LT8705_15 Datasheet, PDF (1/44 Pages) Linear Technology – 80V VIN and VOUT Synchronous 4-Switch Buck- Boost DC/DC Controller

LT8705
80V V_IN and V_OUT
Synchronous 4-Switch Buck-
Boost DC/DC Controller
Features
nn _{Single Inductor Allows VIN Above, Below, or Equal}
to Regulated V_OUT
nn _{VIN Range 2.8V (Need EXTVCC > 6.4V) to 80V}
nn _{VOUT Range: 1.3V to 80V}
nn _{Quad N-Channel MOSFET Gate Drivers}
nn _{Synchronous Rectification: Up to 98% Efficiency}
nn _{Input and Output Current Monitor Pins}
nn _{Synchronizable Fixed Frequency: 100kHz to 400kHz}
nn _{Integrated Input Current, Input Voltage, Output Cur-}
rent and Output Voltage Feedback Loops
nn _{Clock Output Usable To Monitor Die Temperature}
nn _{Available in 38-Lead (5mm × 7mm) QFN and TSSOP}
Packages with the TSSOP Modified for Improved
High Voltage Operation
Applications
nn _{High Voltage Buck-Boost Converters}
nn _{Input or Output Current Limited Converters}
Description
The LT^®8705 is a high performance buck-boost switch-
ing regulator controller that operates from input voltages
above, below or equal to the output voltage. The part has
integrated input current, input voltage, output current
and output voltage feedback loops. With a wide 2.8V to
80V input and 1.3V to 80V output range, the LT8705 is
compatible with most solar, automotive, telecom and
battery-powered systems.
The LT8705 includes servo pins to indicate which feedback
loops are active. The MODE pin selects among Burst Mode^®
operation, discontinuous or continuous conduction mode
at light loads. Additional features include a 3.3V/12mA
LDO, a synchronizable fixed operating frequency, onboard
gate drivers, adjustable UVLO, along with input and output
current monitoring with programmable maximum levels.
L, LT, LTC, LTM, Linear Technology, Burst Mode, µModule and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Typical Application
Telecom Voltage Stabilizer
V_IN
36V TO
80V
1µF
+ _220µF
×2
M1
×2
4.7µF
×4
TO
DIODE
0.22µF
2Ω
×2
22µH
M2
M3
×2
1nF
10Ω
10mΩ
1nF
10Ω
2Ω
×2
M4
TO
DIODE
0.22µF
TG1 BOOST1 SW1 BG1 CSP
CSN
CSNIN
GND BG2 SW2 BOOST2 TG2
CSPOUT
CSPIN
CSNOUT
100k
V_IN
SHDN
SWEN
LDO33
MODE
LT8705
EXTV_CC
FBOUT
INTV_CC
GATEV_CC
SRVO_FBIN
FBIN
SRVO_FBOUT
RT
SRVO_IIN
71.5k
20k
4.7µF
SS
V_C
215k
56.2k
1µF
220pF
3.3nF
CLKOUT
202kHz
SYNC
SRVO_IOUT
IMON_IN
IMON_OUT
4.7µF
×6
V_OUT
+
48V
220µF ^5A
×2
392k
Efficiency and Power Loss
100
6
5
95
4
10k
4.7µF
4.7µF
4Ω
TO
TO
BOOST1 BOOST2
90
3
2
85
1
V_OUT = 48V
I_LOAD = 2A
80
0
30
40
50
60
70
80
V_IN (V)
8705 TA01b
8705 TA01
8705fe
For more information www.linear.com/LT8705
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