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Improved ratings typify 4-channel protection array

Posted: 18 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:ESD? Littefuse SP725? diode arrays?

Littelfuse Inc. has beefed up its SP72x series of SCR diode arrays for ESD and other overvoltage protection of interface circuits used in telecommunications and data communications applications. The 4-channel SP725 is developed for protection of microprocessor/logic inputs, data bus lines, analog device inputs and other voltage clamp applications.

Littelfuse said the SP725 surpasses the closest competition for several ratings. These include an operating voltage range of 2-30V, a surge current of 14A with an 8 x 20?s waveform, a 2ns rise time, 5pF maximum input capacitance and typical leakage current of 5nA, 20nA maximum.

The thyristor-based design of the SP725 silicon diode array uses two bipolar SCR/diode structures to protect each of the four inputs (typically external signal or bus lines). Its operation is similar to a steering diode, but offers lower capacitance and leakage current for a given impulse rating. This means less chance of communication signal distortion, said Littelfuse.

Each SCR structure is triggered on by any current that biases the SCR into conduction against the supply rails. These internally triggered SCRs are said to offer improved impulse protection compared to conventional diode offerings. The device can be used in a broad range of applications including medical imaging, medical analyzers, industrial equipment, test equipment and automotive modules.

Transients are diverted around the SP725 silicon diode array input lines to the power supply rails (or ground). Once the discharge current falls below the forward bias levels, the device stops conducting and returns the input lines to their previous condition. This design can protect up to 30V and will protect at around one volt beyond the supply rail voltage (V+ or V-). The closest competing device protects only at its breakdown voltage of 18V, said Littelfuse.

The SP725 meets the test requirements of IEC 61000-4-2 for 8kV direct discharge and 15kV air discharge. It also meets the requirements of MIL-STD-3015.7 for 25kV testing. The SP725 is available in an 8-lead, narrow body SOIC package, which can be supplied in tape and reel. It is RoHS-compliant and Pb-free.

- Gina Roos

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