STLC3075_09 datasheet(9/36 Pages) STMICROELECTRONICS

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STLC3075

Functional description

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Functional description

The STLC3075 is a device specifically developed for WLL VoIP and ISDN-TA applications. It

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

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

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

STLC3075 can be set in three 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 drives an external power MOS transistor N-Ch plus

transformer (Flyback configuration) or P-Ch plus inductor (Buckboost configuration), in order

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

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

an internal clock generated when the pin CLK is connected to CVCC. One RSENSE in series

to PGND supply (Flyback) or to VPOS supply (Buckboost) 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 110 m

Ω typical value guarantees an average current

consumption from VPOS < 700 mA for buckboost configuration. The 220 mΩ typical value

guarantees an average current consumption from VPOS < 800 mA for flyback configuration.

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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