DC/DC converter. LTC3541 Datasheet

LTC3541 converter. Datasheet pdf. Equivalent

Part LTC3541
Description synchronous buck DC/DC converter
Feature www.DataSheet4U.com LTC3541 High Efficiency Buck + VLDO Regulator FEATURES ■ DESCRIPTIO ■ ■ ■ ■ ■ .
Manufacture Linear Technology
Datasheet
Download LTC3541 Datasheet




LTC3541
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LTC3541
High Efficiency
Buck + VLDO Regulator
FEATURES
DESCRIPTIO
High Efficiency, 500mA Buck Plus 300mA VLDOTM
Regulator
Auto Start-Up Powers Buck Output Prior to
VLDO/Linear Regulator Output
Independent High Efficiency, 500mA Buck
(VIN: 2.7V to 5.5V)
300mA VLDO Regulator with 30mA Standalone Mode
No External Schottky Diodes Required
Buck Output Voltage Range: 0.8V to 5V
VLDO Input Voltage Range (LVIN): 0.9V to 5.5V
VLDO Output Voltage Range VLDO: 0.4V to 4.1V
Selectable Fixed Frequency, Pulse-Skip Operation or
Burst Mode® Operation
Short-Circuit Protected
Current Mode Operation for Excellent Line and Load
Transient Response
Constant Frequency Operation: 2.25MHz
Low Dropout Buck Operation: 100% Duty Cycle
Small, Thermally Enhanced, 10-Lead (3mm × 3mm)
DFN Package U
APPLICATIO S
PDAs/Palmtop PCs
Digital Cameras
Cellular Phones
PC Cards
Wireless and DSL Modems
Other Portable Power Systems
The LTC®3541 combines a synchronous buck DC/DC
converter with a very low dropout linear regulator
(VLDO) to provide up to two output voltages from a single
input voltage with minimal external components. When
configured for dual output operation, the LTC3541’s auto
start-up feature will bring the Buck output into regulation
in a controlled manner prior to enabling the VLDO regulator
output without the need for external pin control. VLDO/
linear regulator output prior to Buck output sequencing
may also be obtained via external pin control. The input
voltage range is ideally suited for Li-Ion battery-powered
applications, as well as powering sub-3.3V logic from 5V
or 3.3V rails.
The synchronous buck converter provides a high efficiency
output, typically 90%, capable of providing up to 500mA
of continuous output current while switching at 2.25MHz,
allowing the use of small surface mount inductors and ca-
pacitors. A mode-select pin allows Burst Mode operation
to be enabled for higher efficiency at light load currents, or
disabled for lower noise, constant frequency operation.
The VLDO regulator provides a low noise, low voltage
output capable of providing up to 300mA of continuous
output current using only a 2.2µF ceramic capacitor. The
input supply voltage of the VLDO regulator (LVIN) may
come from the buck regulator or a separate supply.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
VLDO is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258
TYPICAL APPLICATIO
LTC3541 Typical Application
VIN
2.9V TO 5.5V
SW ENVLDO
VOUT1
2.5V
500mA
2.2µH
243k
22pF
10µF
VIN MODE
LTC3541
ENBUCK GND
BUCKFB LFB
LVIN LVOUT
PGND
115k
150k
412k
VOUT2
1.5V
2.2µF 300mA
3541 TA01a
Buck (Burst) Efficiency and Power Loss vs Load Current
100 1
90
EFFICIENCY
80
70
0.1
60
POWER LOSS
50 0.01
40
30
20
10 VIN = 3.3V
0 VOUT = 2.5V
1 10
100
LOAD CURRENT (mA)
0.001
0.0001
1000
3541 TA01b
3541f
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LTC3541
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LTC3541
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltages:
VIN, LVIN .................................................. –0.3V to 6V
LVIN – VIN ..........................................................<0.3V
Pin Voltages:
ENVLDO, ENBUCK, MODE, SW,
LFB, BUCKFB .............................–0.3V to (VIN + 0.3V)
Linear Regulator IOUT(MAX) (100ms) (Note 9) ......100mA
Operating Ambient Temperature Range
(Note 2).................................................... –40°C to 85°C
Junction Temperature (Note 5) ............................. 125°C
Storage Temperature Range................... –65°C to 125°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
VIN
ENBUCK
BUCKFB
LFB
LVOUT
1
2
3
4
5
10 SW
9 ENVLDO
11 8 MODE
7 GND
6 LVIN
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 43°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER DD PART MARKING
LTC3541EDD
LCBS
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/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V unless otherwise specified (Note 2)
SYMBOL
IPK
IBUCKFB
ILFB
VIN
VIN(LINEREG)
PARAMETER
Peak Inductor Current
BUCKFB Pin Input Current
LFB Pin Input Current
Input Voltage Range
Buck VIN Line Regulation
LVIN(LINEREG)
VLDO VIN Line Regulation
(Referred to LFB)
Linear Regulator VIN Line
Regulation (Referred to LFB)
LVIN Line Regulation
(Referred to LFB)
VLDODO
VLOADREG
LVIN – LVOUT Dropout Voltage
(Note 9)
Buck Output Load Regulation
VLDO Output Load Regulation
Linear Regulator Output Load
VBUCKFB
Reference Regulation Voltage
(Note 6)
VLFB Reference Regulation Voltage
(Note 7)
CONDITIONS
VIN = 4.2V (Note 8)
VBUCKFB = 0.9V
VLFB = 0.45V
(Note 4)
VIN = 2.7V to 5.5V, ENBUCK = VIN,
ENVLDO = 0V, MODE = VIN (Note 6)
VIN = 2.7V to 5.5V, LVOUT = 1.2V, ENBUCK = VIN,
ENVLDO = VIN, IOUT(VLDO) = 100mA, LVIN = 1.5V
VIN = 2.7V to 5.5V, LVOUT = 1.2V, ENBUCK = 0V,
ENVLDO = VIN, IOUT(LREG) = 10mA
LVIN = 0.9V to 5.5V, VIN = 5.5V, LVOUT = 0.4V,
ENBUCK = VIN, ENVLDO = VIN, MODE = VIN,
IOUT(VLDO) = 100mA
LVIN = 1.5V, ENBUCK = VIN, ENVLDO = VIN,
MODE = VIN, IOUT(VLDO) = 50mA, VLFB = 0.3V
ENBUCK = VIN, ENVLDO = 0V, MODE = VIN (Note 6)
IOUT(VLDO) = 1mA – 300mA, LVIN = 1.5V, LVOUT = 1.2V,
ENBUCK = VIN, ENVLDO = VIN, MODE = VIN
IOUT(LREG) = 1mA – 30mA, LVOUT = 1.2V,
ENBUCK = 0V, ENVLDO = VIN
ENBUCK = VIN, ENVLDO = 0V, TA = 25°C
ENBUCK = VIN, ENVLDO = 0V, 0°C ≤ TA ≤ 85°C
ENBUCK = VIN, ENVLDO = 0V, –40°C ≤ TA ≤ 85°C
ENBUCK = 0V, ENVLDO = VIN, TA = 25°C
ENBUCK = 0V, ENVLDO = VIN, 0°C ≤ TA ≤ 85°C
ENBUCK = 0V, ENVLDO = VIN, –40°C ≤ TA ≤ 85°C
MIN
0.8
–200
2.7
0.784
0.782
0.78
0.392
0.391
0.390
TYP MAX
0.95 1.25
±50
–40
5.5
0.04 0.4
0.6
0.6
0.3
28 60
0.5
0.25 0.5
0.25 0.5
0.8 0.816
0.8 0.818
0.8 0.82
0.4 0.408
0.4 0.409
0.4 0.410
UNITS
A
nA
nA
V
%/V
mV/V
mV/V
mV/V
mV
%
%
%
V
V
V
V
V
V
3541f
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