the total power consumption in On-hook to 30mW

(typical).

The Off-Hook detection threshold is not program-

Ground Start.

This mode is selected when the SLIC is adopted

in a system using the Ground Start feature. In this

mode the TIP termination is set in High Imped-

ance (100k

Ω) while the RING one is active and

fixed at Vbat +4.8V. In the case of connection of

RING termination to GND the sinked current is

limited to 30mA. When RING is connected to

GND both Off-Hook and Ground-Key detectors

become active. Power dissipation in this mode

with a -48V battery voltage is 100mW.

PROTECTION CIRCUIT

Suggested protection circuit is based on program-

mable Trisils (like LCP1511/2) as shown in Fig.2

and Fig. 3, and the surge current is limited by the

resistors RPT2 and RPR2, which are PTC types ,

protecting the device against both lightning and

power-cross.

METERING PULSE INJECTION

STLC30R80 provides external pins and compo-

nents for Metering Pulse injection. TTXIN pin is

the input for the 12kHz or 16kHz Metering Pulse

injection. This pin also provides a DC constant

current source that is injected into the external

RDA resistor (typ. 10k

Ω) connected between

TTXIN pin and AGND. The voltage drop across

TIP and RING line amplifiers and, consequentally

the AC swing available.

When Metering Pulse injection is not used and

voltage drop is not required, TTXIN must be

shorted to AGND and RTTX, RDA and CTTX ex-

ternal components must be removed. The TTX

cancellation is obtained through an external

RTTX and CTTX network connected between

TTXIN and CAC pins.

MISCELLANEOUS

- Thermal overload: the integrated thermal pro-

tection is activated when Tj reaches 150°C typ.;

the Slic is forced in Power-down mode, DET

and AL are set Low.

- One low cost external transistor allows to re-

duce the power dissipated in the SLIC itself al-

lowing the use of extreme small size package

(TQFP44). The external transistor size/package

can be selected depending on the max. power

requested by the particular application.

EXTERNAL COMPONENTS LIST

To set the SLIC into operation the following pa-

rameters have to be defined:

- The DC feeding resistance "Rfeed" defined as

the resistance of the traditional feeding sys-

tem (most common Rfeed values are: 400,

800, 1000 ohm).

- The AC SLIC impedance at line terminals "Zs"

to which the return loss measurements is re-

ferred. It can be real (typ. 600 ohm) or com-

plex.

- The equivalent AC impedance of the line "Zl"

used for evaluation of the trans-hybrid loss per-

formance (2/4wire conversion). It is usually a

complex impedance.

- The value of the two protection resistors Rp in

series with the line termination.

- The reverse polarity transition time defined as

"

- Rth: sets the OFF/Hook DETection threshold

Once, the above parameters are defined, it is

possible to calculate all the external components

using the following table.

t3

t1

t2

CSIN

D0.1.2

Figure1_STLC30R80

CSOUT

DET, GDK

t6

t4

t5

Figure 1. Logic Interface Input Timing

Note: All measurements are performed with 100pF on outputs

pin and with TTL compatible voltage levels.

Min.

t1

100ns

t2

100ns

t3

500ns

t4

100ns

t5

100ns

t6

500ns

STLC30R80

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