SAF7741 Просмотр технического описания (PDF) - NXP Semiconductors.
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SAF7741 Datasheet PDF : 83 Pages
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NXP Semiconductors
SAF7741HV
Dual IF car radio and audio DSP (N1F)
7.1.2.6 Stepped gain amplitude
The tuner communicates a new gain setting to the SAF7741HV via the DL interface. The
SAF7741HV has four independent and different stepped AGC banks:
• AGC_A
• AGC_B
• AGC_C
• AGC_D
The number of steps for each AGC bank and the associated resolution is listed in Table 4.
Table 4.
AGC
AGC_A
AGC_B
AGC_C
AGC_D
Stepped AGC gain reduction
Function
Number of Steps Number of Bits
LNA_1
16
12
LNA_2
8
11
Mixer
4
10
IF
4
10
Resolution
50 mdB
50 mdB
50 mdB
50 mdB
The AGC tables contain the corresponding gain reduction values of the tuner, expressed
in bits. Zero gain reduction is at the top of each table. The tuner has random access to the
table. The maximum single amplitude change of the AGC is 16 bits −1 LSB. This is
equivalent to 96 dB. This maximum amplitude change can be made in any combination of
AGC values from AGC_A up to AGC_D. The last gain reduction command from the tuner
is readable by the DSP in the AGC Change registers. Found in AGC Data Out registers
are:
• The total stepped gain reduction
• The linear gain reduction
• The resulting gain reduction
The TEF7000 tuner uses:
• AGC_A and AGC_B for wideband AGC (in this case LNA_1 and LNA_2)
• AGC_C for the mixer AGC
• AGC_D is used as IF_AGC
Remark: The AGC_A, AGC_B and AGC_D replace the pin-diode AGC in the TEF6730.
7.1.2.7 Step-response waveform
The compensating step-response waveform depends on the step response type to be
compensated. Compensating waveforms for the LNA and the mixer gain steps are stored
in ROM for both the IF response and the wideband response. The IF response is derived
from the PDC response before the AGC stage.
The step-response waveform from the ROM is used when the gain change is less than
12 dB. This results in compensation which is not audible and which therefore does not
require muting.
SAF7741_5
Objective data sheet
Rev. 05 — 09 May 2008
© NXP B.V. 2008. All rights reserved.
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