LTC3406
LTC3406-1.5/LTC3406-1.8
1.5MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
FEATURES
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DESCRIPTIO
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.
, 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.
APPLICATIO S
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Cellular Telephones
Personal Information Appliances
Wireless and DSL Modems
Digital Still Cameras
MP3 Players
Portable Instruments
TYPICAL APPLICATIO
V
IN
2.7V
TO 5.5V
4
C
IN
**
4.7µF
CER
1
3
95
90
2.2µH*
C
OUT
†
10µF
CER
5
3406 F01a
V
IN
= 2.7V
EFFICIENCY (%)
V
IN
SW
V
OUT
1.8V
600mA
85
V
IN
= 3.6V
80
V
IN
= 4.2V
75
70
65
60
0.1
V
OUT
= 1.8V
1
10
100
OUTPUT CURRENT (mA)
1000
3406 F01b
LTC3406-1.8
RUN
V
OUT
2
GND
*MURATA LQH32CN2R2M33
**TAIYO YUDEN JMK212BJ475MG
†
TAIYO YUDEN JMK316BJ106ML
Figure 1a. High Efficiency Step-Down Converter
Figure 1b. Efficiency vs Load Current
3406fa
U
U
U
1
LTC3406
LTC3406-1.5/LTC3406-1.8
ABSOLUTE
AXI U
RATI GS
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN 1
GND 2
SW 3
4 V
IN
5 V
FB
ORDER PART
NUMBER
LTC3406ES5
S5 PART MARKING
LTA5
RUN 1
GND 2
SW 3
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.
ELECTRICAL CHARACTERISTICS
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
I
VFB
V
FB
PARAMETER
Feedback Current
Regulated Feedback Voltage
LTC3406 (Note 4) T
A
= 25°C
LTC3406 (Note 4) 0°C T
A
≤
85°C
LTC3406 (Note 4) –40°C
≤
T
A
≤
85°C
V
IN
= 2.5V to 5.5V (Note 4)
LTC3406-1.5, I
OUT
= 100mA
LTC3406-1.8, I
OUT
= 100mA
V
IN
= 2.5V to 5.5V
V
IN
= 3V, V
FB
= 0.5V or V
OUT
= 90%,
Duty Cycle < 35%
●
CONDITIONS
●
∆V
FB
V
OUT
∆V
OUT
I
PK
V
LOADREG
V
IN
I
S
Reference Voltage Line Regulation
Regulated Output Voltage
Output Voltage Line Regulation
Peak Inductor Current
Output Voltage Load Regulation
Input Voltage Range
Input DC Bias Current
Active Mode
Sleep Mode
Shutdown
Oscillator Frequency
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
SW Leakage
(Note 5)
V
FB
= 0.5V or V
OUT
= 90%, I
LOAD
= 0A
V
FB
= 0.62V or V
OUT
= 103%, I
LOAD
= 0A
V
RUN
= 0V, V
IN
= 4.2V
V
FB
= 0.6V or V
OUT
= 100%
V
FB
= 0V or V
OUT
= 0V
I
SW
= 100mA
I
SW
= –100mA
V
RUN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V
●
f
OSC
R
PFET
R
NFET
I
LSW
2
U
U
W
W W
U
W
(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
TOP VIEW
5 V
OUT
4 V
IN
ORDER PART
NUMBER
LTC3406ES5-1.5
LTC3406ES5-1.8
S5 PART MARKING
LTD6
LTC4
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/ W,
θ
JC
= 90°C/ W
MIN
0.5880
0.5865
0.5850
1.455
1.746
0.75
TYP
0.6
0.6
0.6
0.04
1.500
1.800
0.04
1
0.5
MAX
±30
0.6120
0.6135
0.6150
0.4
1.545
1.854
0.4
1.25
UNITS
nA
V
V
V
%/V
V
V
%/V
A
%
●
●
●
●
●
2.5
300
20
0.1
1.2
1.5
210
0.4
0.35
±0.01
5.5
400
35
1
1.8
0.5
0.45
±1
V
µA
µA
µA
MHz
kHz
Ω
Ω
µA
3406fa
LTC3406
LTC3406-1.5/LTC3406-1.8
ELECTRICAL CHARACTERISTICS
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
RUN
I
RUN
PARAMETER
RUN Threshold
RUN Leakage Current
CONDITIONS
●
●
MIN
0.3
TYP
1
±0.01
MAX
1.5
±1
UNITS
V
µA
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
(From Figure1a Except for the Resistive Divider Resistor Values)
Efficiency vs Input Voltage
100
95
90
I
OUT
= 100mA
I
OUT
= 10mA
EFFICIENCY (%)
85 I
OUT
= 1mA
EFFICIENCY (%)
80
75
70
65
60
55
50
V
OUT
= 1.8V
2
3
I
OUT
= 600mA
80
75
70
65
60
0.1
V
IN
= 4.2V
V
IN
= 3.6V
EFFICIENCY (%)
I
OUT
= 0.1mA
4
5
INPUT VOLTAGE (V)
Efficiency vs Output Current
100
95
90
EFFICIENCY (%)
V
OUT
= 2.5V
V
IN
= 2.7V
REFERENCE VOLTAGE (V)
V
IN
= 3.6V
85
80
75
70
65
60
0.1
10
100
1
OUTPUT CURRENT (mA)
1000
3406 G04
0.604
0.599
0.594
0.589
0.584
–50 –25
FREQUENCY (MHz)
V
IN
= 4.2V
U W
6
3406 G01
Efficiency vs Output Current
95
90
85
V
OUT
= 1.2V
V
IN
= 2.7V
95
90
85
Efficiency vs Output Current
V
OUT
= 1.5V
V
IN
= 2.7V
V
IN
= 4.2V
80
V
IN
= 3.6V
75
70
65
60
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
3406 G02
1
10
100
OUTPUT CURRENT (mA)
1000
3406 G03
Reference Voltage vs
Temperature
0.614
V
IN
= 3.6V
0.609
1.65
1.60
1.55
1.50
1.45
1.40
1.35
50
25
75
0
TEMPERATURE (°C)
100
125
1.70
Oscillator Frequency vs
Temperature
V
IN
= 3.6V
1.30
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3406 G05
3406 G06
3406fa
3
LTC3406
LTC3406-1.5/LTC3406-1.8
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure1a Except for the Resistive Divider Resistor Values)
Oscillator Frequency vs
Supply Voltage
1.8
OSCILLATOR FREQUENCY (MHz)
1.7
OUTPUT VOLTAGE (V)
1.6
1.5
1.4
1.3
1.2
1.814
1.804
1.794
1.784
1.774
R
DS(ON)
(Ω)
2
3
4
5
SUPPLY VOLTAGE (V)
R
DS(ON)
vs Temperature
0.7
V
IN
= 2.7V
0.6
V
IN
= 4.2V
0.5
R
DS(ON)
(Ω)
V
IN
= 3.6V
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
0.4
0.3
0.2
0.1
0
–50 –25
MAIN SWITCH
SYNCHRONOUS SWITCH
50
25
75
0
TEMPERATURE (°C)
100
125
Switch Leakage vs Temperature
300
V
IN
= 5.5V
RUN = 0V
250
SWITCH LEAKAGE (nA)
SWITCH LEAKAGE (pA)
200
150
100
50
0
–50 –25
MAIN SWITCH
SYNCHRONOUS SWITCH
50
25
75
0
TEMPERATURE (°C)
4
U W
6
3406 G07
3406 G10
Output Voltage vs Load Current
1.844
1.834
1.824
V
IN
= 3.6V
R
DS(ON
) vs Input Voltage
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
1
5
4
2
3
INPUT VOLTAGE (V)
6
7
3406 G09
MAIN
SWITCH
SYNCHRONOUS
SWITCH
0
100 200 300 400 500 600 700 800 900
LOAD CURRENT (mA)
3406 G08
Supply Current vs Supply Voltage
50
45
40
35
30
25
20
15
10
5
0
2
4
3
5
SUPPLY VOLTAGE (V)
6
3406 G11
Supply Current vs Temperature
50
V
IN
= 3.6V
45 V
OUT
= 1.8V
= 0A
I
40
LOAD
35
30
25
20
15
10
5
0
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
V
OUT
= 1.8V
I
LOAD
= 0A
3406 G12
Switch Leakage vs Input Voltage
120
100
80
60
40
20
0
SYNCHRONOUS
SWITCH
RUN = 0V
SW
5V/DIV
V
OUT
100mV/DIV
AC COUPLED
I
L
200mA/DIV
Burst Mode Operation
MAIN
SWITCH
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 50mA
0
1
2
3
4
INPUT VOLTAGE (V)
5
6
3406 G14
4µs/DIV
3406 G15
100
125
3406 G13
3406fa
LTC3406
LTC3406-1.5/LTC3406-1.8
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Start-Up from Shutdown
RUN
2V/DIV
V
OUT
2V/DIV
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 600mA
40µs/DIV
Load Step
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA TO 600mA
3406 G19
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.
U W
Load Step
V
OUT
100mV/DIV
AC COUPLED
Load Step
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 0mA TO 600mA
3406 G17
I
LOAD
500mA/DIV
3406 G16
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 50mA TO 600mA
3406 G18
Load Step
V
OUT
100mV/DIV
AC COUPLED
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 200mA TO 600mA
3406 G20
U
U
U
3406fa
5
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