TEA7092 datasheet(39/57 Pages) STMICROELECTRONICS

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IV - MICROCONTROLLER INTERFACE

IV.1 - Microcontroller Power Supply

The microcontroller is used in every modes,

speech, dialing and ring.

It is requested to start quickly in ring mode, less

than 200ms and to maintain the supply on the

microcontroller in pulse dialing mode, with a low

voltage across the telephoneset, or during an earth

loop connection, in these two modes the microcon-

troller is supplied through the energy previously

stocked in a capacitor and this capacitor should be

able to maintain the power on the microcontroller

during one second.

This compromise between the different modes is

carried out through the microcontroller power man-

agement which is connectedon Pin VMC (Pin 2) and

on Pin VRMC (Pin 8).

Figure 57 shows the microcontroller power supply

management.

In OFF-HOOK mode :

- C10 on Pin VMC (Pin 2) is charged in priority with

the Istartup (ILS) current source and is, after Reset

high, powered with IVMC (see Section II.1.3 -

START UP CHARACTERISTICS).

- The voltage on Pin VMC (Pin 2) is equal to :

VL (Pin 3) - 0.4V

- In Pulse dialing mode the microcontroller connected

on the 3.5V regulated voltage, Pin VRMC (Pin 8), is

powered through the serial regulator.

In Ring mode :

- For the microcontroller power supply only the

c apac it or C15 of 4. 7

µF connecte d on

Pin VRMC (Pin 8) has to be charged, so the start-

up time in ring mode can be less than 200ms.

IV.2 - Reset and Pon Signals

These two pieces of information give the status of

the Pin VRMC (Pin 8) and of the line current, IL.

In OFF-HOOK mode :

- Pin RESET (Pin 11) goes at high level when VRMC

reaches 2.6V and then remains at high level until

VRMC reaches the decay threshold fixed at 2.5V,

or the Reset code (0 0 1 0 1 1 1) is received

through the serial bus interface when PON is at

low level. If the Reset code has been previously

sent Pin RESET (Pin 11) goes back to an high

level, if VRMC is higher than the rise threshold, on

a rise edge of PON signal.

Note : when PON is at high level, the Reset code

is inhibited.

- Pin PON (Pin 12) goes at high level when the

voltage at Pin VRMC (Pin 8) reaches 2.6V and the

line current (IL) reaches the value of 12mA, and

then remains at high level until the line current (IL)

goes below the threshold level fixed through the

configuration code sent on the serial bus inter-

face.

• Decay threshold level : IL = 12mA by default

configuration.

• Decay threshold level : IL = 4mA if the code

(0 1 1 1 0 0 1) is sent.

VMC

Info for

PON & RESET

BANDGAP

470k

Ω

RMC

C15

4.7

µF

C10

470

µF

START =ILS

Close if

RESET Low and

L Present

TEA7092

µF

LCD

3.5V

Battery

Figure 57

TEA7092 - TELEPHONE SET INTEGRATED CIRCUIT

39/57

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