LT3650-8.4 [ADI]
Wireless Power Receiver and 400mA Buck Battery Charger;型号: | LT3650-8.4 |
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 |
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
n
Fixed 4.2V Float Voltage Option (LTC4120-4.2)
50mA to 400mA Charge Current Programmed with a
Single Resistor
n
n
n
n
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
ꢔꢞ.ꢟꢝꢆ
ꢋꢊꢊ
ꢒꢒꢒ
ꢕꢗꢙ
ꢕꢊꢊ
ꢔꢒꢒ
ꢗꢙ
ꢋꢊ
ꢒꢓ
ꢒꢊ
ꢕꢓ
ꢁꢂ
Rꢉꢂ
ꢁꢂꢃꢄ
ꢅꢅ
ꢆRꢇꢈ
ꢊꢋꢋꢌꢃ
ꢄ
ꢃꢎꢂRGꢏ
ꢚꢂꢍ
ꢔ.ꢔꢕꢆ
ꢔꢔꢝꢆ ꢐꢐꢕꢎ
ꢒꢑꢕꢆ
ꢌ
ꢄꢅ
ꢙꢃꢅꢖꢒꢔꢑ
ꢞ.ꢠꢝꢆ
ꢖꢟꢕꢎ
ꢌꢍ
ꢅꢛꢑ
ꢃꢡ ꢅꢁRꢅꢉꢁꢃRꢢ
ꢠꢕꢎ
ꢏꢎꢅ
ꢅꢎGꢌꢂꢌ
ꢂꢃꢅ
ꢃꢎꢂRGꢄꢅG
FAULT
CHRG
ꢊꢗꢃ
ꢕꢊ
ꢔꢓ
ꢔꢊ
ꢒ.ꢑꢒꢤ
ꢒ.ꢐꢠꢤ
ꢀ
ꢙꢚꢛꢁꢜꢝ
ꢖ.ꢔꢄ
ꢃ
ꢃꢎꢂRGꢄꢅG
ꢆꢊ
Gꢂꢏ ꢣRꢋG ꢆꢊG
ꢐ.ꢑꢒꢓ
ꢔꢔꢕꢆ
ꢊ
ꢊ.ꢋ ꢊ.ꢗ
ꢊ.ꢘ ꢔ.ꢊ ꢔ.ꢕ
ꢀꢁꢂꢃꢄꢅG ꢆꢇꢈꢉ
ꢔ.ꢋ
ꢔ.ꢗ ꢔ.ꢘ
ꢖꢒꢔꢑ ꢃꢗꢑꢒꢘ
ꢋꢔꢕꢊ ꢑꢂꢊꢔꢖ
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
, I .................................................. 5mA
SW
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
ꢇꢈꢉ ꢊꢋꢌꢍ
ꢇꢈꢉ ꢊꢋꢌꢍ
ꢀꢁ ꢀꢂ ꢀꢃ ꢀꢄ
ꢀꢁ ꢀꢂ ꢀꢃ ꢀꢄ
ꢋꢎꢇꢊ
ꢀ
ꢠ
ꢄ
ꢃ
ꢀꢠꢎꢇꢒ
ꢀꢀꢛꢤG
ꢋꢎꢇꢊ
ꢀ
ꢠ
ꢄ
ꢃ
ꢀꢠ ꢎꢇꢒ
ꢀꢀ ꢎꢒ
ꢒꢒ
ꢒꢒ
ꢤꢈꢈꢙꢇ
ꢋꢎ
ꢤꢈꢈꢙꢇ
ꢋꢎ
ꢀꢅ
Gꢎꢏ
ꢀꢅ
Gꢎꢏ
ꢛꢤ
ꢤꢑꢇꢙꢎꢙ
ꢀꢦ
ꢥ
ꢀꢦ
ꢥ
ꢙꢍ
ꢤꢑꢇ
ꢙꢍ
ꢤꢑꢇ
ꢂ
ꢁ
ꢅ
ꢆ
ꢂ
ꢁ
ꢅ
ꢆ
ꢐꢏ ꢉꢑꢒꢓꢑGꢌ
ꢀꢁꢔꢕꢌꢑꢏ ꢖꢄꢗꢗ × ꢄꢗꢗꢘ ꢉꢕꢑꢙꢇꢋꢒ ꢚꢛꢎ
ꢟ ꢀꢠꢂꢡꢒꢢ θ ꢟ ꢂꢃꢡꢒꢣꢍ
ꢐꢏ ꢉꢑꢒꢓꢑGꢌ
ꢀꢁꢔꢕꢌꢑꢏ ꢖꢄꢗꢗ × ꢄꢗꢗꢘ ꢉꢕꢑꢙꢇꢋꢒ ꢚꢛꢎ
ꢟ ꢀꢠꢂꢡꢒꢢ θ ꢟ ꢂꢃꢡꢒꢣꢍ
ꢇ
ꢇ
ꢜꢝꢑꢞ
ꢜꢝꢑꢞ
ꢜꢑ
ꢜꢑ
ꢌꢞꢉꢈꢙꢌꢏ ꢉꢑꢏ ꢖꢉꢋꢎ ꢀꢅꢘ ꢋꢙ Gꢎꢏꢢ ꢝꢐꢙꢇ ꢤꢌ ꢙꢈꢕꢏꢌRꢌꢏ ꢇꢈ ꢉꢒꢤ ꢇꢈ ꢈꢤꢇꢑꢋꢎ θ
ꢌꢞꢉꢈꢙꢌꢏ ꢉꢑꢏ ꢖꢉꢋꢎ ꢀꢅꢘ ꢋꢙ Gꢎꢏꢢ ꢝꢐꢙꢇ ꢤꢌ ꢙꢈꢕꢏꢌRꢌꢏ ꢇꢈ ꢉꢒꢤ ꢇꢈ ꢈꢤꢇꢑꢋꢎ θ
ꢜꢑ
ꢜꢑ
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
16-Lead (3mm × 3mm) Plastic QFN
16-Lead (3mm × 3mm) Plastic QFN
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–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 The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k,
VFB = 2.29V (LTC4120), VBATSNS = 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
l
130
220
100
LTC4120: V = 2.51V (Note 5),
LTC4120-4.2: V
60
µA
FB
= 4.4V
BATSNS
l
l
l
Disabled Mode (Note 3)
Shutdown Mode (Note 3)
37
20
80
70
40
µA
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
CC
IN
CC
BAT
Hysteresis
INTV Falling (Note 4)
mV
CC
Battery Charger
l
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
l
BAT Shutdown Current
Shutdown Mode (LTC4120) (Notes 3, 7, 8)
Shutdown Mode (LTC4120-4.2) (Notes 3, 7, 8)
1100 2000
nA
nA
10
1000
l
l
l
l
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
nA
µA
Ω
BATSNS
1100 2000
I
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
V
FB(REG)
l
l
V
4.188 4.200 4.212
V
V
FLOAT
CHG
4.148
4.227
l
l
I
R
PROG
R
PROG
= 3.01k
= 24.3k
383
45
402
50
421
55
mA
mA
V
V
V
Undervoltage Current Limit
V
V
V
Falling
12.0
–50
–92
988
V
mV
UVCL
IN
l
l
Battery Recharge Threshold
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 < V (LTC4120) (Note 5)
FB(REG)
TRKL_4.2
mA/mA
TRKL
FB
< V
< 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 The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k,
VFB = 2.29V (LTC4120), VBATSNS = 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
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
< V
(LTC4120) (Note 5),
TRKL_4.2
I
/10
CHG
TRKL
LOWBAT
LOWBAT
BAT FB
BATSNS
TRKL
< V
(LTC4120-4.2)
PROG Pin Servo Voltage in Switch Mode
Trickle Charge
V
V
< V , V < V
(LTC4120) (Note 5),
122
mV
LOWBAT
LOWBAT
BAT FB
TRKL
< V
< V
(LTC4120-4.2)
BATSNS
TRKL_4.2
l
l
V
V
Trickle Charge Threshold
Hysteresis
V
V
V
V
Rising (LTC4120) (Note 5)
Falling (LTC4120) (Note 5)
1.64
2.86
1.68
50
1.71
2.98
V
mV
TRKL
FB
FB
Trickle Charge Threshold
Hysteresis
Rising (LTC4120-4.2)
Falling (LTC4120-4.2)
2.91
88
V
TRKL_4.2
BATSNS
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
l
f
Switching Frequency
FREQ = INTV
FREQ = GND
1.0
0.5
1.5
0.75
2.0
1.0
MHz
MHz
OSC
CC
t
Minimum Controllable On-Time
Duty Cycle Maximum
(Note 9)
(Note 9)
120
ns
%
MIN(ON)
94
Top Switch R
I
I
= –100mA
0.8
0.5
750
Ω
DS(ON)
SW
SW
Bottom Switch R
= 100mA
Ω
DS(ON)
I
I
Peak Current Limit
Measured Across R
Series with R
with a 15µH Inductor in
SNS
(Note 9)
585
1250
mA
PEAK
SNS
l
l
Switch Pin Current (Note 8)
V
V
= Open-Circuit, V
= Open-Circuit, V
= 0V, V = 8.4V (LTC4120)
15
7
30
15
µA
µA
SW
IN
IN
RUN
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
l
l
Cold Temperature V /V
Fault
Fault
Rising V
Falling V
Threshold
Threshold
73
35.5
1
74
72
75
%INTVCC
%INTVCC
NTC INTVCC
NTC
NTC
Hot Temperature V /V
Falling V
Rising V
Threshold
Threshold
36.5
37.5
37.5 %INTVCC
%INTVCC
NTC INTVCC
NTC
NTC
NTC Disable Voltage
Falling V
Rising V
Threshold
Threshold
2
3
3
%INTVCC
%INTVCC
NTC
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 The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k,
VFB = 2.29V (LTC4120), VBATSNS = 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
l
V
V
Enable threshold
Hysteresis
V
V
V
V
Rising
Falling
= 40V
Falling
2.35
2.45
200
2.55
V
mV
µA
V
EN
RUN
RUN
RUN
RUN
Run Pin Input Current
Shutdown Threshold (Note 3)
Hysteresis
0.01
0.1
1.2
0.4
0.4
SD
220
mV
FREQ
l
l
FREQ Pin Input Low
FREQ Pin Input High
FREQ Pin Input Current
V
V
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 VFB(REG) vs Temperature
TA = 25°C, unless otherwise noted.
Typical VFLOAT vs Temperature
LTC4120-4.2
ꢍ.ꢋꢎ
ꢊ.ꢕꢌ
ꢊ.ꢕꢊ
ꢊ.ꢕꢖ
ꢊ.ꢕꢕ
ꢊ.ꢕꢋ
ꢊ.ꢕꢗ
ꢊ.ꢋꢐ
ꢊ.ꢋꢏ
ꢊ.ꢋꢎ
ꢊ.ꢋꢍ
ꢊ.ꢋꢌ
ꢋ ꢅꢛꢚꢀꢜ ꢀꢁꢜꢀꢁꢘ
ꢊ ꢅꢘꢙꢀꢚ ꢀꢁꢚꢀꢁꢛ
ꢍ.ꢋꢍ
ꢍ.ꢋꢕ
ꢝꢚGꢝ ꢞꢚꢂꢚꢀ
ꢘꢅꢀꢕ ꢐ
ꢜꢙGꢜ ꢓꢙꢂꢙꢀ
ꢆꢐꢉ
ꢆꢐꢉ
ꢆꢐꢉ
ꢆꢐꢉ
ꢛꢅꢀꢋ ꢑ
ꢑꢒꢆRꢁGꢉ
ꢒꢓꢔꢄꢀ
ꢍ.ꢋꢌ
ꢍ.ꢎꢔ
ꢍ.ꢎꢗ
ꢍ.ꢎꢓ
ꢘꢅꢀꢍ ꢐ
ꢘꢅꢀꢎ ꢐ
ꢘꢅꢀꢋ ꢐ
ꢛꢅꢀꢕ ꢑ
ꢒꢓꢔꢄꢀ
ꢑꢒꢆRꢁGꢉ
ꢑꢒꢆRꢁGꢉ
ꢑꢒꢆRꢁGꢉ
ꢛꢅꢀꢖ ꢑ
ꢒꢓꢔꢄꢀ
ꢛꢅꢀꢊ ꢑ
ꢒꢓꢔꢄꢀ
ꢞꢟꢠ ꢞꢚꢂꢚꢀ
ꢓꢔꢝ ꢓꢙꢂꢙꢀ
ꢘꢅꢀ ꢙ ꢘꢁꢐꢚꢈꢁ
ꢅꢛꢘꢁR ꢀꢁꢜꢀ
ꢍ.ꢎꢏ
ꢊꢋꢌ
ꢖ
ꢎꢖ ꢖꢌ ꢏꢖ ꢗꢌ ꢔꢖ ꢕꢕꢌ ꢕꢍꢖ
ꢊꢍꢖ ꢊꢕꢌ
ꢍꢌ
ꢌꢗ ꢋꢋꢗ ꢋꢕꢌ
ꢍꢌ ꢏꢗ ꢐꢌ
ꢞꢊꢗ ꢞꢕꢌ ꢞꢋꢗ
ꢌ
ꢕꢗ ꢖꢌ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢋꢕꢍꢌ Gꢌꢕ
ꢊꢋꢕꢗ Gꢕꢗ
IN Pin Standby/Sleep Current vs
Temperature
IN Pin Disabled/Shutdown Current
vs Temperature
ꢑꢌ
ꢋꢌ
ꢐꢌ
ꢕꢌ
ꢍꢐꢌ
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 ꢓꢔꢀꢘ
ꢖꢀꢄꢔꢗꢚꢛ ꢜRꢁꢝ ꢙ Gꢔꢗ
ꢖꢀꢄꢔꢗꢚꢛ ꢜRꢁꢝ ꢙ Gꢔꢗ
ꢖꢞꢁꢁꢃ
ꢈꢈ
ꢈꢈ
ꢍꢍꢎ ꢗꢍꢖꢄꢘꢙꢁꢗ
ꢍꢍꢎ ꢗꢍꢖꢄꢘꢙꢁꢗ
ꢖꢞꢁꢁꢃ
ꢒꢌ
ꢔꢌ
ꢌ
ꢍꢍꢎ ꢖꢗ
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 RSNS Current Limit
vs Temperature
ꢔ
ꢏꢌꢐ
ꢏꢌꢒ
ꢐꢐꢑꢌ
ꢐꢐꢌꢌ
ꢐꢌꢔꢌ
ꢐꢌꢓꢌ
ꢐꢌꢒꢌ
ꢐꢌꢑꢌ
ꢐꢌꢌꢌ
ꢕꢔꢌ
ꢗꢅꢀꢐ
ꢗꢅꢀꢑ
ꢗꢅꢀꢘ
ꢑ ꢅꢝꢍꢀꢗ ꢀꢁꢗꢀꢁꢚ
ꢞ
R
R
ꢟ ꢒ.ꢑꢞ
ꢟ ꢓ.ꢌꢓꢂ
ꢟ ꢓ.ꢖꢋꢂ
ꢎꢄꢀ
ꢠꢎꢑ
ꢠꢎꢓ
ꢐ
ꢕ
ꢍ
ꢍ
ꢗꢘꢁꢁꢃ
ꢗꢘꢁꢁꢃ
ꢏꢌꢌ
ꢍꢎꢎ
ꢍꢎꢓ
ꢍꢎꢑ
ꢍꢎꢔ
ꢎꢄꢀ
ꢎꢄꢀ
ꢋ
ꢒ
ꢖ
ꢑ
ꢓ
R
ꢃRꢞG
ꢚ ꢍ.ꢌꢒꢟ
ꢐ ꢅꢛꢕꢀꢠ ꢀꢁꢠꢀꢁꢜ
ꢘRꢁꢙ ꢚ Gꢛꢜ
ꢘRꢁꢙ ꢚ Gꢛꢜ
ꢘRꢁꢙ ꢚ ꢕꢛꢀꢝ
ꢘRꢁꢙ ꢚ ꢕꢛꢀꢝ
ꢍ
ꢍ
ꢗꢙꢅꢀꢚꢛꢜꢝ
ꢗꢙꢅꢀꢚꢛꢜꢝ
ꢎꢄꢀ
ꢎꢄꢀ
ꢕꢓꢌ
ꢈꢈ
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
ꢀꢁꢂꢃꢁRꢄꢀꢅRꢁ ꢆꢇꢈꢉ
ꢒꢐꢑꢌ Gꢌꢓ
ꢒꢓꢑꢌ Gꢌꢒ
ꢏꢒꢐꢌ Gꢌꢋ
Rev. G
6
For more information www.analog.com
LTC4120/LTC4120-4.2
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Frequency
BAT Pin Leakage Current/VBAT-VIN
vs Temperature
vs Temperature
Buck Efficiency vs Battery Current
ꢔꢙ
ꢕꢌꢌ
ꢖꢏ
ꢖꢇ
ꢐꢏ
ꢐꢇ
ꢎꢏ
ꢎꢇ
ꢔꢏ
ꢔꢇ
ꢏꢏ
ꢏꢇ
ꢐ
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
ꢘRꢁꢙ ꢚ ꢝꢛꢀꢞ
ꢈꢈ
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
ꢘRꢁꢙ ꢚ Gꢛꢜ
ꢙ
ꢖ ꢅꢒꢍꢀꢜ ꢀꢁꢜꢀꢁꢝ
ꢕ
ꢍ
ꢎꢄꢀ
ꢎꢄꢀ
ꢎꢄꢀ ꢍꢒ
ꢍ
ꢙ
ꢘ ꢔꢐꢜꢝꢞ ꢚꢙꢉꢒꢓꢏꢏꢏꢃꢟꢔꢐꢇꢠꢒRꢕ
ꢚꢛ
ꢖ
ꢐ
ꢐ
ꢑꢐ
ꢉRꢈꢡ ꢘ Gꢋꢢ
ꢘ ꢑ.ꢓꢗ
ꢑꢐ
ꢗ
ꢐ ꢅꢛꢝꢀꢕ ꢀꢁꢕꢀꢁꢜ
ꢎꢄꢀ ꢍꢒ
ꢁꢂꢃ
ꢌ
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,
VIN_RX vs Battery Current
Typical tMIN(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,
IBAT = 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
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
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
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
IN Pin Shutdown Current
IN Pin Standby Current vs VIN
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
ꢁꢂ
ꢎꢈꢋꢅ Gꢈꢍ
ꢈꢋꢌꢅ Gꢋꢊ
IN Pin Disabled Current
vs Input Voltage
IN Pin Switching Current vs Input
Voltage
UVCL: ICHARGE vs 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
ꢑꢊꢒ
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
ꢁꢂ
ꢁ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
ꢁꢂ
ꢁ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 batLtOeWryB.ADT ecouple 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 ILOWBAT. 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
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 ∆VDUVLO and 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 thisFBpGin 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 VIN(DHC), this pin is high impedance. When VIN is
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 VSD, the device is in shutdown
mode. When the voltage at the RUN pin rises above V ,
EN
the INTVCC LDO turns on. When the INTVCC LDO 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
L
R
SW
33µH
DUVLO
GND
CHGSNS
BAT
5
8
9
IN – 80mV
INTV
CC
+
–
V
IN(DHC)
DHC
DHC
6
R
SNS
0.3Ω
IN
IN
IN
I
C-EA
INTV
FREQ
TH
R
7
NOM
C
BAT
22µF
10k
IN
INTV
CC
INTV
+
CC
CC
FAULT
R
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
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
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. VIN(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
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
LX. 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
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 VIN(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 (LR, 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 RFB1||RFB2 close 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(eDtHuCn)ing the receiver
resonance away from the transmitter frequency fO, 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
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
PROG
I
I
=
=
the resistance of the FBG pin which serves as the ground
CHG
R
R
PROG
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
R
PROG
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
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 VFLOAT
V
R
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
1.01M
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 VFLOAT
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
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
1.02M
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/hPROG, 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 VUVCL
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 RBIAS resistor. 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 RBIAS resistor, or by
adding a desensitizing resistor, RADJ, or by a combination
of these measures as shown in Figure 7. For example, by
increasing RBIAS to 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 INTVCC to 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% (VRCHG or VRCHG_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
High
Low
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 (VIN-
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, fOSC, is programmed by connecting the FREQ pin to
either INTV or to GND to obtain a switching frequency
of 1.5MHz CoCr 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 tLhOeWbBaAtTtery 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
continuesLuOnWtiBlAtThe sensed battery voltage (sensed via
the feedback pin for the LTC4120) rises above the trickle
charge threshold, VTRKL. 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 cycleOs,StChe 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
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
X
V
≅ 2 • π • V
AC
DC
This generates a sinusoidal current in the transmit coil
with peak-to-peak amplitude:
M
k =
V
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
n
L
L
R
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 pXre-regulator DC/DC conRverter
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
L
B2
68µH
B1
68µH
D1
D4
C5
C
L
X
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 tOhe 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
X
X
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. SelecTt the capacitors
R
Resonant Transmitter Tuning: L , C
X
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
X
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 resonaDnce, 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
X
Alternative Transmitter Options
The transmitter inductor and capacitor, L and C , sup-
X
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 selectXed 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, tMIN(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, ηEFF, 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,
IL(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, IPEAK, is at least 585mA
(and at most 1250mA). The typical value of IPEAK is
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, ICHG. 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
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 VIN pin. 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
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
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 (CBAT). 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
(θJA) 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
+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 (VBAT < VTRKL) 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 INTVCC above 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
LX and CX tank 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
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 INTVCC capac-
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 INTVCC capacitor 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 LR to 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
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)
VIN(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
PROG
R
=
= 6.04k
∆I
PROG
L
I
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 CINTVCC = 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
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
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
C
: 760308100110
DR1, DR2, DR3: DFLS240L
TX
TX
FB1
: C3216C0G2A104J160AC
D : BZT52C13
C
4120 F16
: GRM188R72A104KA35D
M1: Si7308DN
DC1: CDBQR70
QR1: PMBT3904M
D
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
ꢁ.ꢤꢁ ±ꢁ.ꢁꢓ
ꢀ.ꢓꢁ ±ꢁ.ꢁꢓ
ꢛ.ꢂꢁ ±ꢁ.ꢁꢓ
ꢂ.ꢄꢓ ±ꢁ.ꢁꢓ
ꢃꢄ ꢅꢆꢇꢈꢅꢉ
ꢏꢐꢊꢘꢐGꢈ ꢋꢙꢑꢎꢆꢍꢈ
ꢁ.ꢛꢓ ±ꢁ.ꢁꢓ
ꢁ.ꢓꢁ ꢞꢅꢊ
Rꢈꢊꢋꢌꢌꢈꢍꢇꢈꢇ ꢅꢋꢎꢇꢈR ꢏꢐꢇ ꢏꢆꢑꢊꢒ ꢐꢍꢇ ꢇꢆꢌꢈꢍꢅꢆꢋꢍꢅ
ꢞꢋꢑꢑꢋꢌ ꢜꢆꢈꢕꢣꢈꢝꢏꢋꢅꢈꢇ ꢏꢐꢇ
ꢏꢆꢍ ꢂ ꢍꢋꢑꢊꢒ R ꢥ ꢁ.ꢛꢁ ꢑꢡꢏ
ꢋR ꢁ.ꢛꢓ × ꢄꢓ° ꢊꢒꢐꢌꢖꢈR
R ꢥ ꢁ.ꢂꢂꢓ
ꢑꢡꢏ
ꢁ.ꢤꢓ ±ꢁ.ꢁꢓ
ꢀ.ꢁꢁ ±ꢁ.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
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
20
20
20
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
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.
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
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
相关型号:
LT3650EDD-4.1#PBF
LT3650-4.X - High Voltage 2 Amp Monolithic Li-Ion Battery Charger; Package: DFN; Pins: 12; Temperature Range: -40°C to 85°C
Linear
LT3650EDD-8.2#PBF
LT3650-8.X - High Voltage 2 Amp Monolithic 2-Cell Li-Ion Battery Charger; Package: DFN; Pins: 12; Temperature Range: -40°C to 85°C
Linear
LT3650EDD-8.2#TRPBF
LT3650-8.X - High Voltage 2 Amp Monolithic 2-Cell Li-Ion Battery Charger; Package: DFN; Pins: 12; Temperature Range: -40°C to 85°C
Linear
LT3650EDD-8.4#PBF
LT3650-8.X - High Voltage 2 Amp Monolithic 2-Cell Li-Ion Battery Charger; Package: DFN; Pins: 12; Temperature Range: -40°C to 85°C
Linear
©2020 ICPDF网 联系我们和版权申明