LTC3780_12 Datasheet, PDF (1/28 Pages) Linear Technology – High Effi ciency, Synchronous, 4-Switch Buck-Boost Controller

LTC3780
High Efficiency, Synchronous,
4-Switch Buck-Boost Controller
FEATURES
DESCRIPTION
n _{Single Inductor Architecture Allows VIN Above,}
Below or Equal to V_OUT
n _{Wide VIN Range: 4V to 36V Operation}
n _{Synchronous Rectification: Up to 98% Efficiency}
n _{Current Mode Control}
n _{±1% Output Voltage Accuracy: 0.8V < VOUT < 30V}
n _{Phase-Lockable Fixed Frequency: 200kHz to 400kHz}
n _{Power Good Output Voltage Monitor}
n _{Internal LDO for MOSFET Supply}
n _{Quad N-Channel MOSFET Synchronous Drive}
n _{VOUT Disconnected from VIN During Shutdown}
n _{Adjustable Soft-Start Current Ramping}
n _{Foldback Output Current Limiting}
n _{Selectable Low Current Modes}
n _{Output Overvoltage Protection}
n _{Available in 24-Lead SSOP and Exposed Pad}
(5mm × 5mm) 32-Lead QFN Packages
APPLICATIONS
n _{Automotive Systems}
n _{Telecom Systems}
n _{DC Power Distribution Systems}
n _{High Power Battery-Operated Devices}
n _{Industrial Control}
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
TYPICAL APPLICATION
V_IN
5V TO 32V
High Efficiency Buck-Boost Converter
22μF
+
50V
4.7μF
CER _A
0.1μF
V_IN PGOOD INTV_CC
TG2
TG1
BOOST2 BOOST1
SW2
SW1
B
LTC3780
BG2
BG1
2200pF
20k
I_TH
SS
0.1μF
PLLIN
RUN
V_OSENSE
SGND
FCB
SENSE⁺ SENSE^– PGND
1μF
CER
D
0.1μF
C
ON/OFF
105k
1%
7.5k
1%
0.010Ω
4.7μH
100μF +
16V
CER
330μF
16V
V_OUT
12V
5A
3780 TA01
Efficiency and Power Loss
V_OUT = 12V, I_LOAD = 5A
100
10
9
95
8
90
7
6
85
5
4
80
3
75
2
1
70
05
0
10 15 20 25 30 35
V_IN (V)
3780 TA01b
3780fe
1