1
LTC3423/LTC3424
34234f
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 V
DD
pin is required
to power the internal control circuitry.
The devices include a 0.16Ω N-channel MOSFET switch
and a 0.21Ω P-channel synchronous rectifier. The LTC3423
is intended for applications requiring less than 0.75W of
output power and the LTC3424 for 1.5W or less. Switching
frequencies up to 3MHz are programmed with an external
timing resistor and the oscillator can be synchronized to
an external clock.
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.
Other features include a 1µA shutdown, thermal shutdown
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
LTC3402 are recommended without the need of a separate
voltage for the V
DD
pin.
1-Cell to 1.8V at 600mA Step-Up Converter
■
Pagers
■
Handheld Instruments
■
Cordless Phones
■
Wireless Handsets
■
GPS Receivers
■
Battery Backup
■
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)
■
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
■
Small 10-Pin MSOP Package
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
Efficiency
Low Output Voltage,
3MHz Micropower Synchronous
Boost Converters
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
6
10
3
2
1
LTC3424
V
DD
SHDN
V
IN
MODE/SYNC
R
t
SW
V
OUT
FB
V
C
GND
4
7
8
9
5
C4
470pF
C2
10µF
RC
82k
R
t
30.1k
R1
110k
R2
249k
L1
2.2µH
C3
44µF
(2× 22µF)
C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ106MM
C3: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CD43-2R2M
V
DD
= 2.7V TO 5.5V
V
IN
= 0.9V TO 1.5V
0 = FIXED FREQ
1 = Burst Mode OPERATION
C5
4.7pF
3423/24 TA01
V
OUT
1.8V
600mA
1
CELL
V
DD
+
–
C1
2.2µF
3223/24 TA02
Burst Mode
OPERATION
V
IN
= 1.5V
V
DD
= 3.3V
V
OUT
= 1.8V
WITH MBRM120T3 SCHOTTKY
V
IN
= 0.9V
OUTPUT CURRENT (mA)
EFFICIENCY (%)
100
90
80
70
60
50
40
30
20
10
0
0.1 10 100 10001
V
IN
= 1.2V
