LM3743_15 Datasheet, PDF (2/38 Pages) Texas Instruments – High-Performance Synchronous Buck Controller with Comprehensive Fault Protection Features

LM3743
SNVS427E – SEPTEMBER 2006 – REVISED APRIL 2013
Connection Diagram
1
VCC
10
BOOT
2
LGATE
9
HGATE
3
GND
LM3743
8
SW
4
ILIM
SS/TRACK ⁷
5
FB
COMP/EN ⁶
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Figure 1. 10-Lead Plastic VSSOP (Top View)
See Package Number DGS
VCC (Pin 1)
LGATE (Pin 2)
GND (Pin 3)
ILIM (Pin 4)
FB (Pin 5)
COMP/EN (Pin 6)
SS/TRACK (Pin 7)
SW (Pin 8)
HGATE (Pin 9)
BOOT (Pin 10)
PIN DESCRIPTIONS
Supply rail for the controller section of the IC. A minimum capacitance of 1 µF, preferably a multi-layer
ceramic capacitor type (MLCC), must be connected as close as possible to the V_CC and GND pin and a
1 to 4.99Ω resistance must be connected in series from the supply rail to the Vcc pin. See V_CC Filtering
in the Design Consideration section for further details.
Gate drive for the low-side N-channel MOSFET. This signal is interlocked with HGATE to avoid a shoot-
through problem.
Power ground (PGND) and signal ground (SGND). Connect the bottom feedback resistor between this
pin and the feedback pin.
Low side current limit threshold setting pin. This pin sources a fixed 50 µA current. A resistor of
appropriate value should be connected between this pin and the drain of the low-side N-FET.
Feedback pin. This is the inverting input of the error amplifier used for sensing the output voltage and
compensating the control loop.
Output of the error amplifier and enable pin. The voltage level on this pin is compared with an internally
generated ramp signal to determine the duty cycle. This pin is necessary for compensating the control
loop. Forcing this pin to ground will shut down the IC.
Soft-start and tracking pin. This pin is connected to the non-inverting input of the error amplifier during
initial soft-start, or any time the voltage is below the reference. To track the rising ramp of another power
supply's output, connect a resistor divider from the output of that supply to this pin as described in
Application Information.
Switch pin. The lower rail of the high-side N-FET driver. Also used for the high side current limit sensing.
Gate drive for the high-side N-channel MOSFET. This signal is interlocked with LGATE to avoid a shoot-
through problem.
Supply rail for the N-channel MOSFET high gate drive. The voltage should be at least one gate
threshold above the regulator input voltage to properly turn on the high-side N-FET. See MOSFET
GATE DRIVE in the Application Information section for more details on how to select MOSFETs.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
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