Request a review about a circuit diagram with HMC721LP3E

Hello,

My customer use HMC721LP3E for the purpose of clock doubling.

(Input datarate is 3Gbps and output datarate is 6Gbps)

And they have some problem about the device damage on their system.

So they are trying to find the reason why HMC721LP3E is damaged.

Q1) Would you confirm their circuit diagram and verify the reason why HMC721LP3E is damaged?

Please refer below circuit diagram and let me know your opinions.

And as below diagram, they are use 100ohm resistor at the output of HMC721 to adjust the Vref voltage of FPGA (DEVICE in diagram).

They guess that the reverse current from VTT source to HMC721 may cause this device damage problem.

Q2) Would you let them know the specification of absolute maximum current from VTT source to VEE pin or DP/DN pins?

      (It means how much current can be allowed in HMC721 if the reverse current is applied from the output pin (DP/DN) to internal VEE path in HMC722 or vice versa.)

Q3) Would you confirm the power ON/OFF sequence of their system in below diagram If HMC721 need any specific power sequence?

They are using below sequences.

  - Power ON sequence : Vee à GND à VR à VTT à memory device voltage

  - Power OFF sequence : memory device voltage à VTT à VR à GND à Vee

    

If you have any questions, please let me know.

Regards,

Se-woong

Parents
  • Hello, Sinan

    Below are additional questions about your answers from my customer.

    Please refer below and let me know your opinions.

    Q4) About your question related Ground paddle.

    They say that as a functional diagram of data sheet, Groundpaddle (bottom side)should be connected to Vee (Negative potential voltage: -1.5V).

    And also they say that hittite engineer recommended that Groundpaddle(bottom side) should be connected to Vee.

    Below is the contents in e-mail from hittite engineer.

    -----------------------------------------------------------------------------------------

     

    For all high-speed digital logic (HSDL) parts ≤ 32 Gbps, the package paddle is connected to the most negative potential voltage.

     

    HMC721LC3C -3.3V 14 Gbps XOR Gate: package paddle = Vee = -3.3V

     

    HMC722LC3C -3.3V 14 Gbps AND/OR Gate: package paddle = Vee = -3.3V

     

    HMC745LC3  +3.3V 14 Gbps XOR Gate: package padd = GND = 0V

     

    In general:

     

    If power supplies are +3.3V/0V, then package paddle potential = 0V

     

    If power supplies are 0V/-3.3V, then package paddle potential = -3.3V  

    ----------------------------------------------------------------------------------------- 

    So would you confirm this again?

    It's very important thing whether Groundpaddle is connected to Vee or GND.

    Please advise me ASAP.

    Q5) Is it possible thing to be damaged by the force of the reverse current from VTT power source to DP pin?

    Please advise me.

    If you have any questions, please let me know.

    Regards,

    Se-woong

Reply
  • Hello, Sinan

    Below are additional questions about your answers from my customer.

    Please refer below and let me know your opinions.

    Q4) About your question related Ground paddle.

    They say that as a functional diagram of data sheet, Groundpaddle (bottom side)should be connected to Vee (Negative potential voltage: -1.5V).

    And also they say that hittite engineer recommended that Groundpaddle(bottom side) should be connected to Vee.

    Below is the contents in e-mail from hittite engineer.

    -----------------------------------------------------------------------------------------

     

    For all high-speed digital logic (HSDL) parts ≤ 32 Gbps, the package paddle is connected to the most negative potential voltage.

     

    HMC721LC3C -3.3V 14 Gbps XOR Gate: package paddle = Vee = -3.3V

     

    HMC722LC3C -3.3V 14 Gbps AND/OR Gate: package paddle = Vee = -3.3V

     

    HMC745LC3  +3.3V 14 Gbps XOR Gate: package padd = GND = 0V

     

    In general:

     

    If power supplies are +3.3V/0V, then package paddle potential = 0V

     

    If power supplies are 0V/-3.3V, then package paddle potential = -3.3V  

    ----------------------------------------------------------------------------------------- 

    So would you confirm this again?

    It's very important thing whether Groundpaddle is connected to Vee or GND.

    Please advise me ASAP.

    Q5) Is it possible thing to be damaged by the force of the reverse current from VTT power source to DP pin?

    Please advise me.

    If you have any questions, please let me know.

    Regards,

    Se-woong

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