LT8310
10
8310f
For more information www.linear.com/LT8310
pin FuncTions
SENSE (Pin 13): Switch Current Sense Input. Positive
input of the low side current sense to the control loops
and the overcurrent comparator. Kelvin-connect this pin to
the sense resistor at the source of the N-channel MOSFET
switch. Exceeding 125mV at this pin triggers an overcur
-
rent fault
, and sends the system into fast shutdown, slow
wake-up, and soft-start.
GA
TE (Pin 14): Switch Control Output. Low side switch
drive (GND to INTV
CC
) for external N-channel MOSFET. The
maximum duty cycle is limited to 78% (typ) because reso-
nant reset
forward converters require time for transformer
flux to reset. Actively pulled to GND during shutdown.
INT
V
CC
(Pin 15): Regulated Supply Output. A 10V LDO
supply generated from V
IN
and capable of supplying the
GATE pin. Must be bypassed with a 4.7µF capacitor or
higher. The regulator voltage can be externally driven up
to 17V, as long as V
IN
≥ V
INTVCC
, to reduce internal power
dissipation from V
IN
or to accommodate more than 10V
gate drive for high voltage N-channel MOSFETs.
RDVIN (Pin 16): Duty Cycle Control Input. This pin sinks
a precise 20µA in normal operation, but less during soft-
start, when the duty cycle
is folded
back. Connect a resistor
R
SET
between the INTV
CC
and RDVIN pins to program the
desired (no opto) application output voltage:
R
SET
=
N
P
N
S
⎛
⎝
⎜
⎞
⎠
⎟
•
OUT
12
⎛
⎝
⎜
⎞
⎠
⎟
20µA
Resistor value accuracy contributes directly to the output
voltage accuracy, choose appropriate tolerance. In current
mode applications, feedback sets V
OUT
, therefore program
R
SET
to set a maximum duty cycle guardrail that constrains
the volt-seconds of flux in the transformer during transients.
This pin must be connected to INTV
CC
by a resistor.
V
IN
(Pin 18): Supply Input and System Input Voltage
Sense. Input supply for the part; operational from 6V to
100V. Accurate duty cycle requires accurate sensing of
the V
IN
voltage, so keep the connection to the transformer
primary short to minimize resistive voltage drops. Bypass
to GND with 1µF.
NC (Pin 20): No Internal Connection. Connect to V
IN
.
GND (Exposed Pad Pin 21): Ground. This pin also senses
the negative terminal of the current sense resistor. Solder
the exposed pad directly to the ground plane.
