FEATURES
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LTC3562
I
2
C Quad Synchronous
Step-Down DC/DC Regulator
2 × 600mA, 2 × 400mA
DESCRIPTION
The LTC
®
3562 is a quad high efficiency monolithic syn-
chronous step-down regulator with an I
2
C interface. Two
regulators are externally adjustable and can have their
feedback voltages programmed between 425mV and
800mV in 25mV steps (Type A). The other two regulators
are fixed output regulators whose output voltages can be
programmed between 600mV and 3.775V in 25mV steps
(Type B). All four regulators operate independently and
can be put into pulse skip, LDO, Burst Mode operation,
or forced Burst Mode operation through I
2
C control. The
Type-A regulators have separate RUN pins that can be
enabled if I
2
C control is unavailable.
The 2.85V to 5.5V input voltage range makes the LTC3562
ideally suited for single Li-Ion battery-powered applica-
tions. At low output load conditions, the regulators can
be switched into LDO, Burst Mode operation, or forced
Burst Mode operation, extending battery life in portable
systems. The quiescent current drops to under 100μA
with all regulators in LDO mode, and under 0.1μA when
all regulators are shut down.
Switching frequency is internally set to 2.25MHz, allowing
the use of small surface mount inductors and capacitors.
All regulators are internally compensated. The LTC3562 is
available in a low profile 3mm
×
3mm QFN package.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Four Independent I
2
C Controllable Step-Down
Regulators (2
×
600mA, 2
×
400mA)
Two I
2
C Programmable Feedback Voltage
Regulators (R600A, R400A): V
FB
425mV to 800mV
Two I
2
C Programmable Output Voltage Regulators
(R600B, R400B): V
OUT
600mV to 3.775V
®
Programmable Modes: Pulse Skip, LDO, Burst Mode,
Forced Burst Mode Operation
Quiescent Current < 100μA (All Regulators Enabled
in LDO Mode)
Fixed 2.25MHz Switching Frequency (Pulse Skip
Mode)
Slew Limiting Reduces Switching Noise
Power-On Reset Output for Regulator R600A
Small, Thermally Enhanced, 20-Lead 3mm
×
3mm
QFN Package
APPLICATIONS
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Miscellaneous Handheld Applications with Multiple
Supply Rails
Personal Information Appliances
Wireless and DSL Modems
Digital Still Cameras
MP3 Players
Portable Instruments
TYPICAL APPLICATION
High Efficiency Quad Step-Down Converter with I
2
C
MICROPROCESSOR
Li-Ion/Polymer
3.4V TO 4.2V
R600x Burst Mode Efficiency
and Power Loss vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
V
OUT
= 1.2V,
1.8V, 2.5V
V
OUT
= 3.3V
1
V
IN
= 3.8V
0.1
1
10
100
LOAD CURRENT (mA)
10
+
10
μ
F
V
IN
SCL SDA DV
CC
POR600A
SW600A
FB600A
RUN600A
499k
4.7
μ
H
10
μ
F
SW400B
SW600B
OUT400B PGND AGND OUT600B
3562 TA01
100k
3.3
μ
H
V
OUT
400A
1.5V
400mA
4.7
μ
H
10
μ
F
10pF
475k
RUN400A
SW400A
LTC3562
V
OUT
600A
1.8V
600mA
634k
SDA
SCL
DV
CC
POR
V
OUT
= 3.3V
V
OUT
=
2.5V
V
OUT
=
1.8V
V
OUT
= 1.2V
10000
1000
POWER LOSS (mW)
100
10pF
10
μ
F
FB400A
536k
V
OUT
400B
1.2V
400mA
3.3
μ
H
V
OUT
600B
3.3V
10
μ
F 600mA
10
0
0.01
0.1
1000
3562 TA01b
3562fa
1
LTC3562
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
RUN600A
V
IN
RUN400A
15
POR600A
14 FB600A
21
13 OUT600B
12 SW600B
11 PGND
6
SW400A
7
V
IN
8
V
IN
9 10
SW600A
DV
CC
V
IN
............................................................... –0.3V to 6V
RUN600A
...................................... –0.3V to (V
IN
+ 0.3V)
RUN400A ...................................... –0.3V to (V
IN
+ 0.3V)
FBx ............................................................... –0.3V to 6V
SWx ............................................................. –0.3V to 6V
OUTx ............................................................ –0.3V to 6V
DV
CC
,
POR600A,
SDA, SCL ......................... –0.3V to 6V
I
SW400x
(DC) ........................................................600mA
I
SW600x
(DC) ........................................................850mA
Operating Temperature (Note 2)...............–40°C to 85°C
Storage Temperature Range...................–65°C to 125°C
Junction Temperature (Note 3) ............................. 125°C
SDA
AGND 1
FB400A 2
OUT400B 3
SW400B 4
PGND 5
20 19 18 17 16
UD PACKAGE
20-LEAD (3mm
×
3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3562EUD#PBF
TAPE AND REEL
LTC3562EUD#TRPBF
PART MARKING
LCPV
PACKAGE DESCRIPTION
20-Lead (3mm
×
3mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
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
= 3.8V, unless otherwise noted.
PARAMETER
V
IN
Input Voltage Range
V
IN
Input Current (Per Regulator Enabled)
Pulse Skip Mode, I
OUT
= 0
Burst Mode Operation, I
OUT
= 0
Forced Burst Mode Operation, I
OUT
= 0
LDO Mode, I
OUT
= 0
Shutdown Mode, I
OUT
= 0, DV
CC
= 1.8V
All Regulators in Shutdown, DV
CC
= 0V
l
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
l
SCL
MIN
2.7
TYP
220
35
25
24
0.7
0.1
MAX
5.5
60
40
40
3
1
0.3
UNITS
V
μA
μA
μA
μA
μA
μA
V
V
μA
μA
%
Ω
ms
3562fa
V
IN
Shutdown Current
RUN600A,
RUN400A Input High Threshold
RUN600A,
RUN400A Input Low Threshold
RUN600A,
RUN400A Input High Current
RUN600A,
RUN400A Input Low Current
POR600A
Threshold
POR600A
On-Resistance
POR600A
Delay
1.0
–1
–1
–8
16
231
40
1
1
RUNx = V
IN
RUNx = 0V
Percentage of R600A’s Final Output Voltage
2
LTC3562
ELECTRICAL CHARACTERISTICS
PARAMETER
I
2
C Port
DV
CC
Operating Voltage
DV
CC
Operating Current
DV
CC
UVLO Threshold Voltage
V
IL
SDA, SCL (Low Level Input Voltage)
V
IH
SDA, SCL (High Level Input Voltage)
V
OL
SDA (Digital Output Low)
Serial Port Timing (Note 4)
t
SCL
t
BUF
t
HD,STA
t
SU,STA
t
SU,STO
t
HD,DAT(OUT)
t
HD,DAT(IN)
t
SU,DAT
t
LOW
t
HIGH
t
f
t
r
t
SP
Clock Operating Frequency
Bus Free Time Between Stop and Start Conditions
Hold Time After (Repeated) Start Condition
Repeated Start Condition Setup Time
Stop Condition Setup Time
Data Hold Time
Input Data Hold Time
Data Setup Time
Clock Low Period
Clock High Period
Clock Data Fall Time
Clock Data Rise Time
Spike Suppression Time
1.3
0.6
0.6
0.6
225
0
100
1.3
0.6
20
20
50
300
300
900
400
kHz
μs
μs
μs
μs
ns
ns
ns
μs
μs
ns
ns
ns
I
PULLUP
= 3mA
0.7 • DV
CC
0.08
DV
CC
= 1.8V, Serial Port Idle
1
0.3 • DV
CC
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 3.8V, unless otherwise noted.
CONDITIONS
MIN
1.5
TYP
MAX
5.5
1
UNITS
V
μA
V
V
V
V
The
l
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 3.8V, V
OUTx
= 1.5V, unless otherwise noted.
PARAMETER
Regulators R600A, R400A, R600B, R400B
f
OSC
Maximum Duty Cycle
LDO Mode Closed Loop R
OUT
Regulators R600A, R600B
PMOS Switch Current Limit
PMOS R
DS(ON)
NMOS R
DS(ON)
LDO Mode Open Loop R
OUT
Available Output Current
SW Pull-Down in Shutdown
LDO Mode
Forced Burst Mode
LDO, V
OUT
= 1.2V
Shutdown
75
50
Pulse Skip Mode
850
1200
0.38
0.38
2.2
140
2.5
1500
mA
Ω
Ω
Ω
mA
mA
kΩ
Pulse Skip Mode
LDO Mode
1.91
100
0.25
2.25
2.59
MHz
%
Ω
CONDITIONS
MIN
TYP
MAX
UNITS
BUCK DC/DC ELECTRICAL CHARACTERISTICS
3562fa
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LTC3562
ELECTRICAL CHARACTERISTICS
PARAMETER
Regulators R400A, R400B
PMOS Switch Current Limit
PMOS R
DS(ON)
NMOS R
DS(ON)
LDO Mode Open Loop R
OUT
SW Pull-Down in Shutdown
Available Output Current
Regulators R600A, R400A
V
FB(MAX)
V
FB(MIN)
V
FB(STEP)
(0 to 15)
I
FB
Regulators R600B, R400B
V
OUT(MIN)
V
OUT(MAX)
V
OUT(STEP)
(0 to 127)
V
IN
= 4V, DAC = 0000000, Pulse Skip Mode
V
IN
= 4V, DAC = 1111111,
Pulse Skip Mode
V
IN
= 4V
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 3.8V, V
OUTx
= 1.5V, unless otherwise noted.
CONDITIONS
Pulse Skip Mode
MIN
600
TYP
800
0.5
0.5
LDO Mode
Shutdown
Forced Burst Mode
LDO Mode, V
OUT
= 1.2V
DAC = XXX1111, Pulse Skip Mode
DAC = XXX0000, Pulse Skip Mode
FB Input Current
DAC = XXX1111
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MAX
1000
UNITS
mA
Ω
Ω
Ω
kΩ
mA
mA
3
2.5
50
50
0.776
0.412
100
0.800
0.425
25
0.824
0.438
V
V
mV
–50
0.582
3.661
0
0.600
3.775
25
50
0.618
3.889
nA
V
V
mV
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 LTC3562E 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 control.
Note 3:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions.
Overtemperature protection is active when junction temperature exceeds
the maximum operating junction temperature. Continuous operation above
the specified maximum operating junction temperature may result in
device degradation or failure.
Note 4:
The serial port is tested at rated operating frequency. Timing
parameters are tested and/or guaranteed by design.
3562fa
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LTC3562
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
90
FORCED
Burst Mode OPERATION
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
600mA
BUCKS
70
60
50
40
30
20
V
IN
= 3.8V
V
OUT
= 1.2V
0.1
1
10
I
OUT
(mA)
100
1000
3562 G01
Efficiency vs Load Current
FORCED
Burst Mode OPERATION
600mA
BUCKS
PULSE SKIP
Burst Mode
OPERATION
100
90
80
70
60
50
40
30
20
V
IN
= 3.8V
V
OUT
= 1.8V
0.1
1
10
I
OUT
(mA)
100
1000
3562 G02
Efficiency vs Load Current
FORCED
Burst Mode
OPERATION
600mA
BUCKS
PULSE SKIP
Burst Mode
OPERATION
EFFICIENCY (%)
80 Burst Mode
70 OPERATION
60
50
40
30
20
10
0
0.01
PULSE SKIP
10
0
0.01
10
0
0.01
0.1
1
10
I
OUT
(mA)
V
IN
= 3.8V
V
OUT
= 2.5V
100
1000
3562 G03
Efficiency vs Load Current
100
FORCED Burst Mode
90 OPERATION
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
I
OUT
(mA)
V
IN
= 3.8V
V
OUT
= 3.3V
100
1000
3562 G04
Efficiency vs Input Voltage
Burst Mode Operation
100
90
600mA
BUCKS
EFFICIENCY (%)
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
2.5
I
OUT
= 0.1mA
I
OUT
= 1mA
I
OUT
= 10mA
I
OUT
= 100mA
I
OUT
= 400mA
3
4
4.5
3.5
INPUT VOLTAGE (V)
5
5.5
V
OUT
= 1.2V
100
90
80
70
60
50
40
30
20
10
0
Efficiency vs Input Voltage
Burst Mode Operation
V
OUT
= 1.8V
PULSE SKIP
Burst Mode
OPERATION
I
OUT
= 0.1mA
I
OUT
= 1mA
I
OUT
= 10mA
I
OUT
= 100mA
I
OUT
= 400mA
2.5
3
4
4.5
3.5
INPUT VOLTAGE (V)
5
5.5
3562 G05
3562 G06
Output Transient
Burst Mode Operation
V
OUT400B
50mV/DIV
AC
COUPLED
V
OUT400A
50mV/DIV
AC
COUPLED
300mA
I
OUT400B
5mA
50μs/DIV
V
OUT400B
= 1.2V
V
OUT400A
= 1.2V
I
OUT400A
= 20mA
3562 G07
Output Transient
Pulse Skip Mode
V
OUT400B
50mV/DIV
AC
COUPLED
V
OUT600B
50mV/DIV
AC
COUPLED
300mA
I
OUT400B
5mA
50μs/DIV
V
OUT400B
= 1.8V
V
OUT600B
= 1.2V
I
OUT600B
= 15mA
3562 G08
Start-Up Transient
Pulse Skip Mode
V
OUT600A
500mV/DIV
INDUCTOR
CURRENT
I
L
= 100mA/
DIV
RUN600A
OFF
2V/DIV ON
50μs/DIV
V
OUT600A
= 1.2V
R
LOAD
= 6Ω
3562 G09
3562fa
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