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The saturation current shall be below the expected peak current of the application. Beyond this point, the inductor will rapidly lose inductance, and can let much higher currents through than what is expected. Care should be taken especially in SMPS applications to account for the peak of the expected ripple current in the inductor.

Diodes - Rectifier

Type

Standard PN junction diodes can be used in rectifying applications where efficiency is not a concern. For cases where higher efficiency is desired, Schottky diodes can be used as they have a lower forward voltage.

Diodes - TVS and Zener

Type

TVS and Zener diodes are similar in their behaviour but differ in their construction. Both used for their reverse breakdown characteristics.

TVS diodes are suitable for high instantaneous current, such as ESD or other forms of transient voltage suppression. Zener diodes have more precise breakdown thresholds, and are suitable for handling continuous reverse current such as for voltage regulation.

FETs

Current

The rated current shall be at least double the expected application. The maximum current is typically defined by the thermal limit of how much heat the part can handle due to IR losses. Note that especially for high current FETs, the max current is given for specific conditions, often at a case (surface) temperature (Tc) of 25C. In reality, it is not realistic to keep the surface of the part at 25C under full load, as this would require sub ambient cooling. Thus, appropriate component derating must be performed.

PCB

Mounting

M2.5

Trace Width

Saturn toolkit

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Standard signals shall use 50ohm traces with an impedance profile set in Altium. Use Saturn Toolkit to calculate required width for higher current applications.

Via Size

Standard vias are generally 0.5/0.3mm pad/hole. For higher current applications, typically multiple standard size vias offer greater layout flexibility than one very large via. Controlled impedance signals shall have controlled impedance vias. Saturn toolkit can be used to calculate via impedance and current carrying capacity. Standard JLC plating thickness is 18um, and the expected temperature rise shall be no more than 25C.

Test Points

The top layer silkscreen shall contain the following graphic, with the board name and revision in smaller next under the “Midnight” letters.

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Silkscreen

All components shall have component designators visible. The standard text has the following properties:

  • Mirror: Mirrored for bottom overlay

  • Text Height: 0.8mm

  • Stroke Width: 0.2mm

  • Font type: Stroke

  • Font: Default

Component Spacing

Small SMD components shall be spaced at least 0.5mm apart, or such that their outermost silkscreen lines do not more than fully overlap.