LTC3810EG LINER [Linear Technology], LTC3810EG Datasheet - Page 23

• Manufacturer Part Number: LTC3810EG
• Description: 100V Current Mode Synchronous Switching Regulator Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
Using an External Supply Connected to the INTV
DRV
If an external supply is available between 6.2V and 14V,
the supply can be connected directly to the INTV
pins. In this mode, INTV
shorted together.
INTV
The LTC3810 contains an internal low dropout regulator to
produce the 10V INTV
pin voltage. This regulator turns on when the EXTV
is above 6.7V and remains on until EXTV
6.4V. This allows the IC/MOSFET power to be derived from
the output or an output derived boost network during
normal operation and from the external NMOS from V
during start-up or short-circuit. Using the EXTV
this way results in signifi cant effi ciency gains compared
to what would be possible when deriving this power
continuously from the typically much higher V
The EXTV
be confi gured in trickle charge mode in which it starts up
with a high valued “bleed” resistor connected from V
to INTV
the output rises above 6.7V the internal EXTV
takes over before the INTV
the UV threshold. When the EXTV
the EXTV
ply more than 15V to the EXTV
summarizes the possible connections for EXTV
1. EXTV
to be powered continuously from an external NMOS
from V
10% at high input voltages.
CC
CC
/DRV
Pins
CC
CC
CC
CC
IN
to charge up the INTV
grounded. This connection will require INTV
pin can supply up to 50mA RMS. Do not ap-
CC
resulting in an effi ciency penalty as high as
connection also allows the power supply to
Supply and the EXTV
CC
/DRV
CC
CC
, EXTV
capacitor discharges below
CC
CC
supply from the EXTV
CC
CC
CC
pin. The following list
capacitor. As soon as
CC
and NDRV must be
regulator is active,
Connection
CC
drops below
CC
IN
CC
CC
regulator
CC
voltage.
/DRV
:
CC
CC
pin in
/
pin
CC
CC
CC
IN
IN
Applications using large MOSFETs with a high input volt-
age and high frequency of operation may result in a large
EXTV
to verify that the maximum junction temperature rating
and RMS current rating are within the maximum limits.
Typically, most of the EXTV
MOSFET gates current. In continuous mode operation,
this EXTV
The junction temperature can be estimated from the
equations given in Note 2 of the Electrical Characteristics
as follows:
If absolute maximum ratings are exceeded, consider
using an external supply connected directly to the
INTV
2. EXTV
3. EXTV
4. EXTV
connection for 6.7V < V
highest effi ciency. The power supply will start up using
an external NMOS or a bleed resistor until the output
supply is available.
If V
using a charge pump or fl yback winding to greater
than 6.7V.
connection for EXTV
external supply where the external supply is 6.2V <
V
T
< 125°C
I
EXTVCC
J
EXT
CC
CC
= T
OUT
CC
pin.
< 15V.
CC
pin current. Therefore, it is good design practice
CC
A
CC
< 6.7V. The low voltage output can be boosted
+ I
connected to an output-derived boost network.
= f Q
connected directly to V
connected to INTV
current is:
EXTVCC
(
G(TOP)
• (V
+ Q
CC
EXTVCC
if INTV
G(BOTTOM)
OUT
CC
– V
CC
< 15V and provides the
current consists of the
. This is the required
OUT
CC
INTVCC
. This is the normal
is connected to an
)
+ 3mA < 50mA
LTC3810
)(100°C/W)
23
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