• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 47 subscribers
  • Views 1182 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Regenerative comparators

Paul Beijer
Intellectual 460 points

Other Parts Discussed in Thread: NE555, TLV3501

Hello all,

I'm not sure if I posted this question in the correct forum, but I couldn't find a forum dedicated to analog comparators.

My question is not so much related to a specific part number. I was wondering why regenerative latched comparators are not offered as discrete parts by any manufacturer. They are a key circuit structure in many high speed A/D architectures but you can't buy them as a component. 

These would open a host of innovative applications where high speed analog comparing and low power are key requirements.

Just wondering......

Regards,

Paul Beijer

--

  • 0
    TI__Guru**** 174676 points
    Paul,

    NE555 is a dual input latched comparator. This is not exactly high speed however.
    I believe you are in the wrong forum to discuss high speed comparators, or A/D converters.
  • 0 in reply to Ron Michallick
    Intellectual 460 points

    Hi Ronald,

    Thanks for your reply.

    In fact what I'm using now is a circuit similar to what's inside a 555. I use a normal linear comparator (TLV3501)  followed by a D type flipflop.

    This performs the functionality I need but it has a fundamental trade-of between Iq and speed.

    Regenerative comparators use a different circuit topology with inherent positive feedback and are essentially zero power when in either stable state. Power is only consumed during transitions.

    For prototyping I used matched mosfet-arrays to build my own, but that's way too bulky and pricey for actual products.

    I tried to find a forum on comparators but could't find one. If there is one, could you please give me link?

    Regards,

    Paul

    --

  • 0 in reply to Paul Beijer
    TI__Guru**** 174676 points
    Paul,

    There is hi speed amp forum, but low ICC might not be available.
    e2e.ti.com/.../

    There is also logic forum, low ICC and hi speed is there, however precise thresholds are not.
    e2e.ti.com/.../
    Would Schmitt triggers or unbuffered gates (like ones used for crystal oscillators) in a regenerative feedback work?
  • 0 in reply to Ron Michallick
    Intellectual 460 points

    Hi Ronald,

    Logic inputs can be used as comparator for some applications where precision is not required, but when operating logic inputs near their threshold level then it's not so low-power anymore. Both P and N channel MOS will partly conduct in that case and the Icc goes up into the mA range.

    The regenerative comparator topologies are widely used in A/D converters, so maybe a forum dedicated to those is a good place to start for my question.

    Regards,

    Paul

    --