STLC3075

Application information

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Table 15.

External components @gain set = 0

Name

Function

Formula

Typ. value

RS

Protection resistance image

RS = 50

⋅ (2Rp)

5 k

Ω @ Rp = 50 Ω

ZAC

Two wire AC impedance

ZAC = 50

⋅ (Zs - 2Rp)

25 k

Ω 1% @ Zs = 600 Ω

SLIC impedance balancing

network

ZA = 50

⋅ Zs

30 k

Ω 1%

@ Zs = 600

Ω

ZB(1)

Line impedance balancing

network

ZB = 50

⋅ Zl

30 k

Ω 1%

@ Zl = 600

Ω

CCOMP

AC feedback loop

compensation

fo = 250 kHz

CCOMP = 1/(2

π⋅fo⋅100⋅(RP))

120 pF 10 % 10 V

@ Rp = 50

Ω

CH

Trans-hybrid Loss frequency

compensation

CH = CCOMP

120 pF 10 % 10 V

Pulse metering cancellation

resistor

RTTX = 50Re (Zlttx+2Rp)

15 k

Ω

@ Zlttx = 200

Ω real

CTTX(2)

Pulse metering cancellation

capacitor

CTTX = 1/{50

⋅ 2π⋅ fttx [-lm(Zlttx)]}

@ Zlttx = 200

Ω real

RLV

Pulse metering level resistor

α·V

LOTTX

α = (|Zlttx + 2Rp|/|Zlttx|)

16.2 k

Ω

CS

Pulse metering shaping

capacitor

CS =

τ/(2⋅RLV)

100 nF 10 % 10 V

@

τ = 3.2 ms, RLV = 16.2 kΩ

CFL

Pulse metering filter capacitor CFL = 2/(2

π⋅fttx⋅RLV)

1.5 nF 10 % 10 V

@fttx = 12 kHz RLV = 16.2 k

Ω

1.

In case Zs=Zl, ZA and ZB can be replaced by two resistors of same value: RA=RB=|Zs|.

2.

Defining ZTTX as the impedance of RTTX in series with CTTX, RTTX and CTTX can also be calculated from the following

formula: ZTTX=50*(Zlttx+2Rp).

3.

In this case CTTX is just operating as a DC decoupling capacitor (fp=100 Hz).