Datasheet

LTC3859A
28
3859af
applicaTions inForMaTion
The following list summarizes the four possible connec-
tions for EXTV
CC
:
1. EXTV
CC
grounded. This will cause INTV
CC
to be powered
from the internal 5.4V regulator resulting in an efficiency
penalty of up to 10% at high input voltages.
2. EXTV
CC
connected directly to the output voltage of one
of the buck regulators. This is the normal connection
for a 5V to 14V regulator and provides the highest ef-
ficiency.
3. EXTV
CC
connected to an external supply. If an external
supply is available in the 5V to 14V range, it may be
used to power EXTV
CC
providing it is compatible with the
MOSFET gate drive requirements. Ensure that EXTV
CC
< V
IN
.
4. EXTV
CC
connected to an output-derived boost network
off one of the buck regulators. For 3.3V and other low
voltage buck regulators, efficiency gains can still be
realized by connecting EXTV
CC
to an output-derived
voltage that has been boosted to greater than 4.7V. This
can be done with the capacitive charge pump shown in
Figure 9. Ensure that EXTV
CC
< V
IN
.
Figure 9. Capacitive Charge Pump for EXTV
CC
3859A F09
LTC3859A
TG
SW
BG
PGND
R
SENSE
MTOP
MBOT
L
EXTV
CC
BAT85 BAT85
C1
V
IN1,2
BAT85
V
OUT1,2