BIAS is connected to the output. This example assumes that the load is close to the output so no bias resistance is necessary. A 0.1-μF capacitor is still recommended close to the bias pin.
FB is connected directly to the output. BIAS and FB are connected to the output through separate traces. This is important to reduce noise and achieve good performances. See Section 11.1 for more details on the proper layout method.
SYNC is connected to ground directly as there is no need for this function in this application.
EN is connected to VIN so the device operates as soon as the input voltage rises above the VIN-OPERATE threshold.
FPWM is connected to GND. This causes the device to operate in AUTO mode. In this mode, the switching frequency is adjusted at light loads to optimize efficiency. As a result the switching frequency changes with the output current until medium load is reached. The part will then switch at the frequency defined by FSW. See Section 8.4 for more details.
A 4.7-μF capacitor is connected between VCC and GND close to the VCC pin. This ensures stable operation of the internal LDO.
RESET is biased to an external rail in this example. A pullup resistor is necessary. A 100-kΩ pullup resistor is selected for this application and is generally sufficient. The value can be selected to match the needs of the application but must not lead to excessive current into the
RESET pin when
RESET is in a low state. Consult Section 7.1 for the maximum current allowed. In addition, a low pullup resistor could lead to an incorrect logic level due to the value of RRESET. Consult Section 7.6 for details on the
RESET pin.
It is important to connect small high frequency capacitors CIN_HF1 and CIN_HF2 as close to both inputs PVIN1 and PVIN2 as possible. For the detailed process of choosing input capacitors, refer to Section 9.2.1.2.2.1.
Inductor selection is detailed in Section 9.2.1.2.2.2.1. In general, a 10-μH inductor is recommended for the fixed output options. For the adjustable output configurations, the inductance can vary with the output voltage due to ripple and current limit requirements.