For all the applications, TI recommends a 0.1 µF
or higher value ceramic decoupling capacitor between IN_SYS terminal and
GND.
The external FET Q1 must be placed with DRAIN
close to the VIN pins of the IC and connected through a plane. The
fast pulldown switch Q2 DRAIN and SOURCE must be placed very close to the GATE
and SOURCE terminals of Q1 with very short loop. See Figure 9-18 and Figure 9-19 for a typical PCB layout example.
The optimum placement of decoupling capacitor is closest to the IN_SYS and GND terminals of the device. Care must be taken to minimize the loop area formed by the bypass-capacitor connection, the IN_SYS terminal, and the GND terminal of the IC.
High-current carrying power path connections must
be as short as possible and must be sized to carry at least twice the full-load
current.
Locate all the TPS2663x family support components R(ILIM), C(dVdT), R(IMON), UVLO, OVP and PGTH resistors close to their connection pin. Connect the other end of the component to the GND with shortest trace length.
The trace routing for the RILIM component to the device must be as short as possible to reduce parasitic effects on the current limit and current monitoring accuracy. These traces must not have any coupling to switching signals on the board.
Protection devices such as TVS, snubbers,
capacitors, or diodes must be placed physically close to the device they are
intended to protect, and routed with short traces to reduce inductance. For
example, TI recommends a protection Schottky diode to address negative
transients due to switching of inductive loads, and it must be physically close
to the OUT and GND pins.
Thermal Considerations: When properly mounted,
the PowerPAD integrated circuit package provides significantly greater cooling
ability. To operate at rated power, the PowerPAD integrated circuit package must
be soldered directly to the board GND plane directly under the device. Other
planes, such as the bottom side of the circuit board, can be used to increase
heat sinking in higher current applications.