• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 83 subscribers
  • Views 601 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TMS320F28377S: TMS320F28377S

vadim piskun
Expert 2220 points
Part Number: TMS320F28377S
Other Parts Discussed in Thread: INA148-Q1, INA148

Hi

I need to monitor voltage from DC to 100V. This is differential output. I need to scale down this voltage for ADC. I need it to draw very little current. I found INA 148 but it can go max to 75V. Is there a better part for such purpose?

Thanks vadim

  • 0
    Guru 30330 points
    Vadim,

    I am guessing that you are using the F28377S MCU?

    An option when measuring high voltages is to use a simple, but high value and high-precision resistor divider as an input into the opamp of your choice.

    I am going to see if the op-amp team has any inputs on this.

    -Mark
  • 0 in reply to Mark Labbato
    Guru 30330 points
    I did just find an FAQ from the amplifiers forum which points to a blog post covering this very topic! e2e.ti.com/.../705618

    Hopefully it helps,
    Mark
  • 0
    TI__Guru 60865 points
    Hi Vadim,

    I think this is more a question about available instrumentation/operational amplifier. I'm going to send this to the precision op-amp engineers. Please let us know if you still have questions about the F2837x ADC or MCU.
  • 0
    TI__Guru 60570 points

    Vadim,

    The INA148-Q1 is a unity-gain difference amplifier with a high common-mode input voltage range. To achieve its

    high common-mode voltage range, the INA148-Q1 features a precision, laser-trimmed, thin-film resistor network

    with a 20:1 input voltage divider ratio. High input voltages are thereby reduced in amplitude, delivering input

    voltages to the op amp that are within its linear operating range. A Tee network in the op amp feedback network

    places the amplifier in a gain of 20 V/V, restoring the overall circuit gain to unity (1 V/V).

    The input common-mode range is a function of the supply voltage and Vref; if you use +/-15V supply the input common-mode voltage range is +/-200V - see below.

    For 5V single supply, Vcm is up to 75V with Vref=0.25V (min Vref is 0.25V  since Vout cannot swing closer than 250mV above negative rail).

    This means that the maximum input voltage right at the input terminal must be 1V less than the positive rail - see below Vcm=~3.988V.

    Since in order to accomodate Vcm of 100V the input terminal must be able to operate linearly at 5.283V (see below), this means that you may use INA148 with Vcm of up to 100V as long as your supply voltage is at least 6.238V or higher.