FAQ_如何为S2-lp选择TCXO

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FAQ_如何为S2-lp选择TCXO [复制链接]

 

本文作者：ST工程师Joshua Zhu

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2019-11-19 10:02 上传

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关键词：S2-lp, TCXO

 

问题: 一些客户不得不在他们的方案设计中使用TCXO，原因如下：

 

1).Customer Required Configuration DR = 2.4Kpbs Fdev = 1.2KhZ Frequency Point: 492.08M GFSK Modulation

2).Passive crystal oscillators are difficult to control frequency offset accuracy according to customers' low-speed requirements. The frequency offset accuracy of some better passive crystal oscillators are 10 ppm at room temperature .

3).

a.EXS00A-CS08403 with S2-LP reference design as an example Normal temperature deviation: +10 ppm Variation of whole temperature range: +15 ppm Looking at the frequency of customer use : Frequency offset at room temperature: +4.92 Khz Full Temperature Range Frequency Offset: +7.38 Khz

b. Active crystal oscillator DSB221SDB provided by customers Normal temperature deviation: +1.5 ppm Change of whole temperature range: +1 ppm Looking at the frequency of customer use Frequency offset at room temperature: +0.738 Khz Full Temperature Range Frequency Offset: +0.492 Khz

 

ST工程师解答:

1. 关于crystal的选择，从datasheet 14页我们可以获得如下信息：

关于 TCXO, 以下更多的信息需要考虑(参考 the mantis:3213):

1) DC coupling with a minimum 0.2 VDC level

2) Minimum AC amplitude of 400 mVpp

3) The instantaneous level at input cannot exceed the 0 – 1.4 V range.

 

2. 这是在我们STEVAL-FKI512V1平台板子上测试验证ok的TCXO型号：

 NDK, NT1612AB 50MHz END5348A;