Datasheet

TPS5432

www.ti.com

SLVSB89A –MARCH 2012–REVISED OCTOBER 2012

LAYOUT

Layout is a critical portion of good power supply design. There are several signal paths that conduct fast

changing currents or voltages that can interact with stray inductance or parasitic capacitance to generate noise

or degrade the power supplies performance. Care should be taken to minimize the loop area formed by the

bypass capacitor connections and the VIN pins. See Figure 31 for a PCB layout example. The GND pin should

be tied directly to the power pad under the IC. The analog ground trace should be connected to the power

groung area at a single point. The power pad should be connected to any internal PCB ground planes using

multiple vias directly under the IC. Additional vias can be used to connect the top side ground area to the internal

planes near the input and output capacitors. For operation at full rated load, the top side ground area along with

any additional internal ground planes must provide adequate heat dissipating area.

Locate the input bypass capacitor as close to the IC as possible.

For two-layer board usage, VIN cap C1 should be very close to IC. The total routing distance to Vin and PGND

pins combined <5mm. (Refer to EVM layout).

The PH pin should be routed to the output inductor. Since the PH connection is the switching node, the output

inductor should be located very close to the PH pins, and the area of the PCB conductor minimized to prevent

excessive capacitive coupling. The boot capacitor must also be located close to the device. To facilitate routing,

the connection trace may be located on the back side or internal layer of the PCB. The sensitive analog ground

connections for the feedback voltage divider, compensation components and slow start capacitor should be

connected to a separate analog ground trace as shown. The additional external components can be placed

approximately as shown. It may be possible to obtain acceptable performance with alternate PCB layouts,

however this layout has been shown to produce good results and is meant as a guideline.

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