LT3758 LINER [Linear Technology], LT3758 Datasheet - Page 9

• Manufacturer Part Number: LT3758
• Description: High Input Voltage, Boost, Flyback, SEPIC and Inverting Controller
• Manufacturer: LINER [Linear Technology]

PIN FUNCTIONS
VC (Pin 1): Error Amplifi er Compensation Pin. Used to
stabilize the voltage loop with an external RC network.
FBX (Pin 2): Positive and Negative Feedback Pin. Re-
ceives the feedback voltage from the external resistor
divider across the output. Also modulates the switching
frequency during start-up and fault conditions when FBX
is close to GND.
SS (Pin 3): Soft-Start Pin. This pin modulates compensa-
tion pin voltage (VC) clamp. The soft-start interval is set
with an external capacitor. The pin has a 10μA (typical)
pull-up current source to an internal 2.5V rail. The soft-
start pin is reset to GND by an undervoltage condition
at SHDN/UVLO, an INTV
condition or an internal thermal lockout.
RT (Pin 4): Switching Frequency Adjustment Pin. Set the
frequency using a resistor to GND. Do not leave this pin
open.
SYNC (Pin 5): Frequency Synchronization Pin. Used to
synchronize the switching frequency to an outside clock.
If this feature is used, an R
program a switching frequency 20% slower than the SYNC
pulse frequency. Tie the SYNC pin to GND if this feature is
not used. SYNC is ignored when FBX is close to GND.
SENSE (Pin 6): The Current Sense Input for the Control
Loop. Kelvin connect this pin to the positive terminal of
the switch current sense resistor in the source of the NFET.
The negative terminal of the current sense resistor should
be connected to GND plane close to the IC.
CC
T
undervoltage or overvoltage
resistor should be chosen to
GATE (Pin 7): N-Channel MOSFET Gate Driver Output.
Switches between INTV
IC is shut down, during thermal lockout or when INTV
is above or below the overvoltage or UV thresholds,
respectively.
INTV
Gate Driver. Supplied from V
cal). INTV
capacitor placed close to pin. INTV
directly to V
be connected to a power supply whose voltage is higher
than 7.5V, and lower than V
not exceed 17.5V.
SHDN/UVLO (Pin 9): Shutdown and Undervoltage Detect
Pin. An accurate 1.22V (nominal) falling threshold with
externally programmable hysteresis detects when power
is okay to enable switching. Rising hysteresis is generated
by the external resistor divider and an accurate internal
2μA pull-down current. An undervoltage condition resets
sort-start. Tie to 0.4V, or less, to disable the device and
reduce V
V
with a 0.22μF , or larger, capacitor placed close to the
pin.
Exposed Pad (Pin 11): Ground. This pin also serves
as the negative terminal of the current sense resistor.
The Exposed Pad must be soldered directly to the local
ground plane.
IN
(Pin 10): Input Supply Pin. Must be locally bypassed
CC
(Pin 8): Regulated Supply for Internal Loads and
IN
CC
quiescent current below 1μA.
IN
must be bypassed with a minimum of 4.7μF
, if V
IN
is less than 17.5V. INTV
CC
and GND. Driven to GND when
IN
IN
, provided that supply does
and regulated to 7.2V (typi-
CC
can be connected
LT3758
CC
can also
9
3758f
CC