U4275B

TELEFUNKEN Semiconductors

Preliminary Information

3

Rev. A1: 14.03.1995

MPXIN / MPXOUT

94 8649

50 k

W

MPXIN

50 k

W

94 8650

60 k

W

60 k

W

MPXOUT

200

mA

The MPX signal is fed directly from the FM demodulator

to input MPXIN and is available amplified by a factor of

1.5 at MPXOUT. The MPX signal is blanked out in the

event of multipath interference or when MUTE is

activated externally in the circuit part MNC (Multipath

Noise Canceller). In all other cases, the MPX signal

passes through the IC unchanged.

GND2

GND2 is the reference potential for the MPX signal.

GND2 should be connected directly with the ground

terminal of the IF FM demodulator to ensure a high

signal-to-noise ratio of the MPX signal.

MUTE

94 8651

MUTE

The function unit MNC can be controlled externally via

this pin. Blanking occurs when the voltage at the MUTE

pin falls below 1 V. A voltage in the range VS/2 > 1 V

defines the switching threshold as from which multipath

interference is signalled at pin INT.

CRIN

94 8652

CRIN

40 k

W

The internal one-pin oscillator is connected to CRIN with

a 456 kHz ceramic resonator. The 456 kHz reference

frequency is used for calibrating the filters and generating

pulses at INT.

ANAOUT

94 8653

ANAOUT

60

mA

+ 5 V

Analyzer output. DC values are available at this pin that

characterize the respective reception situation. The

output voltage is limited to max. 5 V. ANAOUT is a

multiplex output, i.e. the value for the fieldstrength, level

of multipath interference or level of common channel

interference is applied to this output depending on

addressing.

ANAOUT

can

be

switched

to

the

high-impedance state by means of OE.