LMK04828: Cannot Invert SDCLK Outputs

Branden Buckner

Part Number: LMK04828
Other Parts Discussed in Thread: DAC37J82EVM

Hello, I'm running into an issue on the LMK04828 in which the SDCLK outputs don't invert their signals, regardless of their setting in the register map. I am using this part on a DAC37J82EVM board. The original motivation for inverting the SDCLK output is detailed in the related question linked at the top.

Basically, what I've tried to do is check the 'Invert' box for the SDCLK output going to the DAC on the EVM :

Which writes to the SDCLKout3_POL bit in register 0x10F :

However, the polarity of the SYSREF signal looks the same on an o-scope whether it's set to be inverted or not. This also appears to be the case with all other SDCLK outputs.

Is there an updated datasheet with a new register map that I should be using instead?

Thanks,

-Branden

over 5 years ago

0 Shawn Han over 5 years ago

TI__Genius 9920 points

From datasheet change list:
Changed from Sets the polarity of SYSREF clocks to Sets the polarity of clock on SDCLKoutY when device clock
output is selected with SDCLKoutY_MUX............................................................................................................................ 60
• Changed Sets the polarity of the device clocks to Sets the polarity of the device clocks from the DCLKoutX outputs ...... 60

The polarity invert bit is only available for Device Clock, either on DCLKout or SDCLKout ports.

0 Branden Buckner over 5 years ago in reply to Shawn Han

Prodigy 240 points

Thank you that clears this up.

-Branden

Clock & timing

Clock & timing forum

LMK04828: Cannot Invert SDCLK Outputs