UCLAMP3301H.THT データシートの表示（PDF） - Semtech Corporation

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UCLAMP3301H.THT

Low Voltage μClamp™ for ESD and CDE Protection

Semtech Corporation 

uClamp3301H

PROTECTION PRODUCTS

Applications Information

Semtech Low Voltage TVS

Conventional TVS diodes are silicon avalanche, p-n

junction devices designed to operate at voltages as

low as 5 volts. However, many of today's

semiconductor devices operate at voltages below 5

volts, and thus require lower voltage protection

devices. Unfortunately, for operating voltages below 5

volts, conventional TVS diode technology becomes

impractical. This is due to the adverse effects of high

leakage current and high capacitance caused by the

high impurity concentrations that are needed to lower

the device voltage below 5 volts. Semtech's

proprietary low voltage EPD device technology was

developed to provide protection for today's circuits

operating at voltages below 5 volts. Unlike

conventional TVS diodes, the EPD device utilizes a

complex four layer (n-p-p-n) structure. The

construction of these devices results in very low

operating voltage without the adverse effects

mentioned above.

PRELIMINARY

Device Operation

Since the EPD TVS devices use a 4-layer structure,

they exhibit a slightly different IV characteristic curve

when compared to conventional devices. Figure 1

compares the IV characteristic curves of a low voltage

TVS with a working voltage (V ) of 3.3 volts to a

RWM

conventional device with a working voltage of 5 volts.

During normal operation, each device represents a

high-impedance to the circuit up to its working voltage.

During an ESD event, they will begin to conduct and

will enter a low impedance state. For the 3.3 volt

device, this happens when the punch-through voltage

(VPT) is exceeded. Unlike a conventional 5 volt device,

the low voltage TVS will exhibit a slight negative

resistance characteristic as it conducts current. This

characteristic aids in lowering the clamping voltage of

the device. However, the device can latch up if a DC

bias voltage is present. The reason being that in order

for the device to turn off, the voltage must fall below

the snap-back voltage (VSB). This value is normally a

minimum of 2.8 volts. If the device is biased above

the 2.8 volts, it will never fall below the snap-back

voltage and will therefore stay in a conducting state.

Low Voltage TVS

¾ Working Voltage (VRWM): Maximum rated

operating voltage at which the device will

appear as a high impedance to the

protected circuit.

¾ Punch-Through Voltage (VPT): Minimum

rated voltage at which the device will

become a low impedance (i.e. Minimum

Turn-On Voltage). When VPT is exceeded,

the device will conduct.

¾ Snap-Back Voltage (VSB): Minimum rated

voltage when the device is in a conducting

state measured at ISB = 50mA. This

voltage is less than the working voltage.

The voltage must fall below VSB for the

device to turn off.

¾ Clamping Voltage (VC): Maximum voltage

drop across the device at a defined peak

pulse current (IPP). This is the voltage

seen by the protected circuit during a

transient event.

0.05

0.04

0.03

Semtech 3.3 Volt TVS

0.02

0.01

0

0

1

2

-0.01

-0.02

-0.03

VSB

3

VRWM

VPT

4

5

6

VRWM

Voltage - V (V)

© 2012 Semtech Corporation

Figure 1 - 3.3 volt vs. 5 volt TVS IV Curve

4

Semtech

5 Volt TVS

7

8

VBR

9

10

www.semtech.com

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