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Recommendation of fully differential precision amplifier

Idan Ozana
Intellectual 480 points

Other Parts Discussed in Thread: AMC1200, THS4551, THS4131, LMP8350

Hi,

 

In my application I need to sense the load current from isolated 300VDC. In order to do that, I used the TI "AMC1200" with floating supply (to the 300V) and with 5V supply (to logic- analog). Now I need to drive this signal with over the ~70cm between cards, twisted pair and shielded. In the other curt I will have a precision, fix 0.4 Gain, Fully Differential Funnel Amplifier that drive switched capacitor inform of a Σ-Δ ADCs with precision to ~18bits. To make my application more robust I need a fully differential input stage amplifier with gain 2.5 (that will connect to the AMC1200 output) that can drive the twisted 70cm long and the Funnel Amplifier (with ~18bits or the closes to that).  Can you recommend such an fully differential precision amplifier? Operation Temperature must be at least 105 degree.

In addition, is it possible to use the AMC1200 as a driver for the ~70cm between cards or should I use different driver (ignore the 0.4V gain on the other card, let's say I can use it in unity gain)? What it the parameter that effect the driving thought the ~70cm twisted pair, shielded lines)?   

 

The project ADC volume is ~2000 chains.

 

http://www.ti.com/product/AMC1200/technicaldocuments

   

Thanks,

Idan     

  • 0
    TI__Genius 15975 points
    Hi Idan,

    The THS4551 fully differential amplifier could be suitable for your application providing 18bit precision and operating temperature from -40'C to 125'C.

    I would recommend you to post any questions about the AMC1200 in the Precision Amplifiers forum: e2e.ti.com/.../

    Regarding the choice of driver for driving the ~70cm twisted pair shielded lines, what is the maximum frequency and output swing you are planning to drive the twisted pair with?

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Intellectual 480 points

    Hi,

    My signal is some kind of square wave with frequency of ~1kHz and with output differential lines with Voh=3.83V and Vol=1.27V and with Vcm=2.55V (driving amplifier with gain 1). If I'll use the driving amplifier with gain 2.5, I will get Voh=7.66V and Vol=2.54V and with Vcm=5.1V as output swing in the differential lines. With the THS4551 I can only use the first option (Gain 1) and personally, I think that the option with the gain 2.5 (supply till 10V min) will make my design more robust. What do you think? Do you have another Low-Noise, Precision, Fully Differential Amplifier with output swing of 0-10V?

    Thanks,

    Idan

    Figure 1.docx

  • 0 in reply to Idan Ozana
    TI__Genius 15975 points

    Hi Idan,

    Sorry the delay in reply. If you are planning to swing 10Vpp(diff) at the FDA output with ~1kHz, then either the THS4131 or LMP8350 could be used for your application. Both the devices operated on +/-5V supplies should be able to drive the 70-cm long cable with 10Vpp(diff) output swing.

    Best Regards,

    Rohit