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TLV1704-SEP: Comparator or Opamp with low Vol performances

Yves Theroux
Prodigy 110 points
Part Number: TLV1704-SEP
Other Parts Discussed in Thread: LM139, TLV1704, LM139-SP, LM139AQML, , TLV7021, TLV9024, LM339LV

Hello

I was looking for a comparator or operational amplifier to control a NPN base transistor (to be used as a ON/OFF switch)

Need a SEP device

When looking at different datasheet, most of them have very high Vol max value ( equal or above 700mV)

I did not find any component with lower Vol max   < [0.3 - 0.5] V

Any ideas about part number that could be used for such function ?

thanks

Yves

  • 0
    TI__Mastermind 49906 points

    Hello Yves,

    If all you are driving is a base, you should not need more than 1mA - unless it is a big transistor under heavy current.

    VOL will be proportional to the sinking current. The less sinking current, the closer to 0V the output will swing.

    The TLV1704 is a micropower device, so it does not swing as close to the rail as the LM139 family.

    Have a look at the output swing graph of the commercial LM139, figure 3. The LM139-SP devices will be similar.

     https://www.ti.com/lit/ds/symlink/lm2901.pdf

    We do not have a "SEP" version of the LM139, so the packages will mostly be ceramic.

    What is your supply voltage and expected sink current?

    One trick is to add a diode in series with the base, or, use a darlington to increase the base turn-on voltage if you are afraid VOL is not low enough.

  • 0 in reply to Paul Grohe
    Prodigy 110 points

    Thanks Paul for your fast reply

     I saw the LM139AQML,LM139QML datasheet

     There is a LCCC package (NAJ002A) and NAC0014A package that could be considered

    • Vsat is about (@Isink <= 4mA)
      • 400mv max at 25C
      • 700mv max at -55 +125
    • Just to make sure, these Vsat limits include the degradation after 100krad or not …can you explain ?
      • Vcesat variation if probably low…so no effect major effect on Vsat parameter
      • From LM139 curve, at 4ma the Vsat is about  0.2V and this represents the typical value and over temperature the limit will be  between 400 and 700mV (so same limits)

     Still a little bit high… to connect directly to a NPN base

    Our temperature range is -40 +85

    Supply [0-3.3V]

     Yes adding a series diode or Darlington will help !

     I had a look to logic buffer…!  but again the Logic Vil and the Vsat are closed to each other.

     thanks

     Yves

  • 0 in reply to Yves Theroux
    TI__Mastermind 49906 points

    Hello Yves,

    The device will remain within datasheet specifications after exposure.

    See page 25 of the following:

    Explore space products

    Cooler is better, the VOL will be lower at +85.The temp limits are for 125C. VOL increases with temperature - so 125C would be the worst case.

    One warning is that the LM139 is not R-R input and has a limited upper input range of VCC-2V, or 1.3V at a 3.3V supply. The inputs must be below 1.3V.

    The  product folders contains the ELDRS, TID or SEL reports, with data, so you can see the shifts before and after exposure.

     https://www.ti.com/product/TLV1704-SEP#tech-docs

     https://www.ti.com/product/LM139-SP#tech-docs

  • 0 in reply to Paul Grohe
    Prodigy 110 points

    Hi Paul

    is it possible to simulate the TLV1704 with this Vol at 700 or 1100mv ? 

    With Tina ?

    let me know

    thanks

    Yves

  • 0 in reply to Yves Theroux
    TI__Mastermind 49906 points

    Hello Yves,

    You can use the TLV170x family TINA model, but it only models room temp performance, but it seems worst case as it shows about 650mV at 4mA.

     TLV170X TINA-TI MACRO and Reference Design

  • 0 in reply to Paul Grohe
    Prodigy 110 points

    Hi Paul 

    I would like to know what is the behavior of the TLV1704-SEP OPEN-Collector output between 0 and 2.2V (supply ramp-up) ?

    Is it possible to get some current drained by the TLV1704 in normal operation? 

    Figure 17 Short Circuit Current shows that some current can go out when output is shorted

    let me know if there is a configuration that could predict completely the output behavior ?

    thanks

    Yves

  • 0 in reply to Yves Theroux
    TI__Genius 10485 points

    Hello Yves,

    We are currently looking into your follow-up question and we will get back to you soon.

    Kind Regards,

    Joe

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (www.ti.com/.../important-notice.shtml)

  • 0 in reply to Yves Theroux
    TI__Mastermind 49906 points

    Hello Yves,

    I cannot get into internal details, but there is some current that "leaks" (sinks) into the output as part of the ESD protection circuit *IF* the pull-up voltage is higher than the supply voltage and the output is high.

    Shorting the output to ground will hot harm the device as it is open collector (cannot source large currents).

    The TLV1704 does not have a defined power-up state, so we cannot state what it will be when below Vcc min. But the trend is that the output will be "high-Z" (high) up until the device starts to "wake up" about 1.4V, where it can start responding to the input conditions. Again, this is operation below the specified range and power-on behavior is not warranted.

    If you do need controlled start-up, see the newer devices such as the TLV7021 family or TLV9024 and LM339LV which have specified power-on behavior.