LTC3779
150V VIN and VOUT Synchronous
4-Switch Buck-Boost Controller
FEATURES
DESCRIPTION
nn 4-Switch Current Mode Single Inductor Architecture
Allows VIN Above, Below or Equal to VOUT
nn Wide VIN Range: 4.5V to 150V
nn Wide Output Voltage Range: 1.2V ≤ VOUT ≤ 150V
nn Synchronous Rectification: Up to 99% Efficiency
nn ±1% 1.2V Voltage Reference
nn Input or Output Average Current Limit
nn Onboard LDO or External NMOS LDO for DRVCC
nn 36V EXTVCC LDO Powers Drivers
nn Programmable 6V to 10V DRVCC Optimizes Efficiency
nn No Top FET Refresh Noise in Boost or Buck Mode
nn VOUT Disconnected from VIN During Shutdown
nn Phase-Lockable Fixed Frequency (50kHz to 600kHz)
nn No Reverse Current During Start-Up
nn Power Good Output Voltage Monitor
nn 150V Rated RUN Pin with Accurate Turn-On Threshold
nn Programmable Input Overvoltage Lockout
nn Thermally Enhanced FE38 TSSOP Package Modified
for High Voltage Operation
APPLICATIONS
The LTC®3779 is a high performance buck-boost switching
regulator controller that operates from input voltages
above, below or equal to the output voltage. The constant
frequency current mode architecture allows a phase-
lockable frequency of up to 600kHz, while an input/
output constant-current loop provides support for battery
charging.
With a wide 4.5V to 150V input and output range and
seamless transfers between operating regions, the
LTC3779 is ideal for automotive, telecom and battery-
powered systems.
The LTC3779 features a precision 1.2V reference and
power good output indicator. The MODE pin can select
between pulse-skipping mode or forced continuous mode
of operation. Pulse-skipping mode offers high efficiency
at light load while forced continuous mode operates at
a constant frequency for noise sensitive applications.
The PLLIN pin allows the IC to be synchronized to an
external clock. The SS pin ramps the output voltage
during start-up. Current foldback limits MOSFET heat
dissipation during short-circuit conditions.
nn Industrial, Automotive, Medical, Military, Avionics
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TYPICAL APPLICATION
VIN
20V TO 120V
20µF
5µF
1k
5Ω
0.1µF
10k
133k
1.21k
10µF
VINSNS
VIN
RUN
VINOV
NDRV
DRVCC
2.2µF
0.1µF
V5
SS
FREQ
56.2k
100pF
ITH
10k
10nF
BOOST1
SW1
TG1
BG1
SENSEP
LTC3779
SENSEN
SGND
PGND
BG2
BOOST2
SW2
TG2
IAVGSNSP
IAVGSNSN
VOUTSNS
VFB
0.22µF
15µH
100Ω
220pF
100Ω
4mΩ
0.22µF
100Ω
4.7µF 100Ω
1k
12.1k
4mΩ
30µF
VOUT
48V
10A
56µF
475k
3779 TA01a
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Efficiency and Power Loss
vs Input Voltage
100
30
98
24
EFFICIENCY
96
18
94
12
92
6
VOUT = 48V
POWER LOSS
IOUT = 10A
90
0
0 12 24 36 48 60 72 84 96 108 120
VIN VOLTAGE (V)
3779 TA01b
Rev A
1
