TDA9887 Philips Semiconductors, TDA9887 Datasheet - Page 13

• Manufacturer Part Number: TDA9887
• Description: I2C-bus controlled multistandard alignment-free IF-PLL demodulator with FM radio
• Manufacturer: Philips Semiconductors

Philips Semiconductors
8.14
The audio amplifier consists of two parts:
The AF preamplifier used for FM sound is an operational
amplifier with internal feedback, high gain and high
common mode rejection. The AF voltage from the
PLL demodulator is 5 mV (RMS) for a frequency deviation
of 27 kHz and is amplified by 30 dB. By the use of a
DC operating point control circuit (with external
capacitor C
PLL DC voltage. The low-pass characteristic of the
amplifier reduces the harmonics of the sound intercarrier
signal at the AF output terminal.
For FM sound a switchable de-emphasis network (with
external capacitor) is implemented between the
preamplifier and the output amplifier.
The AF output amplifier provides the required AF output
level by a rail-to-rail output stage. A preceding stage
makes use of an input selector for switching between
FM sound, AM sound and mute state. The gain can be
switched between 10 dB (normal) and 4 dB (reduced).
Switching to the mute state is controlled automatically,
dependent on the digital acquisition help in case the VCO
of the FM-PLL is not in the required frequency window.
This is done by a time constant: fast for switching to the
mute state and slow (typically 40 ms) for switching to the
no-mute state.
All switching functions are controlled via the I
8.15
The principle is to multiply the first radio IF (e.g. 33.3 MHz
at tuner output) with 44 MHz reference signal. The result
of the down-conversion is the second radio IF (10.7 MHz)
at intercarrier output.
In the radio mode the tuner delivers a first radio IF signal
of 33.3 MHz. This signal is fed via the SIF SAW filter
(conventional used for QSS TV sound processing) to the
SIF input. The sound IF amplifier supplies this radio
IF signal by means of gain control with constant level to the
QSS mixer. The single reference QSS mixer generates the
second radio IF signal of 10.7 MHz. In the radio mode the
VIF VCO operates as part of a frequency synthesizer and
2004 Aug 25
AF preamplifier
AF output amplifier.
AM sound, FM sound and forced mute
Auto mute enable or disable
De-emphasis off or on with 50 or 75 s
Audio gain normal or reduced.
I
IF-PLL demodulator with FM radio
2
C-bus controlled multistandard alignment-free
Audio amplifier and mute time constant
Radio mode
AF
), the AF preamplifier is decoupled from the
2
C-bus:
13
delivers a constant 44 MHz signal (derived from the
reference signal of 4 MHz) for the down-conversion of the
first radio IF to 10.7 MHz. This signal is fed via the external
ceramic band-pass filter to the FM demodulator. The
demodulated AF signal is amplified by the audio amplifier.
In case of NTSC application (M/N standard) the internal
mixing frequency is 52 MHz. So, the first radio IF has to be
41.3 MHz.
In the radio mode, the tuner AGC is derived from the
SIF-AGC.
For tuning search mode, the device offers certain
monitoring functions. Switchable are radio AFC, FM-AGC
or SIF-AGC to pin AFC.
8.16
The band gap circuit internally generates a voltage of
approximately 2.4 V, independent of supply voltage and
temperature. A voltage regulator circuit, connected to this
voltage, produces a constant voltage of 3.55 V which is
used as an internal reference voltage.
8.17
The device can be controlled via the 2-wire I
microcontroller. Two wires carry serial data (SDA) and
serial clock (SCL) information between the devices
connected to the I
The device has an I
auto-increment. The circuit operates up to clock
frequencies of 400 kHz.
A slave address is sent from the master to the slave
receiver. To avoid conflicts in a real application with other
devices providing similar or complementing functions,
there are four possible slave addresses available. These
Module Addresses (MADs) can be selected by connecting
resistors on pin SIOMAD and/or pins SIF1 and SIF2 (see
Fig.25). Pin SIOMAD relates with bit A0 and pins SIF1
and SIF2 relate with bit A3. The slave addresses of this
device are given in Table 1.
The power-on preset value is dependent on the use of
pin SIOMAD and can be chosen for 45.75 MHz NTSC as
default (pin SIOMAD left open-circuit) or 58.75 MHz NTSC
(resistor on pin SIOMAD). In this way the device can be
used without the I
Remark: In case of using the device without the I
then the rise time of the supply voltage after switching on
power must be longer than 1.2 s.
Internal voltage stabilizer
I
2
C-bus transceiver and module address
2
2
C-bus as an NTSC only device.
C-bus.
2
C-bus slave transceiver with
Product specification
TDA9887
2
C-bus by a
2
C-bus,