LTC3780
High Efficiency, Synchronous,
4-Switch Buck-Boost Controller
FEATURES
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DESCRIPTION
The LTC
®
3780 is a high performance buck-boost switch-
ing regulator controller that operates from input voltages
above, below or equal to the output voltage. The constant
frequency current mode architecture allows a phase-lock-
able frequency of up to 400kHz. With a wide 4V to 30V
(36V maximum) input and output range and seamless
transfers between operating modes, the LTC3780 is ideal
for automotive, telecom and battery-powered systems.
The operating mode of the controller is determined through
the FCB pin. For boost operation, the FCB mode pin can
select among Burst Mode
®
operation, discontinuous mode
and forced continuous mode. During buck operation, the
FCB mode pin can select among skip-cycle mode, discon-
tinuous mode and forced continuous mode. Burst Mode
operation and skip-cycle mode provide high efficiency
operation at light loads while forced continuous mode and
discontinuous mode operate at a constant frequency.
Fault protection is provided by an output overvoltage
comparator and internal foldback current limiting. A power
good output pin indicates when the output is within 7.5%
of its designed set point.
, 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, 6304066, 5929620, 5408150, 6580258,
patent pending on current mode architecture and protection
Single Inductor Architecture Allows V
IN
Above,
Below or Equal to V
OUT
Wide V
IN
Range: 4V to 36V Operation
Synchronous Rectification: Up to 98% Efficiency
Current Mode Control
±1%
Output Voltage Accuracy: 0.8V < V
OUT
< 30V
Phase-Lockable Fixed Frequency: 200kHz to 400kHz
Power Good Output Voltage Monitor
Internal LDO for MOSFET Supply
Quad N-Channel MOSFET Synchronous Drive
V
OUT
Disconnected from V
IN
During Shutdown
Adjustable Soft-Start Current Ramping
Foldback Output Current Limiting
Selectable Low Current Modes
Output Overvoltage Protection
Available in 24-Lead SSOP and Exposed Pad
(5mm
×
5mm) 32-Lead QFN Packages
APPLICATIONS
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Automotive Systems
Telecom Systems
DC Power Distribution Systems
High Power Battery-Operated Devices
Industrial Control
TYPICAL APPLICATION
High Efficiency Buck-Boost Converter
V
IN
5V TO 32V
22μF
50V
CER
+
4.7μF
A
0.1μF
V
IN
PGOOD INTV
CC
TG2
BOOST2
SW2
LTC3780
BG2
2200pF
20k
0.1μF
I
TH
SS
BG1
PLLIN
RUN
V
OSENSE
SGND
FCB
SENSE
+
SENSE
–
PGND
7.5k
1%
ON/OFF
TG1
BOOST1
SW1
0.1μF
1μF
CER
D
100μF
16V
CER
+
330μF
16V
V
OUT
12V
5A
100
95
EFFICIENCY (%)
Efficiency and Power Loss
V
OUT
= 12V, I
LOAD
= 5A
10
9
8
7
6
85
80
75
70
5
4
3
2
1
0
0
5
10
20
15
V
IN
(V)
25
30
35
POWER LOSS (W)
B
C
90
105k
1%
0.010Ω
3780 TA01b
4.7μH
3780 TA01
3780fe
1
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
