ICs & Semiconductors
A variety of protection ICs are available on the market and ar first glance, they look similar - with compatible pin configuration and functionality - but it is important to closely observe their parameters. An incorrectly selected device can interfere not only in the normal functionality of the system but may also be worthless in providing adequate protection. Among the key criteria to consider are:
Signal Integrity - The transparency of
Oxide Varistors (MOV). Gas tubes and MOVs have their advantages in certain applications which require higher surge capabilities, but there are distinct capabilities of silicon devices which make them unique with regards to non–silicon- based solutions. The performance of gas tubes and MOVs degrades with every surge, whereas silicon ICs do not. The breakdown voltage of MOVs and gas tubes is unstable and also increases with
every pulse, whereas the breakdown voltage follows a predefined path in silicon ICs with little deviation from stated value.
Silicon devices also have fast response time, Vbo independent of dv/dt, high reliability with no ageing, and smaller footprints. These advantages make silicon protection ICs the favorite for applications where surge capabilities are not very high.
the protection device is an important criterion. Protection ICs should not interfere with the normal functioning of system. Critical parameters which impact transparency are low leakage current, low capacitance, and high bandwidth. Robustness - Since a protection IC is the insurance of an electrical circuit, it should protect the circuit even in adverse conditions. The device should have high surge capabilities and should not degrade with changes in temperature. Package flexibility - Package flexibility is another important feature of protection devices. New protection ICs come with pass-through rails which means the rails don’t have to be cut to embed protection ICs in the design. This flexibility allows the development and validation of the functionality of the system without the protection IC on board. The protection can then be added during the surge tests and production stage. The pass-through rail feature also saves PCB space and provides the option of adding protection to already developed products. Investment in protection ICs is not a waste of money. In fact, it can prove to be
a money-saver. This can be understood through a typical industry scenario. Suppose a firm is producing a million
boards per month and gets 1% as field returns. Out of the total returns, 45% have been detected to be caused by ESD damage that could have been protected. So, 4.5 thousand boards have to be repaired. If the cost of field service - from shipping damaged boards from retail to service centre, and then providing a repaired box from service centre to the customer - comes out to be $100, the total cost incurred by the company is going to be $450,000.
This scenario could have been avoided by using protection ICs – typically 3 ICs per board at $0.1 each. Thus, the cost of protection ICs for a million boards comes out to be $300,000. Typically, protection ICs not only save money for the manufacturer but also help to avoid the high risk of damage to a brand’s image. Protection ICs have made it possible to make electronics devices rugged. These ICs can protect costly electronic devices from damage because of ESD or EOS. At the same time, continuous innovation has made it possible to make them transparent to the normal function of devices. Investment in protection ICs may add to BOM cost at the beginning, but the advantages - avoiding returns and saving brand image - can have a dramatic effect.
STMicroelectronics |
www.st.com
Vishal Goyal is Technical Marketing Manager, STMicroelectronics Marketing
www.cieonline.co.uk
Components in Electronics
November 2011 29
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46