HMC440 - Problem at low frequencies

Hi Vincent,


The HMC440 chip is rated for 10MHz - 1.3GHz Phase-Frequency Detector under normal conditions. Could you give more information about your usecase that is causing it fail. What is your Fref if your PFD is 10MHz. Did you try to simulate your setup using the ADISIM_PLL software? What model of VCO are you using?

Regards,
Jude

Hi Jude,

I could describe our final need but i think it's would be easier to talk about the test i've done on the HMC440 alone:

As i've seen that ND was always at 5V in our close loop configuration, no matter the frequency of the reference (around 10MHz), i use the set up above to test the HMC440 in open loop.

Using a reference frequency of 25MHz and a VCO frequency of 250MHz, the HMC440 seems to work (i see a sawtooth waveform on ND if Fref < Fvco / 10 or on NU if Fref > Fvco / 10).

But it doesn't work for lower frequencies. In this case, depending on the frequencies and the level of the signals, i see the ND always at 5V or sawtooth waveform on ND and NU at the same time.

Using a square wave for the reference, and an amplitude quite high of 1.6Vp-p, it works with a phase detector frequency of 20MHz but not under.

Please tell me if you need more informations.

Best regards,

Vincent

Hi Vincent,

Spoke with the designer about this, he suggested that at that low frequency you should further increase the amplitude of the square wave form or pulse. This should boost the rise/fall time of the wave.

Regards,
Jude

Hi Jude,

Thank you for your help.

It works but only with amplitude greater than or equal to 650mV rms, i.e a power of 9.27dBm at 50 ohms.

It's almost the maximum operating amplitude given by the datasheet.

Best regards,

Vincent

hi Vincent,

I make reference to the measurement setup in the previous post as I will like to get started to testing out my PLL also - I am also working with the HMC440 which will be paired with the HMC6380 as VCO.

For the testing on the HMC440 above, could you please tell me why the need of the logic buffer at 1.8V was required? I see that it is greyed out in the chart above - does this mean it was optional or is this the block from which you generated the square wave of 1.6Vpk-pk?

I note that on the HMC440, the VCC of +5V is supplied through pin 9 ....

hi Vincent,

I make reference to the measurement setup in the previous post as I will like to get started to testing out my PLL also - I am also working with the HMC440 which will be paired with the HMC6380 as VCO.

For the testing on the HMC440 above, could you please tell me why the need of the logic buffer at 1.8V was required? I see that it is greyed out in the chart above - does this mean it was optional or is this the block from which you generated the square wave of 1.6Vpk-pk?

I note that on the HMC440, the VCC of +5V is supplied through pin 9 ....

Hi,

Sorry for the late reply. The logic buffer enables to have a square signal instead of a sinus signal. The goal is to have a high slew rate. But with a 1.8V supply voltage, it was not enough to work at 10MHz. Using a slightly higher supply voltage (i don't remember how much), it works.

Thanks for the time to reply to me. 
I got back looking into the project again today, and was trying to replicate your setup. I am not sure I have the right results, even when I've tried all possibilities to have similar setup. 

In my setup; using a waveform generator, I have 10MHz at 600mVpp connected to REF of the HMC440 and from a signal generator, I have 60MHz at 7dBm connected to CLK/VCO.

I was expecting to see sawtooth waveform as you mentioned in an earlier post, but what I have is shown above - NU is yellow trace, and ND is green trace. Are these normal results?

Hello,

Yes, in my memories, you should have sawtooth on one of the output at a frequency which correspond to the difference between the two input signal on the phase detector.

Both inputs shall be square.

Maybe the slew rate of your generator is not enough?

You can add a high speed buffer.

600mVp-p is probably not enough.

First, you can try the component with higher frequencies to see if the component works.

Thanks for writing back RFVS 
I came to the conclusion that the part I owned has failed. As I got the buffers, but that didn't help and after some time, I could see no outputs of whatever waveform type.

I have now moved on to HMC3816 as I was told the HMC440 has little to no ESD protection.

Mind to have a look into my recent problem? Your inputs are appreciated in advance.
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