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Using ceramic resonators with PSoC 3 and PSoC 5 | Cypress Semiconductor

Using ceramic resonators with PSoC 3 and PSoC 5

Did you know that in addition to supporting 4 - 25 MHz crystals, PSoC 3 and 5's MHz ECOs also support ceramic resonators? Although they tend to have more frequency error, resonators are cheaper, come in smaller packages, start up faster, and are more mechanically robust than crystals. They also often have their load capacitors built-in to the resonator package. And, because they have no maximum drive level rating, they can be used without the need for an automatic gain control circuit.

To configure the PSoC 3 and 5 ECO for use with a ceramic resonator, simply use the PSoC Creator Design Wide Resources interface to configure the oscillator as you normally would, then add the following lines in your main.c initialization code:

/* Configure MHz XTAL */

/* Turn automatic gain control off (AGC not necessary for resonators */

CY_SET_REG8(CYREG_FASTCLK_XMHZ_CSR, 0x05);

/* Set the XTAL feedback and watchdog voltages to a reasonable value */

CY_SET_REG8(CYREG_FASTCLK_XMHZ_CFG1, 0x55)

 

Also, be sure to check out AN54439 - PSoC® 3 and PSoC 5 External Oscillator to learn more about using PSoC 3 and 5's powerful ECO circuit.

 

Max Kingsbury

Applications Engineer

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