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Original question:

PGA970: PGA970 SPI clock

PGA970: SPI Clock - Maximum clock speed ?

Kalle8319
Prodigy 140 points
Part Number: PGA970

Hi,

we have a question concering the maximum SPI clock speed of the PGA970:

On the one hand there is the information (see 6.17 Electrical Characteristics - SPI) which shows a maximum clock speed of 1MHz

and on the other hand you find a SPI timing requirement (see 6.25) which shows the minimum/maximum allowed times for 

SCK high/low time = 125ns min., SCK rise/fall time = 7ns max.

=> 125ns +125ns +7ns +7ns = 264ns

=> 3.8MHz approx.

Which information is correct?

Is it allowed to use a SPI clock frequency of e.g. 2.5MHz?

I think this issue should be clarified and the datasheet revised.

Kind regards,

Ferdinand.

  • 0
    TI__Guru** 113765 points

    Hi Ferdinand,

    I do realize it is a little confusing.  The information in section 6.17 refers to the maximum SCLK frequency when the system clock is 1MHz.  So essentially 1MHz will work for all microcontroller frequencies selectable.  Section 6.25 refers to the SPI timing that would be the fastest possible when the system clock is faster.  So 1MHz is always the safe solution.

    Best regards,

    Bob B