设计参考

• Items to Confirm (designing of oscillation circuit)
• Selection Guidance for crystal unit
• Epson Crystal Product Lineups

Please note: to design oscillation circuit for MSP430 Family, you need to confirm the electronic characteristics as follows:

Oscillation allowance and Negative resistance (-R):
You need to confirm oscillation capability.
We recommend the condition: (-R) / ESR > 5
* -R: Negative resistance, ESR: Equivalent Series Resistance
Please refer to our web site:
http://epsondevice.com/cn/information/precaution/design.html
Support information > Precautions in Designing oscillation circuits > 2. Allowance for oscillation

Drive Level:
You need to confirm if oscillation is stable, and if the drive level is within the specification.
Please refer to our web site:
http://epsondevice.com/cn/information/precaution/design.html
Support information > Precautions in Designing oscillation circuits > 1. Drive level

Load Capacitance:
Load capacitance affects frequency stability, oscillation allowance, negative resistance, and start-up time of oscillation.
In addition the load capacitance is determinative factor of crystal unit's load capacitance (CL value) directly.
Please refer to our web site:
http://epsondevice.com/cn/information/precaution/design.html
Support information > Precautions in Designing oscillation circuits > 3. Load capacitance

* frequency stability: frequency deviation out of circuit conditions.

When Customer selects crystal unit, load capacitance (CL value) is an important factor of the selection. 
For instance, crystal with small CL(7.0 pF) makes larger oscillation allowance, smaller current consumption and worse frequency stability, 
like below table. Oppositely, crystal with large CL(12.5 pF) makes smaller oscillation allowance, larger current consumption and better frequency stability. 
Please select it in consideration of these characteristics.