STLC3055N_09 datasheet(17/34 Pages) STMICROELECTRONICS

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STLC3055N

Application information

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5.2

External components list

In order to properly define the external components value the following system parameters

have to be defined:

●

The AC input impedance shown by the SLIC at the line terminals "Zs" to which the

return loss measurement is referred. It can be real (typ. 600

Ω) or complex.

●

The AC balance impedance, it is the equivalent impedance of the line "Zl" used for

evaluation of the trans-hybrid loss performances (2/4 wire conversion). It is usually a

complex impedance.

●

The value of the two protection resistors Rp in series with the line termination. The line

impedance at the TTX frequency "Zlttx".

●

The metering pulse level amplitude measured at line termination "VLOTTX". In case of

low order filtering, VLOTTX represents the amplitude (Vrms) of the fundamental

frequency component. (typ 12 or 16 kHz).

●

Pulse metering envelope rise and decay time constant "

τ".

●

The slope of the ringing waveform "

ΔV

TR/ΔT ".

●

The value of the constant current limit current "Ilim".

●

The value of the off-hook current threshold "ITH".

●

The value of the ring trip rectified average threshold current "IRTH".

●

The value of the required self generated negative battery "VBATR" in ring mode (max

value is 70 V). This value can be obtained from the desired ring peak level +5 V.

●

The value of the maximum current peak sunk from Vpos "IPK".

Table 10.

External components

Name

Function

Formula

Typ. value

RRX

Rx input bias resistor

100 k

Ω 5%

RREF

Bias setting current

RREF = 1.3/Ibias

Ibias = 50

μA

26 k

Ω 1%

CSVR

Negative battery filter

CSVR = 1/(2

π ⋅ fp ⋅ 1.8 MΩ)

fp = 50 Hz

1.5 nF 10%

100 V

Ring Trip threshold setting

resistor

RD = 100/IRTH

Ω < RD < 5 kΩ

4.12 k

Ω 1%

@ IRTH = 24 mA

CAC

AC/DC split capacitance

μF 20% 15 V

@ RD = 4.12 k

Line protection resistor

Rp > 30

Ω 1%

RLIM

Current limiting programming

RLIM = 1300/Ilim

32.5k

Ω < RLIM < 65kΩ

52.3 k

Ω 1%

@ Ilim = 25 mA

RTH

Off-hook threshold programming

(ACTIVE mode)

RTH = 290/ITH

27 k

Ω < RTH < 52 kΩ

32.4 k

Ω 1%

@ITH = 9 mA

CREV

Reverse polarity transition time

programming

CREV = ((1/3750) ·

ΔT/ΔV

TR)

22 nF 10% 10 V

@ 12 V/ms

RDD

Pull up resistors

100 k

CVCC

Internally supply filter capacitor

100 nF 20% 10 V

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