LTC3423/LTC3424
Low Output Voltage,
3MHz Micropower Synchronous
Boost Converters
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FEATURES
DESCRIPTIO
The LTC®3423 and LTC3424 are high efficiency, fixed
frequency, step-up DC/DC converters that can regulate
output voltages as low as 1.5V from a single cell. An
applied voltage of at least 2.7V to the VDD pin is required
to power the internal control circuitry.
■
1.5V to 5.5V Adjustable Output Voltage
■
Synchronous Rectification: Up to 95% Efficiency
■
1A Switch Current (LTC3423) or
2A Switch Current (LTC3424)
■
Fixed Frequency Operation Up to 3MHz
■
Wide Input Range: 0.5V to 5.5V (Operating)
The devices include a 0.16Ω N-channel MOSFET switch
anda0.21ΩP-channelsynchronousrectifier.TheLTC3423
is intended for applications requiring less than 0.75W of
outputpowerandtheLTC3424for1.5Worless.Switching
frequencies up to 3MHz are programmed with an external
timing resistor and the oscillator can be synchronized to
an external clock.
Very Low Quiescent Current: 38µA (Burst Mode®
■
Operation)
■
No External Schottky Diode Required
■
Synchronizable Switching Frequency
■
Burst Mode Enable Control
OPTI-LOOP® Compensation
■
■
Very Low Shutdown Current: <1µA
■
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 the operation is at
constant fixed frequency.
Small 10-Pin MSUOP Package
APPLICATIO S
■
Pagers
Handheld Instruments
Cordless Phones
Wireless Handsets
GPS Receivers
Battery Backup
■
■
■
Otherfeaturesincludea1µAshutdown,thermalshutdown
and current limit. The LTC3423 and LTC3424 are available
in the 10-lead MSOP package. For applications requiring
an output voltage greater than 2.6V, the LTC3401 and
LTC3402arerecommendedwithouttheneedofaseparate
voltage for the VDD pin.
■
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
1-Cell to 1.8V at 600mA Step-Up Converter
V
= 2.7V TO 5.5V
DD
L1
2.2µH
Efficiency
V
DD
V
OUT
V
= 0.9V TO 1.5V
IN
1.8V
100
V
= 1.5V
600mA
IN
90
80
70
60
50
40
30
20
10
0
LTC3424
Burst Mode
OPERATION
6
10
3
4
7
8
9
5
R1
V
SW
DD
110k
V
= 1.2V
V = 0.9V
IN
IN
SHDN
V
OUT
FB
+
–
1
C3
CELL
V
IN
44µF
(2× 22µF)
2
MODE/SYNC
V
C
C4
C1
2.2µF
C2
10µF
1
470pF
R2
249k
R
GND
t
C5
4.7pF
V
V
= 3.3V
= 1.8V
DD
OUT
R
30.1k
RC
82k
t
WITH MBRM120T3 SCHOTTKY
0.1
1
10
100
1000
C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ106MM
C3: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CD43-2R2M
OUTPUT CURRENT (mA)
0 = FIXED FREQ
1 = Burst Mode OPERATION
3223/24 TA02
3423/24 TA01
34234f
1