Self-oscillation of HMC434E

In the absence of an input signal the HMC432, 433 and 434 will self-oscillate. A 3.3kΩ resistor should be placed in a shunt configuration from the input pin (3) to ground to prevent this. This does slightly impact the input sensitivity, so be sure that the input power level is sufficient. Please refer to the attached application note which covers this is detail. The app note promotes the use of a 4kΩ resistor to stabilize this divider but recently it was discovered that to this value needed to be reduced to 3.3kΩ to better address lot to lot variations. The application note is currently in the process of being revised to address this change. The impact to the input sensitivity due to the reduction in resistance is negligible (1-2dB). 

Hi Marty-san,

Thank you for your prompt answer.

I already sent your advice to the customer.

But the customer cannot use the shunt resister because of his application structure: FTTH.

So, he said the self-oscillation is Okey but he wants to know the range of self-oscillation frequency.

Please tell me the range of self-oscillation frequency as HMC434E.

His measured result at 3 to 4pcs HMC434Es was range of 500 to 570MHz at OUT-pin.

BR, Tomo

Unfortunately, we don't have that information.

OK. I understand. Thanks!

BR, Tomo