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[Product knowledge] Circuit device selection and EMC

 

(1)When selecting devices, select those that require less input current for logical state transitions. The CURRENT here refers TO THE maximum SURGE CURRENT WHEN ALL THE PINS OF THE device are switched simultaneously under maximum capacitive load, NOT the average or static value.


(2)To meet the requirements, select a slower logic device as far as possible. Although LOW-SPEED devices are becoming increasingly difficult to find, FOR A COMMON logic FUNCTION, do not USE NS-CLASS devices.


(3)Select devices whose power pins and ground pins are located adjacent to each other in the center of the package.


(4)Use A DEVICE WITH A METAL SHIELD SHELL (CRYSTAL OSCILLATOR) AND GROUND THE METAL shell using as many low-IMPEDANCE through-hole connections as POSSIBLE.


(5)A ground heat sink shall be provided for those ceramic encapsulated devices with metal inserts at the top.