LTC3544
Quad Synchronous
Step-Down Regulator: 2.25MHz,
300mA, 200mA, 200mA, 100mA
FEATURES
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DESCRIPTION
The LTC
®
3544 is a quad, high efficiency, monolithic
synchronous buck regulator using a constant-frequency,
current mode architecture. The four regulators operate
independently with separate run pins. The 2.25V to 5.5V
input voltage range makes the LTC3544 well suited for
single Li-Ion/polymer battery-powered applications.
100% duty cycle provides low dropout operation, ex-
tending battery runtime in portable systems. Low ripple
Burst Mode
®
operation increases efficiency at light loads,
further extending battery runtime with typically only 20mV
of ripple.
Switching frequency is internally set to 2.25MHz, allowing
the use of small surface mount inductors and capacitors.
The internal synchronous switches increase efficiency
and eliminate the need for external Schottky diodes. Low
output voltages are easily supported with the 0.8V feedback
reference voltage.
The LTC3544 is available in a low profile (0.75mm) (3mm
×
3mm) QFN package.
, 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 5481178, 6580258, 6304066, 6127815, 6498466, 6611131, 5994885.
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High Efficiency: Up to 95%
Four Independent Regulators Provide Up to 300mA,
200mA, 200mA and 100mA Output Current
2.25V to 5.5V Input Voltage Range
2.25MHz Constant-Frequency Operation
No Schottky Diodes Required
Extremely Low Channel-to-Channel Transient
Crosstalk
Low Ripple (20mV
P-P
) Burst Mode Operation:
I
Q
= 70μA (All Channels On)
0.8V Reference Allows Low Output Voltages
Shutdown Mode Draws <1μA Supply Current
Current Mode Operation for Excellent Line and Load
Transient Response
Overtemperature Protected
Low Profile (3mm
×
3mm) 16-Lead QFN Package
APPLICATIONS
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Cellular Telephones
Personal Information Appliances
Wireless and DSL Modems
Digital Still Cameras
Media Players
Portable Instruments
TYPICAL APPLICATION
High Efficiency Quad Step-Down Converter
V
IN
2.25V TO 5.5V
V
OUT2
1.5V
200mA
4.7μF
CER
4.7μF
CER
4.7μH
93.1k
107k
LTC3544
3.3μH
133k
107k
RUN300
SW300
V
FB300
GNDA
PGND
RUN100
SW100
V
FB100
118k
10μH
59k
V
OUT1
1.2V
100mA
4.7μF
CER
V
CC
PV
IN
Efficiency vs Load Current, 300mA
Channel, All Other Channels Off
100
90
EFFICIENCY
0.1
POWER LOSS (W)
LOSS
V
OUT
= 2.5V
T
A
= 25°C
0.01
1
RUN200B
SW200B
V
FB200B
RUN200A
SW200A
V
FB200A
3.3μH
EFFICIENCY (%)
V
OUT3
0.8V
200mA
4.7μF
CER
80
70
60
50
40
30
20
10
0
0.0001
100k
V
OUT4
1.8V
300mA
4.7μF
CER
0.001
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
0.001
0.01
0.1
LOAD CURRENT (A)
1
3544 TA01b
0.0001
3544B TA01a
3544fa
1
LTC3544
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
RUN200B
SW100
12 RUN100
17
11 V
FB100
10 V
FB300
9
5
SW200A
6
PGND
7
PV
IN
8
SW300
RUN300
GNDA
V
CC
Input Supply Voltage .....................................–0.3V to 6V
RUNx ............................................. –0.3V to (V
IN
+ 0.3V)
V
FBx
................................................ –0.3V to (V
IN
+ 0.3V)
SWx ............................................... –0.3V to (V
IN
+ 0.3V)
300mA P-Channel Source Current (DC) (Note 8) ..450mA
300mA N-Channel Sink Current (DC) (Note 8) ......450mA
200mA P-Channel Source Current (DC) (Note 8) ..300mA
200mA N-Channel Sink Current (DC) (Note 8) ......300mA
100mA P-Channel Source Current (DC) (Note 8) ..200mA
100mA N-Channel Sink Current (DC) (Note 8) ......200mA
Peak 300mA SW Sink and Source Current
(Note 8) ................................................................600mA
Peak 200mA SW Sink and Source Current
(Note 8) ................................................................400mA
Peak 100mA SW Sink and Source Current
(Note 8) ................................................................200mA
Operating Temperature Range ...................–40°C to 85°C
Junction Temperature (Notes 3, 4) ........................ 125°C
Storage Temperature Range ....................–65°C to 125°C
16 15 14 13
V
FB200B
1
V
FB200A
2
RUN200A 3
SW200B 4
UD PACKAGE
16-LEAD (3mm
×
3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3544EUD#PBF
LEAD BASED FINISH
LTC3544EUD
TAPE AND REEL
LTC3544EUD#TRPBF
TAPE AND REEL
LTC3544EUD#TR
PART MARKING
LCXM
PART MARKING
LCXM
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
FBREGx
ΔV
FBREGx
V
LOADREG
PARAMETER
Input Voltage Range
Regulated Feedback Voltage (Note 5)
General Characteristics
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise noted.
CONDITIONS
●
●
MIN
2.25
0.792
0.784
TYP
MAX
5.5
UNITS
V
V
V
%/V
%
0.8
0.8
0.05
0.5
0.808
0.816
0.25
Reference Voltage Line Regulation (Note 5)
Output Voltage Load Regulation (Note 6)
V
IN
= 2.25V to 5.5V
3544fa
2
LTC3544
ELECTRICAL CHARACTERISTICS
SYMBOL
I
S
PARAMETER
Input DC Bias Current Active Mode
(Four Regulators Enabled)
Sleep Mode
(Four Regulators Enabled)
Shutdown
f
OSC
V
RUN(HIGH)
V
RUN(LOW)
I
SWx
I
RUNx
I
VFBx
t
SS
V
UVLO
Oscillator Frequency
RUNx Input High Voltage
RUNx Input Low Voltage
SWx Leakage
RUN Leakage Current
V
FBx
Leakage Current
Soft-Start Period
Undervoltage Lockout
V
FB
= 7.5% to 92.5% Full Scale
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise noted.
CONDITIONS
V
FB
= 0.7V, I
LOAD
= 0A, 2.25MHz
V
FB
= 0.9V, I
LOAD
= 0A, 2.25MHz
MIN
TYP
825
70
0.1
V
IN
= 3V
V
IN
= 2.5V to 5.5V
2.25
●
●
●
MAX
1100
80
2
2.7
0.3
UNITS
μA
μA
μA
MHz
MHz
V
V
μA
μA
nA
μs
V
1.8
1.0
±0.1
V
RUN
= 0V, V
SW
= 0V or 5.5V, V
IN
= 5.5V
V
IN
= 5.5V
●
±1
±1
80
1200
2.25
±0.1
650
875
1.9
Individual Regulator Characteristics
Regulator SW300 – 300mA
I
PK
I
S300
R
PFET
R
NFET
I
PK
I
S200
R
PFET
R
NFET
I
PK
I
S200
R
PFET
R
NFET
I
PK
I
S100
R
PFET
R
NFET
Peak Switch Current Limit
Input DC Bias Current–Reg SW300 Only
Burst Mode Operation (Sleep)
R
DS(ON)
of P-Channel FET (Note 7)
R
DS(ON)
of N-Channel FET (Note 7)
Peak Switch Current Limit
Input DC Bias Current–Reg SW200A Only
Burst Mode Operation (Sleep)
R
DS(ON)
of P-Channel FET (Note 7)
R
DS(ON)
of N-Channel FET (Note 7)
Peak Switch Current Limit
Input DC Bias Current–Reg SW200B Only
Burst Mode Operation (Sleep)
R
DS(ON)
of P-Channel FET (Note 7)
R
DS(ON)
of N-Channel FET (Note 7)
Peak Switch Current Limit
Input DC Bias Current–Reg SW100B Only
Burst Mode Operation (Sleep)
R
DS(ON)
of P-Channel FET (Note 7)
R
DS(ON)
of N-Channel FET (Note 7)
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.9V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.9V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.9V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.9V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
200
300
300
400
600
32
0.55
0.50
400
32
0.65
0.60
400
32
0.65
0.60
300
32
0.80
0.75
400
500
500
800
mA
μA
Ω
Ω
mA
μA
Ω
Ω
mA
μA
Ω
Ω
mA
μA
Ω
Ω
Regulator SW200A – 200mA
Regulator SW200B – 200mA
Regulator SW100 – 100mA
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 LTC3544E 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.
3544fa
3
LTC3544
ELECTRICAL CHARACTERISTICS
Note 3:
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
)(68°C/W).
Note 4:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature is active. Continuous
operation above the specified maximum operating junction temperature
may impair device reliability.
Note 5:
The LTC3544 is tested in a proprietary test mode that connects V
FB
to the output of the error amplifier.
Note 6:
Load regulation is inferred by measuring the regulation loop gain.
Note 7:
The QFN switch on-resistance is guaranteed by correlation to wafer
level measurements.
Note 8:
Guaranteed by long-term current density limitations.
TYPICAL PERFORMANCE CHARACTERISTICS
V
REF
vs Temperature at 2.25V,
3.6V, 5.5V
0.815
0.810
0805
V
REF
(V)
0.800
0.795
0.790
0.785
–50
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 5.5V
0
50
TEMPERATURE (°C)
100
3544 G01
Switching Frequency vs Supply
Voltage and Temperature
3.0
I
LOAD
CHANNEL 100 = 50mA
ALL CHANNELS OPERATING
SWITCHING FREQUENCY (MHz)
100
90
80
EFFICIENCY (%)
2.5
70
60
50
40
30
f
OSC
–40°C
f
OSC
0°C
f
OSC
25°C
f
OSC
80°C
1.5
2
5
3
4
SUPPLY VOLTAGE (V)
6
3544 G02
Efficiency vs Load Current 300mA
Channel. All Other Channels at
50% Peak Current
CHANNEL 200A
I
LOAD
= 100mA
ALL CHANNELS OPERATING
2.0
20
10
0
0.0001
V
IN
= 3.6V
T
A
= 25°C
V
OUT100
= 1.2V
V
OUT200A
= 0.8V
V
OUT200B
= 1.5V
V
OUT300
= 1.8V
ALL OTHER CHANNELS LOADED 50%
0.001
0.01
0.1
LOAD CURRENT 300mA CHANNEL (A)
1
3544B G03
Burst Mode Operation
300mA Channel
V
OUT300
50mV/DIV
AC
COUPLED
SW300
5V/DIV
V
OUT200B
50mV/DIV
AC
COUPLED
SW2B
5V/DIV
Burst Mode Operation
200mA, A-B Channels
V
OUT100
50mV/DIV
AC
COUPLED
SW100
5V/DIV
Burst Mode Operation
100mA Channel
I
L
100mA/DIV
2μs/DIV
T
A
= 25°C
I
LOAD
= 20mA
3544 G04
I
L
50mA/DIV
3544 G05
I
L
50mA/DIV
2μs/DIV
T
A
= 25°C
I
LOAD
= 15mA
2μs/DIV
T
A
= 25°C
I
LOAD
= 12mA
3544 G06
V
IN
= 3.6V
V
OUT
= 1.8V
V
IN
= 3.6V
V
OUT
= 1.5V
V
IN
= 3.6V
V
OUT
= 1.2V
3544fa
4
LTC3544
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current 300mA
Channel. All Other Channels Off
100
90
80
70
EFFICIENCY (%)
EFFICIENCY (%)
60
50
40
30
20
10
0
0.0001
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 4.2V
V
OUT
= 1.8V
T
A
= 25°C
ALL OTHER
CHANNELS OFF
1
3544 G07
Efficiency vs Load Current 200mA
Channel A. All Other Channels Off
100
90
80
70
60
50
40
30
20
10
0
0.0001
V
OUT
= 0.8V
T
A
= 25°C
ALL OTHER CHANNELS OFF
0.01
0.1
0.001
LOAD CURRENT (A)
1
3544 G08
Efficiency vs Load Current 200mA
Channel B. All Other Channels Off
100
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.0001
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 4.2V
V
OUT
= 1.5V
T
A
= 25°C
ALL OTHER
CHANNELS OFF
1
3544 G09
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 4.2V
0.01
0.1
0.001
LOAD CURRENT (A)
0.001
0.01
0.1
LOAD CURRENT (A)
Efficiency vs Load Current 100mA
Channel. All Other Channels Off
100
90
80
V
OUT
ERROR (%)
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.0001
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 4.2V
V
OUT
= 1.2V
T
A
= 25°C
ALL OTHER
CHANNELS OFF
1
3544 G10
Load Regulation
All Channels
1.2
1.0
0.8
0.6
0.4
0.2
0
–0.2
0
100
200
LOAD (mA)
3544 G11
Start-Up Curves
All Channels
V
IN
= 3.6V
T
A
= 25°C
V
OUT100
V
OUT200A
V
OUT200B
100mA = 1.2V
200mA (A) = 0.8V
200mA (B) = 1.5V
300mA = 1.8V
Burst Mode OPERATION
RIPPLE
V
OUT300
RUNx
V
IN
= 3.6V
200μs/DIV
T
A
= 25°C
ALL CHANNELS UNLOADED
300
400
3544 G12
0.001
0.01
0.1
LOAD CURRENT (A)
Load Step Response
300mA Channel
V
OUT300
100mV/DIV
AC
COUPLED
I
L
250mA/DIV
I
LOAD
250mA/DIV
V
IN
= 3.6V
20μs/DIV
V
OUT
= 1.8V
T
A
= 25°C
I
LOAD
= 600μA TO 300mA
3544 G13
Load Step Response
200mA Channel A
V
OUT200A
50mV/DIV
AC
COUPLED
I
L
250mA/DIV
I
LOAD
250mA/DIV
V
IN
= 3.6V
20μs/DIV
V
OUT
= 0.8V
T
A
= 25°C
I
LOAD
= 600μA TO 200mA
3544 G14
Load Step Response
200mA Channel B
V
OUT200B
50mV/DIV
AC COUPLED
I
L
250mA/DIV
I
LOAD
250mA/DIV
V
IN
= 3.6V
20μs/DIV
V
OUT
= 1.5V
T
A
= 25°C
I
LOAD
= 600μA TO 200mA
3544 G15
3544fa
5
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