（8MHz晶振连接电路）
8MHz无源晶振HC-49S-8MHz-20pF-20PPM上板匹配测试数据如下：
| Crystal Unit Characteristic Data | ||||||
| GNW Part Number | Customer Part Number | CL(pF) | FR(HZ) | B:FL(PPM) | RR(Ω) | TS(ppm/pF) |
| 01G8MBB2 | X1 | 20 | 7.999976M | -3.00 | 14.5 | 7.38 |
| Measurement Results | ||||||
| Matching Test | Current Circuit | |||||
| Circuit Constants | 8MHz HC-49S-8MHz-20pF-20PPM C1=C2=30pF |
|||||
| Drive Level | 16.92μW | |||||
| Negative Resistance ( -R ) | 695.5Ω | |||||
| Loading of Output Frequency |
A: On board (PPM) |
8.000012MHz | ||||
| C=A-B Deviation. |
4.5 PPM | |||||
| Conclusion | ||||||
| When C1=C2=30pF, X1: HC-49S 8MHz 20PF ±20PPM frequency deviation is 4.5 PPM. Drive level test result : 16.92μW. (Spec: 300μW Max). −R(Ω) should follow the rule of |−R| >3*ESR max(180 ohm) for stable oscillation. |
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结论：
当 C1=C2=30pF 时，X1：HC-49S 8MHz 20PF ±20PPM，频率偏差为 4.5 PPM；
驱动电平测试结果：16.92μW。（规格：最大 300μW）；
−R（Ω） 应遵循 |−R| > 3×ESR_max（180 欧姆）的规则，以实现稳定振荡。
使用示波器实测8MHz晶振输出波形：
（8MHz晶振输出正弦波OK）
