PolyDiodeTM
Electromagnetic Compatibility
Countermeasure for Transient Surge and Static Electricity
DESCRIPTION
Because electronic systems have been migrated to miniature levels in compact
size,
more and more devices require protection against ElectroStatic Discharge (ESD)
and surge, and increasingly become important.
PolyDiodes are bi-directional transient voltage suppressor devices made of poly- crystalline mixed oxide ceramics, which offer rugged protection and excellent electrostatic absorption and pulse noise absorption in a small package. These devices not only require significantly smaller space than silicon TVS diodes, but also offer greater circuit board layout flexibility for the designer.
Previously, the internal bus lines of mobile equipment and in LCD panels, key switches, battery terminal, microphone, or headphone terminal were protected from ESD surge by Zener diodes or silicon TVS diodes. However, unlike a Zener diode or a TVS diode, a PolyDiode does not require being combined with an EMC capacitor because in its off state the network acts like an EMI filter. Again, thanks to PolyDiode possessing excellent response characteristics and ESD absorption power, its functions are more than that of a MLV or a Zener diode and a Silicon TVS diode.
ELECTRICAL ADVANTAGES
• Extra low clamping voltage
The PolyDiodes have an excellent clamping voltage capability (Typical ratio of clamping voltages to breakdown voltages are between 1.25 and 1.60), that is equal to or better than Zener diodes and Silicon TVS diodes.
The MLV’s clamping voltage is typically higher than comparable PolyDiodes or Silicon TVS diodes. MLVs are mainly uses for ESD on less sensitive lines where their higher clamping voltages can be tolerated.
• Low electrostatic capacity
PolyDiode exhibits a very low capacitance which can be used as an EMI/RFI filter, adequate to support high speed signal line/ data bus use (ESD protection for USB2.0 interfaces and ICs ), without performance distortion and/or attenuation.
The capacitance of a Zener diode or a TVS diode can be made lower by narrowing its connection area, but a lowered wattage or a lowered ESD resistance is unavoidable.• Excellent ESD Endurance capability
Withstands ESD Durability test severity of IEC 61000-4-2 level 4 (8KV contact ESD, 20 shots: 10 positive, 10 negative polarities; repetition rate 1 . sec.-1) without damage or degradation. The electrical performance is Excellent.• PolyDiode has the fastest response time in the industry < 0.5 ns
Poly Diode has no follow on current and their parasitic inductance is very low, which results in response times of < 0.5 ns. Zener diode and silicon TVS diode have a larger parasitic inductance, and the typical values of response times are between 0.8 and 3 ns.• Excellent surge suppression capability
PolyDiode keeps symmetrical I-V characteristics even after suppressing extremely fast voltage transients, including electrostatic absorption and pulse noise absorption.
The Zener diodes or TVS diodes are not sufficient for a peak surge current.• Electrical performance in changes of temperature
The electrical characteristics of PolyDiode include operating voltage, surge current, energy absorption and power dissipation remain unchanged up to temperature of 85℃ of working condition. On the contrary, the TVS diodes start to deteriorate at temperature of 25℃.• Low leakage currents
The leakage currents less than 5 μA for PolyDiode are relatively much lower than those of less than 100 μA for TVS diodes.
PHYSICAL ADVANTAGES
• Excellent mount reliability
The PolyDiodes electrodes are adopted Nickel/ Tin electroplating achieved good solderability and solder heat resistance.• Economical cost in mounting process
Since PolyDiode is bi-directional component, it is easy to mount them onto the circuit boards. In contrast, the mounting machine must position TVS diode with correct polarity due to their natures in unidirectional device. This may cost higher error probability during the mounting process.
• RoHS Compatible
APPLICATIONS
• Pulse noise absorption
• Electrostatic absorption