LTC3709_15 Datasheet, PDF (8/24 Pages) Linear Technology – Fast 2-Phase, No RSENSE Synchronous DC/DC Controller with Tracking/Sequencing

LTC3709
PI FU CTIO S (QFN/SSOP)
NC (Pin 12/Pins 1, 17, 18, 19, 20): No Connect.
V_CC (Pin 17/Pin 25): Main Input Supply. Decouple this pin
to SGND with an RC filter (1Ω, 0.1µF).
DRV_CC (Pin 21/Pin 29): Driver Supply. Provides supply to
the driver for the bottom gate. Also used for charging the
bootstrap capacitor.
BG1, BG2 (Pins 22, 20/Pins 30, 28): Bottom Gate Drive.
Drives the gate of the bottom N-channel MOSFET between
ground and DRV_CC.
PGND1, PGND2 (Pins 23, 19/Pins 31, 27): Power Ground.
Connect this pin closely to the source of the bottom N-
channel MOSFET, the (–) terminal of C_DRVCC and the (–) ter-
minal of C_IN.
SENSE1^–, SENSE2^– (Pins 24,18/Pins 32, 26): Current
Sense Comparator Input. The (–) input to the current
comparator is used to accurately Kelvin sense the bottom
side of the sense resistor or MOSFET.
SENSE1⁺, SENSE2⁺ (Pins 25, 16/Pins 33, 24): Current
Sense Comparator Input. The (+) input to the current
comparator is normally connected to the SW node unless
using a sense resistor (see Applications Information).
SW1, SW2 (Pins 26, 15/Pins 34, 23): Switch Node. The
(–) terminal of the bootstrap capacitor C_B connects here.
This pin swings from a Schottky diode voltage drop below
ground up to V_IN.
TG1, TG2 (Pins 27, 14/Pins 35, 22): Top Gate Drive.
Drives the top N-channel MOSFET with a voltage swing
equal to DRV_CC superimposed on the switch node voltage
SW.
BOOST1, BOOST2 (Pins 28, 13/Pins 36, 21): Boosted
Floating Driver Supply. The (+) terminal of the bootstrap
capacitor C_B connects here. This pin swings from a diode
voltage drop below DRV_CC up to V_IN + DRV_CC.
PGOOD (Pin 29/Pin 2): Power Good Output. Open-drain
logic output that is pulled to ground when output voltage
is not within ±10% of the regulation point. The output
voltage must be out of regulation for at least 100µs before
the power good output is pulled to ground.
I_ON (Pin 30/Pin 3): On-Time Current Input. Tie a resistor
from V_IN to this pin to set the one-shot timer current and
thereby set the switching frequency.
FCB (Pin 31/Pin 4): Forced Continuous and External Clock
Input. Tie this pin to ground to force continuous synchro-
nous operation or to V_CC to enable discontinuous mode
operation at light load. Feeding an external clock signal
into this pin will synchronize the LTC3709 to the external
clock and enable forced continuous mode.
V_RNG (Pin 32/Pin 5): Sense Voltage Range Input. The volt-
age at this pin is ten times the nominal sense voltage at maxi-
mum output current and can be programmed from 0.5V to
2V. The sense voltage defaults to 70mV when this pin is tied
to ground, 140mV when tied to V_CC.
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