CDCE72010: power up time

Hi Puneet,

Thank you for the quick response.

The charge pump current is the default one, 2.2mA and the gain of the VCXO is +100ppm/V.

The control voltage signal is difcult to plot due the amount of time needed, but it is always the same, a ramp from 0V to 0.55 V aprox, and the time it needs to get to that value seems to be the same, a few seconds, maybe 10s or so ....................... BUT, in the first case, the IC is not outputing clock until 30-40 seconds later, and in other cases, the IC outputs clock even when we are measuring 0.35V in the VCO/VCXO control voltage.

Hope this helps to make you an idea, looking forward your answer.

Jose

Hi Puneet,

Thanks for your previous responses.

Because of the nature of our application, we need to power up without any reference clock input signal ..... in our case, this is a must.

We have checked the ramps, not only in power supply nets, but also in reset and power down pins, and they seem to be ok.

We are experiencing the same behaviour explained before, the IC is not outputing the clocks until, may be, 1 minute later than power up. 

We know the device is working, because it gets warm, but the outputs present no clock.

Once the device has reached certain temperature, it powers up well, i mean instantaneously, in every retry.

We think this is a temperature related problem ... 

Can you help us in any way?? ... are these known effects??

Thank you in advance,

Jose

Hello Jose

I have not heard about such chip behavior from any other customer.
Another thing to check is the RESET pin. How is the signal at RESET pin in those two cases?
Have you checked this on single unit or multiple units shows such behavior?

Best regards
Puneet

Hello Puneet,

We have experienced the same behaviour in the only two prototypes we have at the moment.

The RESET pin is connected to a pull-up resistor, but we think this is not affecting to the problem, because is the first power up when we experience problems.

Also, the CDCE72010 starts getting quite warm, or even hot very soon, even when it will put out clocks a minute later .... so we think it is internally operating, configuration has been loaded, and it is not in reset.

Another experience, we have assembled one of the prototypes with the enclosure, which acts as dissipator, and it is not powering up until almost 15 minutes later..

Without the enclosure, it was powering up as described above.

We think this is a temperature related problem. As I described in the previous posts, once it has powered up well, if the circuit is switched off and switched on again, the time to power up depends on the time the circuit has been off ..... i.e. if I keep the board off 5 seconds, the cdce72010 will output clocks almost 5 seconds after been powered ....

Also, as I stated before, we need to start up without any clock reference signal .... can this be a problem??

Thanks in advance!

Jose Luis

Hello Puneet,

Any ideas on this topic?

Thanks in advance!

Jose Luis

Hello Puneet,

I have another question in addition to the previous ones .............. we are using a VCSO (https://www.vectron.com/products_av/vcso/VS-702.pdf, ) instead of a VCXO ....

We think this should not be a problem, could you confirm?

Thanks in advance.