FEATURES
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LTC3552-1
Standalone Linear Li-Ion
Battery Charger and Dual
Synchronous Buck Converter
DESCRIPTIO
The LTC
®
3552-1 is a complete constant-current/constant-
voltage linear charger and dual fixed output DC/DC con-
verter for single cell lithium-ion batteries. Its DFN package
and low external component count make the LTC3552-1
ideally suited for portable applications. Furthermore,
the LTC3552-1 is designed to work within USB power
specifications.
No external sense resistor or external blocking diode are
required due to the internal MOSFET architecture. The
charge voltage is fixed at 4.2V and the charge current is
programmed with a resistor. The charge cycle terminates
when the charge current drops below the programmed
termination threshold after the final float voltage is
reached. When the input supply (wall adapter or USB
supply) is removed, the LTC3552-1 enters a low current
state dropping the battery drain current to less than 2µA.
Thermal regulation maximizes charge rate without risk
of overheating.
The synchronous step-down switching regulators
generate fixed output voltages of 1.8V and 1.575V.
The switching frequency is set at 2.25MHz, allowing the
use of small surface mount inductors and capacitors.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6522118, 6700364, 5481178, 6580258, 6304066,
6127815, 6498466, 6611131.
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Programmable Charge Current Up to 950mA
Complete Linear Charger and Dual DC/DC
Regulator
Dual Fixed Outputs:
1.8V at 800mA
1.575V at 400mA
No MOSFET, Sense Resistor or Blocking Diode
Required
Thermal Regulation Maximizes Charge Rate
Without Risk of Overheating*
Charges Directly from a USB Port
Programmable Charge Current Termination
Preset 4.2V Charge Voltage with ±1% Accuracy
Charge Current Monitor Output for Gas Gauging*
Automatic Recharge
Charge Status Output
“Power Present” Output
Soft-Start Limits Inrush Current
Low Quiescent Current Buck Converter (40µA)
Current Mode Operation, Constant Frequency (2.25MHz)
Low Profile (5mm
×
3mm
×
0.75mm) DFN Package
APPLICATIO S
■
■
Cellular Telephones, PDAs, MP3 Players
Bluetooth Applications
TYPICAL APPLICATIO
Single Cell Li-Ion Battery Charger with
C/5 Termination and Dual DC/DC Converter
V
IN
4.5V TO
6.5V
V
IN
1µF
619Ω
1.24k
ITERM
PROG
CHRG
PWR
V
OUT2
1.575V/
400mA
C
OUT2
10µF
CER
4.7µH
EN
SW2
C
FF2
330pF
V
OUT2
V
FB2
GND
LTC3552-1
RUN1
RUN2
BAT
V
CC
2.2µH
SW1
V
OUT1
V
FB1
C
FF1
330pF
EFFICIENCY (%)
Efficiency Curve/
Power Loss of Regulators
100
95
90 V
OUT1
= 1.8V
V
OUT2
= 1.575V
100
POWER LOSS (mW)
1000
800mA
10µF
+
4.2V
1-CELL
Li-Ion
BATTERY
V
OUT1
1.8V/
800mA
C
OUT1
10µF
CER
35521 TA01
85
80
CHANNEL 1
75
70
65
60
1
CHANNEL 2
V
IN
= 3.6V
Burst Mode OPERATION
10
100
LOAD CURRENT (mA)
1
10
U
U
U
0.1
1000
35521 TAO1b
35521fa
1
LTC3552-1
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
ITERM
BAT
CHRG
RUN2
SW2
RUN1
V
OUT2
V
FB2
1
2
3
4
5
6
7
8
17
16 EN
15 PWR
14 V
IN
13 PROG
12 SW1
11 V
CC
10 V
OUT1
9
V
FB1
Input Supply Voltage (V
IN
) ......................... –0.3V to 10V
PROG, ITERM .................................. –0.3V to V
IN
+ 0.3V
BAT .............................................................. –0.3V to 7V
CHRG, PWR, EN ....................................... –0.3V to 10V
BAT Short-Circuit Duration............................Continuous
BAT Pin Current ..........................................................1A
PROG Pin Current ....................................................1mA
V
CC
Supply Voltage ...................................... –0.3V to 6V
V
OUT1
, V
OUT2
, RUN1,
RUN2 Voltages .............................–0.3V to V
CC
+0.3V
V
FB1
, V
FB2
........................................–0.3V to V
CC
+ 0.3V
SW1, SW2 Voltage ...........................–0.3V to V
CC
+ 0.3V
Ambient Operating Temperature
Range (Note 2) .................................... –40°C to 85°C
Maximum Junction Temperature (Note 8) ............ 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/W (Note 3)
EXPOSED PAD IS GROUND (PIN 17) MUST BE SOLDERED TO PCB
ORDER PART NUMBER
LTC3552EDHC-1
DHC PART MARKING
35521
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
Battery Charger
V
IN
I
IN
Input Supply Voltage
Input Supply Current
Charge Mode (Note 4)
Standby Mode
Shutdown Mode
Regulated Output (Float) Voltage
BAT Pin Current
PARAMETER
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
CC
= 3.6V unless otherwise noted.
CONDITIONS
●
MIN
4.25
TYP
MAX
8
UNITS
V
mA
µA
µA
µA
mA
mA
µA
µA
µA
V
mV
V
V
ΜΩ
mV
mV
mA
mA
35521fa
R
PROG
= 10k
Charge Terminated
EN = 5V, V
IN
< V
BAT
or V
IN
< V
UV
0°C ≤ T
A
≤ 85°C, 4.3V < V
IN
< 8V
R
PROG
= 10k, Current Mode
R
PROG
= 2k, Current Mode
Standby Mode, V
BAT
= 4.2V
Shutdown Mode (EN = 5V, V
IN
< V
BAT
or
V
IN
< V
UV
)
Sleep Mode, V
IN
= 0V
From V
IN
Low to High
●
●
●
0.4
200
25
4.158
4.2
100
500
–2.5
±1
±1
1
500
50
4.242
105
535
–6
±2
±2
3.92
300
1
5
140
50
110
22.5
V
FLOAT
I
BAT
●
●
●
92
465
V
UV
V
UVHYS
V
EN
(IL)
V
EN(IH)
R
EN
V
ASD
I
TERM
V
IN
Undervoltage Lockout Voltage
V
IN
Undervoltage Lockout Hysteresis
EN Pin Input Low Voltage
EN Pin Input High Voltage
EN Pin Pull-Down Resistor
V
IN
– V
BAT
Lockout Threshold Voltage
Charge Termination Current Threshold
●
●
●
●
●
3.7
150
0.4
1.2
70
5
3.8
200
0.7
0.7
2
100
30
100
20
V
IN
from Low to High
V
IN
from High to Low
R
TERM
= 1k
R
TERM
= 5k
●
●
90
17.5
2
U
W
U
U
W W
W
LTC3552-1
ELECTRICAL CHARACTERISTICS
SYMBOL
V
PROG
V
CHRG
V
PWR
ΔV
RECHRG
T
LIM
R
ON-CHRG
t
SS-CHRG
t
RECHRG
t
TERM
Switching Regulator
V
CC
V
OUT1
V
OUT2
ΔV
LINE_REG
ΔV
LOAD_REG
I
S
Operating Voltage Range for Converter
Output Voltage Feedback of Regulator 1
Output Voltage Feedback of Regulator 2
Reference Voltage Line Regulation
Output Voltage Load Regulation
Input DC Supply Current (Note 6)
Active Mode
Sleep Mode
Shutdown
Oscillator Frequency
Peak Switch Current Limit Regulator 1
Peak Switch Current Limit Regulator 2
0°C ≤ T
A
≤ 85°C (Note 5)
–40°C ≤ T
A
≤ 85°C (Note 5)
0°C ≤ T
A
≤ 85°C (Note 5)
–40°C ≤ T
A
≤ 85°C (Note 5)
V
CC
= 2.5V to 5.5V (Note 5)
(Note 5)
V
OUT1
= 1.5V, V
OUT2
= 1.3V
V
OUT1
= 1.89V, V
OUT2
= 1.65V
RUN = 0V, V
CC
= 5.5V
V
OUT1
= 1.8V, V
OUT2
= 1.575V
V
CC
= 3V, Duty Cycle < 35%
V
CC
= 3V, Duty Cycle < 35%
●
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
CC
= 3.6V unless otherwise noted.
PARAMETER
PROG Pin Voltage
CHRG Pin Output Low Voltage
PWR Pin Output Low Voltage
Recharge Battery Threshold Voltage
Junction Temperature in Constant-
Temperature Mode
Charger’s Power FET “ON” Resistance
(Between V
IN
and BAT)
Charger Soft-Start Time
Recharge Comparator Filter Time
Termination Comparator Filter Time
I
BAT
= 0 to I
BAT
= 1000V/R
PROG
V
BAT
High to Low
I
BAT
Drops Below Charge Termination
Threshold
0.75
0.4
CONDITIONS
R
PROG
= 10k, Current Mode
I
CHRG
= 5mA
I
PWR
= 5mA
V
FLOAT
– V
RECHRG
, 0°C < T
A
< 85°C
60
MIN
0.93
TYP
1
0.35
0.35
100
120
600
100
2
1
4.5
2.5
MAX
1.07
0.6
0.6
140
UNITS
V
V
V
mV
°C
mΩ
µs
ms
ms
2.5
1.764
1.755
1.544
1.536
1.8
1.8
1.575
1.575
0.3
0.5
700
40
0.1
1.8
0.95
0.6
2.25
1.2
0.7
0.35
0.3
0.01
5.5
1.836
1.836
1.607
1.607
0.5
V
V
V
V
V
%/V
%
950
60
1
2.7
1.6
0.9
0.45
0.45
1
1.5
1
µA
µA
µA
MHz
A
A
Ω
Ω
µA
V
µA
f
OSC
I
LIM
R
DS(ON)
I
SW(LKG)
V
RUN
I
RUN
Converter Top Switch On-Resistance
(Note 7)
Converter Bottom Switch On-Resistance (Note 7)
Switch Leakage Current
RUN Threshold Voltage
RUN Leakage Current
V
CC
= 5V, V
RUN
= 0V, V
FB
= 0V
●
●
0.3
1
0.01
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:
The LTC3552E-1 is guaranteed to meet performance specifications
from 0°C to 85°C Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
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 4:
Supply current includes PROG pin current and ITERM pin current
(approximately 100µA each) but does not include any current delivered to
the battery through the BAT pin (approximately 100mA).
Note 5:
The converter is tested in a proprietary test mode that connects
the output of the error amplifier to the SW pin, which is connected to an
external servo loop.
Note 6:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 7:
The regulator power switch on-resistances are guaranteed by
correlation to wafer level measurements.
Note 8:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
35521fa
3
LTC3552-1
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C Unless Otherwise Specified.
Battery Charger
PROG Pin Voltage vs Supply
Voltage (Constant-Current Mode)
1.015
1.010
1.005
V
PROG
(V)
V
PROG
(V)
1.000
0.995
0.990
0.985
V
BAT
= 4V
R
PROG
= 10k
1.0100
1.0075
1.0050
I
BAT
(mA)
1.0025
1.0000
0.9975
0.9950
0.9925
4
4.5
5
5.5
6.5
6
V
IN
(V)
7
7.5
8
0.9900
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
35521 G02
Regulated Output (Float) Voltage
vs Charge Current
4.26
V
IN
= 5V
4.24 R
PROG
= 1.25k
4.22
V
FLOAT
(V)
V
FLOAT
(V)
4.215
4.210
4.205
4.200
4.195
4.190
4.18
4.16
4.14
4.12
4.10
0
100
200
300 400
I
BAT
(mA)
500
600
700
35521 G04
V
FLOAT
(V)
4.20
CHRG Pin I-V Curve
(Pull-Down State)
30
T
A
= –40°C
25
20
I
CHRG
(mA)
15
10
5
0
0
1
2
4
3
V
CHRG
(V)
5
6
7
35521 G07
T
A
= 25°C
I
PWR
(mA)
T
A
= 90°C
I
BAT
(mA)
4
U W
V
IN
= 5V
V
BAT
= 4V
PROG Pin Voltage
vs Temperature
600
V
IN
= 5V
V
BAT
= V
BSENSE
= 4V
R
PROG
= 10k
500
400
300
200
100
0
Charge Current
vs PROG Pin Voltage
V
IN
= 5V
R
PROG
= 2k
R
TERM
= 2k
0
0.2
0.4
0.6
0.8
V
PROG
(V)
1
1.2
35521 G03
35521 G01
Regulated Output (Float) Voltage
vs Temperature
V
IN
= 5V
R
PROG
= 10k
4.215
Regulated Output (Float) Voltage
vs Supply Voltage
R
PROG
= 10k
4.210
4.205
4.200
4.195
4.190
4.185
4.185
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
35521 G05
4
4.5
5
5.5
6.5
6
V
IN
(V)
7
7.5
8
35521 G06
PWR Pin I-V Curve
(Pull-Down State)
30
T
A
= –40°C
25
20
15
10
5
0
0
1
2
4
3
V
PWR
(V)
5
6
7
35521 G08
Charge Current vs Battery Voltage
600
T
A
= 25°C
500
400
300
200
100
0
2.4
V
IN
= 5V
θ
JA
= 40°C/W
R
PROG
= 2k
2.7
3
3.3 3.6
V
BAT
(V)
3.9
4.2
4.5
35521 G09
T
A
= 90°C
V
IN
= 5V
V
BAT
= 4V
35521fa
LTC3552-1
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C Unless Otherwise Specified.
Battery Charger
Charge Current vs Supply Voltage
600
500
400
I
BAT
(mA)
300
200
100
0
R
PROG
= 10k
V
BAT
= 4V
θ
JA
= 40°C/W
I
BAT
(mA)
R
PROG
= 2k
500
R
PROG
= 2k
400
300
200
100
0
–50
R
PROG
= 10k
V
IN
= 5V
V
BAT
= 4V
θ
JA
= 40°C/W
600
ONSET OF THERMAL REGULATION
4
4.5
5
Power FET “On” Resistance
vs Temperature
700
V
IN
= 4.2V
I
BAT
= 100mA
650
R
PROG
= 2k
600
R
DS(ON)
(mΩ)
4.12
550
500
450
400
350
–50
V
RECHRG
(V)
4.10
4.08
4.06
4.16
4.14
–25
U W
5.5
Charge Current
vs Ambient Temperature
6
6.5
V
IN
(V)
7
7.5
8
–25
35521 G10
50
25
75
0
TEMPERATURE (°C)
100
125
35521 G11
Recharge Threshold Voltage
vs Temperature
V
IN
= 5V
R
PROG
= 10k
0
25
50
75
TEMPERATURE (°C)
100
125
35521 G12
4.04
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
35521 G13
35521fa
5
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