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Set-top Box Application

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Protection Area

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USB 2.0 Port Protection

Problem: Inductive voltage spikes and overcurrent from a short-circuit

When an unsuitable or faulty USB cable is plugged into the USB port, the applied voltage, polarity and permitted current may exceed the specifications of the power regulation circuits. This can damage the equipment and could become a safety concern.

Solution: PolySwitch and PolyZen devices.

PolySwitch devices limit the flow of dangerously high currents during fault conditions and reset back to normal operating mode once the fault condition is removed; while PolyZen devices help clamp the voltage and shunt excess power to ground .


	Read more about the Raychem Surface-mount (SMD) PolySwitch device Applicable Products: decaSMD, nanoSMD, microSMD, miniSMD, SMD, SMDH. Download SMD Datasheet - (pdf 440KB) Agency Recognition: UL E74889, TÜV R9872049, R9872048, R2172061, CSA 078165_C_000.

	Read more about the PolyZen device Applicable Product(s): ZEN056V130A24LS, ZEN132V130A24LS Download PolyZen Datasheet - (pdf 455KB)

Problem: Electrostatic Discharge (ESD)

USB 2.0 protocol allows for data transfer rates of up to 480Mbps and supports plug and play hot swappable installation and operation. As a result of the increase in speed, low capacitance ESD protection of the bus is needed to maintain data integrity between devices in the network.

Solution: PESD

Extremely low capacitance ESD protection devices (PESD) help shunt ESD away from sensitive circuitry in electronic devices without inducing signal distortion. PESD, which is a low capacitance (typically 0.25pF) ESD protection device, is capable of withstanding numerous ESD transients, and is a RoHS & IEC61000-4-2 compliant device having low leakage current and low clamping voltage.