Replace from HMC346MS8GE to HMC346AMS8GE, Relative Attenuation vs.Control Voltage characteristic data change !

HI all,

Please advise to us.

HMC346MS8G was EOL, then HMC346AMS8G start to evaluate.

Following is our custmor evaluation data with  EV1HMC346AMS8G, using Single-Line Control Driver @ datasheet recommend.

Relative Attenuation vs.Control Voltage characteristic data change !

Insertion Loss (V1=0V,V2=-3.4V) is -7dB (-3.1dB typ @ datasheet)

our custmor evaluation data

datasheet data

What happen is it?

Best regards,


  • Hi all,

    HMC346MS8GE and HMC346AMS8GE is different from internal impeadance, changed from 500 ohm to 600 ohm.

    But single-line control driver is same op-amp circuits.

    Is it correct ?

    would we need to change 500 ohm to 600 ohm?

    HMC346MS8GE datasheet

    HMC346AMS8GE datasheet

    Best regards,


  • +1
    •  Analog Employees 
    on Jun 6, 2019 11:45 PM


    The HMC346AMS8GE is pin-to-pin compatible with HMC346MS8GE but not drop-in replacement due to change in the control voltage range. The new replacement requires a control voltage range from 0V to -5V whereas the old part requires a control voltage range from 0V to -3V.used

    The opamp used in single line driver circuit for the old part is not rail to rail so it may not provide low enough V2 voltage to set new part to set the new part in insertion loss state. This could be why you measure higher loss with respect to datasheet. We used AD8675 rail o rail opamp in single line driver circuit for the new part.

    Can you please confirm if you still use the old opamp or changed it to a proper rail to rail opamp when evaluating the new HMC346AMS8GE?

    I also suggest you to evaluate the insertion loss without single line driver circuit b direcly biasing V1 at 0V and V2 at -5V from power supply.

    The insertion loss measured on evaluation board can be some higher than 2dB at 8 GHz including board losses.



  • 0
    •  Analog Employees 
    on Jun 7, 2019 12:00 AM in reply to sss@jpn


    For old HMC346, the design and measurement had matched on the termination resistor value of 500ohm.

    For new HMC346A designed in another process, the design used a the termination resistor of 500ohm too but the measurement showed 600ohm resistor.

    Despite of that, HMC346AMS8GE was characterized by using 500 Ohm resistor in the single line driver circuit. I also did some measurements changing the resistor from 500 Ohm to 600 Ohm, it did not make any significant change on attenuation and return loss responses.


  • s.ilke - san,

    Thank you for very useful information !

    We will check the single line driver circuit & op amp spec again.

    Best regards,