LTC3520
1
3520fa
V
IN
(V)
2.2
EFFICIENCY (%)
3.7
3520 TA01b
2.7 3.2 4.2 4.7 5.2
70
75
80
85
90
95
100
BUCK-BOOST
I
OUT
= 150mA
BUCK
I
OUT
= 250mA
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
Synchronous 1A
Buck-Boost and 600mA
Buck Converters
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 effi ciency to be optimized while minimizing
the solution footprint. Both converters feature soft-start
and current limit protection. The uncommitted gain block
can be confi gured as an LDO or utilized as a battery-good
comparator.
The buck converter is current mode controlled with internal
synchronous rectifi cation to improve effi ciency. Pin-select-
able Burst Mode operation can be enabled to improve light
load effi ciency, 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 effi ciency and minimize noise.
At light loads, use of Burst Mode operation will improve
effi ciency.
The LTC3520 provides a <1μA shutdown mode and over-
temperature shutdown on both converters. The LTC3520
is available in a low profi le (0.75mm) 24-lead 4mm ×
4mm QFN package.
3.3V at 500mA, 1.8V at 600mA and 1.5V at 200mA Converter
n
Dual High Effi ciency 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)
n
2.2V to 5.5V Input Voltage Range
n
Pin-Selectable Burst Mode
®
Operation
n
Uncommitted Gain Block for LDO Controller, Battery
Good Indication or Sequencing
n
Programmable 100kHz to 2MHz Switching Frequency
n
55μA Total Quiescent Current for Both Converters in
Burst Mode Operation
n
Thermal and Overcurrent Protection
n
<1μA Quiescent Current in Shutdown
n
24-Lead 4mm × 4mm QFN Package
n
Portable Media Players
n
Digital Cameras
n
Handheld PCs, PDAs
n
GPS Receivers
3520 TA01
SW1A
SW1B
V
OUT1
A
OUT
A
IN
V
OUT2
V
C1
FB1
SS1
SV
IN
PV
IN3
PV
IN2
PV
IN1
PGND2SGNDPGND1
SW2
FB2
SS2
R
T
PWM1
PWM2
SD3
SD2
SD1
47μF
4.7μF
1M
309k
15k
470pF
10k
56pF
LTC3520
V
OUT1
3.3V
500mA
1A FOR
V
IN
≥ 3V
V
OUT2
1.8V
600mA
V
IN
2.2V TO
5.5V
V
OUT
1.5V
200mA
10μF
0.01μF
0.01μF
54.9k
PWM
BURST
100k
110k
33pF
255k
27pF
200k
22μF
4.7μH
4.7μH
ON
OFF
Effi ciency vs V
IN
L, LT, LTC, LTM, Linear Technology, the Linear logo 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.
