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ADF4153A Refin type

Possibly a basic questions but I'm trying to determine the type of clock I can use for the Refin on an ADF4153A.  The data sheets states that it is a CMOS input or AC coupled with threshold of VDD/2.  if my VDD is 3V can I run this with an AC-coupled sine wave at 10 MHz where the p2p voltage is say 2V (just over the 1.5 but less than Vdd)?  The max-spec of REFin to GND of -0.3V makes me think not as the Voltage would go to -1V?

Any help much appreciated.

  • Hello Ross,

    Yes, you can run REFIN with an ac coupled sinewave at 10Mhz....we recommend keeping the slew rate greater than 25V/us, using a REFIN of 10Mhz with a pp of 2Volts , is well within 25V/us.


    The choice between the DC-coupled, CMOS compatible square wave and AC-coupled signal depends not only on the frequency, but on the slew rate and amplitude of the signal – if your reference signal of 10 MHz meets the condition for amplitude which is specified in the datasheet (minimum 0.7 Vp-p) and the condition for slew rate (minimum 25 V/us), you do not need to apply the DC coupled square wave. However, if you have an option to apply a square wave reference signal with sharp edges, you might consider it – increasing slew rate of the falling edge of the reference signal can improve the phase noise of the part. The datasheet specifies that the slew rate should be greater than 25 V/us.





  • Hi Brigid,

    Thank you that was very helpful.

    Best Regards,