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LMH6624 open loop and phase

Shinichi Inoue
Guru 22186 points

Other Parts Discussed in Thread: LMH6624, LMH6629, OPA847, TINA-TI

Dear Specialists

My customer is considering LMH6624.

The requirement is over 40dB@10MHz at all lots and temperatures.

Is it possible to use ?

I think it is difficult to achieve over 40dB@10MHz, because graph of the datasheet is just 40dB@10MHz.

It has no margin for lot and temperature.

Could you please advise?

Best regards,

  • 0
    TI__Genius 12631 points

    Hello,

    At what supplies will this be used? The OPA847 and LMH6629 both have higher BW and should be able to meet the customer specs. Are these viable alternatives?

    Also, I was wondering about the reasoning behind the firm need for the 40dB @ 10MHz requirement. Could you please clarify?

    Thanks,

    Samir

  • 0 in reply to Samir Cherian
    Guru 22186 points

    Dear Samir

    Thank you for your reply.

    The customer will use +5V single supply.

    As you mention, he is also considering OPA847 and LMH6629.

    He wants to use the device as low as possible. 

    It is my understanding, LMH6624 is just 40dB at 10MHz, it can't be achieve under all temperature range, deviation of lot to lot and individuals.

    In this case, LMH6624 is out of spec, I think. 

    Could you please advise?

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Genius 12631 points

    Hello Shinichi,

      I agree that the LMH6624 is too close to the edge in this case. If the customer requires low power supplies, then the LMH6629 would be the better choice. The voltage noise is comparable with the LMH6624 and it looks to have sufficient margin as well with regards to Aol @ 10MHz. I will ping a colleague who has more experience with these products and get his recommendation as well.

    Samir

  • 0 in reply to Samir Cherian
    TI__Mastermind 22825 points

    Hello Samir and Shinichi,

    First of all, my condolences to Shinichi.

    I agree with Samir in that the LMH6624 is not going to be adequate to ensure 40dB of flat-gain from DC to 10MHz. With TINA-TI model which has a 43dB gain @ 10MHz, the -3dB bandwidth is 14.7MHz and 10MHz closed loop gain is 38.3dB (1.7dB down from 40dB with RF= 990, RG= 10ohm).

    However, the LMH6629, with COMP pin High or with SOT23-5 package, will provide at least 39.8dB of again at 10MHz (with 40dB closed loop gain setting, 60MHz for -3dB Bandwidth) with up to 3Vpp output swing over the entire temperature range and across all production lots. 

    LMH6629 Open Loop Response:

    Even though the LMH6629 datasheet does not provide the temperature open loop gain / phase information, I expect the variation to be minimal (similar to the LMH6624 open loop gain / phase variation). I will measure the LMH6629 over temperature Bode plot by the middle of next week, as I had promised to you in another post:

    http://e2e.ti.com/support/amplifiers/high_speed_amplifiers/f/10/t/365999.aspx

    Regards,

    Hooman

  • 0 in reply to Samir Cherian
    Guru 22186 points

    Dear Samir

    Thank you for your reply.

    I understand that LMH6624 is impossible to meet the customer's request.

    I'll feedback to him.

    Best regards,

    Shinichi

  • 0 in reply to Hooman Hashemi
    Guru 22186 points

    Dear Hooman

    Thank you for your reply.

    First of all, I appreciate for your kind letter of condolence for my father's funeral.

    As you and Samir mentioned, LMH6624 isn't able to accept the requirement of customer. 

    I agree.

    I am looking forward to your advise in another post about LMH6629. 

    Best regards,

    Shinichi Inoue