1
LTC3406
LTC3406-1.5/LTC3406-1.8
3406fa
High Efficiency: Up to 96%
Very Low Quiescent Current: Only 20
µ
A
During Operation
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
0.6V Reference Allows Low Output Voltages
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 is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. The device is available in an adjustable
version and fixed output voltages of 1.5V and 1.8V. Supply
current during operation is only 20µA and drops to 1µA
in shutdown. The 2.5V to 5.5V input voltage range makes
the LTC3406 ideally suited for single Li-Ion battery-pow-
ered applications. 100% duty cycle provides low dropout
operation, extending battery life in portable systems.
Automatic Burst Mode
®
operation increases efficiency at
light loads, further extending battery life.
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 feed-
back reference voltage. The LTC3406 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
Figure 1a. High Efficiency Step-Down Converter
1.5MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
Figure 1b. Efficiency vs Load Current
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
Protected by U.S. Patents, including 6580258, 5481178.
V
IN
C
IN
**
4.7µF
CER
V
IN
2.7V
TO 5.5V
*
**
LTC3406-1.8
RUN
3
2.2µH*
3406 F01a
MURATA LQH32CN2R2M33
TAIYO YUDEN JMK212BJ475MG
TAIYO YUDEN JMK316BJ106ML
5
4
1
2
SW
V
OUT
GND
C
OUT
10µF
CER
V
OUT
1.8V
600mA
OUTPUT CURRENT (mA)
70
EFFICIENCY (%)
80
90
95
0.1
10
100
1000
3406 F01b
60
1
85
75
65
V
IN
= 2.7V
V
OUT
= 1.8V
V
IN
= 4.2V
V
IN
= 3.6V
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC3406
LTC3406-1.5/LTC3406-1.8
3406fa
LTC3406ES5
T
JMAX
= 125°C,
JA
= 250°C/ W,
JC
= 90°C/ W
ORDER PART
NUMBER
Input Supply Voltage .................................. 0.3V to 6V
RUN, V
FB
Voltages ..................................... 0.3V to V
IN
SW Voltage .................................. 0.3V to (V
IN
+ 0.3V)
P-Channel Switch Source Current (DC) ............. 800mA
N-Channel Switch Sink Current (DC) ................. 800mA
S5 PART MARKING
Consult LTC Marketing for parts specified with wider operating temperature ranges.
LTA5
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
RUN 1
GND 2
SW 3
5 V
FB
4 V
IN
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
(Note 1)
Peak SW Sink and Source Current ........................ 1.3A
Operating Temperature Range (Note 2) .. 40°C to 85°C
Junction Temperature (Note 3) ............................ 125°C
Storage Temperature Range ................ 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
LTC3406ES5-1.5
LTC3406ES5-1.8
ORDER PART
NUMBER
S5 PART MARKING
LTD6
LTC4
T
JMAX
= 125°C,
JA
= 250°C/ W,
JC
= 90°C/ W
RUN 1
GND 2
SW 3
5 V
OUT
4 V
IN
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
VFB
Feedback Current
±30
nA
V
FB
Regulated Feedback Voltage
LTC3406 (Note 4) T
A
= 25°C
0.5880
0.6
0.6120
V
LTC3406 (Note 4) 0°C T
A
85°C
0.5865
0.6
0.6135
V
LTC3406 (Note 4) 40°C T
A
85°C
0.5850
0.6
0.6150
V
V
FB
Reference Voltage Line Regulation
V
IN
= 2.5V to 5.5V (Note 4)
0.04
0.4
%/V
V
OUT
Regulated Output Voltage
LTC3406-1.5, I
OUT
= 100mA
1.455
1.500
1.545
V
LTC3406-1.8, I
OUT
= 100mA
1.746
1.800
1.854
V
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
FB
= 0.5V or V
OUT
= 90%,
0.75
1
1.25
A
Duty Cycle < 35%
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 5)
Active Mode
V
FB
= 0.5V or V
OUT
= 90%, I
LOAD
= 0A
300
400
µA
Sleep Mode
V
FB
= 0.62V or V
OUT
= 103%, I
LOAD
= 0A
20
35
µA
Shutdown
V
RUN
= 0V, V
IN
= 4.2V
0.1
1
µA
f
OSC
Oscillator Frequency
V
FB
= 0.6V or V
OUT
= 100%
1.2
1.5
1.8
MHz
V
FB
= 0V or 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
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
3
LTC3406
LTC3406-1.5/LTC3406-1.8
3406fa
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
RUN
RUN Threshold
0.3
1
1.5
V
I
RUN
RUN Leakage Current
±0.01
±1
µA
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 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: T
J
= T
A
+ (P
D
)(250°C/W)
Note 4: The LTC3406 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.
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Efficiency vs Input Voltage
Efficiency vs Output Current
Efficiency vs Output Current
Efficiency vs Output Current
Reference Voltage vs
Temperature
Oscillator Frequency vs
Temperature
(From Figure1a Except for the Resistive Divider Resistor Values)
INPUT VOLTAGE (V)
2
50
EFFICIENCY (%)
55
65
70
75
100
85
3
4
3406 G01
60
90
95
80
5
6
I
OUT
= 600mA
V
OUT
= 1.8V
I
OUT
= 100mA
I
OUT
= 10mA
I
OUT
= 0.1mA
I
OUT
= 1mA
OUTPUT CURRENT (mA)
70
EFFICIENCY (%)
80
90
95
0.1
10
100
1000
3406 G02
60
1
85
75
65
V
OUT
= 1.2V
V
IN
= 2.7V
V
IN
= 4.2V
V
IN
= 3.6V
OUTPUT CURRENT (mA)
70
EFFICIENCY (%)
80
90
95
0.1
10
100
1000
3406 G03
60
1
85
75
65
V
OUT
= 1.5V
V
IN
= 2.7V
V
IN
= 4.2V
V
IN
= 3.6V
OUTPUT CURRENT (mA)
70
EFFICIENCY (%)
80
85
95
100
0.1
10
100
1000
3406 G04
60
1
90
75
65
V
OUT
= 2.5V
V
IN
= 2.7V
V
IN
= 4.2V
V
IN
= 3.6V
TEMPERATURE (°C)
50
REFERENCE VOLTAGE (V)
0.614
0.609
0.604
0.599
0.594
0.589
0.584
25
75
25
0
50
100
125
V
IN
= 3.6V
3406 G05
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
3406 G06
4
LTC3406
LTC3406-1.5/LTC3406-1.8
3406fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Oscillator Frequency vs
Supply Voltage
Output Voltage vs Load Current
R
DS(ON
) vs Input Voltage
(From Figure1a Except for the Resistive Divider Resistor Values)
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
3406 G07
LOAD CURRENT (mA)
0
OUTPUT VOLTAGE (V)
200 300 400 500 600 700 800
1.844
1.834
1.824
1.814
1.804
1.794
1.784
1.774
3406 G08
100
900
V
IN
= 3.6V
INPUT VOLTAGE (V)
1
0
0.4
0.5
0.7
4
6
3406 G09
0.3
0.2
2
3
5
7
0.1
0
0.6
R
DS(ON)
(
)
MAIN
SWITCH
SYNCHRONOUS
SWITCH
R
DS(ON)
vs Temperature
Supply Current vs Supply Voltage
Supply Current vs Temperature
Switch Leakage vs Temperature
Switch Leakage vs Input Voltage
Burst Mode Operation
TEMPERATURE (°C)
50
0.4
0.5
0.7
25
75
3406 G10
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
3406 G11
10
40
45
30
5
6
V
OUT
= 1.8V
I
LOAD
= 0A
TEMPERATURE (°C)
50
0
SUPPLY CURRENT (
µ
A)
5
15
20
25
50
35
0
50
75
3406 G12
10
40
45
30
25
25
100
125
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 0A
TEMPERATURE (°C)
50
SWITCH LEAKAGE (nA)
200
250
300
25
75
3406 G13
150
100
25
0
50
100
125
50
0
V
IN
= 5.5V
RUN = 0V
MAIN SWITCH
SYNCHRONOUS SWITCH
INPUT VOLTAGE (V)
0
0
SWITCH LEAKAGE (pA)
20
40
60
80
120
1
2
3
4
3406 G14
5
6
100
RUN = 0V
SYNCHRONOUS
SWITCH
MAIN
SWITCH
SW
5V/DIV
I
L
200mA/DIV
V
OUT
100mV/DIV
AC COUPLED
4µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 50mA
3406 G15
5
LTC3406
LTC3406-1.5/LTC3406-1.8
3406fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
(From Figure 1a Except for the Resistive Divider Resistor Values)
Start-Up from Shutdown
Load Step
Load Step
RUN
2V/DIV
I
LOAD
500mA/DIV
V
OUT
2V/DIV
40µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 600mA
3406 G16
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
OUT
100mV/DIV
AC COUPLED
20µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 0mA TO 600mA
3406 G17
I
LOAD
500mA/DIV
I
L
500mA/DIV
V
OUT
100mV/DIV
AC COUPLED
20µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 50mA TO 600mA
3406 G18
Load Step
Load Step
I
LOAD
500mA/DIV
I
L
500mA/DIV
V
OUT
100mV/DIV
AC COUPLED
20µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA TO 600mA
3406 G19
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
OUT
100mV/DIV
AC COUPLED
20µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 200mA TO 600mA
3406 G20
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
FB
(Pin 5) (LTC3406): Feedback Pin. Receives the feed-
back voltage from an external resistive divider across the
output.
V
OUT
(Pin 5) (LTC3406-1.5/LTC3406-1.8): Output Volt-
age Feedback Pin. An internal resistive divider divides the
output voltage down for comparison to the internal refer-
ence voltage.
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