LTC3520 Datasheet, PDF (1/24 Pages) Linear Technology – Synchronous 1A Buck-Boost and 600mA Buck Converters

FEATURES
■ _{Dual High Efficiency DC/DC Converters:}
Buck-Boost (V_OUT: 2.2V to 5.25V, I_OUT = 1A at
V_OUT = 3.3V, V_IN ≥ 3V)
Buck (V_OUT: 0.8V to V_IN, I_OUT = 600mA)
■ _{2.2V to 5.5V Input Voltage Range}
■ _{Pin-Selectable Burst Mode}^® _Operation
■ _{Uncommitted Gain Block for LDO Controller,}
Battery Good Indication or Sequencing
■ _{Programmable 100kHz to 2MHz Switching Frequency}
■ _{55µA Total Quiescent Current for Both Converters in}
Burst Mode Operation
■ _{Thermal and Overcurrent Protection}
■ _{<1µA Quiescent Current in Shutdown}
■ _{24-Lead 4mm × 4mm QFN Package}
APPLICATIONS
■ _{Portable Media Players}
■ _{Digital Cameras}
■ _{Handheld PCs, PDAs}
■ _{GPS Receivers}
, 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 5481178, 6166527, 6304066, 6404251, 6580258.
LTC3520
Synchronous 1A
Buck-Boost and 600mA
Buck Converters
DESCRIPTION
The LTC^®3520 combines 1A buck-boost and 600mA
synchronous buck DC/DC converters in a tiny 4mm ×
4mm package. A programmable switching frequency
allows the efficiency to be optimized while minimizing
the solution footprint. Both converters feature soft-start
and current limit protection. The uncommitted gain block
can be configured as an LDO or utilized as a battery-good
comparator.
The buck converter is current mode controlled with internal
synchronous rectification to improve efficiency. Pin-select-
able Burst Mode operation can be enabled to improve light
load efficiency, or the buck converter can be operated in
low noise PWM mode for sensitive applications.
The buck-boost converter provides continuous conduc-
tion operation to maximize efficiency and minimize noise.
At light loads, use of Burst Mode operation will improve
efficiency.
The LTC3520 provides a <1µA shutdown mode and over-
temperature shutdown on both converters. The LTC3520
is available in a low profile (0.75mm) 24-lead 4mm ×
4mm QFN package.
TYPICAL APPLICATION
3.3V at 500mA, 1.8V at 600mA and 1.5V at 200mA Converter
V_IN
2.2V TO
5.5V
V_OUT2
1.8V
600mA
10µF
22µF
255k
200k
BURST
4.7µH
PV_IN1 PV_IN2 PV_IN3 SV_IN SW1A
SW1B
SW2
V_OUT1
4.7µH
470pF
27pF
FB2
0.01µF
SS2
54.9k
R_T
LTC3520
V_C1
15k
FB1
0.01µF
SS1
V_OUT2
PWM
PWM1
PWM2
A_OUT
SD3
OFF ON
SD2
SD1
A_IN
PGND1 SGND PGND2
56pF
1M
10k
309k
33pF
100k
110k
47µF
V_OUT1
3.3V
500mA
1A FOR
V_IN ≥ 3V
V_OUT
1.5V
200mA
4.7µF
3520 TA01
Efficiency vs V_IN
100
BUCK-BOOST
95
I_OUT = 150mA
BUCK
90
I_OUT = 250mA
85
80
75
70
2.2 2.7 3.2 3.7 4.2 4.7 5.2
V_IN (V)
3520f
1