L3234 datasheet(13/26 Pages) STMICROELECTRONICS

13 / 26 page

FUNCTIONAL DESCRIPTION

DIGITAL INTERFACE

The different operating modes of the L3235 are

programmed through a digital interface based on

two input pins:

1)SBY input programs the stand-by or Ac-

tive/Ringing modes.

2)RNG input programs the ringing ON/OFF acti-

vation condition for the L3234.

The L3235 digital interface has four output pins :

1)OH provides the on hook/off hook or ring trip

informations (active low).

2)GDK provides the ground key on/off informa-

tion (active low).

3)PU must be connected to the enable input pin

of CODEC/FILTER devices like ETC 5054/57

and automatically activates this device when

in active mode off-hook is detected or when

ringing mode is selected.

4)CS output must be connected to the CS en-

able input of the solid state ringing injector

L3234.

In this way the L3234 will be enabled when ring-

ing mode is programmed and will be automat-

ically disabled when the ring trip condition will be

detected reducing the ringing signal disconnec-

tion time after ring trip.

The table 1 here below resumes the different op-

eration modes and the relative logic output sig-

nals.

The two current detection (hook and GND key)

have internal fixed threshold. Externally it is possi-

ble to program their time costant through two R-C

components connected respectively to pin 26

(RTF) and pin 27 (GKF).

L3235 FUNCTIONAL DIAGRAM

L3234 - L3235

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L3234 Datasheet(PDF) 13 Page - STMicroelectronics