Datasheet

LT3791
10
3791fa
pin FuncTions
NC (Pin 23): No Connect Pin. Leave this pin floating.
TG2 (Pin 24): Top Gate Drive. Drives the top N-channel
MOSFET with a voltage equal to INTV
CC
superimposed on
the switch node voltage SW2.
ISP (Pin 25): Connection Point for the Positive Terminal
of the Output Current Feedback Resistor.
ISN (Pin 26): Connection Point for the Negative Terminal
of the Output Current Feedback Resistor.
SNSP (Pin 27): The Positive Input to the Current Sense
Comparator. The V
C
pin voltage and controlled offsets
between the SNSP and SNSN pins, in conjunction with a
resistor, set the current trip threshold.
SNSN (Pin 28): The Negative Input to the Current Sense
Comparator.
TEST1 (Pin 29): This pin is used for testing purposes only
and must be connected to SGND for the part to operate
properly.
SGND (Pin 30, Exposed Pad Pin 39): Signal Ground.
All small-signal components and compensation should
connect to this ground, which should be connected to
PGND at a single point. Solder the exposed pad directly
to the ground plane.
PWMOUT (Pin 31): Buffered Version of PWM Signal for
Driving LED Load Disconnect N-Channel MOSFET. The
PWMOUT pin is driven from INTV
CC
. Use of a MOSFET
with a gate cutoff voltage higher than
1V is recommended.
TEST2 (Pin 32): This pin is used for testing purposes only
and must be connected to INTV
CC
(Pin 13) for the part to
operate properly.
CLKOUT (Pin 33): Clock Output Pin. An in-phase clock is
provided at the oscillator frequency to allow for synchro-
nizing two devices for extending output power capability.
SYNC (Pin 34): External Synchronization Input Pin. This
pin is internally terminated to GND with a 90k resistor.
The rising edge will be synchronized with the rising edge
of the SYNC signal.
RT (Pin 35): Frequency Set Pin. Place a resistor to GND
to set the internal frequency. The range of oscillation is
200kHz to 700kHz.
V
C
(Pin 36): Current Control Threshold and Error Amplifier
Compensation Point. The current comparator threshold
increases with this control voltage. The voltage ranges
from 0.7V to 1.9V.
FB (Pin 37): Voltage Loop Feedback Pin. FB is intended
for LED protection of an open or shorted LED event. The
internal transconductance amplifier with output V
C
will
regulate FB to 1.2V (typical) through the DC/DC converter.
If the FB input is regulating the loop and V
(ISP-ISN)
< 10mV,
the OPENLED pull-down is asserted. If the FB pin is less
than 400mV, the SHOR
TLED pull-down is asserted.
OVLO (Pin 38): Overvoltage Input Pin. This pin is used for
OVLO, if OVLO > 3V then SS is pulled low, the part stops
switching and resets. Do not leave this pin open.