MSP3400C Ver la hoja de datos (PDF) - Micronas

Número de pieza

componentes Descripción

Fabricante

MSP3400C

Multistandard Sound Processor

Micronas 

MSP 3400C

PRELIMINARY DATA SHEET

DCO1

VREFTOP

ANA_IN1+

ANA_IN2+

ANA_IN–

AD_CV[7:1]

AGC

AD

AD_CV[8]

FRAME

FM2

DCO2

Pins

Internal signal lines

Control registers

Fig. 4–2: Demodulator architecture

Oscillator

Mixer

FIR_REG_1

Lowpass

Phase

Phase and

AM Dis-

crimination

Differen-

tiator

MODE_REG[8]

Mute

MSPC sound IF channel 1

(MSP-CH1: FM2)

Amplitude

Carrier

Detect

AD_CV[9,10,11]

MSPC sound IF channel 2

(MSP-CH2: FM1, AM)

Amplitude

Carrier

Detect

Mixer

Lowpass

Phase and

AM Dis-

Differen-

crimination

tiator

Phase

Mute

Oscillator

FIR_REG_2

MODE_REG[8]

DCO2

ADR_DA

Lowpass

FM2

Mixer

IDENT

Lowpass

FM1/AM

4.1.3. Lowpass Filtering Block for Mixed Sound IF

Signals

cy of 32 kHz. The usable bandwidth of the final base-

band signals is about 15 kHz.

FM bandwidth limitation is performed by a linear phase

Finite Impulse Response (FIR-filter). Just like the oscil-

lators’ increments, the filter coefficients are program-

mable and are written into the IC by the CCU via the con-

trol bus. Two not necessarily different sets of coefficients

are required, one for channel 1 (FM2) and one for chan-

nel 2 (FM1=FM-mono). In section 6.2.4., several coeffi-

cient sets are proposed.

4.1.4. Phase and AM Discrimination

The filtered sound IF signals are demodulated by means

of the phase and amplitude discriminator block. On the

output, the phase and amplitude is available for further

processing. AM signals are derived from the amplitude

information, whereas the phase information serves for

FM demodulation.

4.1.5. Differentiators

FM demodulation is completed by differentiating the

phase information output.

4.1.6. Lowpass Filter Block for Demodulated

Signals

The demodulated FM and AM signals are further low-

pass filtered and decimated to a final sampling frequen-

4.1.7. High Deviation FM Mode

By means of MODE_REG [9], the maximum FM-devi-

ation can be extended to approximately $360 kHz.

Since this mode can be applied only for the MSPC sound

IF channel 2, the corresponding matrices in the base-

band processing must be set to sound A. Apart from this,

the coefficient sets 380 kHz FIR_REG2 or 500 kHz

FIR_REG2 must be chosen for the FIR_REG_2. For a

given deviation, in relation to the normal FM-mode, the

audio level of the high-deviation mode is reduced by

6 dB.

4.1.8. MSPC-Mute Function in the Dual Carrier FM

Mode

To prevent noise effects or FM identification problems in

the absence of one of the two FM carriers, the

MSP 3400 C offers a carrier detection feature, which

must be activated by means of AD_CV[9]. The mute lev-

el may be programmed by means of AD_CV[10,11].

(see section 6.2.1.) If no FM carrier is available at the

MSPC channel 1, the corresponding channel FM2 is

muted. If no FM carrier is available at the MSPC channel

2, the corresponding channel FM1 is muted. In case of

the absence of both FM carriers, pure noise will be am-

plified by the input AGC. Therefore, a proper mute func-

tion depends on the noise quality of the TV set’s IF part

and cannot be guaranteed. The mute function is not rec-

ommended for the satellite mode.

10

MICRONAS INTERMETALL

Share Link: