Datasheet M491B Datasheet (SGS Thomson Microelectronics)

M491B

SINGLE-CHIP VOLTAGE SYNTHESIS TUNING SYSTEM

WITH 1 ANALOG CONTROL

.

16-STATION MEMORY - 7-SEGMENT LED
DISPLAY

.

VOLTAGESYNTHESIZER: 13 BITS

.

4-BANDPRESETCAPABILITY

.

NON-VOLATILEMEMORY : 304 BITS

- 16 WORDS OF19 BITS FORTUNINGVOLT­AGE(13 bits)- BAND (2 bits) - FINEDETUN­ING (4 bits)

4

- 10

MODIFYCYCLESPER WORD

- MIN 10 YEARSDATARETENTION

.

PCM REMOTE CONTROL RECEIVER : DE­CODES SIGNAL TRANSMITTEDBY M708

.

VOLUMED/A : 6-BITRESOLUTION/ 8kHz

.

MEMORYSKIP FUNCTION

.

AUTOMATIC SEARCH WITH DIGITAL AFT
CONTROL

.

FINE DETUNING D/A ACTING ON AFT DIS­CRIMINATOR (16 steps) WITH SEPARATE
STORAGE FOR EACH MEMORY POSITION.
ALTERNATIVELYIT CAN BE USED TO CON­TROL BRIGHTNESS OR COLOUR SATURA­TION

.

MANUAL SEARCH WITH DIGITALAFT CON­TROL

.

MANUALSEARCHWITH LINEAR AFT

.

SWEEPSEARCHDISPLAYOUTPUT

.

SUPPLYVOLTAGES : VDD= + 5V,

=+ 25VFOR THE MEMORY

V

PP

.

CLOCKOSCILLATOR: 445TO 510kHz

.

INTEGRATED DIGITAL POWER ON RESET
(no externalinitializationcircuitry required)

DESCRIPTION

The M491B is a monolithic N-MOS LSI circuit in­cluding a Floating-gate Non-Volatile Memory for
storage of up to 16stations. Tuning of the station
is performedwith a 8192 step D/Aconverter,using
the principleof voltagesynthesis.It is designedfor
7-segmentLED displays. Direct memoryselection
is possibleonlyfromremotecontrol whileUp/Down
memory scanningis possible on the set and also
from remote control. An option input for 8 or 16
stations is available. The circuit also includes a
PCM remotecontrol receiveroperating in conjunc-

tionwith the transmitterM708. The highly reliable
transmissioncode ensureserror-free signal detec­tion even in presence of high noise conditions.
Search of the station is possible in automatic or
manual modes. The circuit can operate with a
DigitalorLinearAFTcontrol.TheDigitalAFTmode
isnecessary for automaticsearch and requires an
external circuit (TDA4433 or equivalent,e.g. dual
comparatorplus TVstationdetector)toconvertthe
AFC-S-curveintoan Up/Down command.Finetun­ing(detuning)is alsopossiblewithdifferentmodes
ofoperation.Thecircuitisassembledin 40-pindual
in-lineplastic package.

DIP40

(Plastic Package)

ORDER CODE : M491B1

PIN CONNECTIONS

(GND)

V

SS

MEMORYSUPPLY

MEMORYTIMING
FINE TUNING D/A

TUNINGD/A

DIGITALAFTSTATUS

OSC. IN

OSC. OUT

V

TEST

I.R.INPUT

AFT1
AFT2

SWEEPDISPLAY OUT

VOLUMED/A

LINEARAFT DEF.

DIGITALAFTEN.

1
2
3
4
5
6
7
8
9

DD

10
11
12
13
14
15
16
17
18

V3

19

V2

20

V1 X4

40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21

VHFI
VHFIII
CATV
UHF
SEGM.h + i
SEGM.g
SEGM.f
SEGM.e
V

(GND)

SS

OPT.8/16
SEGM.d
SEGM.c
SEGM.b
SEGM.a
MAINSON/OFF
MAINSON OPTION
X1
X2
X3

491B-01.EPS

September 1992

1/16

M491B

FUNCTIONAL DIAGRAM

+12V

UP

AFC-Scurve

(AFT1)

(AFT2)

DOWN

PP

V (25V)

OSC

445 to 510MHz

OSC

+5V

V

I V

or 8160

TDA2320

TEST

OUT

IN

SS MT MS

DDR

TUNING D/A

FINE TUNING D/A

VHF I

4

5

7 89 1011

1 23

31

32

SS

V

OPT. 8/16

4.5 to 13.2V

BAND OUT

UHF

CAT V

VHF III

39

40

b

a

f

h

37

38

c

g

d

e

i

AUTO SEARCH STOP

DIGITALAFT

SWEEP DISPLAYOUT

AFT1

14

DIGITAL AFT STATUS

AFT2

6

12

13

M491B

27282930333435

a

b

c

DIGITAL AFT ENABLE

17

d

LINEAR AFTDEFEAT

16

e

VOLUME D/A

MAINSON/OFF

MAINSONOPTION

15

25

26

23

24

X1 X2 X3 X4

181920 2122

V2 V3

V1

36

f

g

h - i

2/16

445 to

M708

510MHz

491B-02.EPS

M491B

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

DD

V

PP

V

V

O (off)

I

OL

t

pd

P

tot

T

stg

T

op

Stresses above thoselisted under”Absolute Maximum Ratings” maycause permanent damage to the device. This is a stress rating only and
functional operation ofthe device at these or any other conditions above those indicated in the operational sections of thisspecification is not
implied. Exposure to absolute maximum rating conditions for extended periods may affectdevice reliability.

DC ELECTRICALCHARACTERISTICS

(T

amb

2-Memory Supply I

3–Write Timing Out
4–Fine Tuning D/A

5–Tuning D/A
6–Digital AFT Out

9–Power Supply I
11–I.R. Input V

12–AFT1
13–AFT2

14—Display Out

15–Volume D/A

16–Linear AFT Out

17–Digital AFT En­able

Supply Voltage – 0.3, + 7 V
Memory Supply Voltage – 0.3, + 26 V
Input Voltage – 0.3, + 15 V

I

Off State Input Voltage (except pin 3)

Pin 3

Output Low Current

Led Driver Outputs
Pins 6 – 14
Pins 4 – 5
All Other Outputs

15
28

mA
20
20

7.5
5

Max. Delay between Memory Timing and Memory Supply Pulses 5 µs
Total Package Power Dissipation 1 W
Storage Teperature – 25, + 125 °C
Operating Temperature 0, + 70 °C

=0 to + 70°C, VDD= +5V unless otherwisespecified)

Pin Symbol Parameter Test Conditions Min. Typ. Max. Unit

Memory Supply Current VPP= 25V

PP

R Pull Down Resistor 25 kΩ

V

I

O (off)

I

O (off)

V
V

I

O (off)

V

V

Output Low Voltage VDD= 4.75 V, IOL= 2.5 mA 8 V

OL

Output Leakage Current VDD= 4.75 V, V

VDD= 5.25 V, V

OL
OL

VDD= 4.75 V, IOL= 5 mA 1 V
VDD= 4.75 V, IOL= 20 mA 1.5 V
VDD= 5.25 V, V

Supply Current VDD= 5.25 V 100 mA

DD

Peak-to-Peak Voltage 0.5 13.2 V

IPP

Input low Voltage VDD= 5.25 V 1.5 V

IL

Input High Voltage VDD= 5.25 V 3.5 V

IH

Input Low Current VDD= 5.25 V, VIL= 1.5 V –0.4 mA

I

IL

R Pull-up Resistor 30 kΩ

V

I

O (off)

V

I

O (off)

V

I

O (off)

V
V

I

OL

OL

OL

IL
IH

IL

VDD= 4.75 V, IOL= 20 mA 1.5 V
VDD= 5.25 V, V
VDD= 4.75 V, IOL= 4 mA 1 V
VDD= 5.25 V, V
VDD= 4.75 V, IOL= 1 mA 0.4 V
VDD= 5.25 V, V

VDD= 5.25 V, VIL= 0.8 V –0.4 mA

R Pull-up Resistor 30 kΩ

Write Peak

Average

Erase Peak

Average

Read Peak

Average

= 26 V 100 µA

OUT

= 13.2 V 50 µA

O (off)

= 13.2 V 100 µA

O (off)

= 13.2 V 100 µA

O (off)

= 13.2 V 50 µA

O (off)

= 13.2 V 50 µA

O (off)

42
12

9
5
8

2.5

0.8 V

2.0 V

V
V

mA

491B-01.TBL

491B-02.TBL

3/16

M491B

DC ELECTRICALCHARACTERISTICS (continued)

Pin Symbol Parameter Test Conditions Min. Typ. Max. Unit

18–19–20
V3

Keyboard

V2

}

In

V1
21–22–23–24

X4

Keyboard

X3

}

X2

Out

X1

V

IL

V

IH

I

IL

R Pull-up Resistor 30 kΩ

V

OL

I

O(off)

1.5 V

3.5 V

VDD= 5.25 V, VIL= 0.8 V –0.4 mA

VDD= 4.75 V, IOL= 1 mA 0.4 V

V

= 5.5 V 25 µA

O (off)

V

IL

25–Mains On En­able

26–Mains On/Off

31–Z2
32–Z1
MPX for
Display Out

37–UHF
38–CATV
39–VHFIII
40–VHFI

27-28-29-30-33­34-35 Display Out

36-Display Out V
31-Memory 8/16

}

B
A
N
D

DESCRIPTION(All timingsat f

PIN 1 : V

SS

V

IH

I

IL

R Pull-up Resistor V

V

OL

I

O

V

OL

I

O(off)

V

OL

V

OH

V

IL

V

IH

I

O(off)

V

OL

OL

V

IH

V

IL

= 500kHz)

clock

Thesubstrateof theIC isconnectedto thispin.This
is thereferencepin for all parameters of the IC.

PIN 2 : MEMORY SUPPLYVOLTAGE
A supply voltage of 25 ± 1 V has to be appliedto
this pin duringthe modifyand read cycles.

MODIFYCYCLE
Amodify cycleconsistsof threesteps :

1.All”1”sarewritten inthebitsoftheselectedword.

2. All bits of the selectedword areerased (all ”0”s)

3. Thenew contentis written.
Thus a constantaging of all thebits of theword is

0.8 V

2.4 V

VDD= 5.25 V –0.4 mA

= 0.8 V 30 kΩ

IL

VDD= 4.75 V, IOL= 100 µA 0.4 V
VDD= 4.75 V, VO= 0.7 V –1.6 mA

VDD= 4.75 V, IOL= 1 mA 0.4 V

VDD= 5.25 V, V
VDD= 4.75 V, IOL= 1 mA 3 V

VDD= 4.75 V, IOH= – 150 µA 2.4 V

VDD= 5.25 V, V
VDD= 4.75 V, IOL= 20 mA 1.5 V

VDD= 4.75 V, IOL= 30 mA 1.5 V

= 13.2 V 50 µA

O (off)

3 V

= 13.2 V 50 µA

O (off)

2.0 V

0.3 V

0.8 V

obtained.
During both write and erase cycles the memory
status is checked continuously ; therefore after
eachwriteorerasepulseareadoperationiscarried
out. The write orthe erase operationsare stopped
as soon as the result of theread operationis valid.

WRITE CYCLE. The peak of the current flowing
throughpin 2 duringa writeoperation is shown in
fig. 1, while fig. 2 shows the envelopeof thesame
current.

The typical write time is 3-4 ms for the firstcycles
and increasesto about30 ms after1000 cycles.

491B-03.TBL

4/16

Figure1

M491B

40mA

12mA

6mA

64 32 44 116µs

256µs

Figure2

I (mA)

40

12

5

Typ.max. 20msec Typ.max. 8msec

ERASECYCLE
Figure3 showsthe timingand thewaveform of the
current flowing through Pin 2 during the erase
operation. The peak current is 7mA (max) during
the erase cycle and 6mA (max) during the read
cycle. The typical erase time is 10ms for a new
device and increases with the number of modify

Afterabout30msec

491B-03.EPS

t (ms)

491B-04.EPS

operationsup to200ms after 1000 cycles.
In orderto protect the memoryincase of failureof
some bits the modify operation is stopped after
1sec.
READCYCLE
Figure 4 shows the waveformofthe currentduring
a read operation.

Figure3

128µs 52

32 44

256µs

7mA

6mA

Figure4

491B-05.EPS

44

6mA

84µs

128µs

480µs

491B-06.EPS

5/16

M491B

PIN 3 : MEMORYTIMINGOUTPUT
This output gives the timing for the pulses to be
appliedat Pin 2 during the modify and read cycles.
The output consists of an opendrain transistor.

PIN 4 : FINE TUNING D/A(see Figure 5)
A D/A converter with16-step resolution and a fre­quencyof15kHzcanbeusedtogeneratea voltage
which,iffedtoavaricapdiodeinparalleltothe AFC
discriminator, willdetune the receiver bya small ∆f
whilemaintainingthe actionofthe DigitalAFT.This
output can be used in conjunctionwithboth Linear
and DigitalAFT modes of operations.

The Fine tuningfunction operates as follows :

- At the start of any automatic or manualsearch,
the output is set at the mid range.

- Whenthe search has been completedit ispossi­ble to operateon FT ± commands.
The storecommand memorizes this information

Figure5

together with the 13 tuning voltage bits and 2
informationbits.

- Modification time of FT D/A is of 1 step every
200msifissuedlocallyorevery2receivedsignals
from Remote control transmitter.

PIN 5 : TUNINGD/A (see Figure 6)

13

A 2

= 8192 step pulse modulated signal for the

tuning voltageis available on thispin.
Pulse modulation is implementedby combination

of a rate multiplier andpulse width principle.
With a tuning voltage increasing from zero, the

number of pulses increases continuously up to

8

2

= 256 ; starting from this point the number of
pulses remainsthe same but thepulsesget larger
until they reach the maximumcontentof theinter­nal counter.The output consists of an open drain
transistorwhich offers a low impedance to ground
when in theON state.

64µs

9 7

V

OUT

FineTuning Output

FT
FT

Mid
Range

491B-07.EPS

6/16

Figure6

M491B

D/A

Converter

V

A

V

A

V

B

V

C

PIN 6 :DIGITALAFT STATUSOUTPUT
(see Figure 7)

This outputshowsthe statusof the digitalAFT.Itis
low when the digital AFT is enabled and it can
directly drive a LED.

The outputconsistsof anopen drain transistor.
PINS7 & 8 : OSCILLATORINPUT/OUTPUT

(see Figure8)
The frequency of the clock oscillator should be

between 445and 510kHzusingalow-costceramic
resonator. In these conditions the value of the
referencefrequencyof the transmittercan beinthe
same range. In otherwords the transmitterand the
receiver can operate with different reference fre­quencies.

Figure7

max.13.2V

6

Varicap

V

down-up

B

V

C

Figure8

7 8

455to

510kHz

100pF100pF

PIN 9 : V

DD

The supply voltage has to be comprised in the
range 4.75 to 5.25V. When it is applied an internal
poweron resetof 0.5sis generated.
The memoryposition 1 isautomatically read if the
mains on option input(Pin 25) is grounded.

PIN 10 : TEST
Thispinis usedfor testingandhastobeconnected

to V

.

SS

PIN 11 : I.R.SIGNAL INPUT (see Figure9)
The integrated receiver decodes signals transmit-

ted by M708, address 9.
The minimumsignalto beappliedis 0.5V peak-to­peak. (AC-coupled).
The receiver input section performs the following
tests on the incomingsignal to achievethe neces­sarynoise immunity :

- measurement of the pulse distance (time base

synchronization)

491B-09.EPS

491B-08.EPS

491B-10.EPS

7/16

M491B

- checkof thepositionofthe received bits opening
windowat the time bases

- checkof theparity bit

received word is rejected and not decoded. If the
receivedsignal is acknowledgedas a valid word it
is stored an decoded.

- checkof theabsenceofpulsesbetweentheparity
bit and the stop pulse

- checkof noiselevel;the receiverchecksparasitic
transientsinside and outsidethe time windows.

If the above test conditions are not fulfilled, the

The end of transmissionwill be acknowledged by
receivingthe endoftransmissioncodeorbymeans
of an internal timer if the transmission remains
interruptedfor morethan about 550ms.

Figure9

TDA2320

or TDA8160

R C

M491B

Supply Voltage of

TDA2320

5

12

R C

2.2kΩ
10kΩ

4.7nF

4.7nF

M491B REMOTECONTROLRECEIVER TRUTH TABLE. TransmitterM708 ; AddressCode 9

Command

Number

0 0 0 0 0 0 0 End to Transmission
1

2
3
4
5
6

7
8

9
10
11
12

13
14
15
16
17
18

19
20
21
22
23
24

25
26
27
28
29
30

C1 C2 C3 C4 C5 C6

1
1
0
1
0
1

1
1
0
1
0
1

1
1
0
1
0
1

1
1
0
1
0
1

1
1
0
1
0
1

0
1
0
0
1
1

0
1
0
0
1
1

0
1
0
0
1
1

0
1
0
0
1
1

0
1
0
0
1
1

I.R. Code

0
0
1
1
1
1

0
0
1
1
1
1

0
0
1
1
1
1

0
0
1
1
1
1

0
0
1
1
1
1

Function

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

1
1
1
1
1
1

0
0
0
0
0
0

1
1
1
1
1
1

0
0
0
0
0
0

1
1
1
1
1
1

1
1
1
1
1
1

0

Power On/Off

0

Mute On/Off

0

Memory 1

0

Memory 2

0

Memory 3

0

Memory 4

0

Fine Detuning Up

0

Fine Detuning Down

0

Memory 5

0

Memory 6

0

Memory 7

0

Memory 8

1

Memory Up

1

Memory Down

1

Memory 9

1

Memory 10

1

Memory 11

1

Memory 12

1

Manual Search Up

1

Manual Search Down

1

Memory 13

1

Memory 14

1

Memory 15

1

Memory 16

1

Volume Up

1

Volume Down

1

Memory Addressing

1

Digital AFT On

1

Band Sequential

1

Automatic Search

}

Mute

491B-11.EPS

491B-04.TBL

PINS 12& 13: AFT1-AFT2(STOP/AFTINPUTS)
These pins are enabled during the automatic

search and during normal operation, when the
digitalAFT is enabled (see descriptionof Pin 17).

8/16

The STOP/AFTinputs are also disabled internally
duringanyprogramorbandchangefortheduration
of the Mute signal.

Thesepins workaccordingto thetruth table given below :

M491B

M491B Pin 12

TDA4433 Pin 2

H

L
L

H

M491 B Pin 13

TDA4433 Pin 6

These inputs have two different functionsdepend­ing on whether the system is in the search or in
normal operation(AFT control).

The inputs have internalpull-up resistors of 30kΩ
typ.

A) Searchmode : afterdepressingthe Automatic

searchor presetkeys, thelevels of the signals
coming from the TDA4433, applied to these
pins,controlthe searchfunctionand determine
whenthesearchmuststop,i.e.aTVstationhas
been recognized.

The circuit operates in the following sequence
(see Figure 10 for reference):

1 - after pressing the search start key the

searchoccurs in the FASTUP mode.

2 - eventual transitions available on these

inputsareignoredduringthefirst15search
steps if the system is in the UHF or CATV
bands.

If the system operates in VHF I and III bands,
the first 60 search steps are ignored. The
acceptancedelay of 15 (60) search steps has
been introduced to prevent the system from
stoppingat theprevious station.

After this time the FAST UP speed is
automatically reduced to half during each UP
signal(MEDIUM UP = FASTUP/2).

A DOWN signal preceded by at least an UP
signal will set the search to MEDIUM DOWN
mode(FAST UP/4).

3 - the next UPsignal will switch the search to

SLOWUP speed (61Hz).

At this point the systems is in normal AFT
operation.

(referred to the tuning voltage)

L

H

L

H

Function

Up

Down

Middle

No Operation

B) Digital AFT operation : when a station is

perfectly tuned, the inputsignals coming from
TDA4433are at middle condition.

If the tuning moves lower than the threshold
below 38.9MHz,the Pin 12 is put H and Pin 13
is put L ; the 13 bit internalcounter is moved
SLOW UP speed to increase the varicap
voltage.

When a detuning occurs in the opposite
direction the input 12 goes Low and 13 goes
High and the tuning voltage falls at VERY
SLOWDOWN speed (7.6Hz).

The increaseor decreaseof the tuning voltage
is stopped as soon as the input returns to
middle conditions.

ThereforeduringnormaloperationPins 12and
13 actas digital AFT control commands.

C) Recall from memory : whenthe digital AFT is

enabled and data is recalled from Memory, a
fixed valueof 8steps (≈ 31.2mV)is subtracted
from the tuningvoltage.

This corresponds to a detuning of 0.6MHz
(UHF) andof 0.3MHz in VHFIII into that part of
the IF responsecurvewhichcorrespondsto the
fully transmittedsideband.

At this point the AFT operation takes over as
describedinpointBaboveandtheexacttuning
is achieved in about0.2 sec.

This feature increases the AFT capture range
and fullfills the stability requirements of the
tuner, voltage references and the D/A
converter.

If theDigitalAFTis disabled(Pin 17at V
memory contentis read withoutany change.

SS

461B-05.TBL

), the

9/16

M491B

Figure10

34 35 36 37 38MHz

IF

RESPONSE

SEARCH

DIRECTION

SIGNALS

ON

TDA4433

SEARCH

START

AFC

THESHOLD

Pin6

Pin2

FAST UP

S1

139.0MHz

38.8MHz

TRANSMITTER
IDENTIFICATION

MEDIUM UP

S2= 0.5 S1

DIGITAL

INFORMATION

38.8
39

40MHz

MEDIUMDOWN

S3 = 0.25 S1

NORMALAFC POSITION

t

40 39

38.8

VARICAP VOLTAGE

38.8
MHz

SLOW UP
S3 = 67Hz

NORMAL AFC
OPERATION

STOP

PIN 14 : SWEEPSEARCHDISPLAYOUTPUT
This output, which is normally Low, goes High

during automaticsearch automaticpreset et inter­vals of 160ms for about 40msto blank the LED of
band display.

Figure11

BAND
LEDS

V

SS

10/16

PIN 15 : VOLUME D/AOUTPUT
This output delivers a square wave signal of 7.8

kHzand dutycycle variable in 63 steps.In case of
a continuouscommand for varyingthe volume, the
duty cycle ischangedat the rate of the transmitted
signal (approximately every 102ms with f
500kHz)or every 112ms if issued locally.

Overflowand underflow protection are provided.
The volume output can be switched to V

reset to the previouslevel by means of the Mute
On/Off command. It is also reset by the Volume
Up/Downand the MainsOn/Off commands.

The volume is muted for about 1s at each mains
onandoffcommandduring thepoweron resettime
and program change (0.5s).

At the first power on reset of V

the volume D/A

DD

is setat the level 21/64. Thelast level is preserved
until V

491B-13.EPS

isnot removed.

DD

SS

t

491B-12.EPS

=

ref

and

M491B

PIN16 :LINEAR AFT DEFEATOUTPUT
This output is normallyHighand goesLowwhen a

Manual Up/Down command is issued.
It returns High with a 1 second delay from the

release of the key, in order to give the user the
possibilityof the tuningadjustmentwithoutthe AFT
intervention.It goes Low for 0.5s during program
change.

Figure12

MAN UP/DOWN

KEY PRESSED

LINEAR AFT
DEFEAT OUTPUT

MAN UP/DOWN

KEY RELEASED

1sec

PIN 17 :DIGITALAFT ENABLEINPUT
If this input is connected to V

(GND), the digital

SS

AFT loop is always disabled. If pin17 is left open
or isconnectedto V

, thedigital AFT is automat-

DD

ically enabled at power on. When a manual
up/downsearchcommandisissued,thedigitalAFT
loop isdisabledandthe digitalAFTstatusoutputis
inhibited.
The digitalAFT loop is restoredby the commands:
DigitalAFTon/Automaticsearch/Automaticpreset.

PINS18-19-20-21-22-23-24:
KEYBOARDMATRIX (seeFigure 13)
A command is accepted if the corresponding con-

tacthas beenclosed for a minimumtime of 30ms.
Local input commands and I.R. commands have

the same priority.
If a completeI.R.commandhas been received,the
local inputs are blocked until the command has
been executedand the”end of transmissioncode”
generated.
Viceversa an I.R. signal cannot be decoded until
an issuedlocal command has been executed.

MEMORYUP/DOWN
Depressingone ofthesetwocommands,themem­ory position isstepped in the UP or DOWN direc­tion.
If the key is keptclosed,the channelsare stepped
UP/DOWNevery0.5secondor every5 commands
from the transmitter.
The memorylocations9 to 16 are jumped if pin 31
is at GND level.

491B-14.EPS

BAND SELECTION
The bandscan be selected either directlyor with a
step-by-stepcommand inthe followingsequence:

VHF I
CATV
VHF III
UHF
VHF I and so on

Only one band change is performed at each ac­ceptedcommand.
Disabledbands are automaticallyskipped. A band
canbedisabledconnectingthecorrespondingout­put to V

SS

.

Figure13

V1 V2 V3 X1 X2 X3 X4
20

MEMORY

UP

MEMORY

DOWN

MAN SEARCH

UP

MAN SEARCH

DOWN

DIGITAL

AFT ON

AUTOMATIC

SEARCH

FT.

UP
FT.

DOWN

19 18

BAND

SEQ.

POWER
ON/OFF

VOLUME

UP

VOLUME

DOWN

BAND

I

BAND

III

BAND

UHF

BAND
CATV

AUTOMATIC
PRESET

MEMORY
ADDRESSING

STORE

MUTE

23 22 2124

491B-15.EPS

11/16

M491B

SEARCHMODES
4 modesare available:

a) Automatic search
b) Automatic preset

(digiatlAFT)

c) Manualup/down(digital and linear AFT)
d) Manual up/down(linear AFT)

a) AUTOMATICSEARCH.The searchstarts from
the actual tuning and band position. During the
searchthe tuning voltage is always changingfrom
lower to highervoltagelevels.When the end of the
bandisreachedthesearchrestartsfromthebegin­ning of the next band after a 480 ms interruption
with the sequenceof step-by-stepband selection.
Disabledbandsare automaticallyskipped.

The search is stopped when the first station is
foundor if a channel selectioncommand is given.

Stop of the automatic search is determined by the
STOP/AFTinputscontrolledby theTDA4433which
converts the AFC-S-curve into an up/down com­mand.

At the end of the search the up/down command
controlsthe correcttuning acting on the counter of
the voltage synthesizer(DigitalAFT).

It isimportanttocall the attentiontotheDigitalAFT
capturerangewhichislargerthanthenormallinear
AFT as shownin fig.14.

Figure14

LINEAR AFT

CAPTURE RANGE

DIGITAL AFT

CAPTURE RANGE

Additionallythe use of the DigitalAFT allows stor­age of the tuning informationcorrespondingto the
zero point of the AFC-S-curve. This cannot be
guaranteedusingtheLinearAFTmethodonly.The
latter is a cheaper system, because it does not
require the use of the TDA4433but it cannot guar­antee what described above.

As a resultoftheuseoftheDigitalAFT, therequire­ments for stability of the tuner, of the reference
voltage sourceand of stability of the D/A converter
are less critical.

Tuning speed in automatic search, if no station is
found is :

VHFI 8 second
VHFIII 8 second
UHF 32 second
CATV 32 second
The tuning and band information can be stored
using the store/memory addressing command.
Thesearchcan be stoppedby amemory selection
command.

b) AUTOMATIC PRESET. The search starts from
the lowest memory address, tuning voltage and
VHF I band as described in automatic search
mode.

Whenan active station is encountered, the corre­sponding tuning and band informationis automat­icallystored in theNon-VolatileMemory.

Afterwardsthe system starts tosearch forthe next
station.The cycleis repeated until all bandshave
been scanned or the tuning information has been
stored into all addresslocations. After completing
thiscycle the system reads out the tuning informa­tionof the lowest address.

c) MANUAL UP/DOWN WITH DIGITAL AND LIN­EAR AFT (pin 17 at V

). Holding one of these

DD

commands pressed, the tuning voltage is in­creasedor decreased.

During this operation, the Digital AFT is automat­ically defeated and can only be reconnected with
the ”AFT on” command or byan Automaticsearch
orpreset command.

The search speed is kept at minimum (there isno
incrementwith the time)

Band

VHF I

VHF III

UHF

CATV

seconds

491B-16.EPS

In caseof commandreceivedfromremote control,

Sweep Timefor the

Complete Band

128 seconds
128 seconds
512 seconds

512

16

Number of Tuning

Steps/Second

64
64
16

the counter is increased/decreasedevery two re­ceivedcommands.
Nobandswitchingisprovidedat the upper orlower
tuningpositions.
Thevolume is automaticallymuted 3 secondafter
the key pressure is immediately restored at the
releaseof the key.

d)MANUALUP/DOWNWITHLINEARAFT(pin17
at V

). When this control is used the Digital AFT

SS

isdisabled.
TheLinearAFToutputgoeslowafteranupordown

commandis issued and remains Lowfor 1 second
after the releaseof the key.

12/16

M491B

The volume is automatically muted for 3 seconds
afterthe key pressure and is immediately restored
at the release of thekey.

Tuningspeeds are as follows:

- FINE TUNING UP/DOWN
See description of pin 4.

- DIGITALAFTON
See description of pin 17.

- VOLUMEUP/DOWN
See description of pin 15.

- MAINS ON/OFF
See description of pins 25 and 26.

Band

VHF I

VHF III

UHF

CATV

Number of Tuning Steps Second

Time 0 After 1 s After 2 s After 3 s

64
64
16
16

128
128

32
32

256
256

64
64

512
512
128
128

STORECOMMANDS
2 modesof operationsare available.
a)store

b)memoryaddressing
In order to protect the memory, the store function

is internallydisabled after one storecycle.
It is enabled after a program change or a tuning
operation (it is not disabled by the Digital AFT
control).

a) STORE. The tuning information (Tuning D/A,
Fine tuning D/Aandband) is stored in apreviously
selected memory address when this command is
issued.

b) MEMORY ADDRESSING. The tuning informa­tion can alsobestoredwith this command followed
by thememory positionselection.
When this command is accepted all the memory
LEDs are blanked.
Selectionof the memory positioninitiatesthestore
operationsand restoresthe display.

MUTE ON/OFF
See descriptionof pin 15.

PIN 25 : MAINSON OPTIONINPUT
If connected to V
automaticallyswitchedonwhen V

(GND) the Mains output is

SS

isappliedand

DD

memory 1 is read.
If it is connectedto V

thecircuit goes in stand by

DD

condition.
PIN 26 : MAINSON/OFF OUTPUT

Switch on of the set is controlledby the Mainson
command issued for more than 0.3 s. The output
transistoris set in theoff condition to drive through
an integrated pull-up resistor, an external NPN
transistor.

Figure15

+5V

At each Mains on command a memory read out
occurs.AV

(+25 V)isrequiredforthisoperation,

PP

a 1 second delaystarts when the mains output is
switchedoff. For a correct reading of the memory
the V

supplyvoltage must reach the value of 25

PP

V within 1 secondafter a Mainson command.

491B-06.TBL

In caseof automaticswitch on at poweron caused
bypin 25 at GND, the total delay is of 1.13 second
(0.13s for V

power on reset plus 1 second for

DD

mains on).
TheMains on/off command,ifrepeated, willswitch
the output on (setoff).
Thelast addressinformationis preserved untilV
ispresent.
NextMains on command will switch the set at the
previously selected memory address and a read
operationwill be performed.

PINS27-28-29-30-33-34-35-36:
MEMORYADDRESSOUTPUT
Thesepinsoperateasoutputonlyfordisplayofthe
selected memory location. Max drive capability is
of15 mA/1.2V with the exception of pin 36 that is
of30 mA/1.5 V.
Directmemory selectionis onlypossiblebyremote
control.Alocalmemoryup/downcommandisavail­able in caseof emergency.
Pin32 mustbe grounded.
If pin 31 is grounded, the memory position 9 to 16
are skipped in case of memory up/down com­mands.
For normal operation pin 31 can be left open or,
better,connectedto V

DD

.

PINS31-32
Seedescriptionof pins 27 to 30 and33 to36.

PINS37-38-39-40 : BANDINPUT/OUTPUT
Theseoutputsareprovidedto selectupto 4 bands
viaexternal PNPs.
If one or more bands have to be skipped, the
correspondingoutputshavetobe short-circuitedto
V

.

SS

491B-17.EPS

DD

13/16

M491B

Figure16

The relation between pins and bands are as follows :
Pin 37 = UHF
Pin 38 = CATV
Pin 39 = VHF III
Pin 40 = VHF I

INPUT/OUTPUT CONFIGURATION

max. 13.2V

491B-18.EPS

Output OpenDrain

Pins 3, 4, 5, 6, 14, 15, 16, 30, 33,34, 35, 36

OutputPush-pull

V

DD

26

Inputs with Pull-up Load

V

DD

Inputs/Outputs(std)

Pins37, 38, 39, 40, 21, 22, 23, 24

491B-19.EPS

(21, 22, 23, 24 are used only for testing purposes)

Oscillator

491B-20.EPS

IR Input

491B-22.EPS

V

DD

8

7

491B-23.EPS

V

DD

14/16

Pins12, 13, 17

18, 19, 20, 25, 31

491B-21.EPS

11

491B-24.EPS

TYPICALAPPLICATION

Manual Searchwith LinearAFT (16 memoryoption)

TUNING

VOLTAGE

100nF

82kΩ

or

BSX93

100nF

56kΩ

150nF

47pF

33kΩ 33kΩ

100nF

2N3903

Ω

3.9k

+5V

+12V

10

kΩ

10

kΩ

BC177

10

3.3kΩ

1.5

kΩ

kΩ

5

8.2kΩ8.2kΩ8.2kΩ

373839

BC177

BC177

40

M491B

I

III

UHF

VOLUME

BC108

LINEARAFTDEFEAT

10µF

Ω

22k

ON/OFF

26

+12V

16

RELAY

+12V

5.6kΩ

15

0.68kΩ

14

17

R2

HIGH VOLTAGE

H

V (V) - 33V

R1(kΩ) =

R1

1.6kΩ1%

11mA

R2 =R1/4

33V

TAA550B

5.6

kΩ1%

Ω

82

k

F

22

µ

BC297

4.7kΩ

4.7nF2.2kΩ

+ 5V

kΩ

6.8

or 8160

TDA2320

9 3125

8 110

21222324 7

500kHz

100

100

pF

pF

M491B

2311

32

+12V

27

28

29

30

33

343536

7 x 0.68kΩ

181920

6 - PowerOn/Off

567

123

7 - VolumeUp

8 - VolumeDown

9

8

4

9 - Store

M708

445 to

510MHz

0.33

LOCAL COMMANDS

1 - MemoryUp

2 - MemoryDown

3 - SearchUp

4 - SearchDown

5 - Band Sequential

kΩ

491B-25.EPS

15/16

M491B

PACKAGE MECHANICALDATA

40 PINS- PLASTICDIP

I

L

E

F

40

1 20

Dimensions

a1

b

b2

e3

D

e

21

Millimeters Inches

Min. Typ. Max. Min. Typ. Max.

a1 0.63 0.025

b 0.45 0.018
b1 0.23 0.31 0.009 0.012
b2 1.27 0.050

D 52.58 2.070

E 15.2 16.68 0.598 0.657

e 2.54 0.100
e3 48.26 1.900

F 14.1 0.555

i 4.445 0.175

L 3.3 0.130

b1

PM-DIP40.EPS

DIP40.TBL

Information furnishedis believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility
for the consequences of use of such information nor for any infringement of patents or otherrights of third parties which may result
from its use. No licence is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics.
Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all
information previouslysupplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life
support devices or systems without express written approval of SGS-THOMSON Microelectronics.

 1994 SGS-THOMSON Microelectronics - All Rights Reserved

Purchase of I

2

I

C Patent. Rights to use these components in a I2C system, is granted provided that the system conformsto

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The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A.

2

C Components of SGS-THOMSON Microelectronics, conveys a license under the Philips

2

the I

C Standard Specifications as defined by Philips.

SGS-THOMSON Microelectronics GROUP OF COMPANIES

16/16