LTC3406B-1.2
1.5MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
FEATURES
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DESCRIPTIO
High Efficiency: Up to 96%
600mA Output Current at V
IN
= 3V
2.5V to 5.5V Input Voltage Range
1.5MHz Constant Frequency Operation
No Schottky Diode Required
Low Quiescent Current: 300µA
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
®
3406B-1.2 is a high efficiency monolithic syn-
chronous buck regulator using a constant frequency,
current mode architecture. Supply current with no load is
300µA dropping to <1µA in shutdown. The 2.5V to 5.5V
input voltage range makes the LTC3406B-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 opera-
tion 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
LTC3406B-1.2 is available in a low profile (1mm) ThinSOT
package.
, 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.
APPLICATIO S
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Cellular Telephones
Personal Information Appliances
Wireless and DSL Modems
Digital Still Cameras
MP3 Players
Portable Instruments
TYPICAL APPLICATIO
Efficiency and Power Loss
High Efficiency Step-Down Converter
2.2µH
V
IN
2.7V TO 5.5V
C
IN
4.7µF
CER
V
IN
SW
C
OUT
10µF
CER
3406B12
TA01a
100
90
V
OUT
1.2V
600mA
80
EFFICIENCY (%)
EFFICIENCY
LTC3406B-1.2
RUN
V
OUT
GND
70
60
0.01
50
POWER LOSS
40
30
20
10
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
100
10
LOAD CURRENT (mA)
0.001
U
1
0.1
POWER LOSS (W)
U
U
0.0001
1000
3406B12
TA01b
sn3406b12 3406b12fs
1
LTC3406B-1.2
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN 1
GND 2
SW 3
4 V
IN
5 V
OUT
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
ORDER PART
NUMBER
LTC3406BES5-1.2
S5 PART MARKING
LTBMR
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/ W,
θ
JC
= 90°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
V
OUT
∆V
OVL
∆V
OUT
I
PK
V
LOADREG
V
IN
I
S
PARAMETER
Regulated Output Voltage
Output Overvoltage Lockout
Output Voltage Line Regulation
Peak Inductor Current
Output Voltage Load Regulation
Input Voltage Range
Input DC Bias Current
Shutdown
f
OSC
R
PFET
R
NFET
I
LSW
V
RUN
I
RUN
Oscillator Frequency
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
SW Leakage
RUN Threshold
RUN Leakage Current
(Note 4)
V
OUT
= 1.08V
V
RUN
= 0V, V
IN
= 5.5V
V
OUT
= 1.2V
V
OUT
= 0V
I
SW
= 100mA
I
SW
= –100mA
V
RUN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V
●
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
●
MIN
1.164
2.5
●
TYP
1.2
6.25
0.04
1
0.5
MAX
1.236
10
0.4
1.25
5.5
UNITS
V
%
%/V
A
%
V
µA
µA
MHz
kHz
Ω
Ω
µA
V
µA
∆V
OVL
= V
OVL
– V
OUT
V
IN
= 2.5V to 5.5V
V
IN
= 3V, V
OUT
= 1.08V, Duty Cycle < 35%
0.75
2.5
300
0.1
1.2
1.5
210
0.4
0.35
±0.01
0.3
1
±0.01
400
1
1.8
0.5
0.45
±1
1.5
±1
sn3406b12 3406b12fs
2
U
W
U
U
W W
W
LTC3406B-1.2
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3406BE-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:
LTC3406B-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.
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1)
Efficiency vs Input Voltage
95
90
85
I
OUT
= 100mA
I
OUT
= 600mA
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
80
75
70
65
60
55
50
2
3
REFERENCE VOLTAGE (V)
I
OUT
= 10mA
5
4
INPUT VOLTAGE (V)
Oscillator Frequency vs
Temperature
1.70
V
IN
= 3.6V
1.65
1.8
OSCILLATOR FREQUENCY (MHz)
1.55
1.50
1.45
1.40
1.35
1.30
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1.6
1.5
1.4
1.3
1.2
OUTPUT VOLTAGE (V)
1.60
FREQUENCY (MHz)
U W
3406B12 G01
Efficiency vs Output Current
1.228
V
OUT
= 1.2V
T
A
= 25°C
VIN = 2.7V
Reference Voltage vs
Temperature
V
IN
= 3.6V
1.218
1.208
1.198
1.188
1.178
70
60
50
40
30
20
VIN = 3.6V
VIN = 4.2V
6
10
0.1
1
100
10
OUTPUT CURRENT (mA)
1000
3406B12
GO2
1.168
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3406B12 G03
Oscillator Frequency vs
Supply Voltage
T
A
= 25°C
1.224
Output Voltage vs Load Current
1.7
1.214
1.204
1.194
1.184
1.174
2
3
4
5
SUPPLY VOLTAGE (V)
6
3406B12
G05
0 100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
3406B12
G06
3406B12 G04
sn3406b12 3406b12fs
3
LTC3406B-1.2
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1)
Dynamic Supply Current vs
Supply Voltage
400
V
IN
= 2.7V
V
IN
= 4.2V
0.5
R
DS(ON
) vs Input Voltage
0.7
0.6
T
A
= 25°C
V
IN
= 3.6V
DYNAMIC SUPPLY CURRENT (µA)
R
DS(ON)
(Ω)
R
DS(ON)
(Ω)
0.4
0.3
0.2
0.1
0
0
1
MAIN
SWITCH
SYNCHRONOUS
SWITCH
5
4
2
3
INPUT VOLTAGE (V)
Dynamic Supply Current vs
Temperature
340
DYNAMIC SUPPLY CURRENT (µA)
320
300
280
260
240
220
V
IN
= 3.6V
I
LOAD
= 0A
SWITCH LEAKAGE (nA)
200
–50 –25
Switch Leakage vs Input Voltage
120
100
SWITCH LEAKAGE (pA)
80
60
40
20
0
RUN = 0V
T
A
= 25°C
SYNCHRONOUS
SWITCH
SW
2V/DIV
V
OUT
10mV/DIV
AC COUPLED
MAIN
SWITCH
I
L
200mA/DIV
0
4
U W
6
7
3406B12
G07
R
DS(ON)
vs Temperature
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
–50 –25
MAIN SWITCH
SYNCHRONOUS SWITCH
50
25
75
0
TEMPERATURE (°C)
100
125
380
360
340
320
300
280
260
240
220
200
2
I
LOAD
= 0A
T
A
= 25°C
3
5
4
SUPPLY VOLTAGE (V)
6
3406B12 G09
3406B12
G08
Switch Leakage vs Temperature
300
V
IN
= 5.5V
RUN = 0V
250
200
150
100
50
0
–50 –25
MAIN SWITCH
SYNCHRONOUS SWITCH
50
25
75
0
TEMPERATURE (°C)
100
125
50
25
75
0
TEMPERATURE (°C)
100
125
3406B12 G10
3406B12
G11
Discontinuous Operation
1µs/DIV
V
IN
= 3.6V
I
LOAD
= 50mA
1
2
3
4
INPUT VOLTAGE (V)
5
6
3406B12 G13
3406B12 G12
sn3406b12 3406b12fs
LTC3406B-1.2
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Start-Up from Shutdown
RUN
2V/DIV
V
OUT
1V/DIV
I
L
500mA/DIV
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
3406B12 G14
3406B12 G15
50µs/DIV
V
IN
= 3.6V
I
LOAD
= 600mA
Load Step
V
OUT
100mV/DIV
AC COUPLED
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
I
LOAD
= 100mA TO 600mA
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.
U W
Load Step
V
OUT
100mV/DIV
AC COUPLED
Load Step
I
L
500mA/DIV
I
LOAD
500mA/DIV
25µs/DIV
V
IN
= 3.6V
I
LOAD
= 0mA TO 600mA
25µs/DIV
V
IN
= 3.6V
I
LOAD
= 50mA TO 600mA
3406B12 G16
Load Step
I
L
500mA/DIV
I
LOAD
500mA/DIV
25µs/DIV
3406B12 G17
25µs/DIV
V
IN
= 3.6V
I
LOAD
= 200mA TO 600mA
3406B12 G18
U
U
U
sn3406b12 3406b12fs
5
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