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TLV70730: P-version.

Kenneth Hansen
Prodigy 150 points
Other Parts Discussed in Thread: TLV707, LM317

Hello


In the datasheet for the TLV70730P version its explained that the P version has an active pull down circuitry on the output of 120 Ohm. This pull down resistor is it only active when the TLV707 is disabled? It seems unlikely to me that this will be active in enable mode as the IC then would have a constant current consumption of 3V/120R = 25 mA.


So my question is how does the pull down function work. I would like to know what transient progress of the IC is at shutdown. Hope you can clarify this for me.


/Kenneth

  • 0
    TI__Prodigy 90 points

    Dear Kenneth,

    in the DS on page 4 it says: "For TLV707xxP, output voltage is discharged through an internal 120-Ω resistor when device is shut down."

    Shutdown = Driving EN below 0.4V

    For me this implies that the "active pulldown circuit" is only active in stutdown mode.

    best regards

    Daniel

  • 0 in reply to Daniel Studer
    Prodigy 150 points
    Hello Daniel
    I agree with you. This is also how i interpret the statement. I just needed to be sure before implementing the IC in my next design prototype. We can not afford to much, lets call it leak current, when the supply is enabled.

    Regards
    Kenneth
  • 0 in reply to Kenneth Hansen
    TI__Prodigy 90 points
    Dear Kenneth,

    In shutdown (EN<0.4V)) mode, the current consumption (shutdown current) of the device is dependent on input voltage and temp. (a range of 0.2uA - 1.7uA is to be expected -> fig.27/28), but reduced to 1 μA typically.
    In enabled/on mode the "leakage" or gnd pin current is dependent on Iout and temp. -> fig. 23-26 / typ. 25uA at Iout=0.
    If efficiency is your concern, you might want to consider using a small and cost effective DC/DC regulator. We can recommend parts which are especially designed to replace LDOs.

    Do you need some samples or an EVM? Please contact me at Daniel.Studer@ti.com
    best regards
    Daniel
  • 0 in reply to Daniel Studer
    Prodigy 150 points
    Hello Daniel.
    I actually use an LM317(SOIC-8) voltage regulator to bring down my voltage to 5 VDC from up to 40 VDC on the input. From these 5 VDC i will use an LDO to get a stable regulated voltage for some parts of my circuit. The only reason for using the LM317, instead of other alternatives, is because it is cheap. It actually wastes a lot of power in its conversion. Can you recommend a part which would be more efficient without so much current going for the regulation? It needs to be no bigger than the LM317 and it needs to be a SMD component. Also the price would have to be low as well.

    Regarding the TLV707, i will use two in my design and as long as the leak current is as low as you explained they will work perfectly. We will not need samples at this time i think. But thank you.

    Regards
    Kenneth
  • 0 in reply to Kenneth Hansen
    TI__Mastermind 22610 points

    "... It (LM317) actually wastes a lot of power in its conversion..."

    Yes, and the efficiency, or the power dissipated in the device, will be essentially the same with every other linear regulator as long as Vin and Vout remain the same.

         Efficiency (%) = ( (Vout / Vin) x 100)

         Pdiss (W) = ( (Vin - Vout) x Iout )

    You will need to use SMPS technology to improve efficiency.

    I would suggest using WEBENCH® Designer at TI.com to quickly narrow down the choices.

  • 0 in reply to Donald Jones
    Prodigy 150 points
    Yes that is true. But i will use the LM317 because of its very low price, to start with. I would actually like to hear if it is possible for you guys to send me some samples of the TLV70730 and the TLV70730P for testing anyway? Do you have some that are already soldered to PCB's? I guess soldering on such small components could be tricky but not impossible.

    /Kenneth