LTC3543_15 Datasheet, PDF (1/20 Pages) Linear Technology – 600mA Synchronous Step Down Buck Regulator with PLL, Soft-Start and Spread Spectrum

LTC3543
600mA Synchronous Step
Down Buck Regulator with PLL,
Soft-Start and Spread Spectrum
FEATURES
DESCRIPTION
n _{600mA Output Current}
n _{2.5V to 5.5V Input Voltage Range}
n _{2.25MHz Constant-Frequency Operation, Spread}
Spectrum or Synchronized PLL (1MHz to 3MHz)
n _{High Efficiency: Up to 95%}
n _{1A Peak Inductor Current}
n _{Very Low Quiescent Current: Only 45μA During}
Burst Mode Operation
n _{No Schottky Diode Required}
n _{Low Dropout Operation: 100% Duty Cycle}
n _{Overtemperature Protected}
n _{Stable with Ceramic Capacitors}
n _{Shutdown Mode Draws <1μA Supply Current}
n _{±2% Output Voltage Accuracy}
n _{Current Mode Operation for Excellent Line and Load}
Transient Response
n _Soft-Start
n _{Available in a Low Profile (0.75mm) 2mm × 3mm}
6-Lead DFN Package
APPLICATIONS
n _{Portable Instruments}
n _{Cellular Phones}
The LTC^®3543 is a high efficiency monolithic synchronous
current mode buck regulator.
The switching frequency is internally set at 2.25MHz,
allowing the use of small surface mount inductors and
capacitors. In PLL mode, the LTC3543 can acquire fre-
quencies between 1MHz and 3MHz. Also, the LTC3543
has spread spectrum capability providing a lower noise
regulated output, as well as low noise at the input.
In Burst Mode^® operation, the supply current is only 45μA,
dropping to <1μA in shutdown. The 2.5V to 5.5V input
voltage range makes the LTC3543 ideally suited for single
Li-Ion battery-powered applications. The 100% duty cycle
provides a low dropout operation, extending the battery
life in portable systems. Burst Mode operation increases
efficiency at light loads, further extending battery life.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,
6611131.
TYPICAL APPLICATION
2.5V TO 5.5V
3.3μH
V_IN
SW
10μF
LTC3543
300k
1.5V
10pF
PWR_EN
MODE
RUN
V_FB
MODE CAP
GND
200k
4nF
EXPOSED
PAD
3543 TA01a
MODE = V_IN m PULSE SKIP
MODE = V_FB m PULSE SKIP WITH SPREAD SPECTRUM
MODE = GND m Burst Mode OPERATION
MODE = EXTERNAL CLOCK m PLL
V_OUT
1.5V
10μF
Efficiency and Power Loss vs Load Current
100
1000
90
V_IN = 2.7V
80
70
V_IN = 4.2V
100
60
50
V_IN = 3.6V
10
40
30
POWER LOSS
AT V_IN = 3.6V
10
20
10
0
0.1
Burst Mode OPERATION ENABLED
0.1
1
10
100
1000
LOAD CURRENT (mA)
3543 TA01b
3543fa
1