Hi Team,
TUSB4041I datasheet shows the following and would like to ask two questions.
(page 14)
8.3.5 Crystal Requirements
The crystal must be fundamental mode with load capacitance of 12 to 24 pF and frequency stability rating of ±100 PPM or better. To ensure proper startup oscillation condition, TI recommends a maximum crystal equivalent series resistance (ESR) of 50 Ω. If a crystal source is used, use a parallel load capacitor.
The exact load capacitance value used depends on the crystal vendor. Refer to application note Selection and Specification for Crystals for Texas Instruments USB 2.0 Devices (SLLA122) for details on how to determine the load capacitance value.
1)
Refer to SLLA122, I understand maximum crystal equivalent series resistance (ESR) of 50 Ω isn't mandatory requirement if load capacitance (CLOAD) is < 10pF.
Is my understanding correct?
Please take oscillation margin is sufficient in this case.
2)
Could you tell me why TUSB4041I has lower limit 12pF for load capacitance? Is it mandatory requirement?
>The crystal must be fundamental mode with load capacitance of 12 to 24 pF
The background of the question is my customer want to use small crystal which ESR is more than 50 Ω because of board space limitation.
He wants to extend number of choices for crystal.
Best Regards,
Yaita
