Pular para o conteúdo principal
Knowledgebase
Home
Renesas Brasil - Knowledgebase

How to operate RTC correctly using 32.768kHz, 10 pF for Cin and Cout?

Latest Updated:03/25/2009

Question:

The RTC is not operating correctly. A crystal with 32.768kHz, 10 pF for Cin and Cout is used.

Answer:

The accuracy of RTC depends on several parameters: e.g. type of crystal, the temperature condition, Cin, Cout, Rf and Rd of the oscillation circuit.

The build-in resistors Rf and Rd are fixed within the RTC module.

Recommended value of Cin and Cout is from 10 to 22 pF.

Cin and Cout values include floating capacitance due to the wiring. Take care when using a ground plane.

The crystal oscillation stabilization time depends on the mounted circuit constants, floating capacitance, etc., and should be decided after consultation with the crystal resonator manufacturer.

Suitable Products
SH7729R
SH7727
SH7720
SH7709S
SH7706
SH7705