FM1246SLASHHMSLASHPH datasheet(2/24 Pages) PHILIPS

2 / 24 page

1997 May 14

Philips Components

Preliminary speciﬁcation

Desktop video & FM radio module

system CCIR I

FM1246

FEATURES

• System I and FM radio broadcast

• True 5 V device (low power dissipation)

• Full TV frequency range from channel A (45.75 MHz) to

channel 69 (855.25 MHz)

• FM radio band coverage from 87.50 to 108.00 MHz

• PLL controlled tuning

• Programmable PLL step size (31.25, 50 or 62.5 kHz)

• True-synchronous vision IF demodulator (PLL)

• Ultra-linear FM PLL demodulator for FM radio broadcast

• Demodulated video output, AF sound output, second

sound IF output

• I2C-bus control of tuning, address selection, AFC status

information

• Complies with European regulations on radiation, signal

handling and immunity

“CENELEC 55020, 55013’’

• Small horizontally mounted metal housing.

DESCRIPTION

The FM1246 front-end is designed to receive both TV and

FM stereo signals in the PC Multimedia environment. The

units are available with separate 75

Ω inputs for TV and

FM broadcast reception. The input connectors available

are either standard phono or IEC type (female for TV, male

for FM radio). The tuning, bandswitching and antenna

selection are made through the I2C-bus.

The front-end covers the TV bands from 45.75 MHz to

855.25 MHz. The FM band covers the standard

87.50 MHz to 108.00 MHz. An RDS decoder can be

connected to the AF-MPX output. The FM1246 meets the

input immunity and radiation requirements of CENELEC.

The FM1246 consists of a TV tuner, an FM radio tuner and

an IF section, all on a single PCB. The front-end is

assembled in a metal housing made of a rectangular

tin-plated steel frame, with front and rear covers, which

have soldered contacts to the frame. The two phono or

IEC antenna connectors (female for TV, male for FM

radio) are mounted on one side of the frame for the TV/FM

signal inputs. All other connections are made via pins at

the bottom.

The TV IF section uses an intercarrier SAW filter, followed

by a true-synchronous vision IF demodulator (PLL) IC. The

analog AFC voltage is fed to the 5-level A/D converter in

the PLL tuning IC, so that the AFC status can be read via

the I2C-bus.

In the FM radio mode, the level detector and AFT functions

are provide for the auto-search routines. The level detector

and AFT status can be read from the A/D bits in the

status-byte. The mute function is also provided to

suppress the audio output signal, if required.

The tuner AGC for both TV and FM radio operation, is

generated with a novel AGC detector which measures the

IF signal level directly at the tuner IF output pins. As

opposed to the conventional AGC detector, this new circuit

allows a higher take-over level and offers superior

immunity against tuner overload.

The demodulation of the TV sound and FM radio IF

(10.70 MHz) is done with a PLL demodulation circuit

contained in the IF IC. In the FM radio mode, the

multiplexed AF signal is then channelled to a stereo

decoder IC which extracts the left/right analog signals.

The multiplexed audio signal is also available at pin 25 to

support RDS implementations. The 2nd IF TV sound output

is provided to connect external (analog 2 carrier or digital)

stereo processing.

ORDERING INFORMATION

MARKING

The following items of information are printed on a sticker

that is on the top cover of the tuner:

• Type number

• Code number

• Origin letter of factory

• Change code

• Year and week code.

TYPE

DESCRIPTION

CATALOGUE

NUMBERS

FM1246/HM/PH

standard phono

3139 147 13901

FM1246/HM/I

IEC connector

3139 147 13911

FM1246/HM/PH Datasheet(PDF) 2 Page - NXP Semiconductors

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