Reduce & Test the chip damages by three deatails

We have encountered such a problem, the chips suddenly broken down and programs can not be inputted.But even worse,we can not find the reason after taking a long time to test.For personal developers, maybe it is can be handled easily ,which they need to do just change a part of the chips,although it is still a terrible thing.But for large-scale manufacturers , this is a serious problem. 

The following contents are about how do some small details ruin your chips, maybe it can help you to quickly find the errors.

1. Supply voltage

Maybe you would laugh and feel puzzled.My system board chip‘s power supply is LDO output, it is pretty stable, how will it program the chips？

For many development boards or our own design of the system board,the VCC of the debug interface generally directly pin out from the chips’ power pins. if the programmer power supplies instability, it is likely to cause overvoltage damage to the chip . The following figure shows the voltage range of an MCU:

Lacking stability in the programmer supply voltage, the chip will be easily damaged.

2. Chip encryption

It's easy for the developers to ignore an important function that the chip provides for us, but it's pretty important when your products have a powerful potential market. Encryption can prevent your code being copied. Chip encryption generally has 3 level.From the Cypress manual can get a clear description.

OPEN: chip is not protected.That means you the software in the chip can be directly copied .

PROTECTED: Chip with read protection, meaning that no one can read out the chip data, but the chip can be erased and be used again.

KILL: Your chip is "killed”, no one can read the chip data, but this time, the entire chip erase does not work, your chip can not re-burn, But it is not really "dead", the software written still can operate.

It is important to note that these protections are only valid after power-up again.

Another interesting situation occurred in mass production.Due to various factors,sometimes, the chip would be interrupted when writing the program, and the bits of chips encryption is always on the first half. For some chips‘ writers, they would write the program according to the writing files，which may cause that,the chip has been KILL, and the writing program also be interrupted.

3.The high voltage Program

Some OTP (one-time programmable) chip may need to program the high voltage to write the data,about 6、7 volt,sometimes maybe peaks at 10 volts . But for many chips,the voltage level has been considered as high-voltage.even those OTP chip needed high-voltage can not bear for a long time.As a result, some chips will set the longest time of high-voltage load, once more than this limitation,the OTP part may be permanently damaged. Some programmers will provide high-pressure programming output function, automatically switch the programming voltage.For those who do not have this function should pay more attention when programming the chips.

In addition, there are many other factors that will damage your chip, such as electrostatic protection , the chip storage humidity, the temperature, the chip welding temperature,etc. To improve the rate of high-quality products, we need to draw attention to above details,as well as using a holistic view to produce and test the products.

 Author ：Ferdinand Rinol— WIN SOURCE ELECTRONICS