Philips Components
Preliminary specification
Desktop video & FM radio module
system M, N
FEATURES
•
System M and N, and FM radio broadcast
•
True 5 V device (low power dissipation)
•
Full frequency range from channel 2
(55.25 MHz) to channel 69 (801.25 MHz)
•
FM band coverage from 76.0 MHz to 108.0 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 broadcast
•
Demodulated video output, AF sound output, second
sound IF output
•
I
2
C-bus control of tuning, address selection, AFC status
information
•
Complies with FCC, DOC and JIS regulations on
radiation
•
Small horizontally mounted metal housing.
DESCRIPTION
The FM1236 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 F type. The tuning,
bandswitching and antenna selection are made through
the I
2
C bus.
The front-end covers the TV bands from 55.25 MHz to
801.25 MHz, inclusive of the Japanese TV bands from
91.25 MHz to 765.25 MHz. The FM band covers the
standard 87.50 MHz to 108.00 MHz and also the
Japanese FM band (76.00 MHz to 91.00 MHz). An RDS
decoder can be connected to the AF-MPX output. The
FM1236 meets the input immunity and radiation
requirements of the FCC, DOC and JIS.
The FM1236 consists of a TV tuner, an FM radio tuner and
an IF section, all designed 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
F antenna connectors (female) 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
FM1236
the PLL tuning IC, so that the AFC status can be read via
the I
2
C-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 terminals. 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 (4.5 MHz) and FM 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 or BTSC implementations. The 2
nd
IF sound
output is provided to connect external (analog 2 carrier or
digital) stereo processing.
ORDERING INFORMATION
TYPE
FM1236/HM/PH
FM1236/HM/F
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.
DESCRIPTION
standard phono
F
CATALOGUE
NUMBERS
3139 147 13411
3139 147 13421
1997 Feb 03
2
Philips Components
Preliminary specification
Desktop video & FM radio module
system M, N
LIMITING VALUES
Limiting values under operational conditions
The tuner can be guaranteed to function properly under the following conditions.
SYMBOL
V
S
V
S(ripple)
supply voltage
peak-to-peak ripple voltage susceptibility
(at 5 V
±5%);
note 1:
20 Hz to 100 kHz
>100 kHz to 500 kHz
I
S(tuner)
V
SCL
V
SDA
I
SDA
V
AS
V
AFright(FM)
Z
AFright(FM)
supply current
SCL bus input voltage
SDA bus input voltage
SDA bus current (open collector)
address select voltage; note 2
FM right channel DC voltage
FM right channel load impedance parallel
connected:
resistive value
capacitive value
V
AFleft(FM)
Z
AFleft(FM)
FM left channel DC voltage
FM left channel load impedance:
resistive value
capacitive value
Z
IF
Z
CVBS
t
L
V
S(IF)
I
S(IF)
Z
AF
2
nd
IF sound output load impedance
Composite Video Baseband Signal load
impedance
CVBS load time constant
IF supply voltage
IF supply current
AF sound output load impedance parallel
connected:
resistive value
capacitive value
Notes
25
5.0
−
−
−
−
4
24
22
23
−
4.75
−
−
5.0
−
21
20
−
−
−
−
−
0.5
−
40
9
1.0
40
9
−
75
−
−
−
−
−
−
−
13
14
15
PARAMETER
PIN
MIN.
4.75
TYP.
5.00
FM1236
MAX.
5.25
UNIT
V
12
−
−
−
−0.3
−0.3
−1
−
−
−
−
−
−
−
−
−
1.0
5
10
120
+5.25
+5.25
+5
+5.25
−
mV
mV
mA
V
V
mA
V
V
kΩ
pF
V
kΩ
pF
kΩ
Ω
ns
V
mA
100
5.25
150
kΩ
nF
1. Sinusoidal ripple voltage superimposed on the 5 V supply voltage in the frequency range of 20 Hz to 500 kHz.
Criteria for TV interference >57 dB.
2. For detailed information about the address decoding, refer to Chapter “Application information”.
1997 Feb 03
5
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