Other Parts Discussed in Thread: RM46L830
Tool/software:
Do the RM44L920 and RM46L830 have any requirements for crystal parameters (like load capacitance, drive level, accuracy)? I did not find any in the documentation.
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Hi Yossi,
Please refer below application note for crystal selection:
AN100 - Crystal Selection Guide (Rev. C)
And also refer below thread for calculation of crystal capacitors:
According to them the capacitor values of crystal are:
C1 = C2 = (CLOAD – CSTRAY) * 2
CSTRAY is the Stray capacitance, it is a function of trace lengths, PCB construction, and microcontroller pin design.
CLOAD is manufacturer’s specified crystal load capacitance.
If CLOAD = 18PF and CSTRAY is 2PF then
C1 = C2 = (18PF - 2PF) * 2 = 32PF
These are the values we are using on your launchpad schematic:
similarly calculate for your circuit.
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Thanks & Regards,
Jagadish.
Thanks Jagadish for the quick reply, but I am mostly concerned with the drive level, which is not mentioned in AN-100 and the thread. The datasheets of crystals specify the the Max drive level allowed in [uW]. I expect datasheets of RM44L920 and RM46L830 to specify their drive level so I can select a crystal that allows a higher drive level from the IC or add an appropriate resistor to prevent damage to the crystal. This is the information I am missing.
Datasheets of other TI components provide this information. For example:
Section 6.9.3.4.7.1 Crystal Oscillator Electrical Characteristics (p.71) of the datasheet in the following link:
https://www.ti.com/product/TMS320F28377D-Q1/part-details/TMS320F28377DZWTQ
Hi Yossi,
It is same, i mean the drive level for RM46 is also 1mW.
Please refer below thread to find out.
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Thanks & Regards,
Jagadish.
Thanks, Jagadish, for the helpful answer. I assume that the drive level of RM44 is also 1mW. Is that correct? Is it the same for all TI components? Why isn't it mentioned in the datasheet?
Hi Yossi,
I assume that the drive level of RM44 is also 1mW
Yes, same value applicable for all the Hercules devices.
Why isn't it mentioned in the datasheet?
Not sure why. I will add this into our documentation issues for future action.
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Thanks & regards,
Jagadish.