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1
LTC3406-1.2
340612f
High Efficiency: Up to 90%
Very Low Quiescent Current: Only 20µA
600mA Output Current at V
IN
= 3V
2.5V to 5.5V Input Voltage Range
1.5MHz Constant Frequency Operation
No Schottky Diode Required
Shutdown Mode Draws < 1µA Supply Current
Current Mode Operation for Excellent Line and
Load Transient Response
Overtemperature Protected
Low Profile (1mm) ThinSOT
TM
Package
The LTC
®
3406-1.2 is a high efficiency monolithic syn-
chronous buck regulator using a constant frequency,
current mode architecture. Supply current during opera-
tion with only 20µA drops <1µA in shutdown. The 2.5V to
5.5V input voltage range makes the LTC3406-1.2 ideally
suited for single Li-Ion battery-powered applications. 100%
duty cycle provides low dropout operation, extending
battery life in portable systems. PWM pulse skipping
mode operation provides very low output ripple voltage for
noise sensitive applications.
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. The
LTC3406-1.2 is available in a low profile (1mm) ThinSOT
package.
Cellular Telephones
Personal Information Appliances
Wireless and DSL Modems
Digital Still Cameras
MP3 Players
Portable Instruments
High Efficiency Step-Down Converter
1.5MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
Efficiency and Power Loss
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
V
IN
C
IN
4.7µF
CER
V
IN
2.7V TO 5.5V
LTC3406-1.2
RUN
2.2µH
340612 TA01a
SW
V
OUT
GND
C
OUT
10µF
CER
V
OUT
1.2V
600mA
LOAD CURRENT (mA)
0.1
10
1000
100
90
80
70
60
50
40
30
20
10
0
340612 TA01b
1
100
1
0.1
0.01
0.001
0.00001
0.0001
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
EFFICIENCY
POWER LOSS
POWER LOSS (W)
EFFICIENCY (%)
, LTC and LT are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. ThinSOT is a trademark of Linear
Technology Corporation. Protected by U.S. Patents including 5481178, 6580258, 6304066,
6127815, 6498466, 6611131.
2
LTC3406-1.2
340612f
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
OUT
Regulated Output Voltage
I
OUT
= 100mA
1.164
1.2
1.236
V
V
OVL
Output Overvoltage Lockout
V
OVL
= V
OVL
V
OUT
2.5
6.25
10
%
V
OUT
Output Voltage Line Regulation
V
IN
= 2.5V to 5.5V
0.04
0.4
%/V
I
PK
Peak Inductor Current
V
IN
= 3V, V
OUT
= 1.08V, Duty Cycle < 35%
0.75
1
1.25
A
V
LOADREG
Output Voltage Load Regulation
0.5
%
V
IN
Input Voltage Range
2.5
5.5
V
I
S
Input DC Bias Current
(Note 4)
Active Mode
V
OUT
= 1.08V, I
LOAD
= 0A
300
400
µA
Sleep Mode
V
OUT
= 1.236V, I
LOAD
= 0A
20
35
µA
Shutdown
V
RUN
= 0V, V
IN
= 5.5V
0.1
1
µA
f
OSC
Oscillator Frequency
V
OUT
= 1.2V
1.2
1.5
1.8
MHz
V
OUT
= 0V
210
kHz
R
PFET
R
DS(ON)
of P-Channel FET
I
SW
= 100mA
0.4
0.5
R
NFET
R
DS(ON)
of N-Channel FET
I
SW
= 100mA
0.35
0.45
I
LSW
SW Leakage
V
RUN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V
±0.01
±1
µA
V
RUN
RUN Threshold
0.3
1
1.5
V
I
RUN
RUN Leakage Current
±0.01
±1
µA
Input Supply Voltage .................................. 0.3V to 6V
RUN, V
OUT
Voltages................................... 0.3V to V
IN
SW Voltage (DC) ......................... 0.3V to (V
IN
+ 0.3V)
P-Channel Switch Source Current (DC) ............. 800mA
N-Channel Switch Sink Current (DC) ................. 800mA
Peak SW Sink and Source Current (V
IN
= 3V)........ 1.3A
Operating Temperature Range (Note 2) .. 40°C to 85°C
Junction Temperature (Notes 3, 5) ...................... 125°C
Storage Temperature Range ................ 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
LTC3406ES5-1.2
ORDER PART
NUMBER
S5 PART MARKING
LTBMQ
T
JMAX
= 125°C,
JA
= 250°C/ W,
JC
= 90°C/ W
RUN 1
GND 2
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
SW 3
5 V
OUT
4 V
IN
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.
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3406E-1.2 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.
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC3406-1.2: T
J
= T
A
+ (P
D
)(250°C/W)
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5: 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.
3
LTC3406-1.2
340612f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Efficiency vs Input Voltage
Efficiency and Power Loss
Reference Voltage vs
Temperature
Oscillator Frequency vs
Temperature
(From Figure 1)
TEMPERATURE (°C)
50
REFERENCE VOLTAGE (V)
1.178
1.188
1.198
1.208
1.218
1.228
1.168
25
75
25
0
50
100
125
V
IN
= 3.6V
340612 G03
TEMPERATURE (°C)
50
FREQUENCY (MHz)
1.70
1.65
1.60
1.55
1.50
1.45
1.40
1.35
1.30
25
75
25
0
50
100
125
V
IN
= 3.6V
340612 G04
INPUT VOLTAGE (V)
2
EFFICIENCY (%)
6
340612 G01
3
4
5
100
95
90
85
80
75
70
I
OUT
= 600mA
I
OUT
= 100mA
I
OUT
= 10mA
I
LOAD
(mA)
0.1
EFFICIENCY (%)
10
1000
100
90
80
70
60
50
40
340612 GO2
1
100
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
LOAD CURRENT (mA)
0
OUTPUT VOLTAGE (V)
500
200 300 400
600
800
100
1.225
1.215
1.205
1.195
1.185
1.175
340612 G06
1000
900
700
Oscillator Frequency vs
Supply Voltage
Output Voltage vs Load Current
SUPPLY VOLTAGE (V)
2
OSCILLATOR FREQUENCY (MHz)
1.8
1.7
1.6
1.5
1.4
1.3
1.2
3
4
5
6
340612 G05
T
A
= 25°C
TEMPERATURE (°C)
50
0.4
0.5
0.7
25
75
340612 G08
0.3
0.2
25
0
50
100
125
0.1
0
0.6
R
DS(ON)
(
)
MAIN SWITCH
SYNCHRONOUS SWITCH
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
SUPPLY VOLTAGE (V)
2
0
SUPPLY CURRENT (
µ
A)
5
15
20
25
50
35
3
4
340612 G09
10
40
45
30
5
6
I
LOAD
= 0A
R
DS(ON)
vs Input Voltage
INPUT VOLTAGE (V)
1
0
0.4
0.5
0.7
4
6
340612 G07
0.3
0.2
2
3
5
7
0.1
0
0.6
R
DS(ON)
(
)
MAIN
SWITCH
SYNCHRONOUS
SWITCH
T
A
= 25°C
R
DS(ON)
vs Temperature
Supply Current vs Supply Voltage
T
A
= 25°C unless otherwise specified.
4
LTC3406-1.2
340612f
Load Step
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
20µs/DIV
V
IN
= 3.6V
I
LOAD
= 25mA TO 600mA
340612 G15
Load Step
RUN
2V/DIV
V
OUT
1V/DIV
I
L
500mA/DIV
40µs/DIV
V
IN
= 3.6V
I
LOAD
= 100mA TO 600mA
340612 G14
INPUT VOLTAGE (V)
0
0
SWITCH LEAKAGE (pA)
20
40
60
80
120
1
2
3
4
340612 G12
5
6
100
RUN = 0V
T
A
= 25°C
SYNCHRONOUS
SWITCH
MAIN
SWITCH
TEMPERATURE (°C)
50
0
SUPPLY CURRENT (
µ
A)
5
15
20
25
50
35
0
50
75
340612 G10
10
40
45
30
25
25
100
125
V
IN
= 3.6V
I
LOAD
= 0A
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
(From Figure 1)
Supply Current vs Temperature
Switch Leakage vs Input Voltage
(From Figure 1a Except for the Resistive Divider Resistor Values)
SW
2V/DIV
V
OUT
50mV/DIV
AC COUPLED
I
L
200mA/DIV
4µs/DIV
V
IN
= 3.6V
I
LOAD
= 25mA
3406B12 G13
Discontinuous Operation
TEMPERATURE (°C)
50
SWITCH LEAKAGE (nA)
200
250
300
25
75
340612 G11
150
100
25
0
50
100
125
50
0
V
IN
= 5.5V
RUN = 0V
MAIN SWITCH
SYNCHRONOUS SWITCH
Switch Leakage vs Temperature
5
LTC3406-1.2
340612f
U
U
U
PI FU CTIO S
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 synchro-
nous 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
OUT
(Pin 5): Output Voltage Feedback Pin. An internal
resistive divider divides the output voltage down for com-
parison to the internal reference voltage.
FU CTIO AL DIAGRA
U
U
W
+
+
EA
+
I
RCMP
+
I
COMP
5
1
RUN
OSC
SLOPE
COMP
OSC
FREQ
SHIFT
0.8V
0.65V
FB
0.8V + V
OVL
60k
120k
0.8V REF
SHUTDOWN
V
IN
V
OUT
V
IN
S
R
RS LATCH
OV
SWITCHING
LOGIC
AND
BLANKING
CIRCUIT
ANTI-
SHOOT-
THRU
Q
Q
5
4
SW
3
GND
3406B12 BD
2
+
OVDET
V
OUT
100mV/DIV
AC COUPLED
I
LOAD
500mA/DIV
I
L
500mA/DIV
20µs/DIV
V
IN
= 3.6V
I
LOAD
= 100mA TO 600mA
340612 G16
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
20µs/DIV
V
IN
= 3.6V
I
LOAD
= 200mA TO 600mA
340612 G17
Load Step
Load Step
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
(From Figure 1a Except for the Resistive Divider Resistor Values)
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