LTC3857-1_15 Datasheet, PDF (9/38 Pages) Linear Technology – Low IQ, Dual, 2-Phase Synchronous Step-Down Controller

LTC3857-1
PIN FUNCTIONS
BOOST1, BOOST2 (Pin 24, Pin 17): Bootstrapped Supplies
to the Topside Floating Drivers. Capacitors are connected
between the BOOST and SW pins and Schottky diodes are
tied between the BOOST and INTV_CC pins. Voltage swing
at the BOOST pins is from INTV_CC to (V_IN + INTV_CC).
SW1, SW2 (Pin 25, Pin 16): Switch Node Connections
to Inductors.
TG1, TG2 (Pin 26, Pin 15): High Current Gate Drives for
Top N-Channel MOSFETs. These are the outputs of float-
ing drivers with a voltage swing equal to INTV_CC – 0.5V
superimposed on the switch node voltage SW.
PGOOD1 (Pin 27): Open-Drain Logic Output. PGOOD1 is
pulled to ground when the voltage on the V_FB1 pin is not
within ±10% of its set point.
TRACK/SS1, TRACK/SS2 (Pin 28, Pin 14): External Track-
ing and Soft-Start Input. The LTC3857-1 regulates the
V_FB1,2 voltage to the smaller of 0.8V or the voltage on the
TRACK/SS1,2 pin. An internal 1μA pull-up current source
is connected to this pin. A capacitor to ground at this
pin sets the ramp time to final regulated output voltage.
Alternatively, a resistor divider on another voltage supply
connected to this pin allows the LTC3857-1 output to track
the other supply during start-up.
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