UCLAMP3301P.TCT データシートの表示（PDF） - Semtech Corporation

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UCLAMP3301P.TCT

Low Voltage μClamp™ for ESD and CDE Protection

Semtech Corporation 

uClamp3301P

PROTECTION PRODUCTS

Applications Information

Device Connection Options

The μClamp3301P is designed to protect one data or

I/O line operating at 3.3 volts. It will present a high

impedance to the protected line up to 3.3 volts. It will

“turn on” when the line voltage exceeds 3.5 volts. The

device is unidirectional and may be used on lines

where the signal polarity is above ground. The cathode

band should be placed towards the line that is to be

protected. These devices should not be connected to

DC supply rails as they can latch up as described

below.

Device Schematic & Pin Configuration

Pin 2

Due to the “snap-back” characteristics of the low

voltage TVS, it is not recommended that the I/O line be

directly connected to a DC source greater than snap-

back votlage (VSB) as the device can latch on as

described below.

EPD TVS Characteristics

The μClamp3301P is constructed using Semtech’s

proprietary 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 ava-

lanche technology impractical for most applications.

However, by utilizing the EPD technology, the

μClamp3301P can effectively operate at 3.3V while

maintaining excellent electrical characteristics.

Pin 1

EPD TVS IV Characteristic Curve

IPP

ISB

IPT

VF

IR

VRWM VSB VPT VC

The EPD TVS employs a complex nppn structure in

contrast to the pn structure normally found in tradi-

tional silicon-avalanche TVS diodes. Since the EPD

TVS devices use a 4-layer structure, they exhibit a

slightly different IV characteristic curve when compared

to conventional devices. During normal operation, the

device represents a high-impedance to the circuit up to

the device working voltage (VRWM). During an ESD

event, the device will begin to conduct and will enter a

low impedance state when the punch through voltage

(VPT) is exceeded. Unlike a conventional device, the low

voltage TVS will exhibit a slight negative resistance

characteristic as it conducts current. This characteris-

tic aids in lowering the clamping voltage of the device,

but must be considered in applications where DC

voltages are present.

When the TVS is conducting current, it will exhibit a

slight “snap-back” or negative resistance characteris-

IF

tics due to its structures. This point is defined on the

curve by the snap-back voltage (VSB) and snap-back

current (ISB). To return to a non-conducting state, the

current through the device must fall below the ISB

(approximately <50mA) and the voltage must fall below

the VSB (normally 2.8 volts for a 3.3V device). If a 3.3V

TVS is connected to 3.3V DC source, it will never fall

below the snap-back voltage of 2.8V and will therefore

stay in a conducting state.

© 2008 Semtech Corp.

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