SAF7741 datasheet(11/83 Pages) NXP

11 / 83 page

SAF7741_5

Objective data sheet

Rev. 05 — 09 May 2008

11 of 83

NXP Semiconductors

SAF7741HV

Dual IF car radio and audio DSP (N1F)

Functional description

7.1 Radio subsystem

The complete radio system is able to receive FM, AM, Weatherband, RDS and FM/AM

digital radio. The SAF7741HV radio section will incorporate the following features (see

Figure 1):

• Two IFADCs to digitize the incoming analog IF signals from the tuner(s)

• Two Primary Decimation Chains (PDCs) for analog and digital radio reception,

including digital mixing to Zero IF (ZIF)

• Software-based radio functionality running on one or more DSPs depending on the

features set and dual or single tuner usage

The IFADC digitizes the incoming Near-Zero Intermediate Frequency (NZIF) signals. The

IFADC is a baseband

ΣΔ ADC.

The PDC decimates the incoming data stream by a factor of 128 before passing it to the

software radio for processing.

For digital radio reception the PDC decimates the incoming data stream by 64 before it is

forwarded to the external co-processor.

The software radio consists of three Tuner DSPs: TDSP1, TDSP2 and TDSP1E. All three

TDSPs have a basically identical structure, but TDSP1 and TDSP2 are extended with:

• A Finite Impulse Response (FIR) filter

• CORDIC (COordinate Rotation DIgital Calculation) Rotate and De-rotate (CRD)

TDSP1E is extended with a CRD only. Each FIR (controlled by the TDSP) is used for

variable bandwidth control and for the Polar-to-Rectangular (P->R), Rectangular-to-Polar

(R->P) and DIV conversions that will be used for demodulation. Added to this block is a

2LOG(LD(x)) function.

In addition, a Radio General-Purpose DAC (RGPDAC) and an RDS decoder are included

for each tuner channel.

The SAF7741HV chip is capable of handling full dual radio. Depending on the firmware,

several such configurations are possible:

• Dual radio with two stereo-audio output channels. The attainable performance

depends on the DSP tuner firmware. The available feature set is less than that for

one-channel radio

vddi

VDD pad connected to CORE VDD and internal VDD supply rail in I/O ring

vssi

VSS pad connected to CORE VSS and internal VSS supply rail in I/O ring

vsse

VSS pad connected to external (noisy) VSS supply rail

vssis

VSS pad connected to CORE VSS, internal VSS supply rail in I/O ring and substrate rail in I/O ring

vssco

VSS pad connected to CORE VSS

Table 3.

Pad name description …continued

Pad Name

Description

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