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We recently, worked on a commercial project with target of sealing 1000 + board... currently, we are prototyping a customized teeny board based on our design... we faced problem with bootloader ic and i figured out, that bootloader is not open source... while searching in main page, we found the ic of the bootloader is in your product list which was positive point... i decided to take out the bootloader ic from one of my teensy board and put it in my board however it was not working... i put the ic back into your teensy and it worked... if the schematic is correct, what do think the problem is?
Not enough information. On which Teensy is your project based? Some are for example finicky about starting the Xtal oscillator if the PCB layout does not correspond to the NXP guidelines. Others are unhappy when the power supply does not ramp up quickly enough. A floating reset pin can also cause strange behavior. Afterwards, using the search function of this forum, you'll find hints how to diagnose and fix all these.
Thanks for the fast response... in fact, we replicate teensy 3.2 schematic... we also used your bootloader ic" as i said, we take it from one of our teensy boards" but also it doesn't work..
What do you mean exactly by "it doesn't work" ? If you have a bare, never programmed MK20DX256 (Teensy3) and a known working boot loader, the first question is :
Is it recognized as a USB raw HID device when you connect it to a computer?
If yes, where is the problem? Compile and upload the test blink sketch and proceed to further testing.
If no, what do your oscilloscope or logic analyzer tell about the communication between the boot loader and the MK20? What happens at the MK20 reset pin?

You'll have to check your custom Teensy systematically for static voltages (5V before the voltage regulator and the different 3.3V rails afterwards) and for dynamic signals (data lines between boot loader and MK20, reset pins) and so on to make sure that everything corresponds to the schematic and to the expected boot sequence. Only you have the faulty board in your hands, so it's only you who can do that diagnosing. And as I told you, there is a search function in these forums, where you can find information how other people solved their problems after identifying them, i.e. by searching for "custom+teensy".

There is a good article on the www where someone writes about building a custom Teensy board and potential problems. It is about the older Teensy 3.0/3.1 and the TAN54 boot loader, but the principle remains the same for Teensy 3.2 with the MKL02/04 boot loader:
Thank you so much... very informative... well done... i will check it morning.....
one last question, if someone wants to develop his project with your company "customize board" is there a minimum order? Or i have to send email?
Scroll down to the bottom of the MKL02 page, until you find the "Troubleshooting" section:

The most common problems and solutions are explained in that section.

The very first troubleshoot step is the measure the voltage on the Program and Reset pins. If the MKL02 chip is running, it will turn on the internal pullup resistor on Program, so you should see 3.3V on that pin if the button is not pressed.

A completely blank MK20 chip will repetitively watchdog reboot. With a voltmeter, you will see a voltage like 0.1 to 0.3V. With an oscilloscope, you'll see it's actually pulsing. If the MK20 has a normal program, you should see 3.3V on Reset.

If the MKL02 is running properly, it should detect when Program is low and pull Reset low. If the MK20 is blank, you should still be able to observe 0.1V become 0 volts. This simple test can at least confirm the MKL02 is alive and running.

Many things can go wrong. If you are completely stuck, please read that Troubleshooting section and click the links to the forum conversations. On this forum, you can see how other people perceived the problem before it was diagnosed and understoood. Maybe some of those experiences of other people can help you find a path to fixing your design?