Datasheet

+×

252

RRpF

pole

TPS62140, TPS62140A

TPS62141, TPS62142, TPS62143

SLVSAJ0B –NOVEMBER 2011–REVISED JUNE 2013

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spacing

(14)

spacing

Though the TPS6214X devices are stable without the pole and zero being in a particular location, adjusting their

location to the specific needs of the application can provide better performance in power-save mode and/or

improved transient response. An external feed-forward capacitor can also be added. A more detailed discussion

on the optimization for stability vs transient response can be found in SLVA289 and SLVA466.

Layout Considerations

A proper layout is critical for the operation of a switched-mode power supply, even more at high switching

frequencies. Therefore, the PCB layout of the TPS6214X demands careful attention to ensure operation and to

get the performance specified. A poor layout can lead to issues like poor regulation (both line and load), stability

and accuracy weaknesses, increased EMI radiation, and noise sensitivity.

See Figure 41 for the recommended layout of the TPS6214X, which is designed for common external ground

connections. Therefore both AGND and PGND pins are directly connected to the Exposed Thermal Pad. On the

PCB, the direct common ground connection of AGND and PGND to the Exposed Thermal Pad and the system

ground (ground plane) is mandatory. Also connect the VOS pin in the shortest way to VOUT at the output

capacitor.

Provide low inductive and resistive paths for loops with high di/dt. Therefore, paths conducting the switched load

current should be as short and wide as possible. Provide low capacitive paths (with respect to all other nodes) for

wires with high dv/dt. Therefore, the input and output capacitance should be placed as close as possible to the

IC pins and parallel wiring over long distances as well as narrow traces should be avoided. Loops which conduct

an alternating current should outline an area as small as possible, as this area is proportional to the energy

radiated.

Sensitive nodes like FB and VOS need to be connected with short wires and not nearby high dv/dt signals (that

is, SW). As they carry information about the output voltage, they should be connected as close as possible to the

actual output voltage (at the output capacitor). The capacitor on the SS/TR pin and on AVIN as well as the FB

resistors, R1 and R2, should be kept close to the IC and connect directly to those pins and the system ground

plane.

The Exposed Thermal Pad must be soldered to the circuit board for mechanical reliability and to achieve

appropriate power dissipation.

The recommended layout is implemented on the EVM and shown in its Users Guide, SLVU437. Additionally, the

EVM Gerber data are available for download here, SLVC394.

Product Folder Links: TPS62140 TPS62140A TPS62141 TPS62142 TPS62143