JAJSII9E april 2020 – june 2023 DRA821U , DRA821U-Q1
PRODUCTION DATA
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Figure 7-29 shows the recommended crystal circuit. All discrete components used to implement the oscillator circuit should be placed as close as possible to the OSC1_XI and OSC1_XO pins.
The crystal must be in the fundamental mode of operation and parallel resonant. Table 7-23 summarizes the required electrical constraints.
PARAMETER | MIN | TYP | MAX | UNIT | |||
---|---|---|---|---|---|---|---|
Fxtal | Crystal Parallel Resonance Frequency | 19.2 | 27 | MHz | |||
Fxtal | Crystal Frequency Stability and Tolerance | Ethernet RGMII and RMII not used | ±100 | ppm | |||
Ethernet RGMII and RMII using derived clock | ±50 | ||||||
CL1+PCBXI | Capacitance of CL1 + CPCBXI | 12 | 24 | pF | |||
CL2+PCBXO | Capacitance of CL2 + CPCBXO | 12 | 24 | pF | |||
CL | Crystal Load Capacitance | 6 | 12 | pF | |||
Cshunt | Crystal Circuit Shunt Capacitance | ESRxtal = 30 Ω | 19.2 MHz, 20 MHz, 24 MHz, 25 MHz, 26 MHz, 27 MHz |
7 | pF | ||
ESRxtal = 40 Ω | 19.2 MHz, 20 MHz, 24 MHz, 25 MHz, 26 MHz, 27 MHz |
5 | pF | ||||
ESRxtal = 50 Ω | 19.2 MHz, 20 MHz, 24 MHz, 25 MHz, 26 MHz, 27 MHz |
5 | pF | ||||
ESRxtal = 60 Ω | 19.2 MHz, 20 MHz, 24 MHz | 5 | pF | ||||
ESRxtal = 80 Ω | 19.2 MHz, 20 MHz | 5 | pF | ||||
25 MHz | 3 | pF | |||||
ESRxtal = 100 Ω | 19.2 MHz, 20 MHz | 3 | pF | ||||
ESRxtal | Crystal Effective Series Resistance | 100 | Ω |
When selecting a crystal, the system design must consider the temperature and aging characteristics of a based on the worst case environment and expected life expectancy of the system.
Table 7-24 details the switching characteristics of the oscillator and the requirements of the input clock.
PARAMETER | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|
CXI | XI Capacitance | 1.55 | pF | ||
CXO | XO Capacitance | 1.35 | pF | ||
CXIXO | XI to XO Mutual Capacitance | 0.01 | pF | ||
ts | Start-up Time | 9.5(1) | ms |