Buck Converters. LTC3522 Datasheet

LTC3522 Converters. Datasheet pdf. Equivalent

Part LTC3522
Description Synchronous 400mA Buck-Boost and 200mA Buck Converters
Feature www.DataSheet4U.com LTC3522 Synchronous 400mA Buck-Boost and 200mA Buck Converters FEATURES ■ DESC.
Manufacture Linear Technology
Datasheet
Download LTC3522 Datasheet




LTC3522
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LTC3522
Synchronous 400mA
Buck-Boost and 200mA
Buck Converters
FEATURES
Dual High Efficiency DC/DC Converters:
Buck-Boost (VOUT: 2.2V to 5.25V, IOUT: 400mA
for VIN > 3V, VOUT = 3.3V)
Buck (VOUT: 0.6V to VIN, IOUT: 200mA)
2.4V to 5.5V Input Voltage Range
Pin Selectable Burst Mode® Operation
25μA Total Quiescent Current for Both Converters in
Burst Mode Operation
Independent Power Good Indicator Outputs
Integrated Soft-Start
Thermal and Overcurrent Protection
<1μA Quiescent Current in Shutdown
Small 0.75mm × 3mm × 3mm QFN Package
APPLICATIONS
Flash-Based MP3 Players
Medical Instruments
Digital Cameras
PDAs, Handheld PCs
Personal Navigation Devices
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6404251 and 6166527.
DESCRIPTION
The LTC®3522 combines a 400mA buck-boost DC/DC con-
verter with a 200mA synchronous buck DC/DC converter in
a tiny 3mm × 3mm package. The 1MHz switching frequency
minimizes the solution footprint while maintaining high
efficiency. Both converters feature internal soft-start and
compensation, simplifying the design process.
The buck converter is current mode controlled and utilizes
an internal synchronous rectifier for high efficiency. The
buck converter supports 100% duty cycle operation to
extend battery life. If the PWM pin is held low, the buck
converter automatically transitions from Burst Mode opera-
tion to PWM mode. With the PWM pin held high, the buck
converter remains in low noise, 1MHz PWM mode.
The buck-boost converter provides continuous conduc-
tion operation to maximize efficiency and minimize noise.
At light loads, the buck-boost converter can be placed in
Burst Mode operation to improve efficiency and reduce
no-load standby current.
The LTC3522 provides a 1μA shutdown mode, overtem-
perature shutdown and current limit protection on both
converters. The LTC3522 is available in a 16-pin low profile
3mm × 3mm QFN package.
TYPICAL APPLICATION
VIN
2.4V TO 4.2V +
Li-Ion
VOUT2
1.8V
200mA
6.8μF
4.7μF
137k
L1
8.2μH
12pF
68.1k
ON
OFF
PWM
BURST
L1: COILCRAFT MSS6132-8.2μH
L2: COILCRAFT MSS6132-4.7μH
PVIN1 PVIN2
SW2 SW1A
L2
4.7μH
SW1B
LTC3522
FB2 VOUT1
SHDN2
1M
SHDN1
PWM
FB1
PGOOD2
PGOOD1
432k
PGND1 GND PGND2
3522 TA01a
VOUT1
3.3V
300mA
4.7μF
(400mA
VIN > 3V)
100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
70
2.4
Efficiency vs VIN
BUCK-BOOST
IOUT = 100mA
VOUT = 3.3V
BUCK
IOUT = 100mA
VOUT = 1.8V
3.4 4.4
VIN (V)
5.4
3522 TA01b
3522f
1



LTC3522
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LTC3522
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PVIN1, PVIN2 Voltage .................................... –0.3V to 6V
SW1A, SW1B, SW2 Voltage
DC............................................................ –0.3V to 6V
Pulsed < 100ns........................................... –1V to 7V
Voltage, All Other Pins ................................. –0.3V to 6V
Operating Temperature Range (Note 2) ... –40°C to 85°C
Maximum Junction Temperature (Note 5) ............ 125°C
Storage Temperature Range................... –65°C to 125°C
PACKAGE/ORDER INFORMATION
TOP VIEW
16 15 14 13
FB2 1
12 VOUT1
PWM 2
GND 3
11 SW1A
17
10 SW1B
PGOOD2 4
9 PGND2
5678
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = 68°C/W
EXPOSED PAD (PIN 17) IS GND AND MUST BE SOLDERED TO PCB GROUND
ORDER PART NUMBER UD PART MARKING
LTC3522EUD
LCRQ
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. PVIN1 = PVIN2 = 3.6V, VOUT1 = 3.3V unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Input Voltage
2.4
5.5 V
Quiescent Current—Shutdown
Burst Mode Quiescent Current
Oscillator Frequency
VSHDN1 = VSHDN2 = 0V
VFB1 = 1.1V, VFB2 = 0.66V, VPWM = 0V
0.8
0.01 1
25
1.07 1.33
μA
μA
MHz
SHDN1, SHDN2, PWM Input High Voltage
1.4 V
SHDN1, SHDN2, PWM Input Low Voltage
0.4 V
Power Good Outputs Low Voltage
Power Good Outputs Leakage
Buck Converter
IPGOOD1 = IPGOOD2 = 1mA
VPGOOD1 = VPGOOD2 = 5.5V
0.02 0.1
0.1 10
V
μA
PMOS Switch Resistance
0.41 Ω
NMOS Switch Resistance
0.34 Ω
NMOS Switch Leakage
PMOS Switch Leakage
Feedback Voltage
VSW2 = 5V, PVIN1 = PVIN2 = 5V
VSW2 = 0V, PVIN1 = PVIN2 = 5V
(Note 4)
0.582
0.1
0.1
0.594
5
10
0.606
μA
μA
V
Feedback Input Current
1 50
nA
Peak Current Limit
(Note 3)
300 400
mA
Maximum Duty Cycle
Minimum Duty Cycle
VFB2 = 0.54V
VFB2 = 0.66V
100
%
0%
3522f
2







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