Component Selection (i) ESD, TVs reference

Many developers have encountered this situation: in the laboratory development of good products, testing completely through, but to the customer in the hands of a period of time, there is abnormal phenomenon, even the product failure needs rework, and the failure rate is often not high (less than 1%). In general, most of the above problems are caused by surge impact, ESD impact and so on.

ESD suppressor is currently the latest generation of anti-static products (98 from the military to civilian, the current industry has been fully rolled out), by the polymer (polymer) voltage mutagenesis materials and high-power molecular material core made of a new solid electronic components. Its biggest feature is the physical discharge without the service life limit, coupled with its rapid reaction (<1 NS), ultra-low capacitance (<0.15PF), ultra-low leakage current (<1NA), high signal fidelity, damage to open state and its excellent cost-effective advantages, In recent years, the traditional Zener diode (TVS) components have been gradually replaced.

2. What are the key parameters for the selection of ESD devices? What does this parameter stand for?

The biggest difficulty in choosing the right ESD protection device is to make it easy to identify which device provides maximum protection. The system vendor typically compares the ESD protection device with the ESD rating (or nominal value) on the data sheet. In fact, the power of the device protection system from these ratings is simply not visible, and the key depends on its diode parameters.

1)working Voltage (VDC) is the operating voltage of the ESD element, which is the hard indicator of the selection, but not the key indicator, the working voltage of the selected component is equal to or greater than the operating voltage of the component use position, such as the operating voltage of the USB is 5 V, Just select an ESD element equal to or greater than 5V for protection

2)Trigger Voltage (Vv) is the ESD element of the trigger voltage, that is, the voltage to achieve this parameter component to work, so this parameter is a key factor to measure the sensitivity of ESD components, the lower the better, this parameter is the polymer of the difficulties of the ESD process.

3)clamping Voltage (Vc) is the ESD element clamp voltage, that is, the element triggered immediately after the high-voltage clamp in the range of the parameters passed to the ground, the lower the better the parameter, is also the difficulty of the process.

TVs as a traditional anti-ESD components, has incomparable advantages: low clamping voltage and quasi, but the industry standard requirements of the general chip must have anti-2K ESD capability, so the actual clamp voltage value appears to be less important.

The biggest drawback of ESD suppressors (polymer polymers) is that the clamping voltages do not get very low and are not as common as multi-channel TVs, but this is not the most important performance indicator.

The most important performance indicators for ESD-resistant components should be:

1. Reaction time: Because the speed of ESD is very fast---from a few ns to dozens of NS, so the response speed of anti-static components must be fast, from this point, polymer polymer materials ESD suppressor is the fastest reaction (<1 ns) anti-ESD components, and TVs based on the diode PN-junction reaction principle, has not technically breached this threshold

2. Service life: TVs based on the principle of diode operation, by increasing the number of ESD shocks (the best of about 3,000 electrostatic shock), its internal resistance ESR will continue to rise and lead to the element absorption of ESD is not completely and gradually fail, which is why the general electronic products in use for about one year will cause problems in one of the reasons While the ESD suppressor for polymer polymers works on physical properties to break the limits of service life (about 300,000 times the life of electrostatic shocks), the reliability of the components is greatly improved.

3. Price/performance ratio: TVs that are close to the performance of ESD suppressors are several times higher.

Choosing an ESD device should follow these requirements:

(1) Select electrostatic Protection device Note:

Clamp voltage do not exceed the maximum withstand voltage of the protected device

Circuit voltage does not exceed protection device operating voltage

Low capacitance, leakage current to minimize interference and loss

(2) Electrostatic protection devices should be installed as close as possible to the electrostatic input, away from the protected device

(3) Electrostatic protection devices must be connected to the Earth line, not the digital ground

(4) The circuit to the ground as short as possible, the distance between the electrostatic protection device and the protected line is as short as possible

(5) Try to avoid being protected and unprotected line-by-side routing

Component Selection (i) ESD, TVs reference