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STLC3075

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

Table 6. SLIC operating modes.

3.1 DC/DC Converter

The DC/DC converter controller is driving an external power MOS transistor N-Ch plus transformer (Fly-

back configuration) or P-Ch plus inductor (BuckBoost configuration), in order to generate the negative bat-

tery voltage needed for device operation.

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

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). Typ. value is 110m

Ω for both configuration and it will guarantee an average current con-

sumption from Vpos < 700mA for BuckBoost configuration and < 1.5A for Fly- Back configuration.

The self generated battery voltage is set to a predefined value in on-hook state.

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

lected this value is increased to -70V typ.

Once the line goes in off-hook condition, the DC/DC converter automatically adjusts the generated battery

voltage in order to feed the line with a fixed DC current (programmable via RLIM) optimising the power

dissipation.

3.2 OPERATING MODES

3.2.1 Power Down

When this mode is selected the SLIC is switched off and the TIP and RING pins are in high impedance.

Also the line detectors are disabled therefore the off-hook condition cannot be detected.

This mode can be selected in emergency condition when it is necessary to cut any current delivered to the

line.

In this case the device goes back to the previous status as soon as the junction temperature decrease

under the hysteresis threshold.

No AC transmission is possible

3.2.2 High Impedance Feeding (HI-Z)

This operating mode is normally selected when the telephone is in on-hook in order to monitor the line

status keeping the power consumption at the minimum.

PD

D0

D1

D2

Operating Mode

00

0

X

Power Down

1

0

0

X

H.I. Feeding (HI-Z)

10

10

Active Normal Polarity

1

0

1

1

Active Reverse Polarity

1

1

1

0

Active TTX injection (N.P.)

1

1

1

1

Active TTX injection (R.P.)

1

1

0

0/1

Ring (D2 bit toggles @ fring)