LTC3544B
Quad Synchronous
Step-Down Regulator: 2.25MHz,
300mA, 200mA, 200mA, 100mA
FeaTures
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DescripTion
The LTC
®
3544B is a quad, high efficiency, monolithic
synchronous buck regulator using a constant frequency,
current mode architecture. The four regulators operate in-
dependently with separate run pins. The 2.25V to 5.5V input
voltage range makes the LTC3544B well suited for single
Li-Ion/polymer battery-powered applications. 100% duty
cycle provides low dropout operation, extending battery
runtime in portable systems. At moderate and low output
load levels PWM pulse skip mode operation provides very
low output ripple voltage for noise sensitive applications.
Switching frequency is internally set to 2.25MHz, al-
lowing 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 LTC3544B is available in a low profile (0.75mm)
(3mm
×
3mm) QFN package.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks 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
Low Dropout Operation: 100% Duty Cycle
Pulse Skipping at Low Load for Minimum Ripple
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
4.7µF
CER
4.7µH
93.1k
107k
LTC3544B
3.3µH
133k
107k
RUN300
SW300
V
FB300
GNDA
PGND
RUN100
SW100
V
FB100
10µH
59k
118k
3544B TA01a
Efficiency vs Load Current, 300mA
Channel, All Other Channels Off
100
V
OUT
= 1.5V
90 T
A
= 25°C
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.0001
V
IN
= 2.5V
V
IN
= 3.6V
V
IN
= 4.3V
0.001
0.01
0.1
LOAD CURRENT (A)
1
3544B TA01b
1
RUN200B
SW200B
V
FB200B
V
CC
PV
IN
RUN200A
SW200A
V
FB200A
V
OUT2
1.5V
4.7µF
CER
3.3µH
V
OUT3
0.8V
4.7µF
CER
EFFICIENCY
0.1
POWER LOSS (W)
100k
POWER LOSS
0.01
V
OUT4
1.8V
4.7µF
CER
V
OUT1
1.2V
4.7µF
CER
0.001
3544bfb
LTC3544B
absoluTe MaxiMuM raTings
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
(Note 1)
pin conFiguraTion
TOP VIEW
RUN200B
SW100
12 RUN100
17
GNDA
11 V
FB100
10 V
FB300
9 RUN300
5
SW200A
6
PGND
7
PV
IN
8
SW300
GNDA
V
CC
16 15 14 13
V
FB200B
V
FB200A
RUN200A
SW200B
1
2
3
4
UD PACKAGE
16-LEAD (3mm 3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 17) IS ANALOG GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3544BEUD#PBF
LEAD BASED FINISH
LTC3544BEUD
TAPE AND REEL
LTC3544BEUD#TRPBF
TAPE AND REEL
LTC3544BEUD#TR
PART MARKING
LCLN
PART MARKING
LCLN
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/
The
l
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. (Note 2)
SYMBOL
V
IN
V
FBREGx
ΔV
FBREGx
V
LOADREG
I
S
PARAMETER
Input Voltage Range
Regulated Feedback Voltage (Note 5)
l
elecTrical characTerisTics
CONDITIONS
l
MIN
2.25
0.792
0.784
TYP
MAX
5.5
UNITS
V
V
V
%/V
%
µA
µA
MHz
MHz
3544bfb
General Characteristics
0.8
0.8
0.05
0.5
V
FB
= 0.7V, I
LOAD
= 0A, 2.25MHz,
Four Regulators Enabled
V
IN
= 3V
V
IN
= 2.5V to 5.5V
825
0.1
l
0.808
0.816
0.25
1100
2
2.7
Reference Voltage Line Regulation (Note 5)
Output Voltage Load Regulation (Note 6)
Input DC Bias Current Active Mode (Pulse Skip)
Shutdown
V
IN
= 2.25V to 5.5V
f
OSC
Oscillator Frequency
1.8
2.25
LTC3544B
elecTrical characTerisTics
SYMBOL
V
RUN(HIGH)
V
RUN(LOW)
I
LSW
I
RUN
I
VFB
t
SS
V
UVLO
PARAMETER
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
l
The
l
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
l
l
MIN
1.0
TYP
MAX
0.3
UNITS
V
V
µA
µA
nA
µs
V
V
RUN
= 0V, V
SW
= 0V or 5.5V, V
IN
= 5.5V
V
IN
= 5.5V
l
±0.1
±0.1
650
875
1.9
±1
±1
80
1200
2.25
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
Active Mode (Pulse Skip)
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
Active Mode (Pulse Skip)
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
Active Mode (Pulse Skip)
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
Active Mode (Pulse Skip)
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
= 0.7V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.7V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.7V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
V
FB
< V
FBREG
, Duty Cycle < 35%
V
FB
= 0.7V, I
LOAD
= 0A, 2.25MHz
I
SW
= 100mA
I
SW
= –100mA
200
300
300
400
600
320
0.55
0.50
400
320
0.65
0.60
400
320
0.65
0.60
300
320
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 LTC3544BE 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:
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 LTC3544B 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.
3544bfb
LTC3544B
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
3544B G01
Switching Frequency vs Supply
Voltage and Temperature
3.0
SWITCHING FREQUENCY (MHz)
I
LOAD
CHANNEL 100 = 50mA
ALL CHANNELS OPERATING
100
90
80
EFFICIENCY (%)
f
OSC
–40°C
f
OSC
0°C
f
OSC
25°C
f
OSC
80°C
2
3
5
4
SUPPLY VOLTAGE (V)
6
3544B G02
Efficiency vs Load Current 300mA
Channel. All Other Channels at
50% Peak Current
CHANNEL 200A
I
LOAD
= 100mA
ALL CHANNELS OPERATING
2.5
70
60
50
40
30
20
10
V
IN
= 3.6V
V
OUT
= 1.8V
T
A
= 25°C
ALL OTHER CHANNELS LOADED 50%
0.01
0.1
0.001
LOAD CURRENT 300mA CHANNEL (A)
1
2.0
1.5
0
0.0001
3544B G03
Efficiency vs Load Current 300mA
Channel. All Other Channels Off
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.0001
V
OUT
= 1.8V
T
A
= 25°C
ALL OTHER CHANNELS OFF
0.001
0.01
0.1
LOAD CURRENT (A)
1
3544B G04
Efficiency vs Load Current 200mA
Channel A. All Other Channels Off
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.0001
V
OUT
= 0.8V
T
A
= 25°C
ALL OTHER CHANNELS OFF
0.001
0.01
0.1
LOAD CURRENT (A)
1
3544B G05
Efficiency vs Load Current 200mA
Channel B. All Other Channels Off
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.0001
V
OUT
= 1.5V
T
A
= 25°C
ALL OTHER CHANNELS OFF
0.001
0.01
0.1
LOAD CURRENT (A)
1
3544B G06
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 5.5V
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 5.5V
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 5.5V
Efficiency vs Load Current 100mA
Channel. All Other Channels Off
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.0001
V
OUT
= 1.2V
T
A
= 25°C
ALL OTHER CHANNELS OFF
0.001
0.01
0.1
LOAD CURRENT (A)
1
3544B G07
Efficiency vs Supply Voltage, All
Channels 50% Loaded
100
90
V
OUT
ERROR (%)
EFFICIENCY (%)
1.2
1.0
0.8
0.6
0.4
0.2
0
–0.2
Load Regulation, All Channels
V
IN
= 3.6V
T
A
= 25°C
CHANNELS NOT UNDER
TEST HELD AT CONSTANT
50% MAXIMUM LOAD
100mA
200mA (A)
200mA (B)
300mA
V
IN
= 2.25V
V
IN
= 3.6V
V
IN
= 5.5V
80
70
V
OUT100
= 1.2V
V
OUT200A
= 0.8V
V
OUT200B
= 1.5V
V
OUT300
= 1.8V
T
A
= 25°C
2
4
3
SUPPLY VOLTAGE (V)
5
3544B G08
60
50
0
100
200
LOAD (mA)
300
400
3544B G09
3544bfb
LTC3544B
Typical perForMance characTerisTics
Start-Up Curves, All Channels
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
= 300µA TO 300mA
3544B G11
Load Step Response, 300mA
Channel
V
OUT200A
50mV/DIV
AC-COUPLED
I
L
250mA/DIV
I
LOAD
100mA/DIV
Load Step Response, 200mA
Channel A
V
OUT100
V
OUT200A
V
OUT200B
V
OUT300
RUNx
V
IN
= 3.6V
200µs/DIV
T
A
= 25°C
ALL CHANNELS UNLOADED
3544B G10
V
IN
= 3.6V
20µs/DIV
V
OUT
= 0.8V
T
A
= 25°C
I
LOAD
= 340µA TO 200mA
3544B G12
Load Step Response, 200mA
Channel B
V
OUT200B
50mV/DIV
AC-COUPLED
I
L
250mA/DIV
I
LOAD
100mA/DIV
V
OUT100
50mV/DIV
AC-COUPLED
I
L
100mA/DIV
I
LOAD
100mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.5V
T
A
= 25°C
I
LOAD
= 340µA TO 200mA
3544B G13
Load Step Response, 100mA
Channel
V
OUT100
10mV/DIV
V
OUT200A
10mV/DIV
V
OUT200B
10mV/DIV
V
OUT300
100mV/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.2V
T
A
= 25°C
I
LOAD
= 200µA TO 100mA
3544B G14
Load Step Crosstalk
3544B G15
V
IN
= 3.6V
40µs/DIV
T
A
= 25°C
300mA LOAD STEP ON V
OUT300
OTHER CHANNELS LOADED 50% OF MAXIMUM
3544bfb
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