LT3650-8.2_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 batter-

ies, while the programmable float voltage of the LTC4120

accommodates several battery chemistries. The LTC4120

uses a Dynamic Harmonization Control (DHC) technique that

allows high efficiency contactless charging across an air gap.

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

pin threshold, low voltage battery preconditioning and bad

battery fault detection, timer termination, auto-recharge,

and NTC temperature qualified charging. The FAULT pin

provides an indication of bad battery or temperature faults.

Physically Small Devices

n

Electrically Isolated Devices

All registered trademarks and 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

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Rev. G

1

Document Feedback

For more information www.analog.com

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

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ORDER INFORMATION

LEAD FREE FINISH

LTC4120EUD#PBF

LTC4120IUD#PBF

TAPE AND REEL

PART MARKING*

LGHB

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTC4120EUD#TRPBF

LTC4120IUD#TRPBF

16-Lead (3mm × 3mm) Plastic QFN

–40°C to 125°C

LGHB

LTC4120EUD-4.2#PBF

LTC4120IUD-4.2#PBF

LTC4120EUD-4.2#TRPBF LGMT

LTC4120IUD-4.2#TRPBF LGMT

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

Tape and reel specifications. 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

Rev. G

2

For more information www.analog.com

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

∆V

Differential Undervoltage Lockout

Hysteresis

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

20

160

mV

DUVLO

IN BAT

IN BATSNS

IN

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

INTVCC

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

Rev. G

3

For more information www.analog.com

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

SNS

(Note 9)

585

1250

mA

PEAK

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_CC

NTC INTVCC

NTC

Hot Temperature V /V

Falling V

Rising V

Threshold

36.5

37.5

37.5 %INTV_CC

%INTV_CC

NTC INTVCC

NTC

NTC Disable Voltage

Falling V

Rising V

Threshold

2

3

%INTV_CC

NTC

NTC Input Leakage Current

V

= V

–50

50

nA

NTC

INTVCC

Rev. G

4

For more information www.analog.com

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

BATSNS BAT SW

BAT FBG(LEAK)

(LTC4120-4.2).

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

Rev. G

5

For more information www.analog.com

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

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IN Pin Standby/Sleep Current vs

Temperature

IN Pin Disabled/Shutdown Current

vs Temperature

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ꢍꢒꢌ

ꢒ ꢅꢎꢍꢀꢖ ꢀꢁꢖꢀꢁꢗ

ꢎ ꢅꢔꢓꢀꢖ ꢀꢁꢖꢀꢁꢗ

ꢚ

ꢛ ꢔꢋꢚ

ꢘ

ꢙ ꢍꢋꢘ

ꢍꢎ

ꢓꢔ

ꢍꢏꢌ

ꢍꢎꢌ

ꢍꢌꢌ

ꢐꢌ

ꢓ

ꢓꢔ

ꢓ

ꢓꢔ

ꢓ

ꢓꢔ

ꢓ

ꢓꢔ

ꢓ

ꢓꢔ

ꢓ

ꢓꢔ

ꢖꢀꢄꢔꢗꢚꢛ ꢜRꢁꢝ ꢙ ꢓꢔꢀꢘ

ꢖꢀꢄꢔꢗꢚꢛ ꢜRꢁꢝ ꢙ Gꢔꢗ

ꢖꢞꢁꢁꢃ

ꢈꢈ

ꢍꢍꢎ ꢗꢍꢖꢄꢘꢙꢁꢗ

ꢖꢞꢁꢁꢃ

ꢒꢌ

ꢔꢌ

ꢌ

ꢍꢍꢎ ꢖꢗ

ꢒꢌ

ꢏꢌ

ꢋꢌ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢔꢌꢌ ꢔꢒꢋ

ꢊꢋꢌ ꢊꢒꢋ

ꢌ

ꢒꢋ

ꢓꢋ

ꢋꢌ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢍꢌꢌ ꢍꢎꢋ

ꢊꢋꢌ ꢊꢎꢋ

ꢌ

ꢎꢋ

ꢑꢋ

ꢐꢔꢒꢌ Gꢌꢕ

ꢏꢍꢎꢌ Gꢌꢎ

BAT Pin Sleep/Shutdown Current

vs Temperature

Typical Battery Charge Current

vs Temperature

Typical R_SNSCurrent Limit

vs Temperature

ꢔ

ꢏꢌꢐ

ꢏꢌꢒ

ꢐꢐꢑꢌ

ꢐꢐꢌꢌ

ꢐꢌꢔꢌ

ꢐꢌꢓꢌ

ꢐꢌꢒꢌ

ꢐꢌꢑꢌ

ꢐꢌꢌꢌ

ꢕꢔꢌ

ꢗꢅꢀꢐ

ꢗꢅꢀꢑ

ꢗꢅꢀꢘ

ꢑ ꢅꢝꢍꢀꢗ ꢀꢁꢗꢀꢁꢚ

ꢞ

R

ꢟ ꢒ.ꢑꢞ

ꢟ ꢓ.ꢌꢓꢂ

ꢟ ꢓ.ꢖꢋꢂ

ꢎꢄꢀ

ꢠꢎꢑ

ꢠꢎꢓ

ꢐ

ꢕ

ꢍ

ꢗꢘꢁꢁꢃ

ꢏꢌꢌ

ꢍꢎꢎ

ꢍꢎꢓ

ꢍꢎꢑ

ꢍꢎꢔ

ꢎꢄꢀ

ꢋ

ꢒ

ꢖ

ꢑ

ꢓ

R

ꢃRꢞG

ꢚ ꢍ.ꢌꢒꢟ

ꢐ ꢅꢛꢕꢀꢠ ꢀꢁꢠꢀꢁꢜ

ꢘRꢁꢙ ꢚ Gꢛꢜ

ꢘRꢁꢙ ꢚ ꢕꢛꢀꢝ

ꢍ

ꢗꢙꢅꢀꢚꢛꢜꢝ

ꢎꢄꢀ

ꢕꢓꢌ

ꢈꢈ

ꢕꢒꢌ

ꢘ ꢅꢙꢍꢀꢚ ꢀꢁꢚꢀꢁꢗ

ꢌ

ꢍꢎꢋ

ꢕꢑꢌ

ꢊꢑꢋ

ꢌ

ꢋꢌ

ꢐꢋ ꢓꢌꢌ ꢓꢑꢋ

ꢊꢋꢌ

ꢑꢋ

ꢋꢌ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢒꢌꢌ ꢒꢐꢋ

ꢋꢌ

ꢖꢋ

ꢊꢋꢌ ꢊꢐꢋ

ꢌ

ꢐꢋ

ꢑꢋ

ꢊꢋꢌ ꢊꢑꢋ

ꢌ

ꢑꢋ

ꢐꢌꢌ ꢐꢑꢋ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢒꢐꢑꢌ Gꢌꢓ

ꢒꢓꢑꢌ Gꢌꢒ

ꢏꢒꢐꢌ Gꢌꢋ

Rev. G

6

For more information www.analog.com

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

ꢔꢙ

ꢕꢌꢌ

ꢖꢏ

ꢖꢇ

ꢐꢏ

ꢐꢇ

ꢎꢏ

ꢎꢇ

ꢔꢏ

ꢔꢇ

ꢏꢏ

ꢏꢇ

ꢐ

ꢞ ꢟꢃꢁꢒꢑꢈꢍRꢈꢅꢍꢀ

ꢎꢄꢀ

ꢎ.ꢏ

ꢎ.ꢐ

ꢎ.ꢌ

ꢌ.ꢍ

ꢌ.ꢒ

ꢌ.ꢏ

ꢌ.ꢐ

ꢌ

ꢍꢒ

ꢞ ꢕ.ꢖꢐ

ꢔꢕ

ꢔꢖ

ꢚꢋꢌ

ꢚꢌꢌ

ꢘRꢁꢙ ꢚ ꢝꢛꢀꢞ

ꢈꢈ

ꢔꢌ

ꢘ

ꢖꢋꢌ

ꢖꢌꢌ

ꢔꢋꢌ

ꢔꢌꢌ

ꢋꢌ

ꢗ

ꢀꢋ

ꢗ

ꢀꢋ

ꢗ

ꢀꢋ

ꢗ

ꢀꢋ

ꢘ ꢒꢓ.ꢏꢗ

ꢘ ꢒꢑꢗ

ꢘ ꢓꢇꢗ

ꢘ ꢕꢇꢗ

ꢘRꢁꢙ ꢚ Gꢛꢜ

ꢙ

ꢖ ꢅꢒꢍꢀꢜ ꢀꢁꢜꢀꢁꢝ

ꢕ

ꢍ

ꢎꢄꢀ

ꢎꢄꢀ ꢍꢒ

ꢍ

ꢙ

ꢘ ꢔꢐꢜꢝꢞ ꢚꢙꢉꢒꢓꢏꢏꢏꢃꢟꢔꢐꢇꢠꢒRꢕ

ꢚꢛ

ꢖ

ꢐ

ꢑꢐ

ꢉRꢈꢡ ꢘ Gꢋꢢ

ꢘ ꢑ.ꢓꢗ

ꢑꢐ

ꢗ

ꢐ ꢅꢛꢝꢀꢕ ꢀꢁꢕꢀꢁꢜ

ꢎꢄꢀ ꢍꢒ

ꢁꢂꢃ

ꢌ

ꢋꢌ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢎꢌꢌ ꢎꢐꢋ

ꢊꢋꢌ ꢊꢐꢋ

ꢌ

ꢐꢋ

ꢑꢋ

ꢊꢖꢋ

ꢌ

ꢋꢌ

ꢛꢋ ꢔꢌꢌ ꢔꢖꢋ

ꢊꢋꢌ

ꢖꢋ

ꢓꢇꢇ ꢓꢏꢇ

ꢇ

ꢏꢇ ꢒꢇꢇ ꢒꢏꢇ

ꢀ

ꢕꢇꢇ ꢕꢏꢇ ꢑꢇꢇ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢄꢅꢂꢆ

ꢁꢂꢃ

ꢏꢎꢐꢌ Gꢌꢑ

ꢕꢔꢖꢌ Gꢌꢗ

ꢑꢒꢓꢇ Gꢇꢐ

Wireless Power Transfer Efficiency,

V_{IN_RX}vs Battery Current

Typical t_MIN(ON)vs Temperature

ꢔꢕꢌ

ꢔꢘꢋ

ꢔꢘꢌ

ꢔꢔꢋ

ꢔꢔꢌ

ꢔꢌꢋ

ꢔꢌꢌ

ꢓꢋ

ꢊꢇ

ꢉꢇ

ꢋꢌ

ꢖ

ꢝꢞ

R

ꢜ ꢏ.ꢎꢖ

ꢑꢚꢛꢂꢃ

ꢘ ꢅꢐꢏꢀꢙ ꢀꢁꢙꢀꢁꢚ

ꢚ

ꢜ ꢝꢚꢑꢉꢇꢋꢏꢟꢌꢊꢇꢠRꢈꢙ

ꢋꢋ

ꢜ ꢌ.ꢉꢌꢢ

ꢡRꢛG

ꢈꢇ

ꢌꢇ

ꢎꢇ

ꢋꢇ

ꢍꢇ

ꢇ

ꢋꢇ

ꢍꢏ

ꢍꢉ

ꢍꢌ

ꢍꢋ

ꢍꢇ

ꢙꢅꢅ ꢐꢑꢑꢀꢒꢀꢐꢓꢒꢔ

ꢍꢇꢅꢅ ꢐꢑꢑꢀꢒꢀꢐꢓꢒꢔ

ꢍꢍꢅꢅ ꢐꢑꢑꢀꢒꢀꢐꢓꢒꢔ

ꢙꢅꢅ ꢖꢗRꢘ

ꢍꢇꢅꢅ ꢖꢗRꢘ

ꢍꢍꢅꢅ ꢖꢗRꢘ

ꢓꢌ

ꢍꢋ

ꢍꢌ

ꢈꢇ

ꢍꢇꢇ

ꢍꢈꢇ

ꢄꢅꢂꢆ

ꢋꢈꢇ

ꢇ

ꢋꢇꢇ

ꢊꢋꢌ

ꢌ

ꢘꢋ

ꢋꢌ

ꢖꢋ ꢔꢌꢌ ꢔꢘꢋ

ꢊꢘꢘ

ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ

ꢀ

ꢁꢂꢃ

ꢌꢍꢋꢇ Gꢍꢍ

ꢗꢔꢘꢌ Gꢔꢌ

Typical Burst Mode Waveforms,

I_BAT= 38mA

Typical Wireless Charging Cycle

Burst Mode Trigger Current

ꢖꢓꢊ

ꢖꢊꢊ

ꢗꢓꢊ

ꢗꢊꢊ

ꢕꢓꢊ

ꢕꢊꢊ

ꢔꢓꢊ

ꢔꢊꢊ

ꢓꢊ

ꢖ.ꢓ

ꢖ.ꢊ

ꢗ.ꢓ

ꢗ.ꢊ

ꢕ.ꢓ

ꢕ.ꢊ

ꢔ.ꢓ

ꢔ.ꢊ

ꢊ.ꢓ

ꢎꢆ

ꢒꢆ

ꢑꢆ

ꢐꢆ

ꢍꢆ

ꢌꢆ

ꢋꢆ

ꢏꢆ

ꢅꢆ

ꢑ

ꢋꢌꢀ

R

ꢓRꢔG

ꢕ ꢋꢖ

ꢀ

ꢁꢂ

ꢃꢀꢄꢅꢆꢀ

ꢑ

ꢎꢅRG

ꢁ

ꢋꢌꢀ

R

ꢕ ꢐ.ꢏꢖ

ꢓRꢔG

ꢉꢀ

ꢀ

ꢇRꢈG

ꢃꢉꢉꢊꢀꢄꢅꢆꢀ

ꢉꢀ

ꢆ

ꢋꢁꢂ

ꢋꢌꢀ ꢘ ꢙꢖꢊꢐꢌꢚꢛ

ꢌꢉꢉꢊꢍꢄꢅꢆꢀ

ꢉꢊꢍ

ꢜ

R

ꢘ ꢀꢞꢟ ꢈꢜꢠꢖꢊꢡꢓ ꢔꢓꢢꢅ

ꢈꢝ

ꢠꢋꢔ

ꢘ ꢡꢗꢕꢣꢒ R ꢘ ꢙꢡꢤꢣ

ꢠꢋꢕ

ꢎꢑꢌꢉ Gꢑꢎ

ꢘ ꢗ.ꢊꢔꢣ

ꢥRꢆG

ꢎꢏꢐꢄꢅꢆꢀ

ꢌꢥꢥꢜꢁꢎꢌꢀꢁꢆꢏ ꢎꢎꢀ ꢆꢠ ꢠꢁGꢇRꢃ ꢔꢊ

ꢈꢥꢌꢎꢁꢏG ꢘ ꢔꢖꢐꢐ

ꢊ

ꢆ

ꢊ

ꢔ

ꢕ

ꢗ

ꢅꢆ

ꢅꢍ

ꢏꢆ

ꢏꢍ

ꢃꢀꢄ

ꢌꢆ

ꢋꢆ

ꢋꢍ

ꢀꢁꢂꢃ ꢄꢅꢆꢇRꢈꢉ

ꢀ

ꢁꢂ

ꢖꢔꢕꢊ Gꢔꢕ

ꢌꢅꢏꢆ Gꢅꢋ

Rev. G

7

For more information www.analog.com

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

ꢋꢋꢅ

ꢎꢅ

ꢀ

ꢖ ꢅ.ꢈꢀ

ꢀ

ꢑ ꢎ.ꢋꢈꢀ

Rꢚꢂ

ꢏꢇꢐ

ꢂꢐꢒ ꢑ Gꢂꢓ

ꢏꢅ

ꢊꢅ

ꢉꢅ

ꢈꢅ

ꢍꢅ

ꢌꢅ

ꢋꢅ

ꢅ

ꢋꢅꢅ

ꢈꢊꢅ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢔꢐꢏꢕ ꢖRꢗꢘ ꢙꢁGꢙ ꢈꢌꢅꢚꢒ

ꢔꢐꢏꢕ ꢖRꢗꢘ ꢛꢜꢝ ꢈꢌꢅꢚꢒ

ꢔꢐꢏꢕ ꢖRꢗꢘ ꢙꢁGꢙ ꢋꢍꢚꢒ

ꢔꢐꢏꢕ ꢖRꢗꢘ ꢛꢜꢝ ꢋꢍꢚꢒ

ꢔꢐꢏꢕ ꢖRꢗꢘ ꢙꢁGꢙ ꢞꢎꢍꢚꢒ

ꢔꢐꢏꢕ ꢖRꢗꢘ ꢛꢜꢝ ꢞꢎꢍꢚꢒ

ꢈꢉꢅ

ꢈꢎꢅ

ꢈꢋꢅ

ꢈꢅꢅ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢁ

ꢁꢂ

ꢐꢑ ꢒꢓꢔꢕ ꢖ ꢋꢌꢉꢗꢘ

ꢐꢑ ꢒꢓꢔꢕ ꢖ ꢍꢉꢗꢘ

ꢐꢑ ꢒꢓꢔꢕ ꢖ ꢙꢈꢅꢗꢘ

ꢊꢅ

ꢍ

ꢈꢅ

ꢎꢅ

ꢅ

ꢈꢍ ꢋꢅ ꢋꢍ ꢌꢅ ꢌꢍ

ꢃꢀꢄ

ꢌꢅ

ꢃꢀꢄ

ꢅ

ꢋꢅ

ꢍꢅ

ꢈꢅ

ꢀ

ꢁꢂ

ꢎꢈꢋꢅ Gꢈꢍ

ꢈꢋꢌꢅ Gꢋꢊ

IN Pin Disabled Current

vs Input Voltage

IN Pin Switching Current vs Input

Voltage

UVCL: I_CHARGEvs Input Voltage

ꢈꢅꢅ

ꢏꢅ

ꢎꢅ

ꢌꢅ

ꢐꢅ

ꢋꢅ

ꢊꢅ

ꢉꢅ

ꢍꢅ

ꢈꢅ

ꢅ

ꢉ

ꢍ

ꢇ.ꢎꢇ

ꢇ.ꢐꢏ

ꢇ.ꢐꢇ

ꢇ.ꢍꢏ

ꢇ.ꢍꢇ

ꢇ.ꢅꢏ

ꢇ.ꢅꢇ

ꢇ.ꢇꢏ

ꢇ

ꢀ

ꢗ ꢈ.ꢐꢀ

Rꢛꢂ

ꢁ

ꢒꢋꢓꢔꢕꢅꢍꢏꢖꢈ

ꢒꢋꢓꢔꢕꢐꢏꢖꢈ

ꢒꢋꢓꢔꢕꢗꢎꢇꢖꢈ

ꢅꢋꢆꢖꢑ

ꢊꢈꢖꢑ

ꢗꢇꢈꢖꢑ

ꢑꢊꢒ

ꢁ

ꢜRꢝꢘ ꢛꢁGꢛ

ꢑꢑ

ꢁꢑꢑꢘꢃꢙꢚꢁꢔꢑꢛꢁꢂGꢄ

ꢈ

ꢇ

ꢋ

ꢊ

ꢅ

ꢜRꢝꢘ ꢕ ꢁꢂꢔꢀ

ꢁ

ꢜRꢝꢘ ꢒꢞꢚ

ꢁꢑꢑꢘꢃꢙꢚꢁꢔꢑꢛꢁꢂGꢄ

ꢜRꢝꢘ ꢕ Gꢂꢟ

ꢁ

ꢑꢒ ꢓꢔꢕꢖ ꢗ ꢈꢍꢋꢘꢙ

ꢑꢒ ꢓꢔꢕꢖ ꢗ ꢉꢋꢘꢙ

ꢑꢒ ꢓꢔꢕꢖ ꢗ ꢚꢊꢅꢘꢙ

ꢁꢂ

ꢐꢀꢑꢒ

ꢅꢈ

ꢁ

ꢕ ꢆ

ꢓꢏꢔ

ꢆ

ꢅ

ꢈꢅ

ꢍꢅ

ꢃꢀꢄ

ꢉꢅ

ꢊꢅ

ꢅꢍ.ꢇꢇ ꢅꢍ.ꢇꢏ ꢅꢍ.ꢅꢇ ꢅꢍ.ꢅꢏ

ꢅꢍ.ꢍꢇ

ꢊꢈ

ꢃꢀꢄ

ꢋꢈ

ꢇꢆ

ꢅꢅ.ꢆꢇ ꢅꢅ.ꢆꢏ

ꢅꢆ

ꢊꢆ

ꢋꢆ

ꢀ

ꢃꢀꢄ

ꢀ

ꢁꢂ

ꢇꢅꢊꢆ Gꢅꢌ

ꢊꢈꢍꢅ Gꢈꢌ

ꢎꢅꢍꢇ Gꢅꢆ

Rev. G

8

For more information www.analog.com

LTC4120/LTC4120-4.2

PIN FUNCTIONS

sense resistor. In low battery conditions a small linear

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

CC

charge current, I

, is sourced from this pin to pre-

the output of an internal linear regulator that generates the

condition the bat^Lt^Oe^Wry^B.^AD^Tecouple 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_LOWBAT. Connect a 2.2µF low ESR capacitor from

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

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

connected physically close to the positive battery terminal.

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 (Pin 10, LTC4120 Only): Battery Voltage Feedback Pin.

The charge function operates to achieve a final float voltage

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_DUVLOand its hysteresis, the

charger is enabled.

BOOST (Pin 2): Boosted Supply Pin. Connect a 22nF

boost 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

inductor 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 pin disconnects the external FB divider load from

the battery when it is not needed. When sensing the bat-

tery voltage this pin presents a low resistance, R , to

GND. When in disabled or shutdown modes this^FBp^Gin is

high impedance.

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

to exposed pad. The exposed pad must be soldered to

PCB GND to provide a low electrical and thermal imped-

ance connection to ground.

NTC (Pin 12): Input to the Negative Temperature Coefficient

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 (Pin 6): Dynamic Harmonization Control Pin.

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

and a capacitor from the DHC pin as shown in the Typical

Application or the Block Diagram. When V is greater

IN

than V_IN(DHC), this pin is high impedance. When V_INis

below V

this pin is low impedance allowing the

IN(DHC)

LTC4120 to modulate the resonance of the tuned receiver

network. See Applications Information for more informa-

tion on the tuned receiver network.

required from INTV to NTC and a thermistor is required

CC

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

qualified charging if NTC functionality is not required.

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

PROG (Pin 13): Charge Current Program and Charge

Current Monitor Pin. Connect a 1% resistor between

3.01k (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 average battery charge current using the

following formula:

Connect to INTV to select a 1.5MHz switching frequency

CC

or GND to select a 750kHz switching frequency. Do not float.

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

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

delivered from this pin through the internal charge current

PROG

I

= h

•

BAT

PROG

R

PROG

Rev. G

9

For more information www.analog.com

LTC4120/LTC4120-4.2

PIN FUNCTIONS

where h

is typically 988. Keep parasitic capacitance

as IN 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 volt-

age, the CHRG pin indicates the status of the battery char-

ger. 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_SD, the device is in shutdown

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

EN

the INTV_CCLDO turns on. When the INTV_CCLDO rises

above its UVLO threshold the charger is enabled. The

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

Typically pulled up through a resistor to a reference volt-

age, this status pin indicates fault conditions during a

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

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

Rev. G

10

For more information www.analog.com

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

Rev. G

11

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

Wireless Power System Overview

constant-voltage battery charger with the following built-

in charger functions: programmable charge current, pro-

grammable 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 out-

put 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 Transmitter

Options sections include information necessary to com-

plete 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 transmit-

ter and a series resonant converter for the receiver with

the LTC4120. The LTC4125 advanced transmitter 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

LTC4120 Evaluation Kits

LTC4120 Overview

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

X

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

received input voltage in a resonant coupled power trans-

fer application. The LTC4120 serves as a constant-current/

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

of a basic power transmitter that may be used with the

LTC4120. This transmitter typically operates at a fre-

quency of approximately 130kHz; though the operating

ꢈ

ꢉꢀ

ꢃꢈ

ꢊRꢋꢌꢆꢍꢎꢊꢊꢏR

ꢀꢅꢆ

ꢉꢒ

ꢇꢂ

ꢀꢁ

ꢇꢅ

ꢉꢚ

ꢖꢒꢈ

ꢀ

ꢎꢌ

ꢀ

ꢄ

ꢇ

ꢄ

ꢇ

R

ꢉꢑ

ꢉꢃ

ꢉꢔꢇꢛꢖꢒ

ꢀꢅꢗ

ꢎꢌ

ꢉꢘꢀ ꢙꢝꢝꢆꢊ

ꢀꢃ

ꢀ

ꢙꢆꢊ

ꢆꢜ

ꢇꢊꢀꢁꢂꢅꢕ

Rꢂ

ꢉꢅ

Rꢅ

ꢉꢖ

ꢇ

ꢆꢜ

ꢉꢃꢐ ꢉꢑꢐ ꢉꢒꢓ ꢉꢔꢇꢆꢅꢁꢕꢇ

ꢀꢘGꢆꢌꢆ

ꢙꢋꢊ

ꢍꢂ

ꢍꢅ

ꢢ

ꢇꢞꢟꢎꢠꢡ

ꢀ

ꢙꢋꢊ

ꢉꢂ

ꢉꢁ

Gꢌꢉ

ꢁꢂꢅꢕ ꢔꢕꢁ

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

Rev. G

12

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

frequency varies depending on the load at the receiver

power available at the receiver. The amount that the input

power increases or decreases is a function of the cou-

and the coupling to the receiver coil. For L = 5µH, and

X

C = 300nF, the transmitter frequency is:

X

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

R

the operating frequency.

1

f ≈

= 130kHz

O

Figure 5 illustrates the components that implement the

DHC function to automatically tune the resonance of the

2 • π • L • C

X

receiver. Capacitor C2S and inductor L serve as a series

This transmitter typically generates an AC coil current of

about 2.5A . For more information on this transmitter,

R

resonator. Capacitor C2P and the DHC pin of the LTC4120

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

ance, and disconnect when the DHC pin is high imped-

ance. 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.

RMS

refer to AN138: Wireless Power Users Guide.

The receiver consists of a coil, L , configured in a reso-

R

nant circuit followed by a rectifier and the LTC4120. The

receiver coil presents a load reflected back to the trans-

mitter through the mutual inductance between L and

R

L_X. The reflected impedance of the receiver may influ-

ence 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 by the transmitter varies automati-

cally based on the power 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

transmitter automatically adjusts to the requirements at

the receiver. Furthermore, DHC reduces the rectified volt-

age seen at the input of the LTC4120 under light load

conditions when the battery is fully charged.

Dynamic Harmonization Control

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

ꢀꢂꢃ

ꢉꢌ

ꢄꢅꢆ

ꢀ

ꢑꢒ

ꢉꢋ

ꢀ

ꢇ

R

ꢉꢊ

ꢁ

ꢀꢂꢈ

ꢑꢒ

ꢇꢎꢀꢏꢄꢂꢐ

below the V

set point, the LTC4120 allows more

ꢉꢍꢀ

IN(DHC)

ꢏꢄꢂꢐ ꢓꢐꢋ

power to appear at the receiver by tuning the receiver

resonance closer to the transmitter resonance. If the input

voltage exceeds V_IN(DHC), the LTC4120 tunes the receiver

resonance away from the transmitter, which reduces the

Figure 5. Resonant Receiver Tank

Rev. G

13

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

The design of the resonant receiver circuit (L_R, C2S

Programming The Battery Float Voltage

and C2P), the transmitter circuit, and the mutual induc-

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

tance between L and L determines both the maximum

X

R

unloaded voltage at the input to the LTC4120 as well as

the maximum power available at the input to the LTC4120.

The value and tolerances of these components must be

selected with care for stable operation, for this reason

it is recommended to only use components with tight

tolerances.

float voltage, V , is then governed by the following

FLOAT

equation:

R

+ R

(

)

FB1

FB2

V

= V

•

FLOAT

FB(REG)

R

FB2

To understand the operating principle behind dynamic

harmonization control (DHC), consider the following sim-

plification. Here, a fixed-frequency transmitter is operat-

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

the impedance of ^Othe receiver tuned network so as to

modulate the resonant frequency of the receiver between

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_FB1||R_FB2close to 588k. Start by

calculating R to satisfy the following relations:

FB1

f and f .

T

D

V

• 588k

FLOAT

R

=

FB1

1

V

f ≅

FB(REG)

T

2 • π • L • C2P + C2S

(

)

R

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

value. With R calculate:

1

f ≅

D

FB1

2 • π • L • C2S

R

V

• R

FB1

FB(REG)

When the input voltage is above V

(typically 14V),

R

=

– 1000Ω

the LTC4120 opens the DHC pin,^INd⁽e^Dt^Hu^Cn⁾ing the receiver

resonance away from the transmitter frequency f_O, so that

less power is received. When the input voltage is below

FB2

V

– V

FB(REG)

FLOAT

V

, the LTC4120 shunts the DHC pin to ground,

IN(DHC)

tuning the receiver resonance closer to the transmitter

frequency so that more power is available.

ꢅ

ꢂꢆꢇꢈꢉ

ꢃꢈꢉ

For the resonant converter shown in Figure 4, the operat-

ing frequency of the transmitter is not fixed, but varies

depending on the load impedance. However the basic

operating principle of DHC remains valid. For more infor-

mation on the design of the wireless power receiver reso-

nant circuit refer to the applications section.

ꢆꢉꢔꢏꢄꢀꢐ

ꢆꢊꢋꢌꢍꢎ

R

ꢀꢀꢁꢂ

ꢂꢃꢄ

ꢂꢃ

ꢏꢄꢀꢐ ꢂꢐꢑ

ꢌ

ꢂꢃ

ꢂꢃꢀ

ꢂꢃG

ꢒꢓꢈꢃꢆꢒ

Figure 6. Programming the Float Voltage with the LTC4120

Rev. G

14

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

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

FBG

h

• V

1212V

PROG

I

=

the resistance of the FBG pin which serves as the ground

CHG

R

PROG

return for the battery float voltage divider.

h

• V

120V

PROG

PROG_ TRKL

=

Once R and R are selected, recalculate the value of

FB1

FB2

CHG_ TRKL

R

PROG

V

obtained with the resistors available. If the error

FLOAT

is too large substitute another standard resistor value for

where h

is typically 988, V

is either 1.227V or

PROG

R

and recalculate R . Repeat until the float voltage

FB1

FB2

122mV during trickle charge, and R

is the resistance

PROG

error is acceptable.

of the grounded resistor applied to the PROG pin. The

PROG resistor sets the maximum charge current, or the

current delivered while the charger is operating in con-

stant-current (CC) mode.

Table 1 and Table 2 list recommended standard 0.1% and

1% resistor values for common battery float voltages.

Table 1. Recommended 0.1% Resistors for Common V_FLOAT

V

R

FB2

TYPICAL ERROR

–0.13%

0.15%

FLOAT

FB1

Analog Charge Current Monitor

3.6V

4.1V

4.2V

7.2V

8.2V

8.4V

887k

1.01M

1.8M

1780k

1.42M

1.35M

898k

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.

-

–0.13%

0.08%

2.00M

2.05M

825k

0.14%

816k

0.27%

Table 2. Recommended 1% Resistors for Common V_FLOAT

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 more than one clock cycle as the inductor current

attempts to ramp up to the desired current. If the top

switch remains 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.

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

of the charge current, 1/h_PROG, to the PROG pin. The

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

limit the PROG pin voltage to control charge current. An

Undervoltage Current Limit

The undervoltage current limit (UVCL) feature reduces

charge current as the input voltage drops below V_UVCL

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

which in turn limits the charge current to:

,

Z

PROG

Rev. G

15

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

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

increases to 285% of the R

resistor as the tempera-

BIAS

IN

within 100mV of V

, but if insufficient power is avail-

ture drops. For a Vishay Curve 2 thermistor with B

UVCL

25/85

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

charge current will be reduced to zero.

= 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%

of the R_BIASresistor. For the same Vishay Curve 2 therm-

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.

NTC Thermal Battery Protection

The LTC4120 monitors battery temperature using a therm-

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

The hot and cold trip points may be adjusted using a dif-

ferent type of thermistor, or a different R_BIASresistor, or by

adding a desensitizing resistor, R_ADJ, or by a combination

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

increasing R_BIASto 12.4k, with the same thermistor as

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

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

DIS

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

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 sim-

CC

ple application (R

= 0) a 1% resistor, R

, with a

End-Of-Charge Indication and Safety Timeout

ADJ

BIAS

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

connected from INTV_CCto NTC, and a thermistor is con-

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

pauses charging when the resistance of the thermistor

The LTC4120 uses a safety timer to terminate charging.

Whenever the LTC4120 is in constant current mode the

timer is paused, and if FB transitions through the V

RCHG

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

ꢁꢃꢆ

ꢈꢆꢇꢍꢎꢏꢐ

ꢂꢅꢆꢘ

ꢇꢇ

R

ꢁꢂꢃꢄ

ꢅꢆꢇ

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

C/10

ꢀ

ꢞ

ꢆꢕꢕ ꢇꢕꢈꢓ

ꢆꢕꢕ ꢙꢕꢆ

R

ꢃꢓꢔ

rent continues to flow until the timer finishes. After the

ꢒꢍꢗ ꢂꢅꢆꢘ

ꢇꢇ

ꢕꢖꢆ

timeout, the LTC4120 enters a low power sleep mode.

ꢀ

ꢀ ^{ꢛꢜ.ꢝꢗ ꢂꢅꢆꢘ}

ꢞ

R

ꢅꢆꢇ

ꢆ

ꢇꢇ

ꢈꢉꢊꢂꢋꢌ

ꢍꢎꢏꢐ ꢑꢐꢒ

Automatic Recharge

ꢀ

ꢞ

ꢂGꢅꢕRꢚ ꢅꢆꢇ

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

age. If the battery falls 2.2% (V_RCHGor V_{RCHG_42}) from the

ꢏꢗ ꢂꢅꢆꢘ

ꢇꢇ

Figure 7. NTC Connections

Rev. G

16

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

full-charge float voltage, the LTC4120 engages an auto-

matic 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.

the fault status pin is asserted to indicate a bad battery.

After a bad battery fault, the LTC4120 automatically

restarts 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.

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

battery is reduced to extend battery lifetime, the status

pins are both de-asserted, and the FBG pin is high imped-

ance. 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

SD

condition less than 20µA is drawn from the supply at IN.

Table 3. LTC4120 Open-Drain Indicator Outputs with Resistor

Pull-Ups

FAULT CHRG CHARGER STATE

Differential Undervoltage Lockout

The LTC4120 monitors the difference between the bat-

tery voltage, V , and the input supply, V . If the differ-

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

ence (V -V ) falls to V

, all functions are disabled

IN BAT

DUVLO

and the part is forced into shutdown mode until (V_IN-

Low NTC Thermal Fault Charging Paused

V

BAT

) rises above the V

hysteresis. The LTC4120-

DUVLO

Low Battery Voltage Operation

4.2 monitors the BATSNS and IN pin voltages to sense

DUVLO condition.

The LTC4120 automatically preconditions heavily dis-

charged batteries. If the battery voltage is below V

LOWBAT

User Selectable Buck Operating Frequency

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

protection has been engaged) a DC current, I , is

The LTC4120 uses a constant-frequency synchronous

step-down buck architecture to produce high operat-

ing efficiency. The nominal operating frequency of the

buck, f_OSC, is programmed by connecting the FREQ pin to

either INTV or to GND to obtain a switching frequency

of 1.5MHz ^Co^Cr 750kHz, respectively. The high operating

frequency allows the use of smaller external components.

LOWBAT

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

CC

battery voltage rises above V

, the switching regula-

tor is enabled and charges t^Lh^Oe^Wb^Ba^At^Ttery at a trickle charge

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

to the DC I

current). Trickle charging of the battery

continues^Lu^On^Wti^Bl^At^The sensed battery voltage (sensed via

the feedback pin for the LTC4120) rises above the trickle

charge threshold, V_TRKL. When the battery rises above

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 thresh-

old for more than 30 minutes, charging terminates and

Selection of the operating frequency is a trade-off between

efficiency, component size, and margin from the minimum

on-time of the switcher. Operation at lower frequency

Rev. G

17

For more information www.analog.com

LTC4120/LTC4120-4.2

OPERATION

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.

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

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

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

the CHRG pin to de-assert, indicating C/10. Burst current

ripple depends on the selected switch inductor, and V /

IN

PWM Dropout Detector

V

.

BAT

If the input voltage approaches the battery voltage, the

LTC4120 may require duty cycles approaching 100%.

This mode of operation is known as dropout. In drop-

out, the operating frequency may fall well below the pro-

BOOST Supply Refresh

The BOOST supply for the top gate drive in the LTC4120

switching regulator is generated by bootstrapping the

grammed f

value. If the top switch remains on for eight

BOOST flying capacitor to INTV whenever the bottom

clock cycle^Os,^St^Che 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.

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

capacitor to INTV and ensures that the topside gate

CC

driver has sufficient voltage to turn on the topside switch

at the beginning of the next cycle.

Burst Mode Operation

At low charge currents, for example during constant-

voltage mode, the LTC4120 automatically enters Burst

Mode operation. In Burst Mode operation the switcher is

periodically forced into standby mode in order to improve

efficiency. The LTC4120 automatically enters Burst Mode

operation after it exits constant-current (CC) mode and

as the charge current drops below about 80mA. Burst

Mode operation is triggered at lower currents for larger

PROG resistors, and depends on the input supply volt-

age. Refer to graph Burst Mode Trigger Current and graph

Typical Burst Mode Waveform, in the Typical Performance

Characteristics, for more information on Burst Mode

operation. Burst Mode operation has some hysteresis and

remains engaged for battery currents up to about 150mA.

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 appli-

cations 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.

Rev. G

18

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

ꢂ.ꢃꢂ

ꢂ.ꢏꢃ

ꢀ

ꢄꢅ ꢆꢇꢈꢉꢊꢇGꢄꢆꢋꢄꢌ

R

ꢀ

ꢄꢅ

ꢁ

ꢃꢍꢍ ꢆꢇꢈꢉꢊꢇGꢄꢆꢋꢄꢌ

ꢆ

ꢍ

R

ꢌ

R

ꢂ.ꢏꢂ ^ꢁ

ꢀ

ꢁ

ꢎꢂꢍꢍ ꢆꢇꢈꢉꢊꢇGꢄꢆꢋꢄꢌ

ꢂ.ꢐꢃ ^ꢁ

ꢂ.ꢐꢂ

ꢂ.ꢘꢃ

ꢂ.ꢘꢂ

ꢂ.ꢎꢃ

ꢁꢂꢃ

ꢀ

ꢁ

ꢇꢁꢈꢉ ꢊꢉꢋ

ꢀ

ꢁ

Figure 8. Wireless Power Transfer

ꢁ

ꢀ

ꢁ

ꢀ

ꢁ

Wireless Power Transfer

ꢂ.ꢎꢂ

ꢂ

ꢎ

ꢘ

ꢐ

ꢏ

ꢃ

ꢚ

ꢛ

ꢜ

ꢝ

ꢎꢂ

ꢏꢎꢘꢂ ꢔꢂꢝ

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 transmit-

ter coil. The magnetic field coupling is described by the

mutual 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:

ꢑꢅꢇꢊ ꢙꢇꢈꢌꢉꢄꢑꢋ ꢕꢍꢍꢗ

Figure 9. Coupling Coefficient k vs Distance

capacitor (L ||C ). With a peak-to-peak amplitude that is

proportional 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

DC

AC

L • L

I

=

≅

X

R

AC

2 • π • f • L

f • L

X

O

X

O

And n is the turns ratio—the number of turns in the receiver

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, the

n

L

R

X

n =

=

open-circuit voltage, V

, is approximately:

X

IN(OC)

V

≅ k • n • 2 • π • V

DC

IN(OC)

The turns ratio is proportional to the square root of the

ratio of receiver coil inductance to transmitter coil induc-

tance. In the wireless power transfer system an AC cur-

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

charge a battery. Power delivered to the LTC4120 depends

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

the load goes away (e.g, when the battery is fully charged).

DHC efficiently adjusts the receiver impedance depending

on the load without compromising available power.

rent, I , applied to the transmit coil L , produces an AC

AC

X

current in 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

X

R

is inherently high, even at low coupling ratios. The trans-

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

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

resonant frequency, f , across the transmitter coil and

O

Rev. G

19

For more information www.analog.com

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.

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

higher voltage inputs, a p^Xre-regulator DC/DC con^Rverter

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

transmitted from transmitter to receiver at the resonant

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 addition

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

ꢡꢀ

ꢁꢂ

ꢉꢀ ꢆꢍ ꢇꢉꢀ

ꢑꢘ

ꢈ.ꢖꢗꢔ

Gꢂꢋ

ꢀ

ꢁꢂ

ꢌꢋ

ꢌꢍꢍꢎꢆ

Rꢇ

ꢅꢇ

ꢑꢕ

ꢄꢚꢊꢜ

ꢈ.ꢖꢗꢔ

ꢊ.ꢈꢖꢗꢔ

Rꢃꢂꢒꢎꢎ

ꢎꢏ

ꢋꢚ

ꢋꢔꢅꢎꢛꢈꢊꢅ

ꢑꢖ

ꢊ.ꢊꢘꢉꢗꢔ

ꢑꢄꢊ

ꢛꢛꢗꢔ

Rꢉ

ꢝꢇ

ꢃꢄ

ꢅꢆꢇꢈꢉꢊ

ꢄꢚꢊꢜ

ꢎꢞꢛꢇꢇꢇꢋꢎ

ꢝꢈ

ꢛꢂꢖꢊꢊꢛꢅ

ꢎꢓꢂꢑ

ꢐG

ꢀꢑ

ꢀ

ꢑꢑ

Rꢆ

ꢔꢌ

ꢚꢀ

Rꢄꢊ

ꢄꢊꢊꢜ

Rꢚ

ꢛꢊꢜ

ꢑꢉ

Rꢈ

ꢈꢊ.ꢛꢜ

ꢑꢍꢂꢂꢟꢑꢆ

ꢆꢍ ꢆꢠ ꢀ

Gꢂꢋ

ꢑꢑ

Rꢖ

ꢚꢇꢘꢜ

ꢇꢇꢊꢙꢔ

Rꢘ

ꢄꢊꢊꢜ

ꢈꢄꢛꢊ ꢔꢄꢄ

Figure 11. High Voltage Pre-Regulator for Transmitter

Rev. G

20

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

frequency, f ; which depends on both component values

as well as t^Ohe 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.

Resonant Converter Component Selection

It is recommended to use the components listed in Table 4

and Table 5 for the resonant transmitter and receiver

respectively. Figure 12 illustrates the PCB layout of the

embedded receiver coil. Figure 13 and Figure 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

X

TDK WT-505060-8K2-LT

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

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

R5

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

Rev. G

21

For more information www.analog.com

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

ꢆꢎ ꢑ ꢀꢁꢂ ꢒꢓꢔꢄ

ꢆꢊ

ꢆꢇ

ꢆꢍ ꢑ ꢌꢁꢀꢀꢁꢃ ꢒꢓꢔꢄ

ꢐꢓꢕꢓꢒꢖꢄꢔ ꢀꢖꢓꢗꢘꢕꢄꢒꢒ ꢀꢁ ꢌꢄ ꢏ.ꢏꢇꢎꢙ ꢏ.ꢏꢏꢚꢙ

ꢀꢁꢀꢅꢆ ꢁꢐ ꢍ ꢆꢅꢛꢄRꢒ ꢜꢓꢀꢖ ꢊꢝꢞ ꢗꢟ ꢁꢕ ꢀꢖꢄ

ꢁꢟꢀꢄR ꢆꢅꢛꢄRꢒ ꢅꢕꢔ ꢊꢝꢞ ꢗꢟ ꢁꢕ ꢀꢖꢄ ꢓꢕꢕꢄR

ꢆꢅꢛꢄRꢒ

ꢀꢁꢂ ꢃꢄꢀꢅꢆ

ꢊꢋꢉ ꢃꢄꢀꢅꢆ

ꢇꢈꢉ ꢃꢄꢀꢅꢆ

ꢌꢁꢀꢀꢁꢃ ꢃꢄꢀꢅꢆ

ꢍꢎꢊꢏ ꢐꢎꢊ

Figure 12. 4-Layer PCB Layout of Rx Coil

Rev. G

22

For more information www.analog.com

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

LTC4120 Evaluation Kits

Alternative component values can be chosen by following

the design procedure outlined below.

Resonant Receiver Tuning: L , C2S, C2P

R

The tuned circuit resonance of the receiver, f , is determined

by the selection of L and C2S + C2P. Selec^Tt the capacitors

R

Resonant Transmitter Tuning: L , C

X

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 ≅

O

X

T

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

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

R

X

As in the case of the transmitter, multiple parallel capaci-

tors may need to be used to obtain the optimum value.

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

to 15% higher than the tuned resona^Dnce, keeping the

value of C2P below 30nF to limit power dissipation in

the DHC pin:

Having selected a transmitter inductor, L , the transmitter

X

capacitor should be selected to obtain a resonant

frequency of 130kHz. Due to limited selection of standard

values, several standard value capacitors may need to be

used in parallel to obtain the correct value for f :

O

1

f ≅

D

1

2 • π • L • C2S

f ≅

= 130kHz

R

O

2 • π • L • C

X

Alternative Transmitter Options

The transmitter inductor and capacitor, L and C , sup-

X

port a large circulating current. Series resistance in the

inductor is a source of loss and should be kept to a

minimum for optimal efficiency. Likewise the transmitter

capacitor(s), C , must support large ripple currents and

must be select^Xed with adequate voltage rating and low

dissipation factors.

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 precise 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,

Rev. G

23

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

the operating frequency of the basic transmitter can vary

with component selection.

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 the LTC4120 minimum, t_MIN(ON). This minimum

duty cycle 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 section. If the on-time is driven below

LTC4120 customers can also choose more advanced

transmitter options such as the LTC4125. With addi-

tional features such as: foreign metal detection; optimum

power search and AutoResonant™ operating frequency.

For more information on advanced transmitter options

refer to the Wireless Power Users Guide.

t

, the charge current and battery voltage remain

MIN(ON)

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.

Maximum Battery Power Considerations

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:

V

LOWBAT

V

=

IN(MAX)

f

• t

OSC MIN(ON)

maximum battery charge current, I

, that may be

, can be cal-

EFF

CHG(MAX)

where V

, is the lowest battery voltage where the

programmed for a given float voltage, V

LOWBAT

switcher is enabled.

FLOAT

culated based on the charger efficiency, η , as:

Exceeding the minimum on-time constraint does not

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

be of critical importance in most cases and high switch-

ing frequencies may be used in the design without any

fear of severe consequences. As the sections on Inductor

Selection and Capacitor Selection show, high switching

frequencies allow the use of smaller board components,

thus reducing the footprint of the applications circuit.

η

• 2W

EFF

I

≤

CHG(MAX)

V

FLOAT

The charger efficiency, η_EFF, depends on the operating

conditions and may be estimated using the Buck Efficiency

curve in the Typical Performance Characteristics. Do not

select a charge current greater than this limit when select-

ing R

.

PROG

Fixed-frequency operation may also be influenced by drop-

out and Burst Mode operation as discussed previously.

Input Voltage and Minimum On-Time

The LTC4120 can operate from input voltages up to 40V.

The LTC4120 maintains constant frequency operation

under most operating conditions. Under certain situa-

tions 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

Switching Inductor Selection: L

SW

The primary criterion for switching inductor value selec-

tion 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,

I_L(PEAK). The peak value of the inductor current is the sum

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

CHG

top switch is related to the duty cycle (V /V ) and the

BAT IN

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

L

switching frequency, f

in Hz:

OSC

also remain below the current limit of the LTC4120, I

:

PEAK

V

BAT

∆I

t

=

L

ON

I

= I

+

< I

PEAK

L(PEAK)

CHG

f

• V

IN

OSC

2

Rev. G

24

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

The current limit of the LTC4120, I_PEAK, is at least 585mA

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

Bulk capacitance is a function of the desired input ripple

voltage (∆V ), and follows the relation:

IN

illustrated in graph R

Current Limit vs Temperature,

SNS

V

BAT

I

in the Typical Performance Characteristics.

CHG

V

IN

C

=

µF

( )

IN(BULK)

For a given input and battery voltage, the inductor value

and switching frequency determines the peak-to-peak rip-

ple current amplitude according to the following formula:

∆V

IN

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

IN

mended. 10µF is typically adequate for most charger

V – V

• V

BAT

(

)

IN

BAT

applications, with a voltage rating of 40V.

∆I =

L

f

• V • L

IN

SW

OSC

Reverse Blocking

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

to 40% of the programmed charge current, I_CHG. To obtain

a ripple current in this range, select an inductor value

using the nearest standard inductance value available that

obeys the following formula:

When a fully charged battery is suddenly applied to the

BAT pin, a large in-rush current charges the C capaci-

IN

tor through the body diode of the LTC4120 topside power

switch. While the amplitude of this current can exceed sev-

eral 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 bat-

V

– V

• V

(

)

IN(MAX)

FLOAT

L

≥

SW

f

• V

• 30% •I

(

)

IN(MAX)

OSC

CHG

Then select an inductor with a saturation current rating at

a value greater than I

.

tery drain current due to any load placed at V . As shown

L(PEAK)

IN

in Figure 15, the PFET body diode serves as the blocking

component since CHRG is high impedance when the bat-

tery 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 a reverse breakdown voltage equal to the pro-

grammed float 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_INpin. This supply provides large switched

currents, so a high quality, low ESR decoupling capaci-

tor is recommended to minimize voltage glitches at V .

IN

ꢑ.ꢒꢒꢓꢔ

ꢝ

ꢙꢈ

CHRG

ꢙꢈ

ꢁꢄꢃ

ꢌꢍꢊꢋ

ꢉꢉꢎꢋ

ꢖ

ꢄꢅ

Rꢜꢈ

ꢄꢅ

ꢆꢇGꢄꢈꢄ

ꢁꢂꢃ

ꢑꢒ.ꢒꢓ

ꢖꢃꢆꢑꢌꢉꢍ

ꢑ.ꢕꢊꢋ

ꢉꢉꢊꢋ

ꢀ

ꢑꢕꢍꢓ

ꢖꢗꢘꢙꢚꢎ

ꢄꢙꢉꢞꢑꢞꢛꢄ

ꢙꢈꢃꢝ

ꢆꢆ

ꢉ.ꢉꢊꢋ

R

ꢋꢁꢌ

ꢏRꢐG

ꢋꢁ

R

ꢋꢁꢉ

ꢏRꢐG

ꢋꢁG

Gꢈꢛ

ꢑꢌꢉꢍ ꢋꢌꢟ

ꢔꢂꢛꢛ ꢑ.ꢒꢒꢓ ꢅꢇꢠꢈ ꢡꢂꢢ ꢁꢂꢃ ꢝꢐꢖꢃꢂGꢠ ꢂꢏꢏRꢐꢂꢆꢇꢠꢄ ꢣꢟꢤ ꢐꢋ ꢝGꢄ ꢖꢙꢡꢙꢃ ꢋꢐR ꢄꢗꢉꢞꢑꢞ.

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

Rev. G

25

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

BAT Capacitor and Output Ripple: C

Calculating Power Dissipation

BAT

The LTC4120 charger output requires bypass capaci-

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

capacitor is required for all applications. In systems where

the battery can be disconnected from the charger out-

put, additional bypass capacitance may be desired. In this

type of application, excessive ripple and/or low ampli-

tude oscillations can occur without additional output bulk

capacitance. For optimum stability, the additional bulk

capacitance should also have a small amount of ESR. For

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

capacitor (chip tantalum or organic semiconductor capac-

itors 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

temperature is not exceeded under all operating condi-

tions. The thermal resistance of the LTC4120 package

(θ_JA) is 54°C/W; provided that the exposed pad is sol-

dered to sufficient 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

•I

SNS CHG

V

BAT

2

•

•I

CHG

DS(ON)(TOP)

DS(ON)(BOT)

V

IN

voltage rating of all capacitors applied to C must meet

BAT

⎛

⎞

V

BAT

2

+R

• 1–

•I

CHG

or exceed the battery float voltage.

⎜

⎟

V

⎝

⎠

IN

Boost Supply Capacitor: C

BST

During trickle charge (V_BAT< V_TRKL) the power dissipation

may be significant as I is typically 10mA, however

The BOOST pin provides a bootstrapped supply rail that

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

age of the BOOST pin is internally generated from INTV

TRKL

during normal charging the I

term is zero.

TRKL

CC

The junction temperature can be estimated using the fol-

lowing formula:

whenever the SW pin pulls low. This provides a floating

voltage of INTV_CCabove SW that is held by a capacitor tied

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

T = T + P • θ

JA

J

A

D

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

BST

where T is the ambient operating temperature.

A

INTV Supply and Capacitor: C

Significant power is also consumed in the transmitter

electronics. The large AC voltage generated across the

L_Xand C_Xtank results in power being dissipated in the DC

CC

INTVCC

Power for the top and bottom gate drivers and most other

internal circuitry is derived from the INTV pin. A low

CC

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

X

ESR ceramic capacitor of 2.2µF is required on the INTV

CC

The large induced magnetic field in the L coil may also

X

pin. The INTV supply has a relatively low current limit

CC

induce heating in nearby metallic objects.

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

CC

reduce power dissipation. Do not use the INTV voltage

CC

PCB Layout

to supply power for any external circuitry apart from the

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

NTCBIAS network. When the RUN pin is above V the

EN

INTV supply is enabled, and when INTV rises above

CC

INTVCC

CC

UV

the charger is enabled.

Rev. G

26

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

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

circuit is described. Then consider the design for the char-

ger 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 discontinu-

ous conduction; where switching noise increases.

Advanced transmitters using LTC4125 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

traces possible and a via connection to the GND plane

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:

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 =

= 127kHz

T

2 • π • LR • (C2P + C2S)

5. Route analog ground (RUN ground and INTV_CCcapac-

itor ground) as a separate trace back to the LTC4120

GND pin before connecting to any other ground.

In this design example, the de-tuned resonant frequency

is:

1

f =

= 142kHz

D

6. Place the INTV_CCcapacitor as close as possible to the

2 • π • LR • C2S

INTV pin with a via connection to the GND plane.

CC

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

D

T

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.

higher level gives more control range but results in more

power dissipation.

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

from the transmitter coil, L = 5µH.

X

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.

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

Rev. G

27

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

4.7nF and 1.8nF capacitors in parallel. All of the capacitors

should be selected with 5% or better tolerance.

considered for determining the on-time and selecting the

1.5MHz operating frequency.

5V

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

Schottky diodes.

t

=

= 476ns > t

MIN(ON)

ON

1.5MHz • 17V

Now consider the design circuit for the LTC4120 charger

Now the switching inductor value is 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:

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

,

FB1 FB2

is found using standard 1% values:

8.2V • 588k

R

=

≅ 2.00M

FB1

FB2

2.4V

2.00M • 588k

2.00M – 588k

17V – 8.2V • 8.2V

(

)

L3 >

= 48µH

1.5MHz • 17V • 30% • 200mA

(

)

≅ 825k

56µH is the next standard inductor value that is greater than

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

With these resistors, and including the resistance of the

FBG pin, the battery float voltage is 8.212V.

ripple current at the input open-circuit voltage, V

.

IN(OC)

V_IN(OC)is estimated based on the transmitter design in

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

With an 8.2V float voltage the maximum charge current

available is limited by the maximum power available from

the RCPT at η = 85% charger efficiency:

EFF

V

IN(OC)

V

IN(OC)

= k • n • π • V

IN(TX)

= 0.37 • 3 • 3.14 • 5V = 34.9V

85% • 2W

I

≤

= 207mA

CHG(MAX)

8.2V

34.9V – 8.2V • 8.2V

(

)

∆I =

= 75mA

L

1.5MHz • 56µH • 34.9V

A charge current of 200mA is achieved by selecting a

standard 1% R resistor of:

PROG

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

h

• V

PROG

R

=

= 6.04k

∆I

PROG

L

I

= I

+

= 237mA

CHG

L(PEAK)

CHG

2

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 an inductor with a saturation current rating greater

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

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 •

The maximum loaded input voltage is used to select

the operating frequency and influences the value of the

switching inductor. The saturation current rating of the

switching inductor is selected based on the worst case

conditions at the maximum open-circuit voltage.

17V

∆V =

= 10mV

IN

10µF

And select 6V rated capacitors for C_INTVCC= 2.2µF,

C

= 22nF, and C = 22µF. Optionally add diode

BOOST

BAT

D6, a 1W, 39V Zener diode if the coupling from trans-

mitter to receiver coils is not well enough controlled to

A typical 2-cell Li-Ion battery pack engages pack pro-

tection for V

less than 5V, this is the lowest voltage

BAT

ensure that V remains below 39V when the battery is

IN

fully charged.

Rev. G

28

For more information www.analog.com

LTC4120/LTC4120-4.2

APPLICATIONS INFORMATION

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

2

P = 20V • 5mA + 0.3Ω• 0.2A

D

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

8.2V

20V

2

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

IN

+0.8Ω•

• 0.2A

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, where the switching charge current is 20mA at

⎝

This dissipated power results in a junction temperature

rise of 6°C over ambient.

V

BAT

= 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

2

+0.3Ω• 0.02A + 0.8Ω•

• 0.02A

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.

20V

⎛

⎞

⎟

⎠

3V

2

⎜

+0.5Ω• 1–

⎜

• 0.02A

20V

⎝

= 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

BAT

TRKL

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

ꢀꢁ

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

Figure 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

Rev. G

29

For more information www.analog.com

LTC4120/LTC4120-4.2

PACKAGE DESCRIPTION

UD Package

16-Lead Plastic QFN (3mm × 3mm)

ꢃReꢩeꢪeꢫꢬe ꢎꢑꢊ ꢇꢕG ꢭ ꢁꢓꢚꢁꢮꢚꢂꢢꢨꢂ Rev ꢯꢉ

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ꢀ.ꢁꢁ ±ꢁ.ꢂꢁ

ꢃꢄ ꢅꢆꢇꢈꢅꢉ

ꢂꢓ ꢂꢢ

ꢏꢆꢍ ꢂ

ꢑꢋꢏ ꢌꢐRꢘ

ꢃꢍꢋꢑꢈ ꢢꢉ

ꢁ.ꢄꢁ ±ꢁ.ꢂꢁ

ꢂ

ꢛ

ꢂ.ꢄꢓ ± ꢁ.ꢂꢁ

ꢃꢄꢚꢅꢆꢇꢈꢅꢉ

ꢃꢙꢇꢂꢢꢉ ꢧꢖꢍ ꢁꢨꢁꢄ

ꢁ.ꢛꢁꢁ Rꢈꢖ

ꢁ.ꢛꢓ ±ꢁ.ꢁꢓ

ꢁ.ꢁꢁ ꢦ ꢁ.ꢁꢓ

ꢁ.ꢓꢁ ꢞꢅꢊ

ꢍꢋꢑꢈꢔ

ꢂ. ꢇRꢐꢕꢆꢍG ꢊꢋꢍꢖꢋRꢌꢅ ꢑꢋ ꢗꢈꢇꢈꢊ ꢏꢐꢊꢘꢐGꢈ ꢋꢙꢑꢎꢆꢍꢈ ꢌꢋꢚꢛꢛꢁ ꢜꢐRꢆꢐꢑꢆꢋꢍ ꢃꢕꢈꢈꢇꢚꢛꢉ

ꢛ. ꢇRꢐꢕꢆꢍG ꢍꢋꢑ ꢑꢋ ꢅꢊꢐꢎꢈ

ꢀ. ꢐꢎꢎ ꢇꢆꢌꢈꢍꢅꢆꢋꢍꢅ ꢐRꢈ ꢆꢍ ꢌꢆꢎꢎꢆꢌꢈꢑꢈRꢅ

ꢄ. ꢇꢆꢌꢈꢍꢅꢆꢋꢍꢅ ꢋꢖ ꢈꢝꢏꢋꢅꢈꢇ ꢏꢐꢇ ꢋꢍ ꢞꢋꢑꢑꢋꢌ ꢋꢖ ꢏꢐꢊꢘꢐGꢈ ꢇꢋ ꢍꢋꢑ ꢆꢍꢊꢎꢙꢇꢈ

ꢌꢋꢎꢇ ꢖꢎꢐꢅꢒ. ꢌꢋꢎꢇ ꢖꢎꢐꢅꢒꢟ ꢆꢖ ꢏRꢈꢅꢈꢍꢑꢟ ꢅꢒꢐꢎꢎ ꢍꢋꢑ ꢈꢝꢊꢈꢈꢇ ꢁ.ꢂꢓꢠꢠ ꢋꢍ ꢐꢍꢡ ꢅꢆꢇꢈ

ꢓ. ꢈꢝꢏꢋꢅꢈꢇ ꢏꢐꢇ ꢅꢒꢐꢎꢎ ꢞꢈ ꢅꢋꢎꢇꢈR ꢏꢎꢐꢑꢈꢇ

ꢢ. ꢅꢒꢐꢇꢈꢇ ꢐRꢈꢐ ꢆꢅ ꢋꢍꢎꢡ ꢐ RꢈꢖꢈRꢈꢍꢊꢈ ꢖꢋR ꢏꢆꢍ ꢂ ꢎꢋꢊꢐꢑꢆꢋꢍ

ꢋꢍ ꢑꢒꢈ ꢑꢋꢏ ꢐꢍꢇ ꢞꢋꢑꢑꢋꢌ ꢋꢖ ꢏꢐꢊꢘꢐGꢈ

Rev. G

30

For more information www.analog.com

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.

G

11/18

Removed references to PowerByProxi.

12, 27

Rev. G

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog

Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications

31

subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

For more information www.analog.com

LTC4120/LTC4120-4.2

TYPICAL APPLICATION

ꢄꢉꢍ

ꢉꢒ.ꢖꢛꢆ

ꢐꢠ

ꢀꢁ

ꢀꢁꢂꢃ

ꢄꢄ

ꢆRꢇꢈ

ꢋꢌꢌꢍꢂ

ꢄ

ꢀꢁꢂꢃꢄꢄ

ꢄ

ꢀꢁ

ꢐꢟ

ꢐꢜ

ꢉ.ꢉꢝꢆ

ꢕꢓꢝꢆ

ꢐꢒ

ꢌꢑꢂ

ꢗ

ꢍꢎ

ꢄ

ꢋꢍꢂ

ꢉꢊ

ꢜꢒꢝꢏ

ꢗꢂꢄꢔꢕꢉꢓ

ꢉꢉꢛꢆ

CHRG

FAULT

Rꢅꢁ

ꢍꢎ

ꢤꢖꢔꢊ

ꢕꢓꢉꢊ

ꢄꢏGꢍꢁꢍ

ꢋꢡꢂ

ꢃ

ꢆꢗꢌꢡꢂ

ꢄꢉꢑ

ꢒ.ꢜꢛꢆ

ꢟ.ꢉꢃ

R

ꢄ

ꢉꢉꢝꢆ

ꢆꢋꢕ

ꢉ.ꢓꢓꢢ

ꢋꢡꢂ

ꢂꢪ ꢄꢀRꢄꢅꢀꢂRꢫ

ꢆꢋ

ꢐꢏꢄ

ꢕꢓꢊ

R

ꢆꢋꢉ

ꢟꢉꢜꢊ

ꢗ

ꢜꢝꢏ

ꢗ

R

ꢔꢖꢝꢏ

ꢞ

ꢆꢋG

ꢁꢂꢄ

Gꢁꢐ ꢑRꢌG

ꢣ

ꢂ

ꢗꢘꢙꢀꢚꢛ

R

ꢒ.ꢓꢔꢊ

ꢑRꢌG

ꢐꢜꢥ ꢐꢟꢥ ꢐꢠꢦ ꢐꢆꢗꢍꢉꢔꢓꢗ

ꢐꢒꢦ ꢢꢢꢍꢧꢜꢉꢜꢠꢋꢂꢕG ꢌR ꢐꢆꢗꢧꢤꢠ ꢨꢌꢑꢂꢩ

ꢦ ꢍꢗꢆꢒꢓꢉꢟꢙꢔꢖꢓꢢRꢜꢠ

ꢔꢕꢉꢓ ꢆꢕꢖ

ꢗ

ꢍꢎ

ꢂꢦ ꢁꢂꢏꢍꢓꢔꢓꢉꢁꢓꢉꢁꢕꢓꢓꢉꢆ

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

Rev. G

11/18

www.analog.com

 ANALOG DEVICES, INC. 2013-2018

32

For more information www.analog.com


型号：	LT3650-8.2
厂家：	ADI
描述：	Wireless Power Receiver and 400mA Buck Battery Charger 电池无线
文件：	总32页 (文件大小：1169K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT3650-8.2 [ADI]

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