Datasheet

LTC3766
46
3766fa
For more information www.linear.com/LTC3766
applicaTions inForMaTion
Remote Sensing
The LTC3766 contains a precision differential amplifier for
use in remote sensing applications. As shown in Figure 14a,
this is useful in eliminating the voltage drops associated
with bussing the power supply output voltage to a remote
load. Be aware that the differential amplifier is powered
from the V
IN
pin of the LTC3766, and requires 1.5V of
overhead on V
IN
above the output voltage (V
SOUT
). If the
voltage on the V
IN
pin is not adequate to support the V
SOUT
voltage, the LTC3766 will generate a fault. This is neces-
sary to avoid a potential overvoltage on the main output
of the converter
. In addition, the L
TC3766 will generate a
fault if the polarity of the V
S
+
and V
S
–
pins are reversed
by approximately 0.3V or more.
In rare applications, it may be useful to raise the common
mode voltage of the V
S
+
and V
S
–
inputs. When doing so,
always ensure that V
S
+
< 2(V
IN
– 2V) to prevent saturating
the input stage of the differential amplifier. If the input
stage is saturated, the LTC3766 forces the V
SOUT
pin to
0V. In applications where the differential amplifier is not
needed, connect the inputs as shown in either Figure14b
or Figure 15.
Self-Starting PolyPhase Applications
Figure 34 shows the PolyPhase connections for the
LTC3765 and LTC3766. On the primary side, the design
of one phase of the LTC3765 can be optimized and then
replicated up to four times by simply tying the SSFLT pins
together. The common SSFLT pins are held low until all
phases have adequate voltage on their V
CC
supplies and
RUN pins. This prevents any of the phases from switching
until every phase has satisfied the requirements for start-
up. When start-up conditions have been met, the SSFLT
pin is released and quickly charged until all phases have
IN
+
• •
NDRV
RUN
V
CC
SSFLT
C
SSP
C
VCC
R
FSP
R
FSS
R1
V
IN
+
V
IN
–
R2
IN
–
FS/UV
LTC3765
LTC3766
(MASTER)
GND
NDRV
GND
V
IN
V
BIAS
PHASE 1 (MASTER)
V
CC
FB
V
OUT
+
V
OUT
–
PT
+
SS
ITH
PT
–
FS/SYNC
C
SSS
IN
+
• •
NDRV
RUN
V
CC
SSFLT
C
SSP
C
VCC
R
FSP
R1
V
IN
+
V
IN
–
R2
IN
–
FS/UV
LTC3765
LTC3766
(SLAVE)
GND
NDRV
GND
V
IN
V
BIAS
PHASE 2 (SLAVE)
V
CC
FB
V
OUT
–
3766 F34
C
SSS
PT
+
FS/SYNC
V
S
–
V
S
+
V
SOUT
ITH
SS
PT
–
PHASE
Figure 34. PolyPhase Connections