FAQ_ 如何为BlueNRG-x选择高速晶体

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FAQ_ 如何为BlueNRG-x选择高速晶体 [复制链接]

 

本文作者：ST工程师朱俊伟

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2019-11-29 20:13 上传

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关键字 ：BlueNRG-1/-2, 晶体 

 

问题：一些客户经常问我们如何选择BlueNRG-X的高速晶体? 

ST工程师解答：

1. 从规格书144页，我们可以得到如下信息： 

Characteristics measured over recommended operating conditions unless otherwise specified. Typical value are 

referred to TA = 25 °C, VBAT = 3.0 V. 

 

 我们建议选择在室温下最大+ -20ppm频偏的晶体。 

2. 为了实现较低功率地运行和晶体良好的频率稳定性，对晶体负载电容C0做如下因素的考虑。下图显示了在BlueNRG家族使用的振幅调控振荡器的简化框图。 

Low power consumption and fast startup time is achieved by choosing a quartz crystal with a low load capacitance C0. A reasonable choice for capacitor C0 is 15 pF. To achieve good frequency stability, the following equation needs to be satisfied: 

Where C1’=C1+CPCB1+CPAD, C2’= C2+CPCB2+CPAD, where C1 and C2 are external (SMD) components, CPCB1 and CPCB2 are PCB routing parasites and CPAD is the equivalent small-signal pad-capacitance. 

3. 以下是一些量产客户所使用的晶体型号，供您参考： 

1) Hele, X3S016000b91H for 16Mhz in MP customer; 

2) Yoke,S2016A-032000-F08-BDD-1AXA for 32Mhz in MP customer; 

3) Ndk, NX2016SA/EXS00A-CS06654 for 32Mhz in MP customer; 

4) Ndk, NX3225SA -32.000MHz-EXS00A-CS05997 for 32MHZ in demo board; 

5) Ndk, NX3225SA -16.000MHz-EXS00A-CS05997 for 16MHZ in demo board.