CLP270M-TR 데이터 시트보기 (PDF) - STMicroelectronics

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CLP270M-TR

OVERVOLTAGE AND OVERCURRENT PROTECTION FOR TELECOM LINE

STMicroelectronics 

CLP270M

The figure 2 summarizes the firing modes of the CLP270M which basically hold the SLIC inside its correct

Fig. 3 : CLP270M in line card

Fuse

TIP

FS

RING

Fuse

I

Rsense

TIPL

TIPS

Overcurrent

detector

OR

SW3 SW1

SW4 SW2

OR

Overvoltage

detector

Overvoltage

reference

(+/- 270 V)

Overvoltage

detector

Overvoltage

reference

(+/- 270 V)

GND

Overcurrent

detector

RINGL

Rsense

RINGS

1

Rp

2

1

Rp

2

-Vbat

External

voltage

reference

-Vbat

(*)

TIP

SLIC

RING

Ring

Generator

(*) LCP1511D or THDT series or LCDP1511D

voltage and current values.

2.2 Application circuit: CLP270M in line card.

Figure 3 above shows the topology of a protected analog subscriber line at the exchange side. The

CLP270M is connected to the ring relay via two balanced Rp resistors, and to the Subscriber Line Interface

Circuit. A second device is located near the SLIC : it can be either a LCP1511D, a THDT series or a

LCDP1511D.

These two devices are complementary and their functions are explained below :

s The first stage based on CLP270M manages the high power issued from the external surges. When

used in ringing mode, the CLP270M operates in voltage mode and provides a symmetrical and

bidirectional overvoltage protection at +/- 270 V on both TIP and RING lines. When used in speech

mode, the CLP270M operates in current mode and the activation current of the CLP270M is adjusted

by Rsense.

s The second stage is the external voltage reference device which defines the firing threshold voltage

during the speech mode and also assumes a residual power overvoltage suppression. This protection

stage can be either a fixed or programmable breakover device. The THDTxx family acts as a fixed

breakover device while the LCP1511D or the LCDP1511D operates as a programmable protection.

Thanks to this topology, the surge current in the line is reduced after the CLP270M. Because the

remaining surge energy is low, the power ratings of Rp, the ring relay contacts and the external voltage

reference circuit can be downsized. This results in a significant cost reduction.

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