PRF18BE471RB5RB datasheet(8/104 Pages) MURATA

8 / 104 page

R90E.pdf

Sep.24,2012

!Note • Please read rating and !CAUTION (for storage, operating, rating, soldering, mounting and handling) in this catalog to prevent smoking and/or burning, etc.

• This catalog has only typical speciﬁcations. Therefore, please approve our product speciﬁcations or transact the approval sheet for product speciﬁcations before ordering.

Technical Terms

Load Curve of Circuit and Voltage - Current Characteristics

of POSISTOR

1. Protective Threshold Current

The maximum current value is called the "Protective

Threshold Current" for Voltage vs. Current characteristics

(static).

When smaller than the protective threshold current flows

in POSISTOR

r, it reaches its stability (as shown in figure

on right) at the intersection (A) of the load curve (a) and

voltage-current characteristics of POSISTOR

r(c). And

POSISTOR

r works as a normal fixed resistor.

However, when larger than protective threshold current

flows, it stabilizes at the intersection (B) with the load

curve (b).

2. Protective Threshold Current Range

Protective threshold current varies depending on the

ambient temperature, resistance value, temperature

characteristics and shape. (see Figure on right) The

maximum value of trip current and the minimum value of

the hold current are in the range of ambient temperature

-10 to +60°C.

That is, when a current is smaller than the hold current,

POSISTOR

r works only as a fixed resistor. When larger

than the trip current flows, however, POSISTOR

protects the circuit from overload.

3. Operating Time

A period starting from the voltage input to the moment

current itself sharply attenuates is called "Operating

Time." Conventionally, operation time (t0) is determined

to be the period until inrush current (I0) decreases to a

level one half the original inrush current (I0/2).

I =

E - Vp

Load curve in normal state

(normal current)

Load curve in abnormal state

(abnormal current)

Voltage-current characteristics

of POSISTOR

Voltage (log)

Protective Threshold Current Range

1000

800

600

400

200

-20

Ambient Temperature (°C)

Protective Threshold Current

Hold Current

Trip Current

Operating Current

Time (sec.)

t 0

Operating Time

Basic Characteristics of POSISTOR

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