The recommended PCB layout for optimal thermal performance involves placing the device on a 2-layer or 4-layer board with a solid ground plane on the bottom layer, and using thermal vias to connect the exposed pad to the ground plane. Additionally, keeping the input and output capacitors close to the device and using short, wide traces can help reduce thermal resistance.
To ensure stability and prevent oscillations in the output voltage, it is recommended to use a minimum output capacitance of 10uF with an ESR of less than 1 ohm, and to place the output capacitor close to the device. Additionally, using a low-ESR input capacitor and keeping the input and output traces short and separate can help prevent oscillations.
The maximum ambient temperature for reliable operation of the MPQ4558DN-LF is 85°C, with a derated output current of 1.5A above 70°C. However, it is recommended to keep the ambient temperature below 70°C for optimal performance and reliability.
The power dissipation of the device can be calculated using the formula Pd = (Vin - Vout) x Iout x Efficiency. The junction temperature can be estimated using the formula Tj = Ta + (Pd x Rthja), where Rthja is the junction-to-ambient thermal resistance. The thermal resistance can be found in the datasheet or calculated using the package dimensions and thermal conductivity.
The recommended input capacitor is a 10uF to 22uF X5R or X7R ceramic capacitor with a voltage rating of 10V to 25V. The recommended output capacitor is a 10uF to 47uF X5R or X7R ceramic capacitor with a voltage rating of 2.5V to 6.3V. It is recommended to use capacitors with low ESR and high ripple current ratings.
MPQ4558DN-LF datasheet
by Monolithic Power Systems
