, the LTC4120 engages an

automatic recharge cycle. Automatic recharge has a

built-in filter of about 0.5ms to prevent triggering a new

charge cycle if a load transient causes the battery voltage

to drop temporarily.

+

+ ^{36.5% INTV}

–

R

NTC

T

CC

Li-Ion

4120 F07

+

–

IGNORE NTC

2% INTV

CC

Figure 7. NTC Connections

4120ff

16

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

State of Charge and Fault Status Pins

Precision Run/Shutdown Control

The LTC4120 contains two open-drain outputs which

provide charge status and signal fault indications. The

binary-coded CHRG pin pulls low to indicate charging at a

rate higher than C/10. The FAULT pin pulls low to indicate

a bad battery timeout, or to indicate an NTC thermal fault

condition. During NTC faults the CHRG pin remains low,

but when a bad battery timeout occurs the CHRG pin de-

asserts. When the open-drain outputs are pulled up with

a resistor, Table 3 summarizes the charger state that is

indicated by the pin voltages.

The LTC4120 remains in a low power disabled mode until

the RUN pin is driven above V (typically 2.45V). While

EN

the LTC4120 is in disabled mode, current drain from the

batteryisreducedtoextendbatterylifetime,thestatuspins

are both de-asserted, and the FBG pin is high impedance.

Charging can be stopped at any time by pulling the RUN

pin below 2.25V. The LTC4120 also offers an extremely

low operating current shutdown mode when the RUN pin

is pulled below V (typically 0.7V). In this condition less

SD

than 20µA is drawn from the supply at IN.

Table 3. LTC4120 Open-Drain Indicator Outputs with Resistor

Pull-Ups

Differential Undervoltage Lockout

The LTC4120 monitors the difference between the battery

voltage, V , and the input supply, V . If the difference

FAULT CHRG CHARGER STATE

High

Low

High Off or Topping Off Charging at a Rate Less Than C/10

Low Charging at Rate Higher Than C/10

High Bad Battery Fault

BAT

IN

(V -V ) falls to V

, all functions are disabled and

IN BAT

DUVLO

thepartisforcedintoshutdownmodeuntil(V -V )rises

IN BAT

above the V

hysteresis. The LTC4120-4.2 monitors

theBATSNSandINpinvoltagestosenseDUVLOcondition.

Low NTC Thermal Fault Charging Paused

DUVLO

Low Battery Voltage Operation

User Selectable Buck Operating Frequency

The LTC4120 automatically preconditions heavily dis-

charged batteries. If the battery voltage is below V

The LTC4120 uses a constant-frequency synchronous

step-down buck architecture to produce high operating

efficiency. The nominal operating frequency of the buck,

LOWBAT

minus its hysteresis (typically 2.05V—e.g., battery pack

protection has been engaged) a DC current, I

, is

LOWBAT

applied to the BAT pin from the INTV supply. When the

f

, is programmed by connecting the FREQ pin to

CC

OSC

batteryvoltagerisesaboveV

,theswitchingregula-

either INTV or to GND to obtain a switching frequency

LOWBAT

CC

tor is enabled and charges the battery at a trickle charge

of 1.5MHz or 750kHz, respectively. The high operating

frequency allows the use of smaller external components.

level of 10% of the full-scale charge current (in addition

to the DC I

current). Trickle charging of the battery

LOWBAT

Selectionoftheoperatingfrequencyisatrade-offbetween

efficiency,componentsize,andmarginfromtheminimum

on-time of the switcher. Operation at lower frequency

improves efficiency by reducing internal gate charge and

switching losses, but requires larger inductance values to

maintain low output ripple. Operation at higher frequency

allows the use of smaller components, but may require

sufficient margin from the minimum on-time at the lowest

duty cycle if fixed-frequency switching is required.

continues until the sensed battery voltage (sensed via

the feedback pin for the LTC4120) rises above the trickle

charge threshold, V

. When the battery rises above

TRKL

the trickle charge threshold, the full-scale charge current

is applied and the DC trickle charge current is turned off.

If the battery remains below the trickle charge threshold

for more than 30 minutes, charging terminates and the

fault status pin is asserted to indicate a bad battery.

Afterabadbatteryfault,theLTC4120automaticallyrestarts

a new charge cycle once the failed battery is removed and

replaced with another battery. The LTC4120-4.2 monitors

the BATSNS pin voltage to sense LOWBAT and TRKL

conditions.

4120ff

17

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

OPERATION

PWM Dropout Detector

between bursts, as shown in G14. If the PROG pin voltage

falls below 120mV for longer than 350µs this causes the

CHRGpintode-assert,indicatingC/10.Burstcurrentripple

If the input voltage approaches the battery voltage, the

LTC4120mayrequiredutycyclesapproaching100%.This

mode of operation is known as dropout. In dropout, the

operating frequency may fall well below the programmed

depends on the selected switch inductor, and V /V

.

IN BAT

BOOST Supply Refresh

f

value. If the top switch remains on for eight clock

OSC

The BOOST supply for the top gate drive in the LTC4120

switching regulator is generated by bootstrapping the

cycles, the dropout detector activates and forces the

bottom switch on for the remainder of that clock cycle

or until the inductor current decays to zero. This avoids

a potential source of audible noise when using ceramic

input or output capacitors and prevents the boost sup-

ply capacitor for the top gate drive from discharging. In

dropout operation, the actual charge current may not be

able to reach the full-scale programmed value. In such a

scenario the analog charge current monitor function does

not represent actual charge current being delivered.

BOOST flying capacitor to INTV whenever the bottom

CC

switch is turned on. This technique provides a voltage of

INTV from the BOOST pin to the SW pin. In the event

CC

that the bottom switch remains off for a prolonged period

of time, e.g., during Burst Mode operation, the BOOST

supply may require a refresh. Similar to the PWM dropout

timer, the LTC4120 counts the number of clock cycles

since the last BOOST refresh. When this count reaches

32, the next PWM cycle begins by turning on the bottom

side switch first. This pulse refreshes the BOOST flying

Burst Mode Operation

capacitor to INTV and ensures that the topside gate

CC

Atlowchargecurrents,forexampleduringconstant-voltage

mode,theLTC4120automaticallyentersBurstModeopera-

tion. In Burst Mode operation the switcher is periodically

forced into standby mode in order to improve efficiency.

The LTC4120 automatically enters Burst Mode operation

afteritexitsconstant-current(CC)modeandasthecharge

current drops below about 80mA. Burst Mode operation

is triggered at lower currents for larger PROG resistors,

and depends on the input supply voltage. Refer to graph

Burst Mode Trigger Current and graph Typical Burst Mode

Waveform, intheTypicalPerformanceCharacteristics, for

more information on Burst Mode operation. Burst Mode

operation has some hysteresis and remains engaged for

battery currents up to about 150mA.

driver has sufficient voltage to turn on the topside switch

at the beginning of the next cycle.

Operation Without an Input Supply or Wireless Power

When a battery is the only available power source, care

should be taken to eliminate loading of the IN pin. Load

current on IN drains the battery through the body diode

of the top side power switch as V falls below V . To

IN

SW

prevent this possibility, place a diode between the input

supply and the IN capacitor, C . The rectification diode

IN

(D9 in Figure 5 and Figure 11) in the wireless power ap-

plications also eliminates this discharge path. Alternately,

a P-channel MOSFET may be placed in series with the BAT

pin provided care is taken to directly sense the positive

battery terminal voltage with FB via the battery resistive

divider. This is illustrated in Figure 15.

While in Burst Mode operation, the PROG pin voltage to

average charge current relationship is not well defined.

This is due to the PROG pin voltage falling to 0V in

4120ff

18

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

0.50

0.45

+

I

NO MISALIGNMENT

R

I

AC

X

5mm MISALIGNMENT

L

V

R

X

R

0.40 ^X

+

X

10mm MISALIGNMENT

0.35 ^X

0.30

0.25

0.20

0.15

1:n

+

X

4120 F08

+

X

Figure 8. Wireless Power Transfer

X

+

X

+

X

Wireless Power Transfer

0.10

0

1

2

3

4

5

6

7

8

9

10

4120 F09

In a wireless power transfer system, power is transmitted

using alternating magnetic fields. Power is transferred

based on the principle that an AC current in a transmit-

ter coil produces an AC current in a receiver coil that is

placed in the magnetic field generated by the transmitter

coil. The magnetic field coupling is described by the mu-

tual inductance, M. This term does not have a physical

representation but is referred to using the unit-less terms

k and n. Where k is the coupling coefficient:

COIL DISTANCE (mm)

Figure 9. Coupling Coefficient k vs Distance

(L ||C ).Withapeak-to-peakamplitudethatisproportional

to the applied input voltage:

X

V

≅ 2 • π • V

AC

DC

This generates a sinusoidal current in the transmit coil

with peak-to-peak amplitude:

M

k =

V_AC

V_DC

L_X•L_R

I_AC

=

≅

2 • π • f_O•L_Xf_O•L_X

Andnistheturnsratio—thenumberofturnsinthereceiver

coil divided by the number of turns in the transmitter coil:

The AC voltage induced at the receive coil is a function

of both the applied voltage, the coupling, as well as the

impedance at the receiver. With no load at the receiver,

n_R

n_X

L_R

L_X

n =

=

the open-circuit voltage, V

, is approximately:

IN(OC)

V

≅ k • n • 2 • π • V

DC

IN(OC)

Theturnsratioisproportionaltothesquarerootoftheratio

of receiver coil inductance to transmitter coil inductance.

The receiver (shown in Figures 5 and 10) uses a resonant

tuned circuit followed by a rectifier to convert the induced

AC voltage into a DC voltage to power the LTC4120 and

chargeabattery.PowerdeliveredtotheLTC4120depends

on the impedance of the LTC4120 and the impedance of

the tuned circuit at the resonant frequency of the trans-

mitter. The LTC4120 employs a proprietary circuit, called

dynamic harmonization control (DHC) that modulates the

impedance of the receiver depending on the voltage at the

input to the LTC4120. This technique ensures that over a

wide range of coupling coefficients the induced rectified

voltage does not exceed voltage compliance ratings when

theloadgoesaway(e.g, whenthebatteryisfullycharged).

DHC efficiently adjusts the receiver impedance depending

on the load without compromising available power.

In the wireless power transfer system an AC current, I ,

AC

applied to the transmit coil L , produces an AC current in

X

the receive coil, L of:

R

I

= 2 • π • M • I = 2 • π • k • √L • L • I

AC X R AC

R(AC)

The coupling coefficient is a variable that depends on the

orientation and proximity of the transmitter coil relative

to the receiver coil. If the two coils are in a transformer,

then k = 1. If the two coils are completely isolated from

each other then k = 0. In a typical LTC4120-based wireless

power design, k varies from around 0.18 at 10mm spac-

ing, to about 0.37 with the coils at 3mm spacing. This is

illustrated in Figure 9.

With low resistance in the L and L coils, the efficiency is

X

R

inherentlyhigh,evenatlowcouplingratios.Thetransmitter

In the event that the coupling may become too large (e.g.

receiver coil is placed too close to the transmitter coil)

then it is recommended to place a Zener diode across the

in Figures 4 and 10 generates a sine wave at the resonant

frequency, f , across the transmitter coil and capacitor

O

4120ff

19

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

input to the LTC4120 to prevent exceeding the absolute

maximum rating of the LTC4120. Diode D6 (in Figure 4

and Figure 10) illustrates this connection.

tion of a 39V Zener diode (D6 in Figures 4 and 10) at the

input to the LTC4120 will prevent overvoltage conditions

from damaging the LTC4120.

The RMS voltage at the rectifier output depends on the

load of the LTC4120, i.e., the charge current, as well as the

Resonant Transmitter and Receiver

An example DC/AC transmitter is shown in Figure 10.

A 5V 5% supply to the transmitter efficiently produces a

circulating AC current in L , which is coupled to L . For

applied AC current, I . The applied AC current depends

AC

both on the components of the tuned network as well as

the applied DC voltage. The load at the receiver depends

on the state of charge of the battery. If the coupling and/

or the applied AC current is not well controlled, the addi-

X

R

higher voltage inputs, a pre-regulator DC/DC converter

can be used to generate 5V (see Figure 11). Power is

transmitted from transmitter to receiver at the resonant

V

CC

4.75V TO 5.25V

TRANSMITTER

RECEIVER

C2S2

L

B2

68µH

B1

68µH

D1

D4

C5

C

L

X

39V

OPT

C2S1

C2P1

D2

D3

DHC

L

R

10µF

0.3µF 5µH

IN

C4

0.01µF

C5

0.01µF

BOOST

SW

C3

U1

LTC4120

C2P2

R1

100Ω

R2

100Ω

L1

CHGSNS

D2

D3

BAT

INTV

CC

+

C4

2.2µF

C1

10µF

C2

47µF

M1

M2

FB

D1

D4

FBG

GND

4120 F10

Figure 10. DC/AC Converter, Transmit/Receive Coils, Tuned Series Resonant Receiver and AC/DC Rectifier

HV

IN

8V TO 38V

C6

4.7µF

GND

V

IN

BD

BOOST

R3

L3

C9

150k

4.7µF

0.47µF

RUN/SS

SW

D5

DFLS240L

C7

0.068µF

C10

22µF

R8

M3

U1

LT3480

150k

Si2333DS

M4

2N7002L

SYNC

PG

VC

V

CC

RT

FB

5V

R10

100k

R5

20k

C8

R4

40.2k

CONNECT

TO Tx V

GND

CC

R7

536k

330pF

R6

100k

4120 F11

Figure 11. High Voltage Pre-Regulator for Transmitter

4120ff

20

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

Resonant Converter Component Selection

frequency, f ; which depends on both component values

O

as well as the load at the receiver. The tolerance of the

components selected in both the transmitter and receiver

circuits is critical to achieving maximum power transfer.

The voltages across the receiver components may reach

40V, so adequate voltage ratings must also be observed.

It is recommended tousethe components listedinTable 4

and Table 5 for the resonant transmitter and receiver

respectively. Figure 12 illustrates the PCB layout of the

embedded receiver coil. Figures 13 and 14 show the

finished transmitter and receiver. The 25mm ferrite bead

Table 4. Recommended Transmitter and High Voltage Pre-Regulator Components

Transmitter Components

ITEM

DESCRIPTION

MANUFACTURER/PART NUMBER

ON SEMI NSR10F40NXT5G

DIODES BZX84C16

D2, D3

D1, D4

M1, M2

DIODE, SCHOTTKY, 40V, 2A

DIODE, ZENER, 16V, 350mW, SOT23

MOSFET, SMT, N-CHANNEL, 60V, 11mΩ, S08

IND, SMT, 68µH, 0.41A, 0.4Ω, 20%

CAP, CHIP, X7R, 0.01µF, 10%, 50V, 0402

RES, CHIP, 100Ω, 5%, 1/16W, 0402

CAP, CHIP, PPS, 0.15µF, 2%, 50V

CAP, CHIP, PPS, 0.1µF, 2%, 50V

CAP, CHIP, PPS, 0.033µF, 2%, 50V

CAP, PPS, 0.15µF, 2.5%, 63VAC, MKS02

CAP, PPS, 0.10µF, 2.5%, 63VAC, MKS02

CAP, PPS, 0.033µF, 2.5%, 63VAC, MKS02

5.0µH TRANSMIT COIL

VISHAY Si4470EY-T1GE3

TDK VLCF5028T-680MR40-2

MURATA GRM155R71H103KA88D

VISHAY CRCW0402100RJNED

PANASONIC ECHU1H154GX9

PANASONIC ECHU1H104GX9

PANASONIC ECHU1H333GX9

WIMA MKS0D031500D00JSSD

WIMA MKS0D03100

L

, L

B1 B2

C4, C5

R1, R2

C

X1, 2

C (Opt)

X

WIMA MKS0D03033

L

TDK WT-505060-8K2-LT

X

or 6.3µH TRANSMIT COIL

TDK WT-505090-10K2-A11-G

WÜRTH 760308111

or 6.3µH TRANSMIT COIL

or 5.0µH TRANSMIT COIL

INTER-TECHNICAL L41200T02

High Voltage Pre-Regulator Components

U1

LT3480EDD, PMIC 38V, 2A, 2.4MHz Step-Down Switching

LINEAR TECH LT3480EDD

Regulator with 70µA Quiescent Current

MOSFET, SMT, P-CHANNEL, –12V, 32mΩ, SOT23

MOSFET, SMT, N-CHANNEL, 60V, 7.5Ω, 115mA, SOT23

DIODE, SCHOTTKY, 40V, 2A, POWERDI123

IND, SMT, 4.7µH, 1.6A, 0.125Ω, 20%

CAP, CHIP, X5R, 4.7µF, 10%, 50V, 1206

CAP, CHIP, X5R, 4.7µF, 10%, 50V, 0603

CAP, CHIP, COG, 330pF, 5%, 50V, 0402

CAP, CHIP, X7R, 0.47µF, 10%, 25V, 0603

CAP, CHIP, X5R, 22µF, 20%, 6.3V, 0805

RES, CHIP, 150k, 5%, 1/16W, 0402

M3

VISHAY Si2333DS

M4

ON SEMI 2N7002L

D5

DIODES DFLS240L

L3

COILCRAFT LPS4018-472M

MURATA GRM155R71H4755KA12L

MURATA GRM188R71H683K

TDK C1005COG1H331J

C6

C7

C8

C9

MURATA GRM188R71E474K

TAIYO-YUDEN JMK212BJ226MG

VISHAY CRCW0402150JNED

VISHAY CRCW040240K2FKED

VISHAY CRCW040220K0FKED

VISHAY CRCW0402100KFKED

VISHAY CRCW0402536KFKED

C10

R3, R8

R4

RES, CHIP, 40.2k, 1%, 1/16W, 0402

R5

RES, CHIP, 20k, 1%, 1/16W, 0402

R6, R10

RES, CHIP, 100k, 1%, 1/16W, 0402

R7

RES, CHIP, 536k, 1%, 1/16W, 0402

1

C = 300nF with 5µH L coil, or C = 233nF with 6.3µH L coil.

X

2

Pay careful attention to assembly guidelines when using ECHU capacitors, as the capacitance value may shift if the capacitor is over heated while

soldering. Plastic film capacitors such as Panasonic ECHU series or Metallized Polypropylene capacitors such as WIMA MKP as suitable for the

transmitter

4120ff

21

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

Table 5. Recommended Receiver Components

ITEM

DESCRIPTION

MANUFACTURER/PART NUMBER

DIODES DFLS240L

D1, D2, D3

D4 (Opt)

DIODE, SCHOTTKY, 40V, 2A, POWERDI123

DIODE, ZENER, 39V, 5%, 1W, POWERDI123

DIODES DFLZ39

L

IND, EMBEDDED, 47µH, 43 TURNS WITH 25mm FERRITE BEAD EMBEDDED 4-LAYER PCB (see Figure 12)

ADAMS MAGNETICS B67410-A0223-X195

R

or 47µH RECEIVER COIL

TDK WR282840-37K2-LR3

WÜRTH 760308101303

or 47µH RECEIVER COIL

or 48µH RECEIVER COIL

INTER-TECHNICAL L41200R02

COILCRAFT LPS4018-153ML

MURATA GRM21B5C1H472JA01L

KEMET C0603C182J5GAC7533

MURATA GRM21B5C1H223JA01L

MURATA GRM21B5C1H472JA01L

TDK C2012X5R1C106K

L1

IND, SMT, 15µH, 260mΩ, 20%, 0.86A, 4mm × 4mm

CAP, CHIP, COG, 0.0047µF, 5%, 50V, 0805

CAP, CHIP, COG, 0.00018µF, 5%, 50V, 0603

CAP, CHIP, COG, 0.022µF, 5%, 50V, 0805

CAP, CHIP, COG, 0.0047µF, 5%, 50V, 0805

CAP, CHIP, X5R, 10µF, 20%, 16V, 0805

CAP, CHIP, X5R, 47µF, 10%, 16V, 1210

CAP, CHIP, X7R, 0.01µF, 20%, 6.3V. 0402

CAP, CHIP, X5R, 10µF, 20%, 16V, 0805

C2P1

C2P2

C2S1

C2S2

C1

C2

MURATA GRM32ER61C476KE15L

TDK C1608X7R1H103K

C3

C4

TDK C2012X5R1C106K

U1

400mA WIRELESS SYNCHRONOUS BUCK BATTERY CHARGER LINEAR TECH LTC4120

LAYER STRUCTURE

L1 – TOP SIDE

L2

L3

L4 – BOTTOM SIDE

FINISHED THICKNESS TO BE 0.031" 0.00ꢀ"

TOTAL OF 4 LAYERS WITH 2oz CU ON THE

OUTER LAYERS AND 2oz CU ON THE INNER

LAYERS

TOP METAL

2nd METAL

3rd METAL

BOTTOM METAL

4120 F12

Figure 12. 4-Layer PCB Layout of Rx Coil

4120ff

22

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

Figure 13. Tx Layout: Demo Circuit 1968A

in Figure 14 covers the embedded receiver coil described

in Figure 12. Gerber layout files for both the transmitter

and receiver boards are available at the following link:

Figure 14. Rx Layout with Ferrite Shield: Demo Circuit 1967A-B

http://www.linear.com/product/LTC4120#demoboards

Alternative component values can be chosen by following

the design procedure outlined below.

Resonant Receiver Tuning: L , C2S, C2P

R

Thetunedcircuitresonanceofthereceiver,f ,isdetermined

T

by the selection of L and C2S + C2P. Select the capaci-

R

Resonant Transmitter Tuning: L , C

X

tors to obtain a resonant frequency 1% to 3% below f :

O

The basic transmitter (shown in Figure 4) has a resonant

frequency, f , that is determined by components L , and

1

f_T≅

O

X

2 • π • L • C2P +C2S

(

)

R

C . The selection of L and C are coupled so as to obtain

X

the correct operating frequency. The selection of L and

X

Asinthecaseofthetransmitter,multipleparallelcapacitors

may need to be used to obtain the optimum value. Finally,

L is also coupled to ideally obtain a turns ratio of 1:3.

R

Having selected a transmitter inductor, L , the transmitter

X

select the detuned resonance, f to be about 5% to 15%

D

capacitorshouldbeselectedtoobtainaresonantfrequency

of 130kHz. Due to limited selection of standard values,

several standard value capacitors may need to be used

higher than the tuned resonance, keeping the value of

C2P below 30nF to limit power dissipation in the DHC pin:

1

in parallel to obtain the correct value for f :

f_D≅

O

2 • π • L_R•C2S

1

f_O≅

= 130kHz

2 • π • L_X•C_X

Alternative Transmitter Options

Thetransmitterinductorandcapacitor,L andC ,support

The resonant DC/AC transmitter discussed in the previous

section is a basic and inexpensive to build transmitter.

However, this basic transmitter requires a relatively pre-

cise DC input voltage to meet a given set of receive power

requirements. It is unable to prevent power transmission

to foreign metal objects—and can therefore cause these

objects to heat up. Furthermore, the operating frequency

ofthebasictransmittercanvarywithcomponentselection.

4120ff

X

alargecirculatingcurrent.Seriesresistanceintheinductor

is a source of loss and should be kept to a minimum for

optimal efficiency. Likewise the transmitter capacitor(s),

C ,mustsupportlargeripplecurrentsandmustbeselected

X

with adequate voltage rating and low dissipation factors.

23

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

LTC4120 customers can also choose more advanced

transmitter options such as the LTC4125. With additional

features such as: foreign metal detection; optimum power

search andAutoResonant™operatingfrequency.Formore

information on advanced transmitter options refer to the

Wireless Power Users Guide.

When operating from a high input voltage with a low bat-

tery voltage, the PWM control algorithm may attempt to

enforce a duty cycle which requires an on-time lower than

theLTC4120minimum,t

.Thisminimumdutycycle

MIN(ON)

is approximately 18% for 1.5MHz operation or 9% for

750kHz operation. Typical minimum on-time is illustrated

in graph G11 in the Typical Performance Characteristics

Maximum Battery Power Considerations

section. If the on-time is driven below t

, the charge

MIN(ON)

current and battery voltage remain in regulation, but the

switching duty cycle may not remain fixed, and/or the

switching frequency may decrease to an integer fraction

of its programmed value.

Using one of the approved transmitter options with this

wireless power design provides a maximum of 2W at the

input to the LTC4120. It is optimized for supplying 400mA

of charge current to a 4.2V Li-Ion battery. If a higher bat-

tery voltage is selected, then a lower charge current must

be used as the maximum power available is limited. The

The maximum input voltage allowed to maintain constant

frequency operation is:

maximum battery charge current, I

, that may

, can be

CHG(MAX)

V

LOWBAT

be programmed for a given float voltage, V

V

=

FLOAT

IN(MAX)

f_OSC• t_MIN(ON)

calculated based on the charger efficiency, η , as:

EFF

where V

, is the lowest battery voltage where the

η_EFF• 2W

LOWBAT

switcher is enabled.

I_CHG(MAX)

≤

V

FLOAT

Exceedingtheminimumon-timeconstraintdoesnotaffect

charge current or battery float voltage, so it may not be

of critical importance in most cases and high switching

frequencies may be used in the design without any fear of

severeconsequences.AsthesectionsonInductorSelection

and Capacitor Selection show, high switching frequencies

allowtheuseofsmallerboardcomponents, thusreducing

the footprint of the applications circuit.

The charger efficiency, η , depends on the operating

EFF

conditionsandmaybeestimatedusingtheBuckEfficiency

curve in the Typical Performance Characteristics. Do

not select a charge current greater than this limit when

selecting R

.

PROG

Input Voltage and Minimum On-Time

TheLTC4120canoperatefrominputvoltagesupto40V.The

LTC4120 maintains constant frequency operation under

most operating conditions. Under certain situations with

high input voltage and high switching frequency selected

and a low battery voltage, the LTC4120 may not be able

to maintain constant frequency operation. These factors,

combined with the minimum on-time of the LTC4120,

impose a minimum limit on the duty cycle to maintain

fixed-frequency operation. The on-time of the top switch

Fixed-frequency operation may also be influenced by

dropoutandBurstModeoperationasdiscussedpreviously.

Switching Inductor Selection: L

SW

Theprimarycriterionforswitchinginductorvalueselection

in an LTC4120 charger is the ripple current created in that

inductor. Once the inductance value is determined, the

saturation current rating for that inductor must be equal

to or exceed the maximum peak current in the inductor,

is related to the duty cycle (V /V ) and the switching

BAT IN

I

. The peak value of the inductor current is the sum

L(PEAK)

frequency, f

in Hz:

OSC

of the programmed charge current, I , plus one-half of

CHG

V

BAT

the ripple current, ∆I . The peak inductor current must

also remain below the current limit of the LTC4120, I

L

t_ON

=

f_OSC• V

:

IN

PEAK

∆I_L

2

I_L(PEAK)=I_CHG

+

<I_PEAK

4120ff

24

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

The current limit of the LTC4120, I

, is at least 585mA

capacitanceisafunctionofthedesiredinputripplevoltage

PEAK

(and at most 1250mA). The typical value of I

is

(∆V ), and follows the relation:

PEAK

IN

illustrated in graph R

Current Limit vs Temperature,

SNS

V

BAT

I_CHG

in the Typical Performance Characteristics.

IN

C_IN(BULK)

=

µF

( )

For a given input and battery voltage, the inductor value

and switching frequency determines the peak-to-peak

ripplecurrentamplitudeaccordingtothefollowingformula:

∆V

IN

Input ripple voltages (∆V ) above 10mV are not recom-

IN

mended. 10µF is typically adequate for most charger

V – V

f_OSC• V •L

• V

BAT

(

)

IN

BAT

applications, with a voltage rating of 40V.

∆I_L=

IN

SW

Reverse Blocking

Ripple current is typically set to be within a range of 20%

When a fully charged battery is suddenly applied to the BAT

to40%oftheprogrammedchargecurrent, I . Toobtain

CHG

pin,alargein-rushcurrentchargestheC capacitorthrough

IN

a ripple current in this range, select an inductor value us-

ing the nearest standard inductance value available that

obeys the following formula:

thebodydiodeoftheLTC4120topsidepowerswitch. While

the amplitude of this current can exceed several Amps, the

LTC4120 will survive provided the battery voltage is below

the maximum value of 11V. To completely eliminate this

current, a blocking P-channel MOSFET can be placed in

series with the BAT pin. When the battery is the only source

of power, this PFET also serves to decrease battery drain

V

_IN(MAX)– V

• V

(

)

FLOAT

L_SW

≥

f_OSC• V

• 30% •I

(

)

IN(MAX)

CHG

Then select an inductor with a saturation current rating at

a value greater than I

.

current due to any load placed at V . As shown in Figure

L(PEAK)

IN

15, the PFET body diode serves as the blocking component

since CHRG is high impedance when the battery voltage

is greater than the input voltage. When CHRG pulls low,

i.e. during most of a normal charge cycle, the PFET is on

to reduce power dissipation. This PFET requires a forward

current rating equal to the programmed charge current and

areversebreakdownvoltageequaltotheprogrammedfloat

voltage. Figure 15 illustrates how to add a blocking PFET

connected with the LTC4120.

Input Capacitor: C

IN

The LTC4120 charger is biased directly from the input

supply at the V pin. This supply provides large switched

IN

currents, so a high quality, low ESR decoupling capacitor

is recommended to minimize voltage glitches at V . Bulk

IN

4.99k*

V

IN

CHRG

IN

BST

10µF

22nF

L

SW

RUN

SW

CHGSNS

BAT

49.9k

LTC4120

4.7µF

22µF

+

470k

Li-Ion

SI2343DS

INTV

CC

2.2µF

R

FB1

PROG

FB

R

FB2

PROG

FBG

GND

4120 F15

*ADD 4.99k WHEN MAX BAT VOLTAGE APPROACHES 85% OF VGS LIMIT FOR Si2343.

Figure 15. Reverse Blocking with a P-Channel MOSFET in Series with the BAT Pin

4120ff

25

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

BAT Capacitor and Output Ripple: C

INTV supply is enabled, and when INTV rises above

BAT

CC

UV

the charger is enabled.

INTVCC

The LTC4120 charger output requires bypass capacitance

connected from BAT to GND (C ). A 22µF ceramic

BAT

Calculating Power Dissipation

capacitor is required for all applications. In systems

where the battery can be disconnected from the charger

output, additional bypass capacitance may be desired.

In this type of application, excessive ripple and/or low

amplitudeoscillationscanoccurwithoutadditionaloutput

bulkcapacitance.Foroptimumstability,theadditionalbulk

capacitance should also have a small amount of ESR. For

these applications, place a 100µF low ESR non-ceramic

capacitor(chiptantalumororganicsemiconductorcapaci-

tors such as Sanyo OS-CONs or POSCAPs) from BAT to

GND, in parallel with the 22µF ceramic bypass capacitor,

or use large ceramic capacitors with an additional series

ESR resistor of less than 1Ω. This additional bypass

capacitance may also be required in systems where the

battery is connected to the charger with long wires. The

The user should ensure that the maximum rated junction

temperatureisnotexceededunderalloperatingconditions.

The thermal resistance of the LTC4120 package (θ ) is

JA

54°C/W; provided that the exposed pad is soldered to suf-

ficient PCB copper area. The actual thermal resistance in

the application may depend on forced air cooling or other

heat sinking means, and especially the amount of copper

on the PCB to which the LTC4120 is attached. The actual

power dissipation while charging is approximated by the

following formula:

P ≅ V – V

•I

TRKL

(

)

D

IN

BAT

+V •I

IN IN(SWITCHING)

2

+R_SNS•I_CHG

voltage rating of all capacitors applied to C must meet

BAT

V

BAT

or exceed the battery float voltage.

2

+R_DS(ON)(TOP)

•

•I_CHG

IN

Boost Supply Capacitor: C

BST



_BAT

V

2

+R_DS(ON)(BOT)• 1–

•I_CHG







The BOOST pin provides a bootstrapped supply rail that

provides power to the top gate drivers. The operating volt-

V



IN

age of the BOOST pin is internally generated from INTV

Duringtricklecharge(V <V

)thepowerdissipation

TRKL

CC

BAT

whenever the SW pin pulls low. This provides a floating

may be significant as I

is typically 10mA, however

TRKL

voltage of INTV above SW that is held by a capacitor tied

during normal charging the I

term is zero.

CC

TRKL

from BOOST to SW. A low ESR ceramic capacitor of 10nF

The junction temperature can be estimated using the fol-

lowing formula:

to 22nF is sufficient for C , with a voltage rating of 6V.

BST

INTV Supply and Capacitor: C

T = T + P • θ

JA

CC

INTVCC

J

A

D

Power for the top and bottom gate drivers and most other

internal circuitry is derived from the INTV pin. A low

where T is the ambient operating temperature.

A

CC

Significant power is also consumed in the transmitter

ESR ceramic capacitor of 2.2µF is required on the INTV

CC

electronics. The large AC voltage generated across the L

X

pin. The INTV supply has a relatively low current limit

CC

and C tank results in power being dissipated in the DC

X

(about 20mA) that is dialed back when INTV is low to

CC

resistance of the L coil and the ESR of the C capacitor.

X

reduce power dissipation. Do not use the INTV voltage

CC

The large induced magnetic field in the L coil may also

X

to supply power for any external circuitry apart from the

induce heating in nearby metallic objects.

NTCBIAS network. When the RUN pin is above V the

EN

4120ff

26

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

PCB Layout

8. It is important to minimize parasitic capacitance on

the PROG pin. The trace connecting to this pin should

be as short as possible with extra wide spacing from

adjacent copper traces.

To prevent magnetic and electrical field radiation and

high frequency resonant problems, proper layout of the

components connected to the LTC4120 is essential. For

maximum efficiency, the switch node rise and fall times

should be minimized. The following PCB design priority

list will help insure proper topology. Layout the PCB using

the guidelines listed below in this specific order.

9. Minimize capacitive coupling to GND from the FB pin.

10. Maximize the copper area connected to the exposed

pad. Place via connections directly under the exposed

pad to connect a large copper ground plane to the

LTC4120 to improve heat transfer.

1. Keep foreign metallic objects away from the transmit-

ter coil. Metallic objects in proximity to the transmit

coil will suffer from induction heating and will be a

source of power loss. With the exception of a ferrite

shield that can be used to improve the coupling from

transmitter coil to receiver coil when placed behind

the transmitter coil.

Design Examples

The design example illustrated in Figure 17, reviews the

design of the resonant coupled power transfer charger

application. First the design of the wireless power receiver

circuitisdescribed.Thenconsiderthedesignforthecharger

function given the maximum input voltage, a battery float

voltage of 8.2V, and a charge current of 200mA for the

LTC4120. This example also demonstrates how to select

the switching inductance value to avoid discontinuous

conduction; where switching noise increases.

Advanced transmitters from PowerByProxi include

features to detect the presence of foreign metallic

objects that mitigates this issue.

2. V input capacitor should be placed as close as pos-

IN

sible to the IN and GND pins, with the shortest copper

The wireless power receiver is formed by the tuned net-

work LR and C2P, C2S. This tuned network automatically

modulates the resonance of the tank with the DHC pin of

the LTC4120 to optimize power transfer. The resonant

frequency of the tank should match the oscillation fre-

quency of the transmitter. Given the transmitter shown

in Figure 4 this frequency is 130kHz. The tuned receiver

resonant frequency is:

traces possible and a via connection to the GND plane

3. Place the switching inductor as close as possible to the

SW pin. Minimize the surface area of the SW pin node.

Make the trace width the minimum needed to support

the programmed charge current, and ensure that the

spacing to other copper traces be maximized to reduce

capacitance from the SW node to any other node.

4. Place the BAT capacitor adjacent to the BAT pin and

ensure that the ground return feeds to the same cop-

per that connects to the input capacitor ground before

connecting back to system ground.

1

f_T=

= 127kHz

2 • π • LR •(C2P +C2S)

Inthisdesignexample,thede-tunedresonantfrequencyis:

1

5. Routeanalogground(RUNgroundandINTV capaci-

CC

tor ground) as a separate trace back to the LTC4120

f_D=

= 142kHz

2 • π • LR •C2S

GND pin before connecting to any other ground.

6. Place the INTV capacitor as close as possible to the

f should be set between 5% and 15% higher than f . A

CC

D

T

INTV pin with a via connection to the GND plane.

higher level gives more control range but results in more

CC

power dissipation.

7. Route the DHC trace with sufficient copper and vias

to support 350mA of RMS current, and ensure that

the spacing from the DHC node to other copper traces

be maximized to reduce capacitance and radiated EMI

from the DHC node to other sensitive nodes.

A 47µH coil is selected for L to obtain a turns ratio of 3:1

R

from the transmitter coil, L = 5µH.

X

4120ff

27

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

Now C2S can be calculated to be 26.7nF. Two standard

parallel 50V rated capacitors, 22nF and 4.7nF, provide a

value within 1% of the calculated C2S. Now C2P can be

calculated to be 6.5nF which can be obtained with 4.7nF

and1.8nFcapacitorsinparallel.Allofthecapacitorsshould

be selected with 5% or better tolerance.

Atypical2-cellLi-Ionbatterypackengagespackprotection

for V less than 5V, this is the lowest voltage considered

BAT

for determining the on-time and selecting the 1.5MHz

operating frequency.

5V

t_ON

=

= 476ns > t_MIN(ON)

1.5MHz •17V

The rectifier, D8, D9 and D5 are selected as 50V rated

Schottky diodes.

Nowthe switching inductorvalueis calculated. The induc-

tor value is calculated based on achieving a 30% ripple

current. The ripple current is calculated at the typical input

operating voltage of 17V:

Now consider the design circuit for the LTC4120 charger

function. First, the external feedback divider, R /R

,

FB1 FB2

is found using standard 1% values:

17V – 8.2V • 8.2V

(

)

L3 >

= 48µH

8.2V • 588k

2.4V

2.00M• 588k

R_FB1

R_FB2

=

≅ 2.00M

1.5MHz •17V • 30% • 200mA

(

)

56µHisthenextstandardinductorvaluethatisgreaterthan

this minimum. This inductor value results in a worst-case

≅ 825k

2.00M– 588k

ripple current at the input open-circuit voltage, V

IN(OC)

Figure 4, at the largest coupling coefficient k = 0.37 as:

.

IN(OC)

With these resistors, and including the resistance of the

FBG pin, the battery float voltage is 8.212V.

V

is estimated based on the transmitter design in

With an 8.2V float voltage the maximum charge current

available is limited by the maximum power available from

V

= k • n • π • V

IN(TX)

= 0.37 • 3 • 3.14 • 5V = 34.9V

IN(OC)

the RCPT at η = 85% charger efficiency:

EFF

34.9V – 8.2V • 8.2V

1.5MHz • 56µH• 34.9V

(

)

85% • 2W

∆I_L=

= 75mA

I_CHG(MAX)

≤

= 207mA

8.2V

This results in a worst-case peak inductor current of:

A charge current of 200mA is achieved by selecting a

standard 1% R resistor of:

∆I_L

2

PROG

I_L(PEAK)= I_CHG

+

= 237mA

h_PROG• V

PROG

R_PROG

=

= 6.04k

I_CHG

Select an inductor with a saturation current rating greater

than the worst-case peak inductor current of 237mA.

While charging a battery, the resonant receiver is loaded

by the charge current, this load reduces the input voltage

from the open-circuit value to a typical voltage in a range

from 12V (at UVCL) up to about 26V. The amplitude of

this voltage depends primarily on the amount of coupling

between the transmitter and the receiver, typically this

voltage is about 17V.

Select a 50V rated capacitor for C = 10µF to achieve an

IN

input voltage ripple of 10mV at the typical operating input

voltage of 17V:

8.2V

200mA •

17V

10µF

∆V =

= 10mV

IN

The maximum loaded input voltage is used to select the

operatingfrequencyandinfluencesthevalueoftheswitch-

inginductor.Thesaturationcurrentratingoftheswitching

inductor is selected based on the worst case conditions

at the maximum open-circuit voltage.

And select 6V rated capacitors for C

= 2.2µF,

INTVCC

C

=22nF,andC =22µF.OptionallyadddiodeD6,

BOOST

BAT

a 1W, 39V Zener diode if the coupling from transmitter to

receiver coils is not well enough controlled to ensure that

V remains below 39V when the battery is fully charged.

IN

4120ff

28

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

Finally the RUN pin divider is selected to turn on the char-

P = 20V • 5mA +0.3Ω• 0.2A²

D

ger once the input voltage reaches 11.2V. With R3 = 374k

8.2V

20V

+0.8Ω•

• 0.2A²

and R4 = 102k the RUN pin reaches 2.4V at V = 11.2V.

IN

With this RUN pin divider, the LTC4120 is disabled once

V falls below 10.5V.

IN









8.2V

20V

2



+0.5Ω• 1–

• 0.2A = 0.14mW



For this design example, power dissipation during trickle



charge,wheretheswitchingchargecurrentis20mAatV

BAT

This dissipated power results in a junction temperature

rise of 6°C over ambient.

= 3V and I switching = 5mA, is calculated as follows:

IN

P = 20V – 3V •10mA +20V • 5mA

(

)

D

Design Example 2: Operation with the LTC4125

3V

20V

+0.3Ω• 0.02A²+0.8Ω•

• 0.02A²

The LTC4125 is a 5W AutoResonant wireless power

transmitter that offers several advantages over the simple

transmitter shown in Figure 10, including foreign object

detection, external overtemperature detection, automatic

tuning of switching frequency and transmit power. When

operating the LTC4120 receiver with the LTC4125, the

DHC pin serves to enable an external shunt regulator

that optimizes the input supply voltage to the LTC4120

as shown in Figure 16. For more information on using the

LTC4125 see the LTC4125 data sheet.









3V

20V

2



+0.5Ω• 1–



• 0.02A



= 0.27W

This dissipated power results in a junction temperature

rise of:

P • θ = 0.27W • 54°C/W = 15°C

D

JA

During regular charging with V

dissipation reduces to:

> V , the power

TRKL

BAT

I

IN

33nF

DR1

4.5V

TO

5.5V

20mΩ

V

IN

DFLZ39

10µF

DR2

D

C

2.21k

D

47µF

x 2

M1

10k

1µF

AIR GAP

3mm

R

C

STAT

IN1 IN2

100k

1k

TO

24.9k

10mm

IN

DTH

STAT

L

TX

24µH

QR1

RUN IN

DHC

BOOST

NTC

FTH

47µF

SW1

10nF

7.87k 59.0k

R

L

NTCTX

RX

SW

47µH

PTHM

C

TX

100nF

L1

15µH

LTC4120-4.2

–

LTC4125

IS

SW2

CHGSNS

BAT

10nF

D

FB

11.3k

FAULT

CHRG

+

V

IS

IN

BATSNS

NTC

PTH1

PTH2

EN

100k

100V

DC1

C

FB1

0.1µF

PROG GND FREQ INTV

10k

FB

CC

0.1µF

5.23k

IMON

CTD

CTS

GND

3.01k

SINGLE

CELL

2.2µF

R

+

Li-Ion

NTCRX

470pF

4.7nF

10nF 348k

BATTERY

PACK

L

C

: 760308100110

DR1, DR2, DR3: DFLS240L

TX

FB1

: C3216C0G2A104J160AC

D : BZT52C13

C

4120 F16

: GRM188R72A104KA35D

M1: Si7308DN

DC1: CDBQR70

QR1: PMBT3904M

D

R

: LTST-C193KGKT-5A

R

L

: NTHS0402N02N1002F

STAT

NTCRX

RX

: BAS521-7

FB

: PCB COIL AND FERRITE: B67410-A0223-X195

OR 760308101303

: NTHS0603N02N1002J

NTCTX

RED INDICATES HIGH VOLTAGE PARTS

L1: LPS4018-153ML

Figue 16. LTC4125 Driving a 24μH Transmit Coil at 103kHz, with 1.3A Input Current Threshold, 119kHz Frequency Limit

and 41.5°C Transmit Coil Surface Temperature Limit in a Wireless Power System with LTC4120-4.2 as a 400mA Single

Cell Li-Ion Battery Charger at the Receiver

4120ff

29

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/product/LTC4120#packaging for the most recent package drawings.

UD Package

16-Lead Plastic QFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1691 Rev Ø)

0.70 ±0.05

3.50 ±0.05

2.10 ±0.05

1.45 ±0.05

(4 SIDES)

PACKAGE OUTLINE

0.25 ±0.05

0.50 BSC

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

BOTTOM VIEW—EXPOSED PAD

PIN 1 NOTCH R = 0.20 TYP

OR 0.25 × 45° CHAMFER

R = 0.115

TYP

0.75 ±0.05

3.00 ±0.10

(4 SIDES)

15 16

PIN 1

TOP MARK

(NOTE 6)

0.40 ±0.10

1

2

1.45 ± 0.10

(4-SIDES)

(UD16) QFN 0904

0.200 REF

0.25 ±0.05

0.00 – 0.05

0.50 BSC

NOTE:

1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION

ON THE TOP AND BOTTOM OF PACKAGE

4120ff

30

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

REVISION HISTORY

REV

DATE

12/13

03/14

DESCRIPTION

PAGE

A

Updated Table 4 component values and brands.

20

B

Removed word “battery” from float voltage range bullet.

Modified various specification limits and removed some temp dots.

Modified frequency range, resistor values and Note 3.

1

3

4

Amended I curves.

7

IN

Modified text to reflect typical f

values.

8

OSC

Updated text for V

servo.

D

9

PROG

Amended equation for f .

14

15

16

17

20

Modified I

equation.

CHG

Changed description of End-Of-Charge indication.

Modified typical f

values.

OSC

Modified Resonant Converter Selection.

Added high voltage pre-regulator schematic.

Added Table 4: Recommended Transmitter and High Voltage Pre-Regulator Components.

Added Table 5: Recommended Receiver Components.

20

23

28

29

Added Figure 11, PCB Layout of Rx Coil.

Added Figure 12, Tx layout: photo of Demo Circuit 1968A.

Added Figure 13, Rx layout: photo of Demo Circuit 1967A-B

Modified text of f

and f .

T

OSC

Modified f equation.

T

Modified equation for t , L3, ∆I , and I and changed power dissipation calculations.

L(PEAK)

ON

L

C

05/14

Increased minimum V to 12.5V

1, 3

IN

Added fixed 4.2V float version, throughout document, also added electrical parameters for –4.2

1 to 32

Increased I specification to TYP 25nA

3

FB

Reduced min RECHG threshold to –38mV

3

Modified V

servo voltage spec by +3mV and –3mV

3

PROG

TRKL

Loosened V

threshold voltage spec by –20mV and +10mV

4

Increased TYP V

hysteresis spec to 50mV

4

TRKL

Changed conditions on I specification to IN = Open-Circuit from IN = Float

4

SW

Revised R

current limit typical performance characteristics curve

5

SNS

Added typical V

performance characteristics curve

IN(SWITCHING)

6

FLOAT

Corrected error in I

Current curve (x-axis)

8

11

Added Block Diagram of –4.2 BATSNS connections

Changed V labels to IN in Figure 4, 5, and 10

12, 13, 20

N/A

IN

Remove SW inductor selection Tables 6, 7, 8, and 9

Changed location of BAT decoupling cap in Figure 15 with reverse blocking diode

Corrected error in L3 equation and substituted correct 56µH inductor

25

28

D

E

F

01/15

05/15

02/16

Change CBAT from 10µF to 22µF

1, 9, 10, 11, 14, 25,

26, 29 and 32

22

Add Würth P/N for RX coil

Add INTER-TECH P/N for TX and RX coils

Remove dos on 68µ bias inductor in basic TX schematic for clarity

21, 22

12, 20

Clarified Battery Charge Current vs Temperature curve

Clarified End-of-Charge and Battery Recharge sections

Modified Operation without an Input Supply section

Enhanced Reverse Blocking section

6

16

18

25,26

26

Modified INTV Supply and Capacitor section

CC

Removed INTV spec. Moved Note 4 to UV_INTV spec.

3

9

24

25

29

32

CC

Modified INTV pin definition.

CC

Included LTC4125 in Applications Information.

Added 4.99k Note.

Added paragraph and Figure 16 from LTC4125 data sheet.

Renumbered Figure 17. Added to Related Parts Table.

4120ff

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

31

For more information www.linear.com/LTC4120

LTC4120/LTC4120-4.2

TYPICAL APPLICATION

C2S

26.7nF

D9

IN

INTV

CC

FREQ

BOOST

C

INTVCC

C

IN

D8

D5

2.2µF

10µF

D6

OPT

L

SW

C

BST

2k

56µH

LTC4120

22nF

CHRG

FAULT

RUN

SW

374k

102k

CHGSNS

BAT

V

FLOAT

C2P

6.5nF

8.2V

R

C

BAT

FB1

2.00M

22µF

Tx CIRCUITRY

FB

DHC

10k

R

FB2

825k

L

5µH

L

R

47µH

X

FBG

NTC

GND PROG

+

T

Li-Ion

R

6.04k

PROG

D5, D8, D9: DFLS240L

D6: MMSZ5259BT1G OR DFLZ39 (OPT)

: SLF6028-470MR59

4120 F17

L

SW

T: NTHS0402N02N1002F

Figure 17. Resonant Coupled Power Transfer Charger Application

RELATED PARTS

PART NUMBER DESCRIPTION

COMMENTS

AN138

Wireless Power Users Guide

Nanopower Buck-Boost with

Intergrated Coulomb Counter Up to 50mA of Output Current, Up to 90% Efficiency

Monolithic 2A Switch Mode Standalone 9V ≤ V ≤ 32V (40V Absolute Maximum), 1MHz, 2A Programmable Charge Current, Timer

LTC3335

680nA Input Quiescent Current (Output in Regulation at No Load) 1.8V to 5.5V Input Operating Range,

LT3650-8.2/

LT3650-8.4

IN

Non-Synchronous 2-Cell Li-Ion or C/10 Termination, Small and Few External Components, 3mm × 3mm DFN-12 Package “-8.2” for 2×

Battery Charger

4.1V Float Voltage Batteries, “-8.4” for 2× 4.2V Float Voltage Batteries

LT3650-4.1/

LT3650-4.2

Monolithic 2A Switch Mode

Standalone 4.75V ≤ V ≤ 32V (40V Absolute Maximum), 1MHz, 2A Programmable Charge Current,

IN

Non-Synchronous 1-Cell Li-Ion Timer or C/10 Termination, Small and Few External Components, 3mm × 3mm DFN-12 Package “-4.1”

Battery Charger

for 4.1V Float Voltage Batteries, “-4.2” for 4.2V Float Voltage Batteries

LT3652HV

LTC4070

Power Tracking 2A Battery

Charger

Input Supply Voltage Regulation Loop for Peak Power Tracking in (MPPT) Solar Applications Standalone,

4.95V ≤ V ≤ 34V (40V Absolute Maximum), 1MHz, 2A Charge Current, 3.3V ≤ V

≤ 18V. Timer or

IN

OUT

C/10 Termination, 3mm × 3mm DFN-12 Package and MSOP-12 Packages

Li-Ion/Polymer Shunt Battery Low Operating Current (450nA), 1% Float Voltage Accuracy Over Full Temperature and Shunt Current

Charger System

Range, 50mA Maximum Internal Shunt Current (500mA with External PFET), Pin Selectable Float

Voltages: 4.0V, 4.1V, 4.2V. Ultralow Power Pulsed NTC Float Conditioning for Li-Ion/Polymer Protection,

8-Lead (2mm × 3mm) DFN and MSOP

LTC4071

Li-Ion/Polymer Shunt Battery Integrated Pack Protection, <10nA Low Battery Disconnect Protects Battery From Over-Discharge. Low

Charger System with Low

Battery Disconnect

Operating Current (550nA), 1% Float Voltage Accuracy Over Full Temperature and Shunt Current Range,

50mA Maximum Internal Shunt Current, Pin Selectable Float Voltages: 4.0V, 4.1V, 4.2V. Ultralow Power

Pulsed NTC Float Conditioning for Li-Ion/Polymer Protection, 8-Lead (2mm × 3mm) DFN and MSOP

LTC4065/

LTC4065A

Standalone Li-Ion Battery

Charger in 2mm × 2mm DFN

4.2V 0.6% Float Voltage, Up to 750mA Charge Current ; “A” Version Has /ACPR Function. 2mm × 2mm

DFN Package

LTC4123

25mA NiMH Wireless

Charger-Receiver

Low Minimum Input Voltage: 2.2V, Temperature Compensated Charge Voltage

LTC4125

5W AutoResonant Wireless

Power Transmitter

Monolithic AutoResonant Full Bridge Driver. Transmit Power Automatically Adjusts to Receiver Load,

Foreign Object Detection, Wide Operating Switching Frequency Range: 50kHz to 250kHz, Input Voltage

Range 3V to 5.5V, 20-Lead 4mm × 5mm QFN Package

4120ff

LT 0216 REV F • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

32

For more information www.linear.com/LTC4120

(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC4120

●

 LINEAR TECHNOLOGY CORPORATION 2013


型号：	LTC4120EUD-4.2#PBF
厂家：	Linear
描述：	LTC4120/LTC4120-4.2 - Wireless Power Receiver and 400mA Buck Battery Charger; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C 电池无线
文件：	总32页 (文件大小：858K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC4120EUD-4.2#PBF [Linear]

相关型号：

LTC4120_15

LTC4121

LTC4121-4.2

LTC4121-4.2_15

LTC4121EUD

LTC4121EUD-4.2

LTC4121_15

LTC4123

LTC4124

LTC4125EUFD

LTC4126

LTC4126-10