• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 306 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.

LMH6551Q-Q1: LMH6551Q-Q1 Headroom Range

Niranjan T
Prodigy 20 points
Part Number: LMH6551Q-Q1
Other Parts Discussed in Thread: THS4541-Q1, THS4531, THS4541, TINA-TI

Hi Team,

Was checking the Headroom for LMH6551Q IC and found that it was 1.31V for maximum supply voltage.

If I'm using a single 5V supply what is the headroom one should consider on the positive and negative output.

Hope 1V on the negative side should be fine, Please confirm

Thank you 

Niranjan T

  • 0
    TI__Mastermind 25615 points

    Hello Niranjan,

      For 5V supply, I would use the specifications noted under 5V Electrical Characteristics Table (pages 5 and 6). 

     Output Voltage Swing is specified as +/-2.5V peak to peak voltage of +/-2.8V typically. This denotes OUT+ terminal = +1.4V & OUT- terminal = -1.4V at a split supply configuration. To convert to single supply of 5V, you would take 2.5 - 1.4V which is equal to 1.1V headroom from either supply. In other words, this could also be interpreted as the output swing on single-ended output is limited to approximately 1.1V lower than V+ or 1.1V higher than V-, and is irrespective of whether the supply is +/-2.5V or +5V as long as the Vcm is set to mid-supply which is 0V for +/-2.5V and 2.5V for +5V. 

      Therefore, 5V at 2.5V Vocm would give you a headroom of 1.1V to 3.9V typically. 1V would fall slightly below this range which can place the amplifier in non-linear operation, but we can help suggest another amplifier. Do you require an automotive grade device?

    Thank you,
    Sima

  • 0 in reply to Sima Jalaleddine
    Prodigy 20 points

    Hello Sima,

    Thanks for your inputs, can you also just let me know what would be the case if Vocm is not set to 2.5V. For example if I set my Vocm to 2.1V will my headroom voltage still remain the same(1.1V to 3.9V) for 5V single supply.

    And also suggest me Amplifier which can have a voltage of 1V or below as the headroom, The suggested Amplifier should be an AEC qualified part. Awaiting your response at the earliest.

    Thank you

    Niranjan T

  • 0 in reply to Niranjan T
    TI__Mastermind 25615 points

    Hello Niranjan,

       With Vocm set to non mid-supply, most likely yes, around 1.1 to 3.9V; however, it is not guaranteed. 

       I would recommend the THS4541-Q1; it can be operated at 5V single supply within 200mV from either supply: 0.2V to 4.8V. Its other specifications are an improvement over the LMH6551Q except with a slower slew rate.

    Thank you,

    Sima 

  • 0 in reply to Sima Jalaleddine
    Prodigy 20 points

    Hey Sima 

    Thank you for the part suggestion, In my application I wanted to have the differential Input to the Amplifier of 2V p-p. Just while going through the datasheet in page 4 I came across the data saying Differential input voltage Max of ±1V. So is it saying that I cannot provide a 2Vp-p to the input of THS4541-Q1.

    In my application the inputs are 180deg out of phase, each input is 2V p-p. Will this be acceptable by the THS4541Q. 

    Also attached simulation file. please let me know would that work.

    Resolver_THA4541.TSC

    Also the spice model is for THS4531, is it the same spice model for THS4541.

    Thank you

  • +1 in reply to Niranjan T
    TI__Mastermind 25615 points

    Hello Niranjan,

      The max differential input specification for our amplifiers refer to the voltage differential directly at the IN+ and IN- node. Your differential input voltage will measure lower due to the resistive network. 

      VF1 and VF2 will be your input voltage range which should be within specified in the THS4541-Q1 datasheet: -0.2 to 3.8V, and Vdiff is the input differential specification. 

      THS4531 is not the same spice model as THS4541, you may use THS4541 Spice model which is the same as THS4541-Q1. This is located on each device's product folder under design&development tab. Below is a downloadable link to the Tina-TI reference circuit of the THS4541. 

    6428.sbom907b.tsc

    Thank you,

    Sima 

  • 0 in reply to Sima Jalaleddine
    Prodigy 20 points

    Thank you Sima for your support on this Issues.

    Niranjan T