FEATURES
■
Synchronous Rectification: Up to 97% Efficiency
■
2A Switch Current Rating
■
Fixed Frequency Operation Up to 3MHz
■
Wide Input Range: 0.5V to 5V
■
Very Low Quiescent Current: 38μA (Burst Mode
Operation)
■
2.6V to 5.5V Adjustable Output Voltage
■
0.85V (Typ) Start-Up Voltage
■
No External Schottky Diode Required (V
■
Synchronizable Switching Frequency
■
Burst Mode Enable Control
■
Antiringing Control Reduces Switching Noise
■
PGOOD Output
■
OPTI-LOOP® Compensation
■
Very Low Shutdown Current: <1μA
■
Small 10-Pin MSOP Package
OUT
< 4.3V)
U
APPLICATIO S
■
Cellular Telephones
■
Handheld Computers
■
MP3 Players
■
2-Way Pagers
■
GPS Receivers
■
Battery Backup Supplies
■
CCFL Backlights
LTC3402
2A, 3MHz Micropower
Synchronous Boost Converter
U
DESCRIPTIO
The LTC®3402 is a high efficiency, fixed frequency, stepup DC/DC converter that operates from an input voltage
below 1V. The device includes a 0.16Ω N-channel MOSFET
®
switch and a 0.18Ω P-channel synchronous rectifier.
Switching frequencies up to 3MHz are programmed with
an external timing resistor and the oscillator can be
synchronized to an external clock. An external Schottky
diode is optional but will slightly improve efficiency.
Quiescent current is only 38μA in Burst Mode operation,
maximizing battery life in portable applications. Burst
Mode operation is user controlled and can be enabled by
driving the MODE/SYNC pin high. If the MODE/SYNC pin
has either a clock or is driven low, then fixed frequency
switching is enabled.
Other features include a 1μA shutdown, antiringing con-
trol, open-drain power good output, thermal shutdown
and current limit. The LTC3402 is available in the 10-lead
thermally enhanced MSOP package. Lower current applications should use the 1A rated LTC3401 synchronous
boost converter. Applications that require V
OUT
< 2.6V
should use the LTC3424.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
All Ceramic Capacitor 2-Cell to 3.3V at 1A Step-Up Converter
L1
3
V
10
SHDN
2
MODE/SYNC
6
PGOOD
1
R
R
t
30.1k
2.2μH
LTC3402
IN
V
GND
t
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: COILCRAFT: D03316P-222
VIN = 1.8V to 3V
+
2
CELLS
C1
10μF
0 = FIXED FREQ
1 = Burst Mode OPERATION
SW
OUT
U
Efficiency
100
V
OUT
3.3V
1A
4
7
8
FB
9
V
C
C3
5
470pF
R5
82k
R2
909k
C4
4.7pF
R1
549k
C2
44μF
(2 × 22μF)
3402 TA01
Burst Mode
90
OPERATION
80
70
60
50
40
EFFICIENCY (%)
30
20
10
VIN = 2.4V WITH SCHOTTKY
0
0.1
1MHz
CONSTANT
FREQUENCY
110
I
(mA)
OUT
100
1000
3402 TA02
3402fb
1
LTC3402
PACKAGE/ORDER I FOR ATIO
UU
W
1
2
3
4
5
R
t
MODE
V
IN
SW
GND
10
9
8
7
6
SHDN
V
C
FB
V
OUT
PGOOD
TOP VIEW
MS PACKAGE
10-LEAD PLASTIC MSOP
WWWU
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, V
SW Voltage ................................................. – 0.5V to 6V
, Rt Voltages ......................... – 0.5V to (V
V
C
PGOOD, SHDN, FB, MODE Voltages ........... –0.5V to 6V
Voltages ...................................... – 0.5V to 6V
OUT
OUT
ORDER PART
NUMBER
+ 0.3V)
LTC3402EMS
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range ................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)..................300°C
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
T
= 125°C
JMAX
= 130°C/ W 1 LAYER BOARD
θ
JA
= 100°C/ W 4 LAYER BOARD
θ
JA
Consult LTC Marketing for parts specified with wider operating temperature ranges.
MS PART MARKING
LTSK
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = 1.2V, V
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Start-Up Voltage I
Minimum Operating Voltage (Note 4) ● 0.5 V
Output Voltage Adjust Range ● 2.6 5.5 V
Feedback Voltage ● 1.22 1.25 1.28 V
Feedback Input Current VFB = 1.25V 1 50 nA
Quiescent Current—Burst Mode Operation VC = 0V, MODE/SYNC = 3.3V (Note 3) 38 65 μA
Quiescent Current—SHDN SHDN = 0V, Not Including Switch Leakage 0.1 1 μA
Quiescent Current—Active VC = 0V, MODE/SYNC = 0V, Rt = 300k (Note 3) 440 800 μA
NMOS Switch Leakage 0.1 5 μA
PMOS Switch Leakage 0.1 10 μA
NMOS Switch On Resistance 0.16 Ω
PMOS Switch On Resistance 0.18 Ω
NMOS Current Limit ● 2 2.5 A
NMOS Burst Current Limit 0.66 A
Maximum Duty Cycle Rt = 15k ● 80 85 %
Minimum Duty Cycle ● 0%
Switching Frequency Rt = 15k ● 1.6 2 2.4 MHz
MODE/SYNC Input High 1.4 V
MODE/SYNC Input Low 0.4 V
MODE/SYNC Input Current V
Error Amp Transconductance ΔI = – 5μA to 5μA, VC = V
PGOOD Threshold Referenced to Feedback Voltage – 6 –9 – 12 %
= 3.3V unless otherwise noted.
OUT
= <1mA 0.85 1.0 V
LOAD
MODE/SYNC
= 5.5V 0.01 1 μA
FB
85 μmhos
2
3402fb
LTC3402
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
V
= 1.2V, V
IN
PARAMETER CONDITIONS MIN TYP MAX UNITS
PGOOD Low Voltage I
PGOOD Leakage V
SHDN Input High VIN = V
SHDN Input Low 0.4 V
SHDN Input Current V
= 3.3V unless otherwise noted.
OUT
= 1mA 0.1 0.2 V
PGOOD
= 1V, I
V
OUT
= 5.5V 0.01 1 μA
PGOOD
SHDN
= 5.5V 0.01 1 μA
SHDN
= 20μA 0.1 0.4 V
PGOOD
1V
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 LTC3402E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
with statistical process controls.
Note 3: Current is measured into the V
bootstrapped to the output pin and in the application will reflect to the
input supply by (V
Note 4: Once the output is started, the IC is not dependent upon the V
supply.
temperature range are assured by design, characterization and correlation
UW
TYPICAL PERFOR A CE CHARACTERISTICS
SW Pin and Inductor Current (IC)
in Discontinuous Mode. Ringing
Control Circuitry Eliminates High
Switching Waveform on SW Pin
SW
1V/DIV
50ns/DIV
50mA/DIV
3402 G01
Frequency Ringing Transient Response 5mA to 50mA
I
L
0A
SW
1V/DIV
0V
200ns/DIV
pin since the supply current is
OUT
) • I/Efficiency. The outputs are not switching.
OUT/VIN
(TA = 25°C unless otherwise noted)
V
OUT
100mV/DIV
50mA
I
OUT
5mA
3402 G02
C
= 22μF 200μs/DIV 3402 G03
OUT
L = 3.3μH
= 1MHz
f
OSC
IN
V
OUT
200mV/DIV
550mA
50mA
Transient Response 50mA to 500mA Burst Mode Operation
V
OUT
AC
100mV/DIV
SW
1V/DIV
= 22μF 200μs/DIV 3402 G04
C
OUT
L = 3.3μH
f
= 1MHz
OSC
V
= 1.2V 5ms/DIV 3402 G05
IN
V
= 3.3V
OUT
C
= 100μF
OUT
= 250μA
I
OUT
MODE/SYNC PIN = HIGH
V
OUT
100mV/DIV
SW
1V/DIV
Burst Mode Operation
AC
V
= 1.2V 200μs/DIV 3402 G06
IN
V
= 3.3V
OUT
C
= 100μF
OUT
= 20mA
I
OUT
MODE/SYNC PIN = HIGH
3402fb
3
LTC3402
UW
TYPICAL PERFOR A CE CHARACTERISTICS
(TA = 25°C unless otherwise noted)
Converter Efficiency 1.2V to 3.3V
100
90
Burst Mode
80
OPERATION
70
60
50
40
EFFICIENCY (%)
30
20
10
0
0.1 10 100 1000
300kHz
3MHz
1MHz
1
OUTPUT CURRENT (mA)
Start-Up Voltage
vs I
OUT
500
TA = 25°C
400
300
3402 G07
Converter Efficiency 2.4V to 3.3V
100
Burst Mode
90
OPERATION
80
70
300kHz
60
50
40
EFFICIENCY (%)
30
20
10
0
0.1 10 100 1000
1
OUTPUT CURRENT (mA)
3MHz
1MHz
Efficiency Loss Without Schottky
vs Frequency
14
TA = 25°C
12
10
8
3402 G08
Converter Efficiency 3.6V to 5V
100
Burst Mode OPERATION
90
80
70
60
50
40
EFFICIENCY (%)
30
20
10
VIN = 3.6V
0
0.1
1MHz
FIXED
FREQUENCY
110
LOAD CURRENT (mA)
Current Limit
3.4
3.2
3.0
2.8
100
1000
3402 G10
200
OUTPUT CURRENT (mA)
100
0
0.8
0.9
EA FB Voltage
1.28
1.27
1.26
1.25
VOLTAGE (V)
1.24
1.23
1.22
–15 25 105
–55
TEMPERATURE (°C)
1
1.1 1.2
VIN (V)
6
4
EFFICIENCY LOSS (%)
2
1.3
1.4
3402 G09
0
0.2
0.6 1.0
1.8 2.6 3.0
1.4 2.2
FREQUENCY (MHz)
3402 G11
Oscillator Frequency Accuracy
2.10
= 15k
R
t
2.05
2.00
FREQUENCY (MHz)
1.95
65
125
3402 G13
1.90
–15 25 105
–55
TEMPERATURE (°C)
65
125
3402 G14
2.6
CURRENT (A)
2.4
2.2
2.0
–55
NMOS R
0.30
V
OUT
0.25
0.20
0.15
RESISTANCE (Ω)
0.10
0.05
–55
–15 25 105
TEMPERATURE (°C)
65
DS(ON)
= 3.3V
–15 25 105
TEMPERATURE (°C)
65
125
3402 G12
125
3402 G22
4
3402fb
UW
TYPICAL PERFOR A CE CHARACTERISTICS
LTC3402
(TA = 25°C unless otherwise noted)
PMOS R
0.30
V
= 3.3V
OUT
0.25
0.20
0.15
RESISTANCE (Ω)
0.10
0.05
–55
PGOOD Threshold
–7.0
–7.5
–8.0
–8.5
(%)
FB
–9.0
–9.5
–10.0
–10.5
PERCENT FROM V
–11.0
–11.5
–12.0
–55
DS(ON)
–15 25 105
TEMPERATURE (°C)
–15 25 105
TEMPERATURE (°C)
65
65
3402 G16
3402 G19
125
125
Start-Up Voltage
1.1
1.0
0.9
0.8
VOLTAGE (V)
0.7
0.6
–15 25 105
–55
TEMPERATURE (°C)
Burst Mode Operation Current
44
42
40
38
36
CURRENT (μA)
34
32
30
–15 25 105
–55
TEMPERATURE (°C)
Shutdown Threshold
1.10
1.05
1.00
0.95
0.90
0.85
0.80
VOLTAGE (V)
0.75
0.70
0.65
65
65
125
3402 G17
125
3402 G20
0.60
2.50
2.45
2.40
2.35
2.30
2.25
2.20
VOLTAGE (V)
2.15
2.10
2.05
2.00
–15 25 105
–55
TEMPERATURE (°C)
V
Turn-Off Voltage
OUT
–15 25 105
–55
TEMPERATURE (°C)
65
65
125
3402 G18
125
3402 G21
3402fb
5
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