lt3782aeufd Linear Technology Corporation, lt3782aeufd Datasheet - Page 6

• Manufacturer Part Number: lt3782aeufd
• Description: 2-phase Step-up Dc/dc Controller
• Manufacturer: Linear Technology Corporation

LT3782A
PIN FUNCTIONS
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/Pin 28): Ground.
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 maxi-
mum duty cycle. When connected to V
natural maximum duty cycle, approximately 90%.
SENSE1
Positive Input. An RC fi lter is required across the current
sense resistor. Current limit threshold is set at 63mV.
SENSE1
Negative Input. An RC fi lter is required across the current
sense resistor.
SLOPE (Pin 10/Pin 6): A resistor from SLOPE to GND
increases the internal current mode PWM slope com-
pensation.
R
oscillator charging current and the operating frequency.
SENSE2
Amplifi er Negative Input. An RC fi lter is required across
the current sense resistor.
SENSE2
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.
6
SET
(Pin 11/Pin 7): A resistor from R
+
–
–
+
(Pin 8/Pin 4): First Phase Current Sense Amplifi er
(Pin 9/Pin 5): First Phase Current Sense Amplifi er
(Pin 13/Pin 10): Second Phase Current Sense
(Pin 12/Pin 8): Second Phase Current Sense
(FE/UFD)
SET
RSET
to GND sets the
, it operates at
V
the control signal of the current loop of the current-mode
PWM. Switching starts at 0.7V, and higher V
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
shutdown mode when V
V
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. A bypass low ESR capacitor of 2μF
or larger is needed and should be connected directly to
the pin to minimize parasitic impedance.
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
pin should be connected to ground as close to the IC as
possible.
V
bypassing is required.
GBIAS (Pin 28/Pin 25): Internal 11V regulator output for
biasing internal circuitry. Should be connected to GBIAS1
and GBIAS2.
Exposed Pad (Pin 29/Pin 29): The exposed package pad
is fused to internal ground and is for heat sinking. Solder
the bottom metal plate onto expanded ground plane for
optimum thermal performance. This pad should be con-
nected to ground as close to the IC as possible.
NC (Pins 3, 18, 25, 26/Pins 9, 15, 19, 20): Not Connected.
Can be connected to GND.
C
EE2
EE1
CC
(Pin 15/Pin 12): The output of the g
(Pin 27/Pin 24): Chip Power Supply. Good supply
(Pin 19/Pin 16): Gate Driver BGATE2 Ground. This
(Pin 24/Pin 23): Gate Driver BGATE1 Ground. This
RUN
is below 2.2V and goes to low bias current
RUN
is below 0.3V.
m
error amplifi er and
C
voltages
3782af