• State Answer Suggested
  • Locked Locked
  • Replies 9 replies
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 354 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.

TLV9004: TLV9004

Purva Patil
Prodigy 10 points
Part Number: TLV9004
Other Parts Discussed in Thread: LM7705

Tool/software:

Hi,

I am looking for output current graph for output voltage range of 3.5V-5V where I am using V+ and V- at 5V and Gnd respectively. 

In one scenario I am applying a few mV(4mV-90mV) at input of TLV9004 opamp, and in other a few V (less than 5V).

Could you please share a graph similar to following where output current could be in uA/mA for 3.5V-5V output range?

  • 0
    Guru 311740 points

    Other graphs do not exist. At 3.5 V, the drive strength will be lower.

    What is the desired load? How much less is "less than 5 V"?

    For a noticeable load (more than a few µA) at voltages near GND, consider adding the LM7705.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Thank you for the response Clemens Ladisch!

    The load is 170Kohm with a range of 2.5V to 5V opamp output.  Will the opamp be able to source more than 29uA current at 5V output?

  • 0 in reply to Purva Patil
    Guru 311740 points

    Estimating from the graph, at the highest temperature, the slope is about 1 V / 10 mA = 100 Ω. So the minimum output voltage is about 29 µA × 100 Ω = 2.9 mV. That is higher than 4 mV minus the worst-case offset voltage, so it is possible that the output saturates. (At 25 °C, you would get about 1.5 mV, which is better, but all these are typical values.)

    For such low output voltages, you really should use the LM7705. (This also would allow you to go down to 0 mV, if the other devices can handle it.)

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    The design I am working on is such that it gives 5V output, the load connected to it wants to draw more than 29uA. Referring the graph above, I can see that at saturation voltages +/-2.75V, as the output voltage approaches 2.75V, the acceptable output current is in few uA. 

    Clemens Ladisch said:
    For such low output voltages, you really should use the LM7705. (This also would allow you to go down to 0 mV, if the other devices can handle it.)

    Here I think you are referring to output voltages in mV. 

    My ask is for current availability at 5V output with saturation voltages at +5V and 0V. 

    Please let me know if I am missing something here.

  • 0 in reply to Purva Patil
    Guru 311740 points

    For not-too-large currents, MOSFETs behave like resistors. The voltage drop is 0 V when the current is 0 A.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Ok so my understanding from your response is Opamp TLV9004 at 25 degrees Celsius temperature is not suitable to provide load current more than 29uA at 5V output and is not suitable to provide load current more than 10mA at 2.5V output. I will have to add buffer circuit at the load.

    Is my understanding correct?

  • 0 in reply to Purva Patil
    TI__Genius 13696 points

    Hi Purva, 

    Clemens describes the op amp architecture correctly. 

    If you needed the output to swing all the way to the rail, you would need to use something like the LM7705. 

    Does the output really need to be 5V? Would a few mV from rail be acceptable? 

    Remember, the op amp has a small RDS-on which will prevent the output from swinging all the way to V+ or V-. This resistance causes a voltage drop in the output stage of the amp.

    I can characterize a few parts at 25C to show this behavior on TLV900x.

    Please let me know if you have any questions.

    Best,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 10 points

    Hi Jacob,

    I understand that the opamp output stage can introduce small drop, I was looking for a graph for Opamp output current limitation vs output voltage (2.5V-4.9V) at 5V saturation voltage. But it seems the data is not available.

    Purva Patil said:

    Ok so my understanding from your response is Opamp TLV9004 at 25 degrees Celsius temperature is not suitable to provide load current more than 29uA at 5V output and is not suitable to provide load current more than 10mA at 2.5V output. I will have to add buffer circuit at the load.

    Is my understanding correct?

    Is my above understanding correct? I am in need of load current in uA/mA data for which I am awaiting TI's confirmation.

  • 0 in reply to Purva Patil
    TI__Genius 13696 points

    Correct, the OPA cannot output 5.0000000V at 29uA with 5V supply as this is not possible for any real-world device.

    I took room temperature data to better show what the device claw curve looks like with light load current:

    Note, we do not guarantee any form of performance this close to the rail, but at room temp and ~29uA of output current, I see about 650uV of output swing from rail.

    In summary, if you can accept close to 5V output swing (about 4.9993V on average at room temp) then this device will work for you. As you can see from my chart, 2.5V output at 10mA is no problem for the device. 

    Please let me know if you have any questions.

    Best,

    Jacob