crystal selection

[MikeC1]

what is the absolute negative resistance value (Rs) for DSP56F803?

Need the value to select 8Mhz crystal oscillator, without load caps

[xiangjun_rong]

Hi,

Pls refer to the fig for the external crystal connection without capacitor load.

I attach the user manual of DSP56F803-EVK, I copy the fig from the user manual of DSP56F803-EVK at page A-3.

xiangjun_rong_0-1663228103186.png

Hope it can help you

BR

XiangJun Rong

[MikeC1]

Thanks for responding

The info you provided me shows connectors in series with crystal and DSP on a development board, does not show driver circuit inside the DSP56F803. I need to know what the absolute negative resistance value (Rn) for DSP56F803? Need this value to select an alternative  8Mhz crystal oscillator with ESR=100, without load caps. Need to verify Rn is at least 500 ohms because the ESR need to be 1/5 of Rn.  Attached below shows a method to find Rn. Do you have any test data values for  Max ESR or Max Rn  you can recommend for the DSP56F803?

MikeC1_1-1663253585572.png

Rx needs to be an RF SMD type pot. and soldered in series very close to the  processor

MikeC1_2-1663254106209.png

The NXT/Freescale/Motorola Semi datasheets and manuals for this DSP56F803 do not mention or recommend an ESR or Rn value.

We are using the crystal in application shown below

MikeC1_0-1663252421826.png

[xiangjun_rong]

Hi, Mike,

Unfortunately, I have checked all the data sheet and the other file, I did not find the negative resistor spec for the crystal circuit.

I am sorry.

BR

XiangJun Rong