Capacitor Value on the VCCD Pin of USB-Serial Bridge Controllers - KBA91052

Version: *A

 

Question:

What value of capacitance should be used on the VCCD pin of USB-Serial Bridge Controllers?

 

Answer:

A capacitor is used on the VCCD pin for noise decoupling. This pin is the output pin of the core voltage regulator and cannot drive external devices. Decouple this pin to ground using a 1-µF capacitor when the VCCIO (or VDDD) voltage is greater than 2 V. Connect this pin to the VCCIO (or VDDD) supply when the VCCIO (or VDDD) voltage is less than 2 V.

Table 1: State of VCCD Pin With Respect to the Voltage Level on the VCCIO (or VDDD) Pin                                                               
VCCIO (or VDDD) Voltage LevelCapacitance at VCCD Pin
    
VCCIO (or VDDD) ≤ 2 V
   
    
Short the VCCD pin with the VCCIO (or VDDD) pin
   
    
VCCIO (or VDDD) > 2 V
   
    
Connect a 1-μF capacitor (Cefc) between the VCCD pin and ground
   

Note 1: Decoupling capacitor should be placed as close to the VCCD pin as possible.
Note 2: VCCIO is the pin name used in CY7C65213, while VDDD is the pin name used in CY7C65211 and CY7C65215