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.
, LT, LTC, LTM and Burst Mode 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
Internal Soft-Start
Selectable 1.7MHz or 2.6MHz Constant Frequency
Operation
Internal Oscillator can be Synchronizable to an
External Clock, 1MHz to 3MHz Range
High Efficiency: Up to 95%
Very Low Quiescent Current: Only 65μA During
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
0.613V 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
■
■
■
Cellular Phones
Digital Cameras
MP3 Players
TYPICAL APPLICATION
100
90
Burst Mode Efficiency, 1.8V
OUT
1.0
2.5V
IN
, BURST
4.2V
IN
, BURST
3.6V
IN
, BURST
0.01
POWER LOST
3.6V
IN
, BURST
0.1
POWER LOSS (W)
High Efficiency Step-Down Converter
V
IN
1.8V TO 5.5V
LTC3409
SW
V
IN
RUN
MODE
SYNC
*SUMIDA CDRH2D18/LD
V
FB
GND
133k
255k
2.2μH*
10pF
10μF
CER
EFFICIENCY (%)
80
70
60
50
40
30
20
10
4.7μF
CER
V
OUT
1.8V
0.001
3409 TA01
0
0.1
1
10
100
LOAD CURRENT (mA)
0.0001
1000
3409 TA01b
3409fc
1
LTC3409
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
LTC3409EDD#PBF
LTC3409IDD#PBF
TAPE AND REEL
LTC3409EDD#TRPBF
LTC3409IDD#TRPBF
PART MARKING*
LBNM
LBNM
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/
ELECTRICAL CHARACTERISTICS
SYMBOL
V
RUN
I
RUN
V
MODE
I
MODE
V
SYNCTH
I
SYNC
V
FB
PARAMETER
RUN Threshold
RUN Leakage Current
MODE Threshold
MODE Leakage Current
SYNC Threshold
SYNC Leakage Current
Regulated Feedback Voltage
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
●
MIN
0.3
0.3
0.3
0.6007
0.5992
0.5977
35
●
TYP
0.65
0.01
0.65
0.01
0.65
0.01
0.6130
0.6130
0.6130
61
0.04
0.04
MAX
1.1
1
1.1
1
1.1
1
0.6252
0.6268
0.6283
±30
85
0.4
0.4
1.3
5.5
UNITS
V
μA
V
μA
V
μA
V
V
V
nA
mV
%/V
%/V
A
%
V
V
RUN
= 0V or = 2.2V
●
V
MODE
= 0V or = 2.2V
●
V
SYNC
= 0V or = 2.2V
(Note 4) T
A
= 25°C
(Note 4) 0°C ≤ T
A
≤ 85°C
(Note 4) –40°C ≤ T
A
≤ 85°C
ΔV
OVL
= ΔV
FBOVL
– V
FB
(Note 6)
1.6V < V
IN
< 5.5V (Note 4)
I
OUT
= 100mA, 1.6V < V
IN
< 5.5V
V
FB
= 0.5V or V
OUT
= 90%
V
OUT
= 1.2V, Pulse Skip Mode, 0 < I
LOAD
< 600mA
●
●
I
VFB
ΔV
OVL
ΔV
FB
ΔV
OUT
I
PK
V
LOADREG
V
IN
Feedback Current
ΔV
FBOVL
Overvoltage Lockout
Reference Voltage Line Regulation
Output Voltage Line Regulation
Peak Inductor Current
Output Voltage Load Regulation
Input Voltage Range
0.75
1.6
1
0.5
3409fc
2
LTC3409
ELECTRICAL CHARACTERISTICS
SYMBOL
I
S
PARAMETER
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
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
(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)
●
●
MIN
TYP
350
65
0.1
MAX
475
120
1
2.1
3.0
UNITS
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 LTC3409E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3409I 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:
LTC3409: 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 LTC3409 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.
3409fc
3
LTC3409
TYPICAL PERFORMANCE CHARACTERISTICS
(From Typical Application on the front page except for the resistive divider resistor values)
Efficiency/Power Lost
vs Load Current, V
OUT
= 1.8V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
10
100
LOAD CURRENT (mA)
0.0001
1000
3409 G01
Efficiency vs Input Voltage
V
OUT
= 1.2V, Burst Mode Operation
1.0
Efficiency vs Input Voltage
V
OUT
= 1.2V, Pulse Skip
100
90
80
I
OUT
= 800mA
I
OUT
= 100mA
I
OUT
= 10mA
I
OUT
= 1mA
I
OUT
= 0.1mA
I
OUT
= 600mA
100
90
80
1
2
0.1
EFFICIENCY (%)
60
50
40
30
20
10
0
1.5
I
OUT
= 0.1mA
I
OUT
= 1mA
I
OUT
= 10mA
2.5
I
OUT
= 100mA
I
OUT
= 600mA
I
OUT
= 800mA
5.5
3409 G02
EFFICIENCY (%)
4.5
3.5
INPUT VOLTAGE (V)
3
8
10
12
4 5
6
70
70
60
50
40
30
20
10
0
1.5
POWER LOSS (mW)
0.01
7
11
9
0.001
2.5
4.5
3.5
INPUT VOLTAGE (V)
5.5
3409 G03
1: 2.5V
IN
, BURST
2: 3.6V
IN
, BURST
3: 4.2V
IN
, BURST
4: 2.5V
IN
, PULSE SKIP
5: 3.6V
IN
, PULSE SKIP
6: 4.2V
IN
, PULSE SKIP
7: POWER LOST, 2.5V
IN
, BURST
8: POWER LOST, 2.5V
IN
, PULSE SKIP
9: POWER LOST, 3.6V
IN
, BURST
10: POWER LOST, 3.6V
IN
, PULSE SKIP
11: POWER LOST, 4.2V
IN
, BURST
12: POWER LOST, 4.2V
IN
, PULSE SKIP
Efficiency vs Load Current
V
OUT
= 2.5V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
10
100
LOAD CURRENT (mA)
1000
3409 G04
Efficiency vs Load Current
V
OUT
= 1.2V
100
90
BURST
2.5V
IN
REFERENCE VOLTAGE (V)
Reference Voltage
vs Temperature
0.618
0.617
0.616
0.615
0.614
0.613
0.612
0.611
0.610
0.609
BURST
2.7V
IN
4.2V
IN
1.6V
IN
80
EFFICIENCY (%)
70
60
50
40
30
20
10
3.6V
IN
3.6V
IN
2.7V
IN
4.2V
IN
PULSE SKIP
3.1V
IN
3.1V
IN
2.5V
IN
1.6V
IN
PULSE SKIP
0
0.1
1
10
100
LOAD CURRENT (mA)
1000
3409 G05
0.608
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
3409 G06
3409fc
4
LTC3409
TYPICAL PERFORMANCE CHARACTERISTICS
(From Typical Application on the front page except for the resistive divider resistor values)
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