FEATURES
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LTC3550-1
Dual Input USB/AC Adapter
Li-Ion Battery Charger with
600mA Buck Converter
DESCRIPTIO
The LTC
®
3550-1 is a standalone linear charger with a
600mA monolithic synchronous buck converter. It is
capable of charging a single-cell Li-Ion battery from both
wall adapter and USB inputs. The charger automatically
selects the appropriate power source for charging.
Internal thermal feedback regulates the battery charge
current to maintain a constant die temperature during high
power operation or high ambient temperature conditions.
The float voltage is fixed at 4.2V and the charge currents
are programmed with external resistors. The LTC3550-1
terminates the charge cycle when the charge current drops
below the programmed termination threshold after the
final float voltage is reached. With power applied to both
inputs, the LTC3550-1 can be put into shutdown mode
reducing the DCIN supply current to 20μA, the USBIN
supply current to 10μA, and the battery drain current to
less than 2μA.
The synchronous buck converter generates a fixed output
voltage of 1.875V. The switching frequency is internally
set at 1.5MHz, allowing the use of small surface mount
inductors and capacitors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. patents, includng 6522118, 6700364, 6580258, 5481178, 6304066,
6127815, 6498466, 6611131
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Charges Single-Cell Li-Ion Batteries from Wall
Adapter and USB Inputs
Automatic Input Power Detection and Selection
Charge Current Programmable Up to 950mA from
Wall Adapter Input
High Efficiency 600mA Synchronous DC/DC
Converter
No External MOSFET, Sense Resistor or Blocking
Diode Needed
Thermal Regulation Maximizes Charge Rate Without
Risk of Overheating*
Preset Charge Voltage with ±0.6% Accuracy
Programmable Charge Current Termination
1.5MHz Constant Frequency Operation (Step-Down
Converter)
18μA USB Suspend Current in Shutdown
Independent “Power Present” Status Outputs
Charge Status Output
Automatic Recharge
Available in a Thermally Enhanced, Low Profile
(0.75mm) 16-Lead (5mm x 3mm) DFN Package
APPLICATIO S
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Cellular Telephones
TYPICAL APPLICATIO
Complete Charge Cycle (1100mA Battery)
1000
800
600
400
200
0
4.2
4.0
3.8
3.6
3.4
5.0
2.5
0
–2.5
0
0.5
1.0
2.0
1.5
TIME (HR)
2.5
3.0
35501f
3550-1 TA02
Dual Input Battery Charger and DC/DC Converter
LTC3550-1
SW
RUN
DCIN
USBIN
1µF
2k
1%
1µF
1.24k
1%
IUSB
IDC
V
OUT
V
CC
BAT
ITERM
GND
800mA (WALL)
500mA (USB)
4.7µF
2k
1%
2.2µH
C
OUT
10µF
CER
V
OUT
1.875V
600mA
WALL
ADAPTER
USB
PORT
BATTERY
CHARGE
VOLTAGE (V) CURRENT (mA)
+
4.2V
SINGLE-CELL
Li-Ion BATTERY
3550-1 TA01
DCIN
VOLTAGE (V)
U
U
U
CONSTANT VOLTAGE
USBIN = 5V
T
A
= 25°C
R
IDC
= 1.25k
R
IUSB
= 2k
1
LTC3550-1
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
USBIN
IUSB
ITERM
PWR
CHRG
V
OUT
V
CC
GND
1
2
3
4
5
6
7
8
17
16 DCIN
15 BAT
14 IDC
13 USBPWR
12 ENABLE
11 RUN
10 SW
9
GND
DCIN, USBIN .............................................. –0.3V to 10V
ENABLE,
⎯
C
⎯
H
⎯
R
⎯
G,
⎯
P
⎯
W
⎯
R, USBPWR ............... –0.3V to 10V
BAT, IDC, IUSB, ITERM ................................ –0.3V to 7V
V
CC
............................................................... –0.3V to 6V
RUN, V
OUT
..................................................–0.3V to V
CC
SW (DC)........................................–0.3V to (V
CC
+ 0.3V)
DCIN Pin Current (Note 2) ..........................................1A
USBIN Pin Current (Note 2) .................................700mA
BAT Pin Current (Note 2) ............................................1A
P-Channel SW Source Current (DC).....................800mA
N-Channel SW Source Current (DC) ....................800mA
Peak SW Sink and Source Current ...........................1.3A
Operating Temperature Range (Note 3) ... –40°C to 85°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range................... –65°C to 125°C
DHC PACKAGE
16-LEAD (5mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 40°C (Note 4)
EXPOSED PAD IS GROUND (PIN 17)
MUST BE SOLDERED TO PCB
ORDER PART NUMBER
LTC3550EDHC-1
PART MARKING
35501
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
DCIN
V
USBIN
V
CC
V
ENABLE
R
ENABLE
V
RUN
I
RUN
V
⎯
C
⎯
H
⎯
R
⎯
G
V
⎯
P
⎯
W
⎯
R
V
USBPWR
V
UVDC
V
UVUSB
PARAMETER
Wall Adapter Input Supply Voltage
USB Port Input Supply Voltage
Buck Regulator Input Supply Voltage
ENABLE Input Threshold Voltage
ENABLE Pulldown Resistance
RUN Threshold Voltage
RUN Leakage Current
⎯
C
⎯
H
⎯
R
⎯
G Output Low Voltage
⎯
PW
⎯
R Output Low Voltage
⎯
USBPWR Output Low Voltage
DCIN Undervoltage Lockout Voltage
USBIN Undervoltage Lockout Voltage
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DCIN
= 5V, V
USBIN
= 5V, V
CC
= 3.6V unless otherwise noted.
CONDITIONS
●
●
●
MIN
4.3
4.3
2.5
0.4
1.2
●
●
TYP
MAX
8
8
5.5
UNITS
V
V
V
V
MΩ
V
µA
V
V
V
V
mV
V
mV
35501f
0.7
2
1
±0.01
0.35
0.35
0.35
1.0
5
1.5
±1
0.6
0.6
0.6
4.3
4.1
0.3
I
⎯
C
⎯
H
⎯
R
⎯
G
= 5mA
I
⎯
P
⎯
W
⎯
R
= 5mA
I
USBPWR
= 200µA
From Low to High
Hysteresis
From Low to High
Hysteresis
4.0
3.8
4.15
200
3.95
200
2
U
W
U
U
W W
W
LTC3550-1
ELECTRICAL CHARACTERISTICS
SYMBOL
V
ASD-DC
V
ASD-USB
Battery Charger
I
DCIN
DCIN Supply Current
Charge Mode (Note 5)
Standby Mode
Shutdown Mode
USBIN Supply Current
Charge Mode (Note 6)
Standby Mode
Shutdown Mode
Shutdown Mode
Regulated Output (Float) Voltage
BAT Pin Current
Constant-Current Mode
Constant-Current Mode
Constant-Current Mode
Standby Mode
Shutdown Mode
Sleep Mode
IDC Pin Regulated Voltage
IUSB Pin Regulated Voltage
Charge Current Termination Threshold
R
IDC
= 10k
Charge Terminated
ENABLE = 5V
R
IUSB
= 10k, V
DCIN
= 0V
Charge Terminated
V
DCIN
= 0V, ENABLE = 0V
V
DCIN
> V
USBIN
I
BAT
= 1mA
I
BAT
= 1mA, 0°C < T
A
< 85°C
R
IDC
= 1.25k
R
IUSB
= 2.1k
R
IDC
= 10k or R
IUSB
= 10k
Charge Terminated
Charger Disabled
DCIN = 0V, USBIN = 0V
Constant-Current Mode
Constant-Current Mode
R
ITERM
= 1k
R
ITERM
= 2k
R
ITERM
= 10k
R
ITERM
= 20k
V
FLOAT
– V
RECHRG
, 0°C < T
A
< 85°C
V
BAT
from High to Low
I
BAT
Drops Below Termination Threshold
I
BAT
= 10% to 90% Full-Scale
●
●
●
●
●
●
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DCIN
= 5V, V
USBIN
= 5V, V
CC
= 3.6V unless otherwise noted.
PARAMETER
CONDITIONS
MIN
140
20
140
20
TYP
180
50
180
50
MAX
220
80
220
80
UNITS
mV
mV
mV
mV
V
DCIN
– V
BAT
Lockout Threshold Voltage V
DCIN
from Low to High, V
BAT
= 4.2V
V
DCIN
from High to Low, V
BAT
= 4.2V
V
USBIN
– V
BAT
Lockout Threshold
Voltage
V
USBIN
from Low to High, V
BAT
= 4.2V
V
USBIN
from High to Low, V
BAT
= 4.2V
250
50
20
250
50
18
10
4.175
4.158
760
450
93
4.2
4.2
800
476
100
–3
–1
±1
1.0
1.0
100
50
10
5
100
6
1.5
250
400
550
105
800
100
40
800
100
36
20
4.225
4.242
840
500
107
–6
–2
±2
1.05
1.05
110
55
11.5
6
135
9
2.2
325
µA
µA
µA
µA
µA
µA
µA
V
V
mA
mA
mA
µA
µA
µA
V
V
mA
mA
mA
mA
mV
ms
ms
µs
mΩ
mΩ
°C
I
USBIN
●
●
V
FLOAT
I
BAT
V
IDC
V
IUSB
I
TERMINATE
0.95
0.95
90
45
8.5
4
65
3
0.8
175
ΔV
RECHRG
t
RECHRG
t
TERMINATE
t
SS
R
ON-DC
R
ON-USB
T
LIM
Switching Regulator
V
OUT
ΔV
OUT
I
PK
V
LOADREG
I
S
Recharge Battery Threshold Voltage
Recharge Comparator Filter Time
Termination Comparator Filter Time
Soft-Start Time
Power FET On-Resistance (Between
DCIN and BAT)
Power FET On-Resistance (Between
USBIN and BAT)
Junction Temperature in Constant-
Temperature Mode
Regulated Output Voltage
Output Voltage Line Regulation
Peak Inductor Current
Output Voltage Load Regulation
Input DC Bias Current
Active Mode
Sleep Mode
Shutdown
I
OUT
= 100mA
V
CC
= 3V, V
OUT
= 1.7V
(Note 7)
V
OUT
= 1.7V, I
LOAD
= 0A
V
OUT
= 1.94V, I
LOAD
= 0A
V
RUN
= 0V, V
CC
= 5.5V
●
●
1.819
0.75
1.875
0.04
1
0.5
300
20
0.1
1.931
0.4
1.25
V
%/V
A
%
400
35
1
µA
µA
µA
35501f
3
LTC3550-1
ELECTRICAL CHARACTERISTICS
SYMBOL
f
OSC
R
PFET
R
NFET
I
LSW
PARAMETER
Oscillator Frequency
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
SW Leakage Current
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DCIN
= 5V, V
USBIN
= 5V, V
CC
= 3.6V unless otherwise noted.
CONDITIONS
V
OUT
= 100%
V
OUT
= 0V
MIN
1.2
TYP
1.5
210
0.4
0.35
0.01
±1
MAX
1.8
UNITS
MHz
kHz
Ω
Ω
µA
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 2:
Guaranteed by long term current density limitations.
Note 3:
The LTC3550E-1 is guaranteed to meet the performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 4:
Failure to solder the exposed backside of the package to the PC
board will result in a thermal resistance much higher than 40°C/W. See
Thermal Considerations.
Note 5:
Supply Current includes IDC and ITERM pin current (approx-
imately 100μA each) but does not include any current delivered to the
battery through the BAT pin (approximately 100mA).
Note 6:
Supply Current includes IUSB and ITERM pin current (approx-
imately 100μA each) but does not include any current delivered to the
battery through the BAT pin (approximately 100mA).
Note 7:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
35501f
4
LTC3550-1
TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Charger Output (Float)
Voltage vs Charge Current
4.26
4.24
4.22
V
FLOAT
(V)
V
FLOAT
(V)
4.20
4.18
4.16
4.14
4.12
4.10
0
100 200 300 400 500 600 700 800
CHARGE CURRENT (mA)
3550-1 G01
V
DCIN
= V
USBIN
= 5V
4.215
4.210
4.205
4.200
4.195
4.190
4.185
4.180
–50
V
IDC
(V)
R
IDC
= R
IUSB
= 2k
R
IDC
= 1.25k
IUSB Pin Voltage vs Temperature
(Constant-Current Mode)
1.008
1.006
1.004
V
IUSB
(V)
I
BAT
(mA)
1.002
V
USBIN
= 8V
1.000
0.998
0.996
0.994
0.992
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
V
USBIN
= 4.3V
900
800
700
600
500
400
300
200
100
0
I
BAT
(mA)
⎯
PW
⎯
R Pin I-V Curve
⎯
35
V
DCIN
= V
USBIN
= 5V
30
25
I
PWR
(mA)
20
15
10
5
0
0
1
2
4
3
V
PWR
(V)
5
6
7
T
A
= – 40°C
T
A
= 25°C
I
CHRG
(mA)
T
A
= 90°C
35
30
25
20
15
10
5
0
I
USBPWR
(mA)
U W
3550-1 G04
T
A
= 25°C, unless otherwise noted.
IDC Pin Voltage vs Temperature
(Constant-Current Mode)
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
V
DCIN
= 4.3V
V
DCIN
= 8V
Regulated Charger Output (Float)
Voltage vs Temperature
4.220
V
DCIN
= V
USBIN
= 5V
–25
0
25
50
TEMPERATURE (°C)
75
100
0.992
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
3550-1 G02
3550-1 G03
Charge Current vs IDC Pin Voltage
V
DCIN
= 5V
R
IDC
= 1.25k
900
800
700
600
R
IDC
= 2k
500
400
300
200
R
IDC
= 10k
100
0
0
0.2
0.4
0.6
0.8
V
IDC
(V)
1.0
1.2
Charge Current
vs IUSB Pin Voltage
V
USBIN
= 5V
R
IUSB
= 1.25k
R
IUSB
= 2k
R
IUSB
= 10k
0
0.2
0.4
0.6
0.8
V
IUSB
(V)
1.0
1.2
3550-1 G05
3550-1 G06
⎯
C
⎯
H
⎯
R
⎯
G Pin I-V Curve
V
DCIN
= V
USBIN
= 5V
6
T
A
= – 40°C
5
T
A
= 25°C
T
A
= 90°C
4
3
2
1
0
USBPWR Pin I-V Curve
V
DCIN
= 5V
V
USBIN
= 0V
T
A
= – 40°C
T
A
= 25°C
T
A
= 90°C
0
1
2
4
3
V
CHRG
(V)
5
6
7
0
1
2
4
3
5
V
USBPWR
(V)
6
7
3550-1 G07
3550-1 G08
3550-1 G09
35501f
5
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