LTC3560
2.25MHz, 800mA
Synchronous Step-Down
Regulator in ThinSOT
FEATURES
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DESCRIPTIO
High Efficiency: Up to 95%
Low Output Ripple (<20mV
P-P
): Burst Mode
®
Operation: I
Q
= 16
µ
A
2.5V to 5.5V Input Voltage Range
2.25MHz Constant Frequency Operation
Synchronizable to External Clock
No Schottky Diode Required
Stable with Ceramic Capacitors
Low Dropout Operation: 100% Duty Cycle
0.6V Reference Allows Low Output Voltages
Shutdown Mode Draws < 1µA Supply Current
±2%
Output Voltage Accuracy
Current Mode Operation for Excellent Line and
Load Transient Response
Overtemperature Protected
Low Profile (1mm) ThinSOT
TM
Package
The LTC
®
3560 is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. Supply current during operation is
only 16µA, dropping to <1µA in shutdown. The 2.5V to
5.5V input voltage range makes the LTC3560 ideally suited
for single Li-Ion/Li-Polymer battery-powered applications.
100% duty cycle provides low dropout operation, extend-
ing battery life in portable systems.
Switching frequency is internally set at 2.25MHz, allowing
the use of small surface mount inductors and capacitors.
For noise sensitive applications the LTC3560 can be
externally synchronized from 1MHz to 3MHz. Burst Mode
operation is inhibited during synchronization or when the
SYNC/MODE pin is pulled high, preventing low frequency
ripple from interfering with audio circuitry.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Low
output voltages are easily supported with the 0.6V feed-
back reference voltage. The LTC3560 is available in a low
profile (1mm) ThinSOT package.
, LTC, LT and Burst Mode are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6580258, 5481178, 5994885,
6304066, 6498466, 6611131
APPLICATIO S
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Cellular Telephones
Wireless and DSL Modems
Digital Still Cameras
Media Players
Portable Instruments
TYPICAL APPLICATIO
100
90
80
70
EFFICIENCY (%)
V
IN
2.7V
TO 5.5V
2.2µH
C
IN
10µF
CER
V
IN
LTC3560
RUN
SYNC/MODE V
FB
GND
806k
255k
3405A F01a
60
50
40
30
20
10
0
0.1
1
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
10
100
LOAD CURRENT (mA)
0.01
SW
10pF
V
OUT
2.5V
C
OUT
10µF
CER
Figure 1a. High Efficiency Step-Down Converter
Figure 1b. Efficiency vs Load Current
3560f
U
1
0.1
POWER LOSS (W)
U
U
0.001
0.0001
1000
3560 F01b
1
LTC3560
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN 1
GND 2
SW 3
6 SYNC/MODE
5 V
FB
4 V
IN
Input Supply Voltage .................................. – 0.3V to 6V
SYNC/MODE, RUN, V
FB
Voltages ............... – 0.3V to V
IN
SW Voltage (DC) ......................... – 0.3V to (V
IN
+ 0.3V)
P-Channel Switch Source Current (DC) (Note 6) ... 1.2A
N-Channel Switch Sink Current (DC) (Note 6) ....... 1.2A
Peak SW Sink and Source Current (Note 6)........... 2.1A
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Junction Temperature (Note 3) ............................ 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/ W
ORDER PART NUMBER
LTC3560ES6
S6 PART MARKING
LTCFY
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
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 3.6V unless otherwise specified.
SYMBOL
I
VFB
I
PK
V
FB
∆V
FB
V
LOADREG
V
IN
I
S
PARAMETER
Feedback Current
Peak Inductor Current
Regulated Feedback Voltage
Reference Voltage Line Regulation
Output Voltage Load Regulation
Input Voltage Range
Input DC Bias Current
Pulse Skipping Mode
Burst Mode
®
Operation
Shutdown
Oscillator Frequency
SYNC Frequency Range
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
SW Leakage
RUN Threshold
RUN Leakage Current
SYNC/MODE Leakage Current
Soft-Start Time
V
FB
from 10% to 90% Full Scale
I
SW
= 100mA
I
SW
= –100mA
V
RUN
= 0V, V
SW
= 0V or 5.5V, V
IN
= 5.5V
●
●
●
●
●
CONDITIONS
●
MIN
1.0
●
●
TYP
1.5
0.6
0.04
0.5
MAX
±30
2.0
0.612
0.4
5.5
UNITS
nA
A
V
%/V
%
V
µA
µA
µA
MHz
MHz
Ω
Ω
µA
V
µA
V
µA
ms
V
IN
= 3V, V
FB
= 0.5V, Duty Cycle < 35%
(Note 4)
V
IN
= 2.5V to 5.5V (Note 4)
0.588
2.5
200
16
0.1
(Note 5)
V
FB
= 0.63V, Mode = High, I
LOAD
= 0A
V
FB
= 0.63V, Mode = Low, I
LOAD
= 0A
V
RUN
= 0V, V
IN
= 5.5V
V
FB
= 0.6V
●
●
300
30
1
2.7
3
0.35
0.35
±1
1.5
±1
1.5
±1
1.2
f
OSC
f
SYNC
R
PFET
R
NFET
I
LSW
V
RUN
I
RUN
I
SYNC/MODE
t
SOFTSTART
1.8
1
2.25
0.23
0.21
±0.01
0.3
0.3
0.6
1
±0.01
1.0
±0.01
0.9
V
SYNC/MODE
SYNC/MODE Threshold
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 LTC3560E 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.
2
U
3560f
W
U
U
W W
W
LTC3560
ELECTRICAL CHARACTERISTICS
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3560: T
J
= T
A
+ (P
D
)(250°C/W)
Note 4:
The LTC3560 is tested in a proprietary test mode that connects
V
FB
to the output of the error amplifier.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 6:
Guaranteed by long-term current density limitations.
Note 7:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure1a Except for the Resistive Divider Resistor Values)
Efficiency vs Input Voltage
100
95
90
EFFICIENCY (%)
EFFICIENCY (%)
I
OUT
= 100mA
I
OUT
= 10mA
I
OUT
= 1mA
I
OUT
= 900mA
85
80
75
70
65
60
55
50
60
50
40
30
20
10
V
OUT
= 3.3V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
1000
3560 G24
EFFICIENCY (%)
I
OUT
= 0.1mA
V
OUT
= 1.8V
2.5
3
4
4.5
3.5
INPUT VOLTAGE (V)
5
5.5
3560 G01
Efficiency vs Output Current
100
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
10
100
OUTPUT CURRENT (mA)
1000
3560 G03
V
OUT
= 1.3V
70
EFFICIENCY (%)
60
50
40
30
20
10
V
OUT
= 1.8V
0
1
0.1
10
100
OUTPUT CURRENT (mA)
V
IN
= 4.2V
V
IN
= 3.6V
1000
3560 G04
REFERENCE VOLTAGE (V)
U W
Efficiency vs Output Current
100
90
80
70
100
90
80
70
60
50
40
30
20
10
Efficiency vs Output Current
V
OUT
= 1.8V
0
0.1
1
10
100
OUTPUT CURRENT (mA)
0
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
1
10
100
OUTPUT CURRENT (mA)
1000
3560 G02
Efficiency vs Output Current
100
90
80
Burst Mode OPERATION
Reference Voltage vs
Temperature
0.615
0.610
0.605
0.600
0.595
0.590
0.585
–50 –25
V
IN
= 3.6V
PULSE SKIP MODE
50
25
75
0
TEMPERATURE (°C)
100
125
3560 G05
3560f
3
LTC3560
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Oscillator Frequency vs
Temperature
2.50
2.45
OSCILLATOR FREQUENCY (MHz)
2.40
2.35
2.30
2.25
2.20
2.15
2.10
2.05
2.00
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
V
IN
= 3.6V
OSCILLATOR FREQUENCY (MHz)
OUTPUT VOLTAGE (V)
R
DS(ON
) vs Input Voltage
0.40
0.35
0.30
R
DS(0N)
(Ω)
0.30
MAIN SWITCH
0.25
SYNCHRONOUS
SWITCH
0.20
0.15
0.10
0
1
4
3
5
2
INPUT VOLTAGE (V)
6
7
R
DS(ON)
(Ω)
V
IN
= 2.7V
V
IN
= 3.6V
DYNAMIC SUPPLY CURRENT (µA)
Dynamic Supply Current
vs Temperature
300
DYNAMIC SUPPLY CURRENT (µA)
250
200
150
100
50
V
IN
= 3.6V
V
OUT
= 1.2V
I
LOAD
= 0A
SWITCH LEAKAGE (nA)
100
80
MAIN SWITCH
60
40
20
0
–50 –25
SYNCHRONOUS
SWITCH
SWITCH LEAKAGE (pA)
PULSE SKIPPING MODE
Burst Mode OPERATION
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
4
U W
3560 G06
Oscillator Frequency vs
Supply Voltage
2.4
2.3
2.2
2.1
2.0
1.9
1.8
2
2.5
3
1.84
1.83
1.82
1.81
Output Voltage vs Load Current
V
IN
= 3.6V
Burst Mode OPERATION
1.80
1.79
1.78
PULSE SKIP MODE
4.5 5
3.5 4
INPUT VOLTAGE (V)
5.5
6
0
200
400
600
800
LOAD CURRENT (mA)
1000
1200
3560 G07
3560 G08
R
DS(ON)
vs Temperature
0.40
0.35
300
250
200
Dynamic Supply Current
V
OUT
= 1.2V
I
LOAD
= 0A
0.25
0.20
0.15
0.10
0.05
0
–50 –25
0
SYNCHRONOUS SWITCH
MAIN SWITCH
V
IN
= 4.2V
PULSE SKIPPING MODE
150
100
50
Burst Mode OPERATION
0
2
2.5
3
4.5 5
3.5 4
INPUT VOLTAGE (V)
5.5
6
50
75
25
TEMPERATURE (°C)
100
125
3560 G10
3560 G09
3560 G12
Switch Leakage vs Temperature
140
120
1000
900
800
700
600
500
400
300
200
100
0
50
25
75
0
TEMPERATURE (°C)
100
125
Switch Leakage vs Input Voltage
RUN = 0V
MAIN SWITCH
SYNCHRONOUS
SWITCH
0
1
3
4
2
INPUT VOLTAGE (V)
5
6
3560 G14
3560 G11
3560 G13
3560f
LTC3560
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Burst Mode Operation
Pulse Skipping Mode Operation
RUN
2V/DIV
V
OUT
1V/DIV
SW
2V/DIV
V
OUT
20mV/DIV
AC COUPLED
I
L
200mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 25mA
2µs/DIV
3560 G15
Load Step
V
OUT
200mV/DIV
AC COUPLED
I
L
1A/DIV
I
LOAD
1A/DIV
3560 G18
V
OUT
200mV/DIV
AC COUPLED
I
L
1A/DIV
I
LOAD
1A/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 0A TO 800mA
PULSE SKIPPING MODE
Load Step
V
OUT
200mV/DIV
AC COUPLED
I
L
1A/DIV
I
LOAD
1A/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 0A TO 800mA
Burst Mode OPERATION
3560 G21
U W
Start-Up from Shutdown
SW
2V/DIV
V
OUT
20mV/DIV
AC COUPLED
I
L
200mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 25mA
500ns/DIV
3560 G16
I
L
500mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 800mA
500µs/DIV
3560 G17
Load Step
V
OUT
200mV/DIV
AC COUPLED
I
L
1A/DIV
I
LOAD
1A/DIV
Load Step
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 50mA TO 800mA
PULSE SKIPPING MODE
3560 G19
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA TO 800mA
PULSE SKIPPING MODE
3560 G20
Load Step
V
OUT
200mV/DIV
AC COUPLED
I
L
1A/DIV
I
LOAD
1A/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 50mA TO 800mA
Burst Mode OPERATION
3560 G22
Load Step
V
OUT
200mV/DIV
AC COUPLED
I
L
1A/DIV
I
LOAD
1A/DIV
20µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA TO 800mA
Burst Mode OPERATION
3560 G23
3560f
5
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