LTC3424_15 Datasheet, PDF (1/12 Pages) Linear Technology – Low Output Voltage, 3MHz Micropower Synchronous Boost Converters

LTC3423/LTC3424
FEATURES
s _{1.5V to 5.5V Adjustable Output Voltage}
s _{Synchronous Rectification: Up to 95% Efficiency}
s _{1A Switch Current (LTC3423) or}
2A Switch Current (LTC3424)
s _{Fixed Frequency Operation Up to 3MHz}
s _{Wide Input Range: 0.5V to 5.5V (Operating)}
s _{Very Low Quiescent Current: 38µA (Burst Mode}^®
Operation)
s _{No External Schottky Diode Required}
s _{Synchronizable Switching Frequency}
s _{Burst Mode Enable Control}
s _OPTI-LOOP^® _Compensation
s _{Very Low Shutdown Current: < 1µA}
s _{Small 10-Pin MSOP Package}
U
APPLICATIO S
s _Pagers
s _{Handheld Instruments}
s _{Cordless Phones}
s _{Wireless Handsets}
s _{GPS Receivers}
s _{Battery Backup}
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
Low Output Voltage,
3MHz Micropower Synchronous
Boost Converters
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 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.
TYPICAL APPLICATIO
1-Cell to 1.8V at 600mA Step-Up Converter
V_DD
C1
2.2µF
V_DD = 2.7V TO 5.5V
V_IN = 0.9V TO 1.5V
L1
2.2µH
+
1
– CELL
C2
10µF
LTC3424
6
4
V_DD
SW
10
SHDN
7
V_OUT
3
V_IN
8
FB
2
9
MODE/SYNC V_C
1
R_t
5
GND
R_t
30.1k
R1
110k
V_OUT
1.8V
600mA
C4
470pF
RC
82k
R2
C5 ^249k
4.7pF
C3
44µF
(2× 22µF)
0 = FIXED FREQ
1 = Burst Mode OPERATION
C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ106MM
C3: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CD43-2R2M
3423/24 TA01
Efficiency
100
90
80
70
60
50
40
30
20
10
0
0.1
V_IN = 1.5V
Burst Mode
OPERATION
V_IN = 1.2V
V_IN = 0.9V
V_DD = 3.3V
V_OUT = 1.8V
WITH MBRM120T3 SCHOTTKY
1
10
100
OUTPUT CURRENT (mA)
1000
3223/24 TA02
34234f
1