• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 3 answers
  • Subscribers 50 subscribers
  • Views 278 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.

TLV3601: 5V output drops to 3V at 30mA?

ArTzy
Genius 15899 points
Part Number: TLV3601
Other Parts Discussed in Thread: SN74LVC1G34

Hi Experts,

Customer has been using TLV3601 Comparator and have one doubt regarding it.

For 5V Output voltage to VCC they need to know how much the comparator can support the output sourcing current.

They have connected the TLV3601 output to MOSFET for both gate and drain. The actual output of TLV3601 is 5V. But when they connect to the Mosfet, the output voltage drops to 3v and current consumed was around 30 ma. So we need to know why it happens.

Because in the Mosfet we have connected the source to ground and we measuring across the drain so if Mosfet is on the output voltage should be zero or if its off it should be 5V. But here it stands at in between 3V so we have doubt like when we applying 5V to the Mosfet, the Mosfet is not completely ON due to the current controlled by TLV3601.

So, we need to clarify why it happens and then for 5V output how much maximum current TVL3601 can support.

Please let me know if any other information is required.

Regards,
Archie A.

  • 0
    Guru 286890 points

    As shown in figure 6-29, higher output currents increase the voltage drop. It might be possible to insert a buffer (e.g., SN74LVC1G34) to increase the drive strength.

    Why do you have the output connected to both gate and drain? What is the actual problem you're trying to solve?

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24560 points

    Archie

    Thanks for posting and thanks Clemens for trying to assist.  Can you clarify with a picture exactly what you are trying to accomplish?

    It is common for the comparator to drive the gate of a MOSFET like this but what you described has me slightly confused as Clemens noted.

    The curve you noted is generated by applying a positive differential input while pulling current from the output and monitoring the voltage.  If you are driving a MOSFET gate as shown below, initially the load (gate capacitance) looks like a short to GND and then approaches high impedance as we reach steady state.

    Chuck

  • 0 in reply to Chuck Sins
    TI__Genius 15899 points

    Hi Chuck/Clemens,

    Thank you.

    Actually we are doing some testing so we are connecting the output to the both gate and drain. So we need to know for 5V output how the much maximum current can be supported by this comparator . So if the current less so we can conclude that voltage drop is due to current. Because as I mentioned before when we apply 5v the voltage at output is dropped to 3v so we need to know reason for the drop.

    So can you please provide the exact current value that can be supported by comparator for the 5v voltage output.

    Please let me know if you have any other queries related to it.

    Regrads,
    Archie A.

  • 0 in reply to ArTzy
    Guru 286890 points

    Figure 6-29 answers your question, but with typical values; you have to add a safety factor for temperature and manufacturing variations.

    Section 6.5 specifies VOH for 1 mA. This is the only current for which there is a guarantee.

  • 0
    Guru 140200 points

    Hi Archie,

    ArTzy said:
    They have connected the TLV3601 output to MOSFET for both gate and drain. The actual output of TLV3601 is 5V. But when they connect to the Mosfet, the output voltage drops to 3v and current consumed was around 30 ma. So we need to know why it happens.

    Because the TLV3601 begins to enter the short circuit current limitation mode. Remember that the short circuit current is specified to 30mA typically.

    More can only be said when seeing a complete schematic.

    Kai

  • 0 in reply to kai klaas69
    TI__Genius 11701 points

    Thanks Kai and Clemens, these are valid points. 

    Archie, the output current of 30 mA is significantly high which would bring down the VOH. This current needs to be limited