FEATURES
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LTC3406AB
1.5MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
DESCRIPTION
The LTC
®
3406AB is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. Supply current with no load is 200μA,
dropping to <1μA in shutdown. The 2.5V to 5.5V input
voltage range makes the LTC3406AB ideally suited for
single Li-Ion battery-powered applications. 100% duty
cycle provides low dropout operation, extending battery
run time in portable systems. PWM pulse skipping mode
operation provides very low output ripple voltage for noise
sensitive applications. Refer to LTC3406A for applications
that require Burst Mode
®
operation.
Switching frequency is internally set at 1.5MHz, allowing
the use of small surface mount inductors and capacitors.
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
feedback reference voltage. The LTC3406AB is available
in a low profile (1mm) ThinSOT package.
, LT, LTC, LTM 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 5481178, 6580258.
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High Efficiency: Up to 96%
600mA Output Current
2.5V to 5.5V Input Voltage Range
1.5MHz Constant Frequency Operation
No Schottky Diode Required
Low Dropout Operation: 100% Duty Cycle
Low Quiescent Current: 200μA
±2%
0.6V Reference
Shutdown Mode Draws <1μA Supply Current
Internal Soft-Start Limits Inrush Current
Current Mode Operation for Excellent Line and
Load Transient Response
Overtemperature Protected
Low Profile (1mm) ThinSOT
TM
Package
APPLICATIONS
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Cellular Telephones
Satellite and GPS Receivers
Wireless and DSL Modems
Digital Still Cameras
Media Players
Portable Instruments
TYPICAL APPLICATION
Efficiency vs Load Current
100
2.2μH
V
IN
4.7μF
CER
V
IN
SW
22pF
10μF
CER
619k
309k
3406AB TA09
V
OUT
= 1.8V
1.8V, 600mA
V
OUT
EFFICIENCY (%)
90
80
70
60
50
40
30
20
10
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
100
10
OUTPUT CURRENT (mA)
1000
3406B TA14
LTC3406AB
RUN
GND
V
FB
3406abf
1
LTC3406AB
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
RUN 1
GND 2
SW 3
4 V
IN
5 V
FB
Input Supply Voltage ....................................– 0.3V to 6V
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 7)................................................................800mA
N-Channel Switch Sink Current (DC) (Note 7) .....800mA
Peak SW Sink and Source Current (Note 7) .............1.3A
Operating Temperature Range (Note 2) ...– 40°C to 85°C
Junction Temperature (Notes 3, 6) ....................... 125°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/W,
θ
JC
= 90°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3406ABES5#PBF
TAPE AND REEL
LTC3406ABES5#TRPBF
PART MARKING
LTCXZ
PACKAGE DESCRIPTION
5-Lead Plastic TSOT-23
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/
ELECTRICAL CHARACTERISTICS
SYMBOL
I
VFB
V
FB
ΔV
FB
I
PK
V
LOADREG
V
IN
I
S
PARAMETER
Feedback Current
Regulated Feedback Voltage
Reference Voltage Line Regulation
Peak Inductor Current
Output Voltage Load Regulation
Input Voltage Range
Input DC Bias Current
Active Mode
Shutdown
Oscillator Frequency
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
SW Leakage
Soft-Start Time
(Note 4)
The
●
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 specified.
CONDITIONS
●
●
●
MIN
0.5880
0.75
TYP
0.6
0.04
1
0.5
MAX
±30
0.6120
0.4
1.25
UNITS
nA
V
%/V
A
%
V
IN
= 2.5V to 5.5V (Note 4)
V
IN
= 3V, V
FB
= 0.5V
Duty Cycle < 35%
●
2.5
200
0.1
5.5
300
1
1.8
0.35
0.35
±1
1.2
V
μA
μA
MHz
Ω
Ω
μA
ms
(Note 5)
V
FB
= 0V
V
RUN
= 0V, V
IN
= 5.5V
V
FB
= 0.6V
I
SW
= 100mA
I
SW
= –100mA
V
RUN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V
V
FB
from 10% to 90% Full-scale
0.6
●
f
OSC
R
PFET
R
NFET
I
LSW
t
SOFTSTART
1.2
1.5
0.23
0.21
±0.01
0.9
3406abf
2
LTC3406AB
ELECTRICAL CHARACTERISTICS
SYMBOL
V
RUN
I
RUN
PARAMETER
RUN Threshold
RUN Leakage Current
The
●
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 specified.
CONDITIONS
●
●
MIN
0.3
TYP
1
±0.01
MAX
1.5
±1
UNITS
V
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 LTC3406ABE 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:
LTC3406AB: T
J
= T
A
+ (P
D
)(250°C/W)
Note 4:
The LTC3406AB 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:
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.
Note7:
Limited by long term current density considerations.
TYPICAL PERFORMANCE CHARACTERISTICS
(From Front Page Figure Except for the Resistive Divider Resistor Values)
Efficiency vs Input Voltage
100
90
80
EFFICIENCY (%)
70
EFFICIENCY (%)
60
50
40
30
20
10
0
2
V
OUT
= 1.8V
3
I
L
= 100mA
I
L
= 600mA
I
L
= 10mA
5
4
INPUT VOLTAGE (V)
6
3406B G01
Efficiency vs Load Current
100
90
80
70
60
50
40
30
20
10
0
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
100
10
OUTPUT CURRENT (mA)
1000
3406B G02
V
OUT
= 1.2V
Efficiency vs Load 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
100
10
OUTPUT CURRENT (mA)
1000
3406B G03
Reference Voltage vs
Temperature
0.615
0.610
REFERENCE VOLTAGE (V)
0.605
0.600
0.595
0.590
0.585
–50 –25
V
IN
= 3.6V
V
OUT
= 2.5V
50
25
75
0
TEMPERATURE (°C)
100
125
3406AB G21
3406abf
3
LTC3406AB
TYPICAL PERFORMANCE CHARACTERISTICS
(From Front Page Figure Except for the Resistive Divider Resistor Values)
Oscillator Frequency vs
Temperature
1.60
OSCILLATOR FREQUENCY (MHz)
1.55
1.50
1.45
1.40
1.35
1.30
–50 –25
V
IN
= 3.6V
OSCILLATOR FREQUENCY (MHz)
1.60
1.55
OUTPUT VOLTAGE (V)
1.50
1.45
1.40
1.35
1.30
1.25
50
25
0
75
TEMPERATURE (°C)
100
125
1.20
2.0
2.5
3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
5.5
6.0
Oscillator Frequency vs Supply
Voltage
1.820
1.816
1.812
1.808
1.804
1.800
1.796
1.792
1.788
1.784
1.780
Output vs Load Current
V
OUT
= 1.8V
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
0
200
400
600
3406B G24
OUTPUT CURRENT (mA)
3406B G07
3406B G22
R
DS(ON)
vs Input Voltage
0.40
0.35
0.30
R
DS(ON)
(Ω)
R
DS(0N)
(Ω)
0.25
0.20
0.15
0.10
0
1
4
3
5
2
INPUT VOLTAGE (V)
6
7
MAIN SWITCH
SYNCHRONOUS SWITCH
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
R
DS(ON)
vs Input Voltage
300
V
IN
= 2.7V
V
IN
= 3.6V
DYNAMIC SUPPLY CURRENT (μA)
250
200
150
100
50
0
Dynamic Supply Current
V
OUT
= 1.2V
I
LOAD
= 0A
V
IN
= 4.2V
MAIN SWITCH
SYNCHRONOUS SWITCH
0
50
75
25
TEMPERATURE (°C)
100
125
0
–50 –25
2
2.5
3
4.5 5
3.5 4
INPUT VOLTAGE (V)
5.5
6
3406B G25
3406B G26
3406B G27
Dynamic Supply Current vs
Temperature
300
DYNAMIC SUPPLY CURRENT (μA)
250
200
150
100
50
0
–50 –25
V
IN
= 3.6V
V
OUT
= 1.2V
I
LOAD
= 0A
SWITCH LEAKAGE (nA)
140
120
100
80
60
40
20
Switch Leakage vs Temperature
1000
MAIN SWITCH
SYNCHRONOUS SWITCH
SWITCH LEAKAGE (pA)
900
800
700
600
500
400
300
200
100
0
50
25
75
0
TEMPERATURE (°C)
100
125
Switch Leakage vs Input Voltage
MAIN SWITCH
SYNCHRONOUS SWITCH
RUN = 0V
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
0
1
3
4
2
INPUT VOLTAGE (V)
5
6
3406B G30
3406B G28
3406B G29
3406abf
4
LTC3406AB
TYPICAL PERFORMANCE CHARACTERISTICS
(From Front Page Figure Except for the Resistive Divider Resistor Values)
Start-Up from Shutdown
V
OUT
200mV/DIV
Load Step
V
OUT
200mV/DIV
Load Step
RUN
2V/DIV
V
OUT
1V/DIV
I
LOAD
500mA/DIV
I
L
500mA/DIV
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
400μs/DIV
V
OUT
= 1.8V
I
LOAD
= 600mA (3Ω RES)
3406B G31
I
LOAD
500mA/DIV
V
IN
= 3.6V
20μs/DIV
V
OUT
= 1.8V
I
LOAD
= 0mA TO 600mA
3406B G32
V
IN
= 3.6V
20μs/DIV
V
OUT
= 1.8V
I
LOAD
= 50mA TO 600mA
3406B G33
Load Step
V
OUT
200mV/DIV
V
OUT
200mV/DIV
Load Step
Discontinuous Operation
SW
(2V/DIV)
I
L
500mA/DIV
I
L
500mA/DIV
V
OUT
20mV/DIV
AC COUPLED
I
LOAD
500mA/DIV
I
LOAD
500mA/DIV
I
L
200mA/DIV
V
IN
= 3.6V
20μs/DIV
V
OUT
= 1.8V
I
LOAD
= 200mA TO 600mA
3406B G35
V
IN
= 3.6V
20μs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA TO 600mA
3406B G34
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 25mA
500ns/DIV
3406B G36
PIN FUNCTIONS
RUN (Pin 1):
Run Control Input. Forcing this pin above 1.5V
enables the part. Forcing this pin below 0.3V shuts down
the device. In shutdown, all functions are disabled drawing
<1μA supply current. Do not leave RUN floating.
GND (Pin 2):
Ground Pin.
SW (Pin 3):
Switch Node Connection to Inductor. This pin
connects to the drains of the internal main and synchronous
power MOSFET switches.
V
IN
(Pin 4):
Main Supply Pin. Must be closely decoupled to
GND, Pin 2, with a 2.2μF or greater ceramic capacitor.
V
FB
(Pin 5):
Feedback Pin. Receives the feedback voltage
from an external resistive divider across the output.
3406abf
5
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