SLAA423A December   2009  – November 2018 MSP430F4132 , MSP430F4152 , MSP430F47126 , MSP430F47127 , MSP430F47163 , MSP430F47166 , MSP430F47167 , MSP430F47173 , MSP430F47176 , MSP430F47177 , MSP430F47183 , MSP430F47186 , MSP430F47187 , MSP430F47193 , MSP430F47196 , MSP430FG4616 , MSP430FG4617 , MSP430FG4618

 

  1.   XOSC8 Guidance
    1.     Trademarks
    2. 1 Introduction
    3. 2 Contribution of ESR, Load Capacitance, VCC, and Temperature
      1. 2.1 Crystal ESR
        1. 2.1.1 ESR and Start-up Reliability
        2. 2.1.2 ESR Specification
      2. 2.2 Load Capacitance
      3. 2.3 Temperature and VCC
    4. 3 Using a Shunt Resistor From XIN to GND
    5. 4 Failsafe Mechanisms
      1. 4.1 2xx Family
      2. 4.2 4xx Family
    6. 5 Summary
    7. 6 References
  2.   Revision History

2.1 Crystal ESR

In the 2xx and 4xx family of devices that exhibit XOSC8, the increase in crystal ESR causes an increase in oscillator output in an attempt to maintain the same level of oscillation allowance (robustness). This provides the flexibility to choose higher ESR crystals without significantly impacting operation. While unintentional, this is extremely important in addressing XOSC8, where a higher ESR crystal is recommended.

Table 1 shows the parameters of several crystals tested. Testing with test crystal 1a at -40°C resulted in failures for all combinations of VCC and load settings. The failure rate was approximately 1%.

Table 1. Crystal Parameters for Test Crystals

Test Crystal fs
(Hz)		 FL(nom)
(Hz)		 RM
(Ω)		 LM
(H)		 CM
(fF)		 C0
(pF)		 CL(nom)
(pF)
1a 32762.83 32768.000 16331.20 7506.01 3.14 2.05 7.92
1b 32762.972 32768.000 13907.60 8985.880 2.626 2.004 6.552
2 32763.917 32768.000 41128.600 9626.190 2.451 1.689 8.147

When the same units are tested with test crystal 2, there were no failures for the 10-pF and 12.5-pF load cases. This confirms the higher resistance crystal (RM > 40 kΩ) requirement found in the XOSC8 erratum, but also indicates the importance of using the correct or greater load capacitance.