FEATURES
■
■
■
■
■
■
■
■
■
■
■
■
LTC3406AB-2
2.25MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
DESCRIPTION
The LTC
®
3406AB-2 is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. Supply current with no load is 200μA
and drops to <1μA in shutdown. The 2.5V to 5.5V input
voltage range makes the LTC3406AB-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 op-
eration provides very low output ripple voltage for noise
sensitive applications.
Switching frequency is internally set at 2.25MHz, 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-2 is available in a low
profile (1mm) ThinSOT package. Refer to LTC3406A for
applications that require Burst Mode
®
operation.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 5481178, 6580258.
■
■
High Efficiency: Up to 96%
600mA Output Current
2.5V to 5.5V Input Voltage Range
2.25MHz Constant Frequency Operation
No Schottky Diode Required
Low Dropout Operation: 100% Duty Cycle
±2% Output Voltage Accuracy
Low Quiescent Current: 200µA
0.6V Reference Allows Low Output Voltages
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
■
■
■
■
■
■
Cellular Telephones
Personal Navigation Devices
Wireless and DSL Modems
Digital
Still
Cameras
Media Players
Portable Instruments
TYPICAL APPLICATION
Efficiency vs Output Current
2.2μH*
V
IN
C
IN
†
4.7μF
CER
V
IN
SW
22pF
100
V
OUT
1.8V
600mA
C
OUT
**
10μF
CER
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
10
100
OUTPUT CURRENT (mA)
1000
3406AB2 TA01b
V
OUT
= 1.8V
LTC3406AB-2
RUN
GND
V
FB
619k
309k
* MURATA LQH32CN2R2M33
** TAIYO YUDEN JMK316BJ106I
†
TAIYO YUDEN JMK212BJ475
3406AB2 TA01a
3406ab2f
1
LTC3406AB-2
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
Maximum 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
LTC3406ABES5-2#PBF
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
5-Lead Plastic TSOT-23
TEMPERATURE RANGE
–40°C to 85°C
LTC3406ABES5-2#TRPBF LTDBB
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
Shutdown
Oscillator Frequency
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
SW Leakage
Soft-Start Time
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
●
●
TYP
0.6
0.04
1
0.5
MAX
±30
0.6120
0.4
1.25
UNITS
nA
V
%/V
A
%
(Note 4)
V
IN
= 2.5V to 5.5V (Note 4)
V
IN
= 3V, V
FB
= 0.5V
Duty Cycle < 35%
0.5880
0.75
●
2.5
200
0.1
5.5
300
1
2.7
0.35
0.35
±1
1.2
V
μA
μA
MHz
Ω
Ω
μA
ms
(Note 5)
V
FB
= 0.63V
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
SOFT-START
1.8
2.25
0.23
0.21
±0.01
0.9
3406ab2f
2
LTC3406AB-2
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 LTC3406AB-2E is guaranteed to meet performance
specifications from 0°C to
85°C. Specifi
cations 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-2: T
J
= T
A
+ (P
D
)(250°C/W)
Note 4:
The LTC3406AB-2 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.
Note 7:
Limited by long term current density considerations.
TYPICAL PERFORMANCE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Efficiency vs Input Voltage
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
10
0
2
V
OUT
= 1.8V
I
L
= 10mA
I
L
= 100mA
I
L
= 600mA
6
3406AB2 G01
Efficiency vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
10
100
OUTPUT CURRENT (mA)
1000
3406AB2 G02
Efficiency vs Input Voltage
100
90
80
70
60
50
40
30
20
10
0
2
V
OUT
= 1.2V
3
I
L
= 10mA
I
L
= 100mA
I
L
= 600mA
5
4
INPUT VOLTAGE (V)
6
3406AB2 G03
V
OUT
= 1.2V
3
5
4
OUTPUT CURRENT (mA)
Efficiency vs Load Current
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
10
100
OUTPUT CURRENT (mA)
1000
3406AB2 G04
Efficiency vs Input Voltage
100
90
REFERENCE VOLTAGE (V)
80
70
60
50
40
30
20
10
0
2
V
OUT
= 2.5V
3
I
L
= 10mA
I
L
= 100mA
I
L
= 600mA
5
4
INPUT VOLTAGE (V)
6
3406AB2 G05
Reference Voltage vs
Temperature
0.615
0.610
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
3406AB2 G06
3406ab2f
3
LTC3406AB-2
TYPICAL PERFORMANCE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Oscillator Frequency vs
Temperature
2.50
2.45
OSCILLATOR FREQUENCY (MHz)
2.40
2.35
2.30
2.25
2.20
2.15
2.10
2.05
2.00
–50 –25
1.8
50
25
0
75
TEMPERATURE (°C)
100
125
2
2.5
3
4.5 5
3.5 4
INPUT VOLTAGE (V)
5.5
6
V
IN
= 3.6V
OSCILLATOR FREQUENCY (MHz)
2.4
2.3
OUTPUT VOLTAGE (V)
2.2
2.1
2.0
1.9
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 Voltage vs Load Current
V
OUT
= 1.8V
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
0
400
200
OUTPUT CURRENT (mA)
600
3406AB2 G09
3406AB2 G07
3406AB2 G08
R
DS(ON)
vs Input Voltage
0.40
0.35
0.30
R
DS(0N)
(Ω)
MAIN SWITCH
0.25
SYNCHRONOUS
SWITCH
0.20
0.15
0.10
0
1
4
3
5
2
INPUT VOLTAGE (V)
6
7
0.40
0.35
0.30
R
DS(ON)
(Ω)
0.25
0.20
0.15
0.10
0.05
R
DS(ON)
vs Temperature
300
V
IN
= 3.6V
DYNAMIC SUPPLY CURRENT (μA)
250
200
Dynamic Supply Current
V
OUT
= 1.2V
I
LOAD
= 0A
V
IN
= 2.7V
PULSE SKIPPING MODE
150
100
50
0
2
2.5
3
V
IN
= 4.2V
SYNCHRONOUS SWITCH
MAIN SWITCH
0
50
75
25
TEMPERATURE (°C)
100
125
0
–50 –25
4.5 5
3.5 4
INPUT VOLTAGE (V)
5.5
6
3406AB2 G10
3406AB2 G11
3406AB2 G12
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
Switch Leakage vs Temperature
1000
900
800
SWITCH LEAKAGE (pA)
700
600
500
400
300
200
100
0
50
25
75
0
TEMPERATURE (°C)
100
125
Switch Leakage vs Input Voltage
RUN = 0V
PULSE SKIPPING MODE
MAIN SWITCH
60
40
20
0
–50 –25
SYNCHRONOUS
SWITCH
MAIN SWITCH
SYNCHRONOUS
SWITCH
50
25
75
0
TEMPERATURE (°C)
100
125
0
1
3
4
2
INPUT VOLTAGE (V)
5
6
3406AB2 G13
3406AB2 G14
3406AB2 G15
3406ab2f
4
LTC3406AB-2
TYPICAL PERFORMANCE CHARACTERISTICS
(From Figure 1a Except for the Resistive Divider Resistor Values)
Start-Up from Shutdown
RUN
2V/DIV
V
OUT
2V/DIV
I
L
500mA/DIV
Load Step
Load Step
V
OUT
200mV/DIV
I
L
500mA/DIV
I
LOAD
500mA/DIV
3406AB2 G16
V
OUT
100mV/DIV
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 0mA TO 600mA
3406AB2 G17
V
IN
= 3.6V
400μs/DIV
V
OUT
= 1.8V
I
LOAD
= 600mA (3Ω RES)
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 50mA TO 600mA
3406AB2 G18
Load Step
Load Step
SW
2V/DIV
Discontinuous Operation
V
OUT
100mV/DIV
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA TO 600mA
3406AB2 G19
V
OUT
100mV/DIV
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
IN
= 3.6V
20µs/DIV
V
OUT
= 1.8V
I
LOAD
= 200mA TO 600mA
3406AB2 G20
V
OUT
20mV/DIV
AC COUPLED
I
L
200mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 25mA
400ns/DIV
3406AB2 G21
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.
3406ab2f
5
嵌入式系统
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
