LTC3859AL_15 Datasheet, PDF (28/44 Pages) Linear Technology – Triple Output, Buck/Buck/Boost Synchronous Controller with 28A Burst Mode IQ

LTC3859AL
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_BIAS.
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_BIAS.
LTC3859AL
V_IN1,2
C1
BAT85
BAT85
MTOP
TG
EXTV_CC
SW
MBOT
BG
L
R_SENSE
BAT85
V_OUT1,2
PGND
3859al F09
Figure 9. Capacitive Charge Pump for EXTV_CC
28
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3859alf