LTC3402
2A, 3MHz Micropower
Synchronous Boost Converter
FEATURES
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DESCRIPTIO
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
OUT
< 4.3V)
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
The LTC
®
3402 is a high efficiency, fixed frequency, step-
up 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 appli-
cations 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.
APPLICATIO S
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Cellular Telephones
Handheld Computers
MP3 Players
2-Way Pagers
GPS Receivers
Battery Backup Supplies
CCFL Backlights
TYPICAL APPLICATIO
V
IN
= 1.8V to 3V
L1
2.2μH
All Ceramic Capacitor 2-Cell to 3.3V at 1A Step-Up Converter
100
V
OUT
3.3V
1A
90
80
EFFICIENCY (%)
Burst Mode
OPERATION
1MHz
CONSTANT
FREQUENCY
3
10
LTC3402
V
IN
SHDN
SW
V
OUT
4
7
8
9
5
C3
470pF
R5
82k
R2
909k
C2
44μF
(2
×
22μF)
R1
549k
C4
4.7pF
70
60
50
40
30
20
10
0
+
2
CELLS
2
6
MODE/SYNC FB
PGOOD
R
t
V
C
GND
C1
10μF
1
R
t
30.1k
V
IN
= 2.4V WITH SCHOTTKY
0.1
1
10
I
OUT
(mA)
100
1000
3402
TA02
C1: TAIYO YUDEN JMK212BJ106MG
0 = FIXED FREQ
C2: TAIYO YUDEN JMK325BJ226MM
1 = Burst Mode OPERATION
L1: COILCRAFT: D03316P-222
3402 TA01
U
Efficiency
3402fb
U
U
1
LTC3402
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
R
t
MODE
V
IN
SW
GND
1
2
3
4
5
10
9
8
7
6
SHDN
V
C
FB
V
OUT
PGOOD
V
IN
, V
OUT
Voltages ...................................... – 0.5V to 6V
SW Voltage ................................................. – 0.5V to 6V
V
C
, R
t
Voltages ......................... – 0.5V to (V
OUT
+ 0.3V)
PGOOD, SHDN, FB, MODE Voltages ........... – 0.5V to 6V
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/
ORDER PART
NUMBER
LTC3402EMS
MS PART MARKING
LTSK
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C
θ
JA
= 130°C/ W 1 LAYER BOARD
θ
JA
= 100°C/ W 4 LAYER BOARD
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications that apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= 1.2V, V
OUT
= 3.3V unless otherwise noted.
PARAMETER
Minimum Start-Up Voltage
Minimum Operating Voltage
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current—Burst Mode Operation
Quiescent Current—SHDN
Quiescent Current—Active
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
NMOS Current Limit
NMOS Burst Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
MODE/SYNC Input High
MODE/SYNC Input Low
MODE/SYNC Input Current
Error Amp Transconductance
PGOOD Threshold
V
MODE/SYNC
= 5.5V
ΔI
= – 5μA to 5μA, V
C
= V
FB
Referenced to Feedback Voltage
–6
0.01
85
–9
– 12
R
t
= 15k
R
t
= 15k
●
●
●
●
CONDITIONS
I
LOAD
= <1mA
(Note 4)
●
●
●
MIN
TYP
0.85
MAX
1.0
0.5
5.5
UNITS
V
V
V
V
nA
μA
μA
μA
μA
μA
Ω
Ω
A
A
%
2.6
1.22
1.25
1
38
0.1
440
0.1
0.1
0.16
0.18
2
80
1.6
1.4
2.5
0.66
85
1.28
50
65
1
800
5
10
V
FB
= 1.25V
V
C
= 0V, MODE/SYNC = 3.3V (Note 3)
SHDN = 0V, Not Including Switch Leakage
V
C
= 0V, MODE/SYNC = 0V, R
t
= 300k (Note 3)
0
2
2.4
0.4
1
μmhos
%
2
U
%
MHz
V
V
μA
3402fb
W
U
U
W W
W
LTC3402
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications that apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= 1.2V, V
OUT
= 3.3V unless otherwise noted.
PARAMETER
PGOOD Low Voltage
PGOOD Leakage
SHDN Input High
SHDN Input Low
SHDN Input Current
V
SHDN
= 5.5V
0.01
CONDITIONS
I
PGOOD
= 1mA
V
OUT
= 1V, I
PGOOD
= 20μA
V
PGOOD
= 5.5V
V
IN
= V
SHDN
1
0.4
1
MIN
TYP
0.1
0.1
0.01
MAX
0.2
0.4
1
UNITS
V
V
μA
V
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 LTC3402E 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:
Current is measured into the V
OUT
pin since the supply current is
bootstrapped to the output pin and in the application will reflect to the
input supply by (V
OUT
/V
IN
) • I/Efficiency. The outputs are not switching.
Note 4:
Once the output is started, the IC is not dependent upon the V
IN
supply.
TYPICAL PERFOR A CE CHARACTERISTICS
(T
A
= 25°C unless otherwise noted)
SW Pin and Inductor Current (I
C
)
in Discontinuous Mode. Ringing
Control Circuitry Eliminates High
Frequency Ringing
I
L
50mA/DIV
0A
SW
1V/DIV
Switching Waveform on SW Pin
50ns/DIV
Transient Response 50mA to 500mA
V
OUT
AC
100mV/DIV
V
OUT
200mV/DIV
550mA
50mA
C
OUT
= 22μF
L = 3.3μH
f
OSC
= 1MHz
200μs/DIV
3402 G04
U W
Transient Response 5mA to 50mA
V
OUT
100mV/DIV
SW
1V/DIV
50mA
I
OUT
0V
3402 G01
5mA
200ns/DIV
3402 G02
C
OUT
= 22μF
L = 3.3μH
f
OSC
= 1MHz
200μs/DIV
3402 G03
Burst Mode Operation
V
OUT
AC
100mV/DIV
Burst Mode Operation
SW
1V/DIV
SW
1V/DIV
V
IN
= 1.2V
5ms/DIV
V
OUT
= 3.3V
C
OUT
= 100μF
I
OUT
= 250μA
MODE/SYNC PIN = HIGH
3402 G05
V
IN
= 1.2V
200μs/DIV
V
OUT
= 3.3V
C
OUT
= 100μF
I
OUT
= 20mA
MODE/SYNC PIN = HIGH
3402 G06
3402fb
3
LTC3402
TYPICAL PERFOR A CE CHARACTERISTICS
Converter Efficiency 1.2V to 3.3V
100
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.1
10
100
1
OUTPUT CURRENT (mA)
1000
3402 G07
300kHz
Burst Mode
OPERATION
3MHz
EFFICIENCY (%)
60
50
40
30
20
10
0
0.1
EFFICIENCY (%)
1MHz
Start-Up Voltage
vs I
OUT
500
T
A
= 25°C
14
12
OUTPUT CURRENT (mA)
400
EFFICIENCY LOSS (%)
300
CURRENT (A)
200
100
2
0
0.8
0.9
1
1.1
V
IN
(V)
1.2
1.3
1.4
3402 G09
EA FB Voltage
1.28
1.27
2.05
FREQUENCY (MHz)
VOLTAGE (V)
1.26
1.25
1.24
1.23
1.22
–55
RESISTANCE (Ω)
–15
65
TEMPERATURE (°C)
25
4
U W
3402 G13
(T
A
= 25°C unless otherwise noted)
Converter Efficiency 3.6V to 5V
100
Burst Mode OPERATION
90
Converter Efficiency 2.4V to 3.3V
100
90
80
70
300kHz
3MHz
1MHz
Burst Mode
OPERATION
80
70
60
50
40
30
20
10
V
IN
= 3.6V
0.1
1
100
10
LOAD CURRENT (mA)
1000
3402
G10
1MHz
FIXED
FREQUENCY
1
10
100
OUTPUT CURRENT (mA)
1000
3402 G08
0
Efficiency Loss Without Schottky
vs Frequency
T
A
= 25°C
Current Limit
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
–55
10
8
6
4
0
0.2
0.6
2.2
1.0 1.4 1.8
FREQUENCY (MHz)
2.6
3.0
–15
65
TEMPERATURE (°C)
25
105 125
3402 G12
3402 G11
Oscillator Frequency Accuracy
2.10
R
t
= 15k
0.30
NMOS R
DS(ON)
V
OUT
= 3.3V
0.25
0.20
2.00
0.15
1.95
0.10
105 125
1.90
–55
–15
65
TEMPERATURE (°C)
25
105 125
3402 G14
0.05
–55
–15
65
TEMPERATURE (°C)
25
105 125
3402 G22
3402fb
LTC3402
TYPICAL PERFOR A CE CHARACTERISTICS
(T
A
= 25°C unless otherwise noted)
PMOS R
DS(ON)
0.30
V
OUT
= 3.3V
1.1
0.25
RESISTANCE (Ω)
VOLTAGE (V)
0.20
0.9
VOLTAGE (V)
0.15
0.10
0.05
–55
–15
65
TEMPERATURE (°C)
25
PGOOD Threshold
–7.0
–7.5
44
42
40
CURRENT (μA)
PERCENT FROM V
FB
(%)
–8.0
–8.5
–9.0
–9.5
VOLTAGE (V)
–10.0
–10.5
–11.0
–11.5
–12.0
–55
–15
65
TEMPERATURE (°C)
25
105 125
3402 G19
U W
Start-Up Voltage
1.10
1.05
1.0
1.00
0.95
0.90
0.85
0.80
0.75
0.7
0.70
0.65
105 125
3402 G16
Shutdown Threshold
0.8
0.6
–55
–15
65
TEMPERATURE (°C)
25
105 125
3402 G17
0.60
–55
–15
65
TEMPERATURE (°C)
25
105 125
3402 G18
Burst Mode Operation Current
2.50
2.45
2.40
2.35
2.30
2.25
2.20
2.15
2.10
32
30
–55
2.05
–15
65
TEMPERATURE (°C)
25
105 125
3402 G20
V
OUT
Turn-Off Voltage
38
36
34
2.00
–55
–15
25
65
TEMPERATURE (°C)
105 125
3402 G21
3402fb
5
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