About the minimum input of AC recitified of TOP242G

We don't provide Pspice models of our devices. However, if you can give me some general specs for what you're trying to do, I'd be happy to put together a quick design for you and recommend which one of our products would be best suited for your application.

-The Traveler

ok, I know, the attachment is my design, please give me your advice and send my mailbox: jerry.ruan@sick-rnd.com, thanks a lot.

Jerry - 

I really not sure how to advise you on the schematic you sent me.  What did you use to come up with this design?

Also, is the 24Vac input a typo?  Should it be 240-250Vac input?

Given the information you've sent, TOP242G really isn't going to be a good device to use.  It's rated for a much higher power level than you're using in this application.  I think one of our LinkSwitch-CV parts would be a better fit for this application.

I've attached a quick design using LinkSwitch-CV.

-The Traveler

First the use of this schematic is AC/DC, before the input to TOP242G, we had rectified the AC power input;

Second, about the AC input range, our requirement is 24V~240V AC, so it is wide range input, not only the 220V input;

Third one is your sent me a attachment, but I think it not fit my requirement, because we don't need the transformer, our PCB board very small, only about 30mm*16mm, we use TOP242G only for the buck regulator, no isolate requirement.

I have found a similar design using TOP222P in your web, I had added it as the attachment, but I don't know the difference between TOP242G and TOP222P, can you give me some explanation, because i want to compare these two devices in your web, but can't find method. By the way, the TOP242G has stopped production? why i can't found it in your product catalog?

The reason I communicate with you is about the value of Capacitor 2 in my design sent to you before, we want to minish the Capacitor 2 value from 4.7uF now to 3.3uF, because we had used and confirmed that there is no problem in the existing product using 4.7uF, but we don't know if we only change the Capacitor 2 value, whether it will influence the output. This is our problem.

Of course, if you have some new replacement component for TOP242G with smaller package, please tell me, thanks.

 There are quite a few differences between TOP222 and TOP242.  They're in the same product family but they have many different features.  Fortunately, you can put the TOP242 into three-terminal operation mode by connecting the M pin to SRC as you've already done in your schematic. In this mode of operation, the most notable difference is the MOSFET current limit of 450 mA vs 500 mA in the TOP242.

 TOP242 is still being manufactured but it isn't one of our "current" products becuase it was released quite a while ago.

For the input capacitor, you will need to experiment and find what works best for your application.  The main consideration is that the drain voltage on the controller needs to stay above a certain voltage threshold.  This is because the controller inside TOP242 pulls off a small amount of current from the drain pin to power the controller circuitry.  If the input voltage falls below this threshold, the device could possibly stop switching or enter auto-restart.

As this isn't a "typical" design or use for one of our TopSwitch products, I can't give you a definite answer on what size capacitor to use.  It should be pretty easy to verify experimentally though.

-The Traveler

The minimum Drain Supply Voltage for TOP242G is 36V.  The device will most likely start up with less voltage but proper operation isn't guaranteed below  that level.

-The Traveler

Hi, like the below attachment file, in the schematic, c2 is a polarized capacitor, my problem is:

1) the C2 is a aluminum electrolytic capacitor or tantalum capacitor?

2) as far as i know, the polarized capacitor can't bear reverse voltage, but in our use, when the top222p at "ON" state, the inverse side of the C2 will have much high voltage reference the positive side(fixed at 5.7V) of C2, of course, this inverse voltage is not DC, but the switching frequency is very high(100khz), I want to if we use polarized capacitor in this point, is there any risk?

thanks a lot!

 C2 is an aluminumelectrolytic.  When the IC MOSFET is on, the control pin is still held ~5V above the source pin.  So you should be having any reverse polarity problems.

-The Traveler