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LMH6551: work as fda for high speed adc adc3444 125M

hai xuan
Intellectual 735 points
Part Number: LMH6551
Other Parts Discussed in Thread: ADC3444, THS4541,

Dear all, 

I am trying to find low-cost FDA for adc3444, 125M 14bit ADC. 

I saw the official design with ths4541 as an ADC driver. will the cheaper one,  lmh6551 do the job?

  • 0
    Intellectual 735 points
    The target bandwidth of my applicaiton is 50Mhz and the basic info of analog input of the adc3444:

    ANALOG INPUT:
    Differential input full-scale 2.0 VPP

    ri Input resistance Differential at dc 6.6 kΩ

    ci Input capacitance Differential at dc 3.7 pF

    VCM common-mode voltage output 0.8 0.95 1.1 V
    VCM output current capability 10 mA
    Input common-mode current Per analog input pin 1.5 μA/MSPS
    Analog input bandwidth
    (–3-dB point)
    50-Ω differential source driving 50-Ω
    termination across INP and INM 540 MHz
  • 0 in reply to hai xuan
    TI__Expert 7875 points
    Hi,

    The LMH6551 should work similarly as the THS4541 for your application. The main difference between the amplifiers is that the LMH6551 can not swing as low on the input as the THS4541 can. What are the voltage levels on the input of the amplifier?

    Regards,
  • 0 in reply to Jacob Freet
    Intellectual 735 points
    Thanks Jacob, my understanding is "THS4541 Negative Rail Input" so that ths4541 can swing lower input?

    My application is a ADC driver:
    - the Diff input signal for the amplifier will be in the range of ( -1V to 1V )
    - Gain = 2
    - Vcom = 1.0V (the 100M ADC has a Vcom = 1.0V and a input signal range of (-1V, +1V) in Diff format)
    - If applicable, I will put a +V and -V as the power supply; such as +/-4.5V for LMH6551. May be just Single-Supply V=4.0 V for THS4541 in my application ?

    So, in this case, will the lmh6551 works well?
  • 0 in reply to hai xuan
    TI__Expert 7875 points
    Hi,

    Yes that LMH6551 should work well in that application. With a gain of 2V/V and 2Vpp input signal, that means your output will be swinging 4Vpp differential. In that case each signal output will only be swinging 2Vpp around your common mode of 1V, so the min and max voltage at each output pin are 0V to 2V. A +/- 4.5V supply will have more than enough headroom for those voltage swings.

    Regards,