FEATURES
■
■
LTC3552
Standalone Linear Li-Ion
Battery Charger and Dual
Synchronous Buck Converter
DESCRIPTIO
The LTC
®
3552 is a complete constant-current/constant-
voltage linear charger with a dual DC/DC converter for
single cell lithium-ion batteries. Its DFN package and low
external component count make the LTC3552 ideally suited
for portable applications. Furthermore, the LTC3552 is
designed to work within USB power specifications.
No external sense resistor or external blocking diode is
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 enters a low current state dropping
the battery drain current to less than 2µA. Thermal regula-
tion maximizes charge rate without risk of overheating.
The synchronous step-down switching regulators gen-
erate adjustable output voltages from 5V down to 0.6V.
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.
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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■
■
■
■
■
■
■
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■
■
■
Programmable Charge Current Up to 950mA
Complete Linear Charger and Dual DC/DC
Regulator
Buck Converter Output Voltage from 0.6V to 5V
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
2.9V Trickle Charge Threshold
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
LTC3552
1µF
619Ω
1.24k
RUN2
BAT
V
CC
POR
MODE/SYNC
SW1
R2
604k
R1
301k
3552 TA01
100
95
ITERM
PROG
CHRG
PWR
EN
SW2
800mA
10µF
EFFICIENCY (%)
V
IN
4.5V TO
6.5V
V
IN
RUN1
4.2V
1-CELL
Li-Ion
BATTERY
90
85
80
+
75
70
65
60
1
10
100
LOAD CURRENT (mA)
0.1
1000
3552 TA01b
V
OUT2
2.5V/
400mA
C
OUT2
4.7µF
CER
4.7µH
2.2µH
C
FF2
68pF
R4
887k
R3
280k
V
FB2
GND
V
FB1
C
FF1
33pF
V
OUT1
1.8V/
800mA
C
OUT1
10µF
CER
V
CC
= 3.3V, V
OUT
= 1.8V
Burst Mode OPERATION
REGULATOR 1, NO LOAD ON REGULATOR 2
U
U
U
Efficiency Curve/
Power Loss of Regulators
1000
EFFICIENCY
100
POWER LOSS (mW)
10
POWER LOSS
1
3552f
1
LTC3552
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
ITERM
BAT
CHRG
MODE/SYNC
SW2
POR
RUN2
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 RUN1
9
V
FB1
Charger Input Supply (V
IN
) ........................ –0.3V to 10V
PROG, ITERM .................................. –0.3V to V
IN
+ 0.3V
BAT .............................................................. –0.3V to 7V
⎯
C
⎯
H
⎯
R
⎯
G,
⎯
P
⎯
W
⎯
R,
⎯
E
⎯
N......................................... –0.3V to 10V
BAT Short-Circuit Duration............................Continuous
BAT Pin Current ..........................................................1A
PROG Pin Current ....................................................1mA
Converter Input Supply (V
CC
)....................... –0.3V to 6V
V
FB1
, V
FB2
, RUN1, RUN2 ...................–0.3V to V
CC
+0.3V
MODE/SYNC ....................................–0.3V to V
CC
+ 0.3V
SW1, SW2 .......................................–0.3V to V
CC
+ 0.3V
⎯
P
⎯
O
⎯
R ............................................................. –0.3V to 6V
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
DHC PART MARKING
3552
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
V
mA
mA
µA
µA
µA
mA
V
mV
V
mV
R
PROG
= 10k
Charge Terminated
⎯
E
⎯
N = 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 (
⎯
E
⎯
N = 5V, V
IN
< V
BAT
or
V
IN
< V
UV
)
Sleep Mode, V
IN
= 0V
V
BAT
< V
TRIKL
, R
PROG
= 2k
R
PROG
= 10k, V
BAT
Rising
R
PROG
= 10k
From V
IN
Low to High
●
●
●
0.4
200
25
4.158
4.2
100
500
–2.5
±1
±1
92
465
1
500
50
4.242
105
535
–6
±2
±2
60
3
3.92
300
V
FLOAT
I
BAT
●
●
●
I
TRIKL
V
TRIKL
V
TRHYS
V
UV
V
UVHYS
Trickle Charge Current
Trickle Charge Threshold Voltage
Trickle Charge Hysterisis Voltage
V
IN
Undervoltage Lockout Voltage
V
IN
Undervoltage Lockout Hysteresis
●
30
2.8
45
2.9
80
3.8
200
●
●
3.7
150
2
U
3552f
W
U
U
W W
W
LTC3552
ELECTRICAL CHARACTERISTICS
SYMBOL
V
⎯
E
⎯
N(IL)
V
⎯
E
⎯
N(IH)
R
⎯
E
⎯
N
V
ASD
I
TERM
V
PROG
V
⎯
C
⎯
H
⎯
R
⎯
G
V
⎯
P
⎯
W
⎯
R
ΔV
RECHRG
T
LIM
R
ON-CHRG
t
SS-CHRG
t
RECHRG
t
TERM
Switching Regulator
V
CC
I
FB
V
FB
ΔV
LINE_REG
ΔV
LOAD_REG
I
S
Operating Voltage Range for Regulator
Feedback Pin Input Current
Feedback Voltage (Note 5)
Reference Voltage Line Regulation
Output Voltage Load Regulation
Input DC Supply Current
Active Mode
Sleep Mode
Shutdown
Oscillator Frequency
Synchronization Frequency
Peak Switch Current Limit Regulator 1
Peak Switch Current Limit Regulator 2
Top Switch On-Resistance
Bottom Switch On-Resistance
Switch Leakage Current
Power-On Reset Threshold
Power-On Reset On-Resistance
Power-On Reset Delay
V
RUN
I
RUN
RUN Threshold Voltage
RUN Leakage Current
●
●
●
●
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
⎯
E
⎯
N Pin Input Low Voltage
⎯
E
⎯
N Pin Input High Voltage
⎯
EN Pin Pull-Down Resistor
V
IN
– V
BAT
Lockout Threshold Voltage
Charge Termination Current Threshold
PROG Pin Voltage
⎯
C
⎯
H
⎯
R
⎯
G Pin Output Low Voltage
⎯
P
⎯
W
⎯
R 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
V
IN
from Low to High
V
IN
from High to Low
R
TERM
= 1k
R
TERM
= 5k
R
PROG
= 10k, Current Mode
I
⎯
C
⎯
H
⎯
R
⎯
G
= 5mA
I
⎯
P
⎯
W
⎯
R
= 5mA
V
FLOAT
– V
RECHRG
, 0°C < T
A
< 85°C
60
●
●
CONDITIONS
●
●
●
MIN
0.4
1.2
70
5
90
17.5
0.93
TYP
0.7
0.7
2
100
30
100
20
1
0.35
0.35
100
120
600
100
2
1
MAX
1
5
140
50
110
22.5
1.07
0.6
0.6
140
UNITS
V
V
MΩ
mV
mV
mA
mA
V
V
V
mV
°C
mΩ
µs
4.5
2.5
ms
ms
2.5
0.588
0.585
0.6
0.6
0.3
0.5
700
40
0.1
5.5
30
0.612
0.612
0.5
V
nA
V
V
%/V
%
0°C ≤ T
A
≤ 85°C
–40°C ≤ T
A
≤ 85°C
V
CC
= 2.5V to 5.5V (Note 5)
(Note 5)
V
FB1
= V
FB2
= 0.5V
V
FB1
= V
FB2
= 0.63V, MODE/SYNC = 3.6V
RUN = 0V, V
CC
= 5.5V, MODE/SYNC = 0V
V
FB
= 0.6V
V
CC
= 3V, V
FB
= 0.5V, Duty Cycle < 35%
V
CC
= 3V, V
FB
= 0.5V, Duty Cycle < 35%
(Note 6)
(Note 6)
V
CC
= 5V, V
RUN
= 0V, V
FB
= 0V
V
FB
Ramping Down, MODE/SYNC = 0V
●
950
60
1
2.7
1.6
0.9
0.45
0.45
1
200
1.5
1
µA
µA
µA
MHz
MHz
A
A
Ω
Ω
µA
%
Ω
Cycles
V
µA
f
OSC
f
SYNC
I
LIM
R
DS(ON)
I
SW(LKG)
POR
●
1.8
0.95
0.6
2.25
2.25
1.2
0.7
0.35
0.30
0.01
–8.5
100
262,144
0.3
1
0.01
3552f
3
LTC3552
ELECTRICAL CHARACTERISTICS
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. Pins of regulators should not exceed 6V.
Note 2:
The LTC3552E 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 regulator is tested in a proprietary test mode that connects
V
FB
to the output of the error amplifier.
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
)
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C Unless Otherwise Specified.
Battery Charger
PROG Pin Voltage vs V
IN
(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
3552 G02
Regulated Output (Float) Voltage
vs Charge Current
4.26
4.215
4.210
4.205
V
FLOAT
(V)
4.200
4.195
4.190
V
IN
= 5V
4.24 R
PROG
= 1.25k
4.22
V
FLOAT
(V)
4.18
4.16
4.14
4.12
4.10
0
100
200
300 400
I
BAT
(mA)
500
600
700
3552 G04
V
FLOAT
(V)
4.20
4
U W
PROG Pin Voltage
vs Temperature
600
V
IN
= 5V
V
BAT
= 4V
R
PROG
= 10k
500
400
300
200
100
0
Charge Current
vs PROG Pin Voltage
V
IN
= 5V
R
PROG
= 2k
R
ITERM
= 2k
0
0.2
0.4
0.6
0.8
V
PROG
(V)
1
1.2
3552 G03
3552 G01
Regulated Output (Float) Voltage
vs Temperature
V
IN
= 5V
R
PROG
= 10k
4.215
Regulated Output (Float)
Voltage vs V
IN
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
3552 G05
4
4.5
5
5.5
6.5
6
V
IN
(V)
7
7.5
8
3552 G06
3552f
LTC3552
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C Unless Otherwise Specified.
Battery Charger
⎯
C
⎯
H
⎯
R
⎯
G 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
3552 G07
T
A
= 25°C
I
PWR
(mA)
T
A
= 90°C
I
BAT
(mA)
Trickle Charge Current
vs Temperature
60
50
R
PROG
= 2k
40
I
TRKL
(mA)
I
TRKL
(mA)
30
20
10
0
–50
R
PROG
= 10k
40
30
20
10
0
–25
0
25
50
TEMPERATURE (°C)
75
100
V
IN
= 5V
V
BAT
= 2.5V
60
50
V
TRKL
(V)
Charge Current vs V
IN
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
600
4
4.5
U W
V
IN
= 5V
V
BAT
= 4V
3552 G09a
⎯
P
⎯
W
⎯
R 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
3552 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
3552 G09
T
A
= 90°C
V
IN
= 5V
V
BAT
= 4V
Trickle Charge Current vs V
IN
V
BAT
= 2.5V
R
PROG
= 2k
3.000
2.975
2.950
2.925
2.900
2.875
R
PROG
= 10k
2.850
2.825
4
4.5
5
5.5
V
IN
(V)
6
6.5
7
Trickle Charge Threshold Voltage
vs Temperature
V
IN
= 5V
R
PROG
= 10k
2.800
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
3552 G09c
3552 G09b
Charge Current
vs Ambient Temperature
ONSET OF THERMAL REGULATION
R
PROG
= 2k
400
300
200
100
0
–50
R
PROG
= 10k
V
IN
= 5V
V
BAT
= 4V
θ
JA
= 40°C/W
5
5.5
6
6.5
V
IN
(V)
7
7.5
8
–25
3552 G10
50
25
75
0
TEMPERATURE (°C)
100
125
3552 G11
3552f
5
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