TDA7705 datasheet(33/42 Pages) STMICROELECTRONICS

33 / 42 page

TDA7705

Weak signal processing

Doc ID 15938 Rev 9

33/42

Weak signal processing

All the parameters in this section refer to the programmability of the DSP part of the device.

The typical values are those set by default parameters (start-up without parametric change

from main µP); the max and the min values refer to the programmability range. The values

are referred to the typical application (Figure 16: Example of FM tuned (narrow-band)

application / SPI control). Wherever the possible values are a discrete set, all the possible

programmable values are displayed.

5.1

FM IF-processing

5.1.1

Dynamic channel selection filter (DISS)

5.1.2

Soft mute

Table 26.

Dynamic channel selection filter (DISS)

(discrete set)

Symbol

Parameter

Test condition

Min

Typ

Max

Units

DISS BW

IF filter #6

response: - 3dB

±150

kHz

IF filter #5

±110

kHz

IF filter #4

±80

kHz

IF filter #3

±60

kHz

IF filter #2

±45

kHz

IF filter #1

±35

kHz

IF filter #0

±25

kHz

Table 27.

Soft mute

(continuous set)

Symbol

Parameter

Test condition

Min

Typ

Max

Units

SMsp

Start point vs. field strength

audio atten = 1 dB

read “FM_softmute”

no adjacent channel present

dBµV

SMep

End point vs. field strength

audio atten = SMd + 1 dB

read “FM_softmute”

no adjacent channel present

-6

dBµV

SMd

Depth

-30

-15

SMtauatt

Field strength LPF cut-off

frequency for soft mute

activation

0.1

100

4000

SMtaurel

Field strength LPF cut-off

frequency for soft mute

release

0.1

4000

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