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PROTECTION PRODUCTS

PROTECTION PRODUCTS

SLVU2.8

Applications Information (continued)

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EPD TVS VI Characteristic Curve

The SLVU2.8 is constructed using Semtech’s propri-

etary EPD technology. The structure of the EPD TVS is

vastly different from the traditional pn-junction devices.

At voltages below 5V, high leakage current and junction

capacitance render conventional avalanche technology

impractical for most applications. However, by utilizing

the EPD technology, the SLVU2.8 can effectively

operate at 2.8V while maintaining excellent electrical

characteristics.

The EPD TVS employs a complex nppn structure in

contrast to the pn structure normally found in tradi-

tional silicon-avalanche TVS diodes. The EPD mecha-

nism is achieved by engineering the center region of

the device such that the reverse biased junction does

not avalanche, but will “punch-through” to a conduct-

ing state. This structure results in a device with supe-

rior dc electrical parameters at low voltages while

maintaining the capability to absorb high transient

currents.

The IV characteristic curve of the EPD device is shown

in Figure 1. The device represents a high impedance

to the circuit up to the working voltage (V

transient event, the device will begin to conduct as it is

biased in the reverse direction. When the punch-

through voltage (V

low impedance state, diverting the transient current

away from the protected circuit. When the device is

conducting current, it will exhibit a slight “snap-back” or

negative resistance characteristic due to its structure.

This must be considered when connecting the device

to a power supply rail. To return to a non-conducting

state, the current through the device must fall below

the snap-back current (approximately < 50mA).