tery life in portable systems. Burst Mode operation can be
user-enabled, increasing efficiency at light loads, further
extending battery life.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Internal
soft-start offers controlled output voltage rise time at start-
up without the need for external components.
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.
1.6V to 5.5V Input Voltage Range
0.62V to 5.5V Output Voltage Range
Internal Soft-Start
Selectable 1.7MHz or 2.6MHz Constant Frequency
Operation
Internal Oscillator Can Be Synchronized to an
External Clock, 1MHz to 3MHz Range
High Efficiency: Up to 95%
65μA Quiescent Current, Burst Mode
®
Operation
600mA Output Current (V
IN
= 1.8V, V
OUT
= 1.2V)
750mA Peak Inductor Current
No Schottky Diode Required
Low Dropout Operation: 100% Duty Cycle
0.612V Reference Voltage
Stable with Ceramic Capacitors
Shutdown Mode Draws <1μA Supply Current
Current Mode Operation for Excellent Line and Load
Transient Response
Overtemperature Protection
Available in a Low Profile (0.75mm)
8-Lead (3mm
×
3mm) DFN Package
APPLICATIONS
n
n
n
Cellular Phones
Digital Cameras
MP3 Players
TYPICAL APPLICATION
High Efficiency Step-Down Converter
V
IN
1.8V TO 5.5V
4.7μF
LTC3409A
SW
V
IN
RUN
MODE
SYNC
*SUMIDA CDRH2D18/LD
V
FB
GND
137k
2.2μH*
10pF
267k
22μF
2
V
OUT
1.8V
Burst Mode Efficiency, 1.8V
OUT
100
90
80
EFFICIENCY (%)
70
60
50
40
30
3409A TA01
1
2.5V
IN
, BURST
0.1
POWER LOSS (W)
3.6V
IN
, BURST
0.01
4.2V
IN
, BURST
POWER LOST
3.6V
IN
, BURST
20
10
0
0
1
100
10
LOAD CURRENT (mA)
0.001
0.0001
1000
3409A TA01b
3409af
1
LTC3409A
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
V
FB
GND
V
IN
V
IN
1
2
3
4
9
8
7
6
5
SYNC
RUN
SW
MODE
Input Supply Voltage ................................... –0.3V to 6V
RUN, V
FB
, MODE, SYNC Voltages . –0.3V to (V
IN
+ 0.3V)
SW Voltage ................................... –0.3V to (V
IN
+ 0.3V)
Operating Temperature Range (Note 2) ..–40°C to 85°C
Junction Temperature (Note 3) ........................... 125°C
Storage Temperature Range.................. –65°C to 125°C
DD PACKAGE
8-LEAD (3mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3409AEDD#PBF
LTC3409AIDD#PBF
TAPE AND REEL
LTC3409AEDD#TRPBF
LTC3409AIDD#TRPBF
PART MARKING*
LFGY
LFGY
PACKAGE DESCRIPTION
8-Lead (3mm
×
3mm) Plastic DFN
8-Lead (3mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container.
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
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 2.2V unless otherwise specified.
SYMBOL
V
IN
V
FB
PARAMETER
Input Voltage Range
Regulated Feedback Voltage
(Note 4) T
A
= 25°C
(Note 4) 0°C ≤ T
A
≤ 85°C
(Note 4) –40°C ≤ T
A
≤ 85°C
V
FB
= 0.612V
ΔV
OVL
=
ΔV
FBOVL
– V
FB
(Note 6)
1.6V < V
IN
< 5.5V (Note 4)
1.9V ≤ V
IN
≤ 3.6V, 0°C ≤ T
A
≤ 85°C (Note 4)
V
FB
= 0.5V or V
OUT
= 90%
V
OUT
= 1.8V, V
MODE
= 0V, 1mA < I
LOAD
< 210mA,
0°C ≤ T
A
≤ 85°C (Note 8)
l
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
l
MIN
1.6
0.604
0.600
0.598
35
TYP
0.612
0.612
0.612
61
0.04
0.05
MAX
5.5
0.620
0.624
0.626
±30
85
0.4
0.5
1.3
0.5
1.1
1
1.1
1
UNITS
V
V
V
V
nA
mV
%/V
%
A
%
V
μA
V
μA
l
I
VFB
ΔV
OVL
ΔV
FB
I
PK
V
LOADREG
V
RUN
I
RUN
V
MODE
I
MODE
Feedback Current
ΔV
FBOVL
Overvoltage Lockout
Reference Voltage Line Regulation
Peak Inductor Current
Output Voltage Load Regulation
RUN Threshold
RUN Leakage Current
MODE Threshold
MODE Leakage Current
0.75
1
0.2
0.3
0.3
0.65
0.01
0.65
0.01
V
RUN
= 0V or = 2.2V
l
V
MODE
= 0V or = 2.2V
3409af
2
LTC3409A
ELECTRICAL CHARACTERISTICS
SYMBOL
V
SYNCTH
I
SYNC
I
S
PARAMETER
SYNC Threshold
SYNC Leakage Current
Input DC Bias Current
Active Mode
Sleep Mode
Shutdown
Nominal Oscillator Frequency
SYNC Threshold
Minimum SYNC Pin Frequency
Maximum SYNC Pin Frequency
Minimum SYNC Pulse Width
Soft-Start Period
SYNC Timeout
R
DS(ON)
of P-channel FET
R
DS(ON)
of N-channel FET
SW Leakage
RUN↑
Delay from Removal of EXT CLK Until Fixed
Frequency Operation Begins (Note 7)
I
SW
= 100mA, Wafer Level
I
SW
= 100mA, DD Package
I
SW
= 100mA, Wafer Level
I
SW
= 100mA, DD Package
V
RUN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V
V
SYNC
= 0V or = 2.2V
(Note 5)
V
OUT
= 90%, I
LOAD
= 0A
V
OUT
= 103%, I
LOAD
= 0A
V
RUN
= 0V, V
IN
= 5.5V
SYNC = GND
SYNC = V
IN
When SYNC Input is Toggling (Note 7)
l
l
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 2.2V unless otherwise specified.
CONDITIONS
l
MIN
0.3
TYP
0.65
0.01
350
65
0.1
MAX
1.1
1
475
120
1
2.2
3.2
UNITS
V
μA
μA
μA
μA
MHz
MHz
V
MHz
MHz
ns
ms
μs
Ω
Ω
Ω
Ω
f
OSC
SYNC TH
SYNC f
MIN
SYNC f
MAX
SYNC PW
t
SS
SYNC t
O
R
PFET
R
NFET
I
LSW
0.9
1.8
1.7
2.6
0.63
1
3
100
1
30
0.33
0.35
0.22
0.25
±0.1
±3
μA
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 LTC3409AE 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. The LTC3409AI is guaranteed to meet
specified performance over the full –40°C to 85°C operating temperature
range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3409A: T
J
= T
A
+ (P
D
)(43°C/W)
This IC includes overtemperature protection that is intended to protect the
device during momentary overload conditions. Overtemperature protection
becomes active at a junction temperature greater than the maximum
operating junction temperature. Continuous operation above the specified
maximum operating junction temperature may impair device reliability.
Note 4:
The LTC3409A 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:
ΔV
OVL
is the amount V
FB
must exceed the regulated feedback
voltage.
Note 7:
Determined by design, not production tested.
Note 8:
Guaranteed by measurement at the wafer level and design,
characterization and correlation with statistical process controls.
3409af
3
LTC3409A
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C, from Typical Application on the front page except for the resistive divider resistor values)
Pulse-Skipping Efficiency/Power
Lost vs Load Current, V
OUT
= 1.8V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
1
V
IN
= 2.5V
V
IN
= 4.2V 0.01
V
IN
= 3.6V
EFFICIENCY
V
IN
= 3.6V
V
IN
= 4.2V
EFFICIENCY (%)
0.1
V
IN
= 2.5V
POWER LOST (W)
1
100
90
80
70
60
50
40
30
20
10
0.001
1000
3409A G01
Efficiency vs Input Voltage,
V
OUT
= 1.2V, Burst Mode Operation
POWER LOST
10
100
LOAD CURRENT (mA)
0
1.6
I
OUT
= 0.1mA
I
OUT
= 1mA
I
OUT
= 10mA
I
OUT
= 100mA
I
OUT
= 600mA
5.5
3409A G02
2.6
3.6
4.6
INPUT VOLTAGE (V
IN
)
Efficiency vs Input Voltage
V
OUT
= 1.2V, Pulse-Skipping
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1.5
I
OUT
= 0.1mA
3.5
4.5
2.5
INPUT VOLTAGE (V
IN
)
5.5
3409A G03
Efficiency vs Load Current,
V
OUT
= 2.5V
100
100
2.7V
IN
4.2V
IN
EFFICIENCY (%)
3.6V
IN
90
80
70
60
50
40
30
20
10
90
Efficiency vs Load Current,
V
OUT
= 1.2V
2.5V
IN
1.6V
IN
I
OUT
= 100mA
I
OUT
= 600mA
EFFICIENCY (%)
80
70
60
50
40
30
20
10
3.1V
IN
3.1V
IN
2.5V
IN
1.6V
IN
I
OUT
= 10mA
I
OUT
= 1mA
4.2V
IN
2.7V
IN
3.6V
IN
BURST
PULSE-SKIPPING
1
10
100
LOAD CURRENT (mA)
1000
3409A G04
0
0.1
0
0.1
BURST
PULSE-SKIPPING
1
10
100
LOAD CURRENT (mA)
1000
3409A G05
Reference Voltage
vs Temperature
0.616
OSCILLATOR FREQUENCY (MHz)
0.615
REFERENCE VOLTAGE (V)
0.614
0.613
0.612
0.611
0.610
0.609
0.608
–50 –30 –10 10 30 50 70
TEMPERATURE (°C)
90 110 125
3409A G06
Oscillator Frequency
vs Temperature
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
–50
6
OSCILLATOR FREQUENCY SHIFT (%)
V
IN
= 2.7V
V
IN
= 1.6V
V
IN
= 4.2V
OSC 2.6MHz
4
2
0
–2
–4
–6
–8
Oscillator Frequency Shift
vs Input Voltage
f
LOW
1.7MHz
f
HIGH
2.6MHz
V
IN
= 4.2V
OSC 1.7MHz
V
IN
= 1.6V
V
IN
= 2.7V
–25
50
25
75
0
TEMPERATURE (°C)
100
125
–10
1.5
2.5
3.5
INPUT VOLTAGE (V)
4.5
5.5
3409A G08
3409A G07
3409af
4
LTC3409A
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C, from Typical Application on the front page except for the resistive divider resistor values)
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51mcu
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