LTC3714 Linear, LTC3714 Datasheet - Page 18

• Manufacturer Part Number: LTC3714
• Description: Wide Operating Range / Step-Down Controller with Internal Op Amp
• Manufacturer: Linear

APPLICATIO S I FOR ATIO
LTC3714
EXTV
The EXTV
and control power from the output or another external
source during normal operation. Whenever the EXTV
pin is above 4.7V the internal 5V regulator is shut off and
an internal 50mA P-channel switch connects the EXTV
pin to INTV
this pin drops below 4.5V. Do not apply more than 7V to
the EXTV
ing list summarizes the possible connections for EXTV
1. EXTV
internal 5V regulator.
2. EXTV
ciency supply compatible with the MOSFET gate drive
requirements (typically 5V) can improve overall
efficiency.
18
CC
CC
CC
Connection
CC
CC
CC
grounded. INTV
connected to an external supply. A high effi-
pin and ensure that EXTV
pin can be used to provide MOSFET gate drive
. INTV
CC
U
power is supplied from EXTV
U
CC
is always powered from the
TG
W
CC
10
V
BOOST
Figure 6. Optional External Gate Driver
SW
IN
Q1
FMMT619
Q2
FMMT720
. The follow-
U
CC
until
GATE
OF M1
CC
CC
CC
:
3. EXTV
The low voltage output can be boosted using a charge
pump or flyback winding to greater than 4.7V. The system
will start-up using the internal linear regulator until the
boosted output supply is available.
External Gate Drive Buffers
The LTC3714 drivers are adequate for driving up to about
60nC into MOSFET switches with RMS currents of 50mA.
Applications with larger MOSFET switches or operating at
frequencies requiring greater RMS currents will benefit
from using external gate drive buffers such as the LTC1693.
Alternately, the external buffer circuit shown in Figure 6
can be used. Note that the bipolar devices reduce the
signal swing at the MOSFET gate, and benefit from in-
creased EXTV
BG
10
CC
INTV
PGND
connected to an output derived boost network.
Q3
FMMT619
Q4
FMMT720
CC
CC
voltage of about 6V.
GATE
OF M2
3714 F06
3714f