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TLV1701: Follow up with the startup behavior

Part Number: TLV1701
Other Parts Discussed in Thread: TLV7011, TLV1805

Hi team; 

1,Per the following thread, I know that the output state of TLV1701 is not garanteed, and team would do some test, could you share the test result?

https://e2e.ti.com/support/amplifiers/f/amplifiers-forum/922302/tlv1701-questions-regarding-recommended-operating-condition-on-supply-voltage

2, I wanna use TLV1701 with 5V V+ supply , and 4.7K PU with 5V pullup voltage,to drive a BSS138W NMOS, I check th output swing could be 900mV at 4mA which be bigger than the Vgsth;

BSS138W DS as follow:

www.infineon.com/.../

  • A MOSFET gate will not have a continuous current of 4 mA.

    Anyway, just use a better device. The TLV7011 has power-on reset, and an output that goes to GND (see figure 17), and a push/pull output (which makes the pull-up resistor unnecessary).

  • 2, I wanna use TLV1701 with 5V V+ supply , and 4.7K PU with 5V pullup voltage,to drive a BSS138W NMOS, I check th output swing could be 900mV at 4mA which be bigger than the Vgsth;

    Hhm, why would you be interested in the output low saturation voltage when turning on a NMOSFET? A NMOSFET is turned-on with Vgs=5V but not with Vgs=0V.

    Can you post a schematic?

    Kai 

  • Thanks Clemens and Kai for the support.

    Jingjing

    Based on this application of controlling a MOSFET switch, I would not be recommending the TLV1701.  A comparator with a push pull output stage is probably better suited to turn the MOSFET on and off.  Also, since the supply is only 5V, there is no need to use a high voltage device.  Devices like the TLV7011 are better suited for this use case.

    Chuck

  • Thanks to all of you;  For my question , the MRDRVMID is connected to the GATE of BSS138,  I should guarantee when the comparator goes low,the vgs of NMOS is low enough than Vgsth;In the red rectangle , currently I add a diode to lower down the saturation voltage of comparator low output;

    For start up, I could not use TLV7011, because the UBM may goto 20V.

     

  • Sorry for my confusion.  You mentioned previously that you will power the comparator with 5V and use a pullup voltage of 5V.  If the voltage can go as high as 20V, I would suggest you use the TLV1805 instead and remove the pullup resistor since it has a push pull output stage.  It also has POR integrated.  And since the POR state for the TLV1805 is high Z on the output, a simple weak pulldown on the output pin will guarantee that the output starts low as the power supply ramps up.  

    Chuck

  • Sorry to make you confused, Chuck;

    At the beginning , I said 5V, because the comparator transition point is around 5V,  so for the saturation output voltage , It make sense when the supply voltage is 5V, and for the supply range, that should be 20V. 

    Besides, I need automotive qualified comparator, TLV1805 is really a better choice for me, Many thanks!