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| LTC3706 Datasheet, PDF (17/20 Pages) Linear Technology – Secondary-Side Synchronous Forward Controller with PolyPhase Capability | |||
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LTC3706
APPLICATIONS INFORMATION
PolyPhase Applications
Figure 4 shows the basic connections for using the LTC3705
and LTC3706 in PolyPhase applications. One of the phases
is always identiï¬ed as the âmaster,â while all other phases
are âslaves.â For the LTC3705 (primary side), the master
monitors the VIN voltage for undervoltage, performs the
open-loop start-up and supplies the initial VCC voltage for
the master and all slaves. The LTC3705 slaves simply stand
by and wait for PWM signals from their respective pulse
transformers. Since the SS/FLT pins of master and slave
LTC3705âs are interconnected, a FAULT (overcurrent, etc.)
on any one of the phases will perform a shutdown/restart
on all phases together. The LTC3705 is put into slave mode
by omitting the resistor on FS/INâ. For the LTC3706, the
master performs soft-start and voltage-loop regulation by
driving all slaves to the same current as the master using
the ITH pins. Faults and shutdowns are communicated via
the interconnection of the RUN/SS pins. The LTC3706 is
put into slave mode by tying the FB pin to VCC.
VIN+
VOUT+
VBIAS
VIN NDRV VCC
NDRV
UVLO FB/IN+
VCC
FS/INâ
SS/FLT
LTC3705
(MASTER)
â¢â¢
FS/SYNC
PT+
FB
PTâ
ITH
RUN/SS
LTC3706
(MASTER)
VINâ
NDRV
SS/FLT FB/IN+
VCC
UVLO FS/INâ
LTC3705
(SLAVE)
â¢â¢
VIN NDRV VCC
RUN/SS FS/SYNC
PT+
FB
ITH
PTâ
PHASE
LTC3706
(SLAVE)
3706 F05
Figure 4. Connections for PolyPhase Operation
3706fb
17
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