M494 Datasheet, PDF (4/22 Pages) STMicroelectronics – SINGLE-CHIP VOLTAGE TUNING SYSTEM WITH 4 ANALOG CONTROLS AND mP INTERFACE

M494
DEFINITION OF TERMS
The M494 has four conditions or states that it can
be in which are defined below. Logic LO 0V and
logic HI = 5V.
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V_DD = 0V. V_PP = 0V
On
V_DD = 5V. V_PP = 25V.
Device driving display normally.
Data Handshake pin configured as RTS i/p.
Standby o/p = HI. All other functions operating
normally.
Standby
VDD = 5V. VPP = 0V.
Device driving display to show a single static bar
(g segment).
Data Handshake pin configured as RTS i/p. Stanby
o/p = LO.
All keyboard commands are disabled except any
program command On/Off, On/Stanby.
Memory sequence up or down, 1 * and ±10 (dec-
ade) commands.
Analog controls. Tuning, AV, MS and AFC defeat
o/p’s = LO. Band o/p’s = HI (externally pulled up).
See Standby section for more detail.
Off
V_DD = 5V. V_PP = 0V. Device not driving display.
Data Handshake pin configured as OFF o/p.
Standby o/p = LO. Display disabled and Display
drive o/p = HI (externally pulled up).
All keyboard commands disabled except ON/OFF.
Remote and data command sources disabled.
Analog controls, Tuning, AV, MS and AFC defeat
o/p’s = HI (externally pulled up).
FUNCTIONAL DESCRIPTION (clock frequency = 500kHz)
VDD & VSS
VDD = + 5V ± 5%. When applied, an internal power
on reset of 110ms is generated. The voltage thresh-
old for the reset is in the range 3 to 3.5V but is in
fact the point at which the internal clock phases
start.
VSS = 0V. This pin is connected to the substrate of
the i.c. and is the reference for all parameters of
the device.
Oscillator I/O
The frequency of the oscillator should be between
445 and 510kHz using a cheap ceramic resonator.
The reference frequency of the remote control
transmitter must also be in the same range i.e. if
the oscillator frequency is 455kHz then the trans-
mitter frequency could be 510kHz or vice versa.
Test
This pin is normally used for post fabrication testing
purposes only and should be tied to VSS. However
this pin can be used by SGS-THOMSON or the
OEM to enable external loading of the memory.
Details of how to achieve this can be furnished by
SGS-THOMSON.
The signal from the preamplifier (TDA8160) is
brought to the RC signal input via an AC coupling
network (see Figure 1).
VDD (TDA8160)
5V
12V
R
2.2kΩ
10kΩ
C
4.7nF
4.7nF
Figure 1
TDA8160
R
C
M494
The input is self biased to approx. 1.5V. When a
large signal is applied to the input a level shift will
take place predominantly due to the coupling net-
work.
However another time constant is also visible due
to the coupling C and the internal resistor Ri. (see
Figures. 2 & 3).
Figure 2
V_DD
Remote Control Input
The integrated RC receiver decodes signals trans-
1.5V
mitted by the M708 (address 10). The minimum
signal amplitude should be 0.5V peak to peak at
the input pin. The minimum pulse width should be
8µs.
Ri
Remote
Control I/P
to Cct
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