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AN95089 - PSoC® 4/PRoC™ BLE Crystal Oscillator Selection and Tuning Techniques | Cypress Semiconductor

AN95089 - PSoC® 4/PRoC™ BLE Crystal Oscillator Selection and Tuning Techniques

Last Updated: 
Oct 04, 2017
Version: 
*D

AN95089 provides insights into the selection and tuning of the external crystal oscillator (ECO) and watch crystal oscillator (WCO) for PSoC 4/PRoC BLE devices to achieve a good RF performance. This application note introduces basics of crystals and clock accuracy measurements. Cypress-recommended crystals and tuning techniques for optimum performance are also discussed.

Introduction

This application note helps you select the ECO crystal and the WCO crystal for PSoC 4/PRoC BLE devices and tune them for optimum performance.

Bluetooth Low Energy (BLE) is a timing-sensitive technology in which an inaccurate ECO clock can degrade the physical layer RF performance; similarly, an inaccurate WCO clock can lead to increased power consumption in a peripheral.

The on-chip ECO circuit with an external crystal is used to synthesize a 24-MHz clock to run the BLE subsystem. The clock sets the protocol timing for link-layer operations and derives the carrier frequency for physical-layer RF circuits.

An external WCO crystal is used to derive the 32.768-kHz clock that maintains link-layer timing synchronization when the BLE subsystem is in a low-power mode.