BIAS is connected to the output. This example assumes that the load is connected to the output through long wires so a 3 Ω resistor is inserted to minimize risks of damage to the part during load shorts. As a result a 0.1-µF capacitor is required close to the bias pin.
FB is connected directly to the output. BIAS and FB are connected to the output via separate traces. This is important in order to reduce noise and achieve good performances. SeeLayout Guidelines for more details on the proper layout method.
SYNC is connected to ground through a pulldown resistor, and an external synchronization signal can be applied. The pulldown resistor ensures that the pin is not floating when the SYNC pin is not driven by any source.
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 VCC. This causes the device to operate in FPWM mode. In this mode, the switching frequency is not affected by the output current and is ensured to be within the boundaries set by FSW. The drawback is that the efficiency is not optimized for light loads. SeeDevice Functional Modes 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 the output in this example. A pullup resistor is necessary. A 100-kΩ 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. ConsultAbsolute Maximum Ratings 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 Electrical Characteristics for details on the RESET pin.
Input capacitor selection is detailed in Input Capacitors. It is important to connect small high-frequency capacitors CIN_HF1 and CIN_HF2 as close to both inputs PVIN1 and PVIN2 as possible.
Inductor selection is detailed in Inductor Selection. In general, a 2.2-µH inductor is recommended for the fixed output options. For the adjustable options, the inductance can vary with the output voltage due to ripple and current limit requirements.