STLC3055N_09 datasheet(9/34 Pages) STMICROELECTRONICS

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STLC3055N

Functional description

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Functional description

The STLC3055N is a device specifically developed for WLL VoIP and ISDN-TA applications.

It is based on a SLIC core, on purpose optimised for these applications, with the addition of

a DC/DC converter controller to fulfil the WLL and ISDN-TA design requirements.

The SLIC performs the standard feeding, signalling and transmission functions.

It can be set in four different operating modes via the D0, D1, D2 pins of the control logic

interface (0 to 3.3 V logic levels). The loop status is carried out on the DET pin (active low).

The DET pin is an open drain output to allow easy interfacing with both 3.3 V and 5 V logic

levels.

The four possible SLIC’s operating modes are:

●

Power down

●

High impedance feeding (HI-Z)

●

Active

●

Ringing

Table 6 shows how to set the different SLIC operating modes.

4.1

DC/DC converter

The DC/DC converter controller is driving an external power MOS transistor (P-channel) in

order to generate the negative battery voltage needed for device operation.

The DC/DC converter controller is synchronised with an external CLK (125 kHz typ.) or with

an internal clock generated when the pin CLK is connected to CVCC. One sensing resistor

in series to Vpos supply allows to fix the maximum allowed input peak current. This feature

is implemented in order to avoid overload on Vpos supply in case of line transient (ex. ring

trip detection).

The typical value is obtained for a sensing resistor equal to 110 m

Ω that will guarantee an

average current consumption from Vpos < 700 mA. When in on-hook the self generated

battery voltage is set to a predefined value.

This value can be adjusted via one external resistor (RF1) and it is typical -50 V. When

RING mode is selected this value is increased to -70 V typ.

Table 6.

SLIC operating modes.

Operating mode

Power down

H.I. feeding (HI-Z)

Active normal polarity

Active reverse polarity

Active TTX injection (N.P.)

Active TTX injection (R.P.)

0/1

Ring (D2 bit toggles @ fring)

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