LT3782_15 Datasheet, PDF (6/20 Pages) Linear Technology – 2-Phase Step-UP DC/DC Controller

LT3782
PIN FUNCTIONS (FE/UFD)
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): Chip 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_RSET, it operates at
natural maximum duty cycle, approximately 90%.
SENSE1⁺ (Pin 8/Pin 4): First Phase Current Sense Amplifier
Positive Input. An RC filter is required across the current
sense resistor. Current limit threshold is set at 60mV.
SENSE1^– (Pin 9/Pin 5): First Phase Current Sense Amplifier
Negative Input. An RC filter 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_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
Amplifier Negative Input. An RC filter is required across
the current sense resistor.
SENSE2⁺ (Pin 13/Pin 10): Second Phase Current Sense
Amplifier Positive Input. An RC filter is required across
the current sense resistor. Current limit threshold is set
at 60mV.
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 amplifier 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 Amplifier Inverting Input. A
resistor divider to this pin sets the output voltage.
RUN (Pin 17/Pin 14): LT3782 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 the ground side of the second
current sense resistor.
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_EE1 (Pin 24/Pin 23): Gate Driver BGATE1 Ground. This
pin should be connected to the ground side of the second
current sense resistor.
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.
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.
NC (Pins 3, 18, 25, 26/Pins 9, 15, 19, 20): Not Connected.
Can be connected to GND.
3782fg
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