Basics: Why Active low signals used?

Basics: Why Active low signals used?

Are you working on digital circuits? Then you must be using control signals in your design and must be hearing about terminologies like ACTIVE LOW, ACTIVE HIGH. We sometimes just follow the design recommendations and never think of the need to do it. Let us analyse the need for Active Low in our designs.

What is active low?
A general criteria while using any control signals (like Enable) is to make it HIGH from LOW state. But in some cases, like the chip select and reset it is in reverse, the signal will be initially HIGH and when it is turned LOW, it means that particular signal is asserted (when asserted, it changes the connected chip functionality as desired, can say connected chip changes state). Control signals which are used in this manner are termed Active Low. The terminology itself tells that signal is termed active when it is LOW.

How is Active LOW signal differentiated from Active HIGH signal?
The representation of the signal (as per the Active HIGH or Active LOW ) in the datasheet of that particular chip is different. Active LOW is represented by having a dash on top of the signal name. Chip Select if active low is represented as (CS).

Reasons for using Active LOW only:
  • Let us assume that you want to choose a device between n-channel MOSFET and p-channel MOSFET for your application. One would always prefer going for n-channel as electrons are the majority carriers in this type of device and have the highest mobility then holes. In this case, when the transistor is ON, the output is driven low. So, a normal condition is that output is high and when transistor in on output is low. This is one of the factor which makes implementation of active low state easy. Same mobility case applies to BJT also where NPN is preferred compared to PNP.
  • Active LOW always helps eliminate indeterminate states due to improper supply voltages. 
  • A genuine reason is that it is easier to pull down a signal than pulling it up. 
  • Under a Active low condition, it is always easy to use wired-or condition and apply common reset to several chips. So, fanout can be increased. Control signal count can be reduced.
  • For critical signals like Reset, it is always important that a state is maintained properly, if they are made active high, any noisy transitions may cause improper reset in the circuit. So, a state of high initially and then making it low to reset the chip can be the best option. 
  • Consider the sourcing capability for example of a micro controller which doesn't go beyond 10 mA. If you want to source more you may have to use an external driver. In these cases, it is always preferable that we use Active LOW. For digital circuits, sink current capability is more than source current.

Post a Comment

10 Comments

  1. I like the helpful info you provide in your articles.
    I will bookmark your blog and check again here regularly.

    I am quite certain I will learn lots of new stuff right here!
    Best of luck for the next!

    ReplyDelete
  2. The Positive Effects of Reiki for the Human Body

    Reiki is acknowledged for its positive results on the human body.

    However, a lot of people of people who have not yet experienced its power determine
    what exactly Reiki does and what its final results are.
    If you are enthusiastic about how Reiki can help you, then keep reading and discover what Reiki are able to do for your body, mind and soul.

    1. Increases one's body's ability to heal itself.
    Normally, our bodies has a defense system which functions good provided that the Ki flow is just not interrupted.
    When the Ki is no longer in a position to flow through our bodies,
    illnesses and diseases can appear. Reiki stimulates the flow of
    positive energy, thus enabling the body to heal itself and fight the
    external and internal attacks more effectively.

    2. Cleans our bodies of toxins. Because it
    acts on the physique, it can be one of the few complete detox
    programs one can follow. In addition to that it doesn't involve refraining from food or other type
    of activity. Yet, mental poison need to be banned from the individual's mind while they may have a negative impact
    upon the treatment.
    3. Promotes health, positive thoughts and relaxation.
    The principles of Reiki depend upon positive thinking, thus a satisfaction and relaxation is induced towards the individual.
    By removing negative energy and promoting feeling
    of peace, the healing process will probably be easier
    and shorter, no matter the illness or disease from where the average person suffers.

    4. Works around the gastrointestinal tract and enhances the benefic outcomes
    of almost everything someone ingests, from food and water to medicines and curative
    herbs. Thus, it could be proven to work as a complementary therapy for all those already taking medicine,
    but at the same time it really is ideal for maintain the individual's health in good parameters.

    5. Works on personal feelings, helping people overcome negative
    experiences from their lives and coping with unexpected or unpleasant situations off
    their lives. People with depressions, anxieties or suffering from stress is able to
    see dramatic improvements of these conditions after the Reiki sessions.

    6. Makes the transition from life to death much easier.
    It helps the soul transcend into immortality and your body feel less struggling with this transformation. This is why many Reiki adepts make use of
    the Ki to make their transition from world to a new smoother.



    Reiki offers healing for those forms of bodily conditions, and
    for the spiritual problems. It is like a best friend for all those people in need of assistance, however it may also relieve healthy people from quotidian stress and problems.



    You can understand more info here on website : https://new-giveaways.win/

    ReplyDelete
  3. Benefits of Magnetic Power Generator

    All all over the world shortage of power is a
    common problem which is why people are seeking some reliable and cheap
    electric source. Many folks are using magnetic generators and the reason behind this is
    that they get several benefits through them.
    This generator is very an easy task to install at your residence in a limited
    place without disturbing the initial settings in your home.

    All you need is a little spare space to setup this. This will help you to lessen your normal
    power bill. You can use this as a possible energy supplier for most in the
    times which means you don't need to switch time for your old means of power
    consumption. As soon as you begin using this source
    of energy in your own home you will see an evident saving with your income.

    It doesn't produce any harmful gases that may damage environment.
    In this generator, magnets will generate energy which is usable in any condition. The cost of having one of these power generator is not high in any respect.
    It is the cheapest supply of power generation nowadays in this era of technology.
    The main thing in this generator is a magnet which works as well as a small wheel.

    As you are already aware it is without charge and there is no third party involved
    in installing this generator, which means you won't need any maintenance from some
    expert. You can maintain it all on your own by cleaning it at regular intervals.
    This is the best thing to position at home being a
    electric source. It can retain the energy sufficient to take
    care of all the appliances of the house. A family of four years old to six is incredibly
    perfect for this type of energy generation device.

    No harmful rays with no complex electric motors could happen here so you shouldn't be worried about the security of your family and friends.
    Unlike other free electric generation devices, it doesn't need any solar technology or wind.

    It will develop its own without supply of external natural energy.
    Weather will not modify the performance or
    generation of energy out of this magnetic generator.

    As it doesn't depend on any external source this will be an uninterrupted supply of power generation.


    Check more info on site : http://magnets4energy.cf/

    ReplyDelete
  4. A Clever Way to Find Free Adult Chat Rooms!

    Chatting on the internet is hugely popular. The
    problem is you can find very few free adult forums
    where we can discuss adult topics. Due to their popularity, webmasters increasingly choose to charge to the service.

    In this article, become familiar with how to easily find hundreds of these chat communities,
    many of which are entirely free.
    It has grown to be nearly impossible to find good
    places for adults to have a chat. Most of this is due to the spread of instant messengers, virtual worlds, and social networks.
    The few good chat sites available are generally full or, worse still, full and intent on asking
    you to pay a subscription fee. To most people, it seems the
    times of good, fun, lively free places for adults to
    have an adult chat have died. Thankfully, there exists a significant clever means for us to still find good rooms.

    All of the big dating communities offer their members free adult boards.
    Now, I'm sure you might be thinking, "Yes, that dating sites also ask you for a subscription for these free rooms!"
    This is not forever the situation. Many such chat communities are free, others are free but have limited features for that non-paying
    members, and others still provide a cost-free service for
    women.
    The beauty of joining a large, well-known dating community is that you simply get given use of a tremendous adult chatting community
    that has hundreds, sometimes many people using it at any one time.

    Better yet, their rooms tend to offer users to be
    able to hook of their webcams. So you could be chatting away in a room
    and have the ability to click on a user profile
    watching them on the webcam, too!

    Free Adult Chat Rooms : https://goo.gl/ETrLYm

    ReplyDelete
  5. The Positive Effects of Reiki for the Human Body

    Reiki is renowned for its positive results on the human body.

    However, a lot of people of those that have never yet experienced its power determine
    what exactly Reiki does and what its benefits are.

    If you are enthusiastic about the way Reiki can help you, then keep reading and discover what Reiki are able to do for your body, mind
    and soul.
    1. Increases your body's power to heal itself. Normally, your body includes a defense system which functions good as long as the Ki flow is not
    interrupted. When the Ki is not really capable of flow through
    the body, illnesses and diseases can appear. Reiki stimulates the flow
    of positive energy, thus enabling one's body to heal itself and
    fight the bodily and mental attacks more effectively.

    2. Cleans one's body coming from all toxins. Because it acts about the human body, it
    is one of the few complete detox programs you can follow.

    In addition to that it does not involve refraining from food or
    some other sort of activity. Yet, mental poison should be banned from the individual's mind while they could have a negative impact upon the therapy.

    3. Promotes health, positive thoughts and relaxation. The principles of Reiki depend upon positive thinking, thus a peace of mind and relaxation is induced for the individual.
    By removing negative energy and promoting a feeling of peace, the healing process will
    be easier and shorter, regardless of illness or disease from where the person suffers.


    4. Works for the digestive system and improves the benefic effects of almost
    everything an individual ingests, from food and water to medicines and curative herbs.
    Thus, it could be used successfully as being a complementary therapy for
    anyone already taking medicine, but concurrently it is great for maintain the individual's health in good parameters.

    5. Works on personal feelings, helping people conquer
    negative experiences off their lives and coping with unexpected or unpleasant situations from other lives.

    People with depressions, anxieties or suffering from stress is able to see dramatic improvements of the conditions
    after the Reiki sessions.
    6. Makes the transition from life to death much simpler.
    It helps the soul transcend into immortality and one's body
    feel less being affected by this transformation. This is why many Reiki adepts utilize
    Ki to generate their transition from one world
    to another smoother.

    Reiki offers healing for all those varieties of bodily conditions, and for the spiritual problems.

    It is like a companion for those those people short of funds, nonetheless it
    may also relieve healthy people from quotidian stress and problems.


    You can see more details here on website : https://new-giveaways.win/

    ReplyDelete
  6. Adult Webcam Performer Tips - Make Your First $5000

    The adult web cam companies are one of the most lucrative
    opportunities you will find anywhere online today. As an web
    cam performer, you can make a per hour pay much like that regarding company executive;
    not only does it pay exceptionally well, but you can also acquire a great deal of time by not having to waste time commuting to be effective every day.

    Male or female, you can start setting up a substantial cost working from your
    comfort of your own property, with as low as couple of hours a day.

    How much you will make depends upon several factors like your physical attractiveness, your personality, and
    your willingness to do inside the private room. New adult webcam
    performers can expect to create $2000 to $5000 within their very first month working
    as few as 2 hours day, while top performing models will make over $20,000 on a monthly
    basis.
    You may think that doing its job a grown-up webcam performer is easy work, but you may not have what it takes to be a online model?

    Below will be the trade secrets for making your first $5000.


    Webcam Model Tip #1 - Have Fun
    Don't think of it as work. Think of it as flirting. Get on camera to have fun! Keep this your primary focus and you will have no problem
    making lots of money.
    Webcam Model Tip #2 - Be Prepared
    Never make your visitors wait. To stay on camera, keep your props, toys, or any changes in your outfit nearby so that you can won't
    need to go "off cam" to go get something.
    Webcam Model Tip #3 - Get Repeat Visitors
    Letting your clients know when you will end up back
    online (be it hours from now and other day) is an easy method of getting paying customers to
    return for more! And when one does set a period and date, be sure you
    be on time. This helps build trust using your customers, meaning more money for you personally.


    Webcam Model Tip #4 - Use Visitors Name
    In free chat, ensure you make use of customers' nickname.
    Visitors want to know that you're chatting for many years personally.

    Also, learn their real names. Paying customers want to
    feel an emotional link to you. Learning and memorizing names provide more repeat paying customers.

    Webcam Model Tip #5 - Look Sexy
    Wear makeup and still have flowing hair done. Also be sure to own a variety of sexy lingerie, outfits, look out of clothing, etc.
    and change outfits every day to offer customers variety.
    Bright colors such as red, orange, blue, green and pink get more customers,
    so that you should also be matching the colours of one's sheets/curtains along
    with your clothing.

    Chat with sexy girls and and handsome boys :
    http://live-cam-girls.ml/

    ReplyDelete
  7. At this momеnt I am ready to do my breakfast, when having my breakfast сoming yet again to read further news.

    ReplyDelete
  8. I blog often and I truly thank you for your content.
    This great article has truly peaked my interest.
    I will take a note of your blog and keep checking for new information about once per
    week. I opted in for your Feed too.

    ReplyDelete
  9. Thanks for sharing your info. I truly appreciate your efforts and I will be waiting for
    your next post thank you once again.

    ReplyDelete