LTC3777
150V VIN and VOUT Synchronous
4-Switch Buck-Boost Controller +
Switching Bias Supply
FEATURES
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 Integrated 12µA IQ, 150V, 85mA, Switching Bias
for Optimal Thermal Performance
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 150V Rated RUN Pin with Accurate Turn-On Threshold
nn Thermally Enhanced 48-Lead e-LQFP Package
APPLICATIONS
nn Industrial, Transportation, Medical, Military, Avionics
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DESCRIPTION
The LTC®3777 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. The
150V integrated switching bias supply is a high efficiency
step-down regulator that draws only 12µA typical DC supply
current with a regulated output voltage at no load.
With a wide 4.5V to 150V input and output range and
seamless transfers between operating regions, the
LTC3777 is ideal for industrial, telecom and battery-
powered systems.
The LTC3777 features a power good output indicator
and a MODE pin to select between pulse-skipping mode
or forced continuous mode of operation. 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.
TYPICAL APPLICATION
VIN
16V TO 120V
20µF
5µF
1k
5Ω
0.1µF
133k 10µF
1.21k
BVOUT
12V
85mA
44µF
1µF
220µH
715k 51.1k
1µF
10k
2.2µF 100k
0.1µF
56.2k
VINSNS
BOOST1
VIN
DRVCC
SW1
TG1
LTC3777 BG1
VINOV
BVIN
BOV
BRUN
BSW
BVFB
BGND
EXTVCC
SENSEP
SENSEN
SGND
PGND
BG2
BOOST2
SW2
TG2
IAVGSNSP
RUN
PGOOD
V5
SS
FREQ
IAVGSNSN
VOUTSNS
VFB
ITH
MODE
PLLIN
Document Feedback
0.22µF
30µF
15µH
4mΩ
100Ω
220pF 100Ω
4mΩ
VOUT
48V, 10A
56µF
Efficiency and Power Loss
vs Input Voltage
100
30
98
24
EFFICIENCY
475k
96
18
0.22µF
4.7µF 100Ω
1k
100Ω
100pF
12.1k
10k 10nF
3777 TA01a
For more information www.analog.com
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)
3777 TA01b
Rev A
1
