• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 47 subscribers
  • Views 494 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMH6574: Is there any opamp in TI products, which has integrated multiplexer with a GPBW > 10MHz and SR > 66V/uS. This part seems to be overqualified for our application.

Dileep P
Prodigy 20 points
Part Number: LMH6574
Other Parts Discussed in Thread: TLV9062, OPA2863, TMUX1204, VCA822, VCA824, LMH6518, VCA810

Tool/software:

Hi,

 Is there any opamp in TI products, which has integrated multiplexer similar to LMH6574 with a GPBW > 10MHz and SR > 66V/uS. LMH6574 seems to be overqualified for our application.

  • 0
    TI__Mastermind 30765 points

    Hello Dileep,

       Is your application space constrained? If not, these are other options you can use for multiplexor + amplifier applications or with dual channel amplifier with shutdown (the second option would actually be same size as integrated mux, but signal integrity depends on feedback path unless in buffer configuration):

       

    or 

       

       First image is from this app note: https://www.ti.com/lit/ab/sboa311a/sboa311a.pdf

       Second image is from TLVx888 datasheet page 16: https://www.ti.com/lit/ds/symlink/tlv2888.pdf?

    Thank you,

    Sima

  • 0 in reply to Sima Jalaleddine
    Prodigy 20 points

    Hi,

     I need 4 channel, the TLV9062 does only support up to 10MHz with 6.5V/us slew rate. I am planning to use OPA2863RUN, Do you have any better alternative for this then please let me know.

  • 0 in reply to Dileep P
    TI__Mastermind 30765 points

    Hello Dileep,

      Will you be configuring the OPA2863 as a 4x1 channel mux by using two devices and toggling the shutdown pin like shown below: 

      If so, will there be gain, or as a buffer configuration?

    Thank you,

    Sima

  • 0 in reply to Sima Jalaleddine
    Prodigy 20 points

    Yes, it will be an application with gain. Each of the 4 opamp will have different gain varies from 2-11. 

  • 0 in reply to Dileep P
    TI__Mastermind 30765 points

    Hello Dileep,

      Understood, makes sense. The issue I see is that when you disable the amplifier, the output will be high impedance for the device you selected. However, when you have a gain configuration, the signal at output (connected to the other amplifiers) will appear at the input of the amplifier of all 4 devices since the signal can travel via the feedback path of the amplifier (RF/RG path) even in shutdown. 

      Are you able to instead to keep the 4 amplifiers with the different gains then follow this with a dedicated 4 x 1 mux? If so, then you can use the OPA2863, then would have to choose a 4x1 mux such as the TMUX1204 or a similar device.

    Thank you,

    Sima 

  • 0 in reply to Sima Jalaleddine
    Prodigy 20 points

    Hi Sima,

     This is helpful. Instead of using 4 different opamps, will the below configuration is usable? One opamp with selectable feedback resistors

  • +1 in reply to Dileep P
    TI__Mastermind 30765 points

    Hello Dileep,

      Yes, that is another usable configuration!

      As well as something like this:

      (Image from link). 

      If you just need to select gain with the same input, we also have an easier way to implement this without needing to calibrate for the on-resistance and capacitance contributed by the mux. We have amplifiers called programmable/digital variable gain amplifiers (PGA/VGA), a list of them can be located at this link: https://www.ti.com/amplifier-circuit/pga-vga/products.html

       For example, for your requirements I would recommend the VCA810, VCA822, VCA824 (listed in order of speed, depending on your gain * bandwidth + 10x headroom). These can be controlled via analog voltage and can select gain up to 40dB or attenuate signal specified in datasheet. And can step between this range via specified gain steps usually between 0.1 to 2dB depending which one you choose. Also, if you are using an differential ADC following this amplifier, we have VGA/PGAs with differential output such as the LMH6518 which can be controlled via digital. 

    Thank you,
    Sima