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TPS61222-EP

SLVSBI2 – SEPTEMBER 2012

www.ti.com

The following inductor series from different suppliers have been used with TPS61222 converters:

VENDOR

INDUCTOR SERIES

EPL3015

Coilcraft

EPL2010

Murata

LQH3NP

Tajo Yuden

NR3015

Wurth Elektronik

WE-TPC Typ S

(1)

Design was tested using these components at 25°C ambient

temperature.

Capacitor Selection

Input Capacitor

At least a 10-

μF input capacitor is recommended to improve transient behavior of the regulator and EMI behavior

of the total power supply circuit. A ceramic capacitor placed as close as possible to the VIN and GND pins of the

IC is recommended.

Output Capacitor

the VOUT and GND pins of the IC. If, for any reason, the application requires the use of large capacitors which

can not be placed close to the IC, the use of a small ceramic capacitor with an capacitance value of around

2.2

μF in parallel to the large one is recommended. This small capacitor should be placed as close as possible to

the VOUT and GND pins of the IC.

A minimum capacitance value of 4.7

μF should be used, 10 μF are recommended. If the inductor value exceeds

4.7

μH, the value of the output capacitance value needs to be half the inductance value or higher for stability

reasons, see Equation 4.

(4)

The TPS61222 is not sensitive to the ESR in terms of stability. Using low ESR capacitors, such as ceramic

capacitors, is recommended anyway to minimize output voltage ripple. If heavy load changes are expected, the

output capacitor value should be increased to avoid output voltage drops during fast load transients.

Layout Considerations

As for all switching power supplies, the layout is an important step in the design, especially at high peak currents

and high switching frequencies. If the layout is not carefully done, the regulator could show stability problems as

well as EMI problems. Therefore, use wide and short traces for the main current path and for the power ground

paths. The input and output capacitor, as well as the inductor should be placed as close as possible to the IC.

The feedback divider should be placed as close as possible to the control ground pin of the IC. To lay out the

ground, it is recommended to use short traces as well, separated from the power ground traces. This avoids

ground shift problems, which can occur due to superimposition of power ground current and control ground

current. Assure that the ground traces are connected close to the device GND pin.

THERMAL INFORMATION

Implementation of integrated circuits in low-profile and fine-pitch surface-mount packages typically requires

special attention to power dissipation. Many system-dependent issues such as thermal coupling, airflow, added

heat sinks and convection surfaces, and the presence of other heat-generating components affect the power-

dissipation limits of a given component.

12

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