EM92547A Ver la hoja de datos (PDF) - ELAN Microelectronics

Número de pieza

componentes Descripción

Fabricante

EM92547A

CALLER ID FSK DECODER

ELAN Microelectronics 

EM92547A/B/D

CALLER ID FSK DECODER

A /PWR UP input pin is provided to activate the chip regardless of the presence of a

power ring signal. If /PWR UP is sent high, the IC can still power itself up whenever it

detects a valid ring signal, but will back to its normal power-down mode after a time period.

The input buffer accepts a differential AC coupled input signal through the TIP and

RING input and feeds this signal to a band pass filter. Once the signal is filtered, the FSK

demodulator decodes the information and sents it to a post filter. The output data is then

made available at DATA OUT pin. This data, as sent by the central office, includes the

header information (alternate "1" and "0") and 150msec of marking which precedes the date,

time and calling number. If no data is present, the DATA OUT pin is held in a low state.

This is accomplished by a carrier detect circuit which determines if the in-band energy is

high enough. If the incoming signal is valid and thus the demodulated data is transferred to

DATA OUT pin. If it is not, then the FSK demodulator is blocked. This device uses a 3.58

MHz crystal or a 455KHz(for EM92547A only) resonator as a timing source for all the

internal blocks.

* Ring detect circuit

When Vdd is applied to the circuit, the RC network will charge cap C1 to Vdd

/PWR UP

VDD R1 /Ring Time

C1

(form bridge) R2 Ring det1

Power Up

Logic

R3

Ring det2

Ring

/RD

R4

1.2V Counter

holding /RING TIME off. If /PWRUP is also held at Vdd, the whole circuit will be in a

power down mode, and will consume less than 1uA of supply current. The resistor network

R2 to R4 attenuates the incoming power ring applied to the top of R2. The values given

have been chosen to provide a sufficient voltage at pin3, to turn on the Schmitt trigger input.

When Vt+ of the Schmitt is exceeded, cap C1 will discharge. This will initialize a partial

power up, and enable the ring detect circuit.

The value of R1 and C1 must be chosen to hold the /RING TIME pin voltage below

the Vt+ of the Schmitt between the individual cycle of the power ring. The values shown

will work for ring frequencies of 15.3 Hz minimum.

________________________________________________________________________________________________________________________________________________________

* This specification are subject to be changed without notice.

1998

~4~

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