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TMS320F280021: Help for crystal selection

Manu36
Expert 1300 points
Part Number: TMS320F280021
Other Parts Discussed in Thread: LAUNCHXL-F2800137, LAUNCHXL-F280025C, TMDSCNCD2800137

Dear all,

I need help to define a crystal for TMS320F28002x and/or TMS320F280013x.

It seems to be very difficult to comply all the requirment, especially:

On the other hands I saw that some TI expert advice to use the same than used on TI evaluation board.

From my analysis, the different evaluation use those compnents:

LAUNCHXL-F2800137 EVM

'ECS-200-8-30B-CKM

LAUNCHXL-F280025C

ECS-200-8-30B-CKM

TMDSCNCD2800137

ECS-200-8-30B-CKM

TMDSCNCD280025

ECS-200-18-30B-AGN-TR

None of this component is specified >=1mW and no dampening resistor is used. Is there a risk?

A 3 pin resonnator can also be used, I saw in a post that you can share some data from Murata:

Is it possible to receive?

Thank for your help.

  • 0
    TI__Expert 5450 points

    Hi Manu,

    Drive level refers to how much power is provided by the electrical oscillator and dissipated by the crystal. The maximum drive level specified in the crystal manufacturer’s data sheet is usually the maximum the crystal can dissipate without damage or significant reduction in operating life. On the other hand, the drive level specified by the electrical oscillator is the maximum power it can provide. The actual power provided by the electrical oscillator is not necessarily the maximum power and depends on the crystal and board components.

    For cases where the actual drive level from the electrical oscillator exceeds the maximum drive level specification of the crystal, a dampening resistor (Rd) should be installed to limit the current and reduce the power dissipated by the crystal. Note that Rd reduces the circuit gain; and therefore, the actual value to use should be evaluated to make sure all other conditions for start-up and sustained oscillation are met

    Yes, using ECS-200-8-30B-CKM is what we advice, as we validate using those crystal circuitry on our EVMs and having a dampening resistor is better depending on the crystal you choose. 

    Also refer this E2E which describes in detail: https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/768014/tms320f280049-crystal-driving

    Best,

    Uttam Reddy Pailla