JAJSNH5B february 2022 – may 2023 LMQ66410 , LMQ66420 , LMQ66430
PRODUCTION DATA
The LMQ664x0 step-down DC-to-DC converters are typically used to convert a higher DC voltage to a lower DC voltage. The LMQ66430 supports a maximum output current of 3 A while the LMQ66420 and LMQ66410 support a maximum output current of 2 A and 1 A, respectively. The following design procedure can be used to select components for the LMQ66430. The design procedure can also be used to select components for the LMQ66420 or LMQ66410 by limiting the maximum output current to 2 A or 1 A, respectively.
All of the capacitance values given in the following application information refer to effective values unless otherwise stated. The effective value is defined as the actual capacitance under DC bias and temperature, not the rated or nameplate values. Use high-quality, low-ESR, ceramic capacitors with an X7R or better dielectric throughout. All high value ceramic capacitors have a large voltage coefficient in addition to normal tolerances and temperature effects. Under DC bias the capacitance drops considerably. Large case sizes and higher voltage ratings are better in this regard. To help mitigate these effects, multiple capacitors can be used in parallel to bring the minimum effective capacitance up to the required value. This can also ease the RMS current requirements on a single capacitor. A careful study of bias and temperature variation of any capacitor bank must be made to ensure that the minimum value of effective capacitance is provided.