Datasheet

LT3782A
6
3782afb
SGATE2 (Pin 1/Pin 26): Second Phase Synchronous Drive
Signal. An external driver buffer is needed to drive the top
synchronous power FET.
SGATE1 (Pin 2/Pin 27): First Phase Synchronous Drive
Signal. An external driver buffer is needed to drive the top
synchronous power FET.
GND (Pin 4, Exposed Pad Pin 29/Pin 28, Exposed Pad
Pin 29): Ground. Solder the exposed pad to the PCB
ground plane for rated thermal performance. The exposed
pad should be connected to the GND pin as close to the
IC as possible.
SYNC (Pin 5/Pin 1): Synchronization Input. The pulse
width can range from 10% to 70%. Note that the operating
frequency is half of the sync frequency.
DELAY (Pin 6/Pin 2): When synchronous drivers are used,
the programmable delay that delays BGATE turns on after
SGATE turns off.
DCL (Pin 7/Pin 3): This pin programs the limit of the
maximum duty cycle. When connected to V
RSET
, it operates
at natural maximum duty cycle, approximately 90%.
SENSE1
+
(Pin 8/Pin 4): First Phase Current Sense Amplifi er
Positive Input. An RC fi lter is required across the current
sense resistor. Current limit threshold is set at 63mV.
SENSE1
–
(Pin 9/Pin 5): First Phase Current Sense Ampli-
fi er Negative Input.
SLOPE (Pin 10/Pin 6): A resistor from SLOPE to
GND increases the internal current mode PWM slope
compensation.
R
SET
(Pin 11/Pin 7): A resistor from R
SET
to GND sets the
oscillator charging current and the operating frequency.
SENSE2
–
(Pin 12/Pin 8): Second Phase Current Sense
Amplifi er Negative Input.
SENSE2
+
(Pin 13/Pin 10): Second Phase Current Sense
Amplifi er Positive Input. An RC fi lter is required across
the current sense resistor. Current limit threshold is set
at 63mV.
SS (Pin 14/Pin 11): Soft-Start. A capacitor on this pin sets
the output ramp up rate. The typical time for SS to reach
the programmed level is (C • 2.44V)/10µA.
V
C
(Pin 15/Pin 12): The output of the g
m
error amplifi er and
the control signal of the current loop of the current-mode
PWM. Switching starts at 0.7V, and higher V
C
voltages
corresponds to higher inductor current.
FB (Pin 16/Pin 13): Error Amplifi er Inverting Input. A
resistor divider to this pin sets the output voltage.
RUN (Pin 17/Pin 14): LT3782A goes into shutdown mode
when V
RUN
is below 2.2V and goes to low bias current
shutdown mode when V
RUN
is below 0.3V.
V
EE2
(Pin 19/Pin 16): Gate Driver BGATE2 Ground. This
pin should be connected to ground as close to the IC as
possible.
BGATE2 (Pin 20/Pin 17): Second Phase MOSFET Driver.
GBIAS2 (Pin 21/Pin 18): Bias for Gate Driver BGATE2.
Should be connected to GBIAS or an external power supply
between 12V to 14V.
GBIAS1 (Pin 22/Pin 21): Bias for Gate Driver BGATE1.
Should be connected to GBIAS2.
BGATE1 (Pin 23/Pin 22): First Phase MOSFET Driver.
V
EE1
(Pin 24/Pin 23): Gate Driver BGATE1 Ground. This
pin should be connected to ground as close to the IC as
possible.
V
CC
(Pin 27/Pin 24): Chip Power Supply. Good supply
bypassing is required.
GBIAS (Pin 28/Pin 25): Internal 11V regulator output for
biasing internal circuitry. Should be connected to GBIAS1
and GBIAS2. A bypass low ESR capacitor of 2µF or larger
is needed and should be connected directly to the pin to
minimize parasitic impedance.
NC (Pins 3, 18, 25, 26/Pins 9, 15, 19, 20): Not Connected.
Can be connected to GND.
(FE/UFD)
PIN FUNCTIONS