SAA6581T/V1,518 NXP Semiconductors, SAA6581T/V1,518 Datasheet - Page 5

• Manufacturer Part Number: SAA6581T/V1,518
• Description: IC DEMODULATOR RDS/RBDS 16SOIC
• Manufacturer: NXP Semiconductors

Specifications of SAA6581T/V1,518

• Function: Demodulator, Filter
• Lo Frequency: 4.332MHz, 8.664MHz
• Gain: 20dB
• Current - Supply: 6mA
• Voltage - Supply: 4 V ~ 5.5 V
• Package / Case: 16-SOIC (0.300", 7.50mm Width)
• Pin Count: 16
• Screening Level: Industrial
• Package Type: SO
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Noise Figure: -
• P1db: -
• Rf Frequency: -
• Lead Free Status / Rohs Status: Compliant
• Other names: 935268605518; SAA6581TD-T; SAA6581TD-T

Philips Semiconductors
FUNCTIONAL DESCRIPTION
RDS/RBDS signal demodulation
B
The bandpass filter has a centre frequency of 57 kHz. It
selects the RDS/RBDS sub-band from the multiplex signal
MPX and suppresses the audio signal components. The
filter block contains an analog anti-aliasing filter at the
input followed by an 8th order switched capacitor
bandpass filter and a reconstruction filter at the output.
C
The comparator digitizes the output signal from the 57 kHz
bandpass filter for further processing by the digital
RDS/RBDS demodulator. To attain high sensitivity and to
avoid phase distortion, the comparator input stage has
automatic offset compensation.
D
The demodulator provides all functions of the SAA6579
and improves performance under weak signal conditions.
Demodulator functions include:
The RDS/RBDS demodulator recovers and regenerates
the continuously transmitted RDS/RBDS data stream in
the MPX signal and provides clock RDCL for the output
signals and data output RDDA for further processing by an
RDS/RBDS decoder, for example CCR921 or CCR922.
ARI
The demodulator checks the input signal for presence of
RDS only, or RDS plus ARI transmissions. After a fixed
test period, if the SYNC input is set HIGH the demodulator
locks in the ‘verified’ condition (see Table 1). If SYNC is set
LOW, the ARI clamping is reset (disabled). After SYNC
returns to HIGH, the demodulator resumes checking the
input signal.
2003 Oct 10
ANDPASS FILTER
LOCKED COMPARATOR
EMODULATOR
57 kHz carrier regeneration from the two sidebands
(Costas loop)
Symbol integration over one RDS clock period
Bi-phase symbol decoding
Differential decoding
Synchronization of RDS/RBDS output data.
RDS/RBDS demodulator
CLAMP
5
Table 1 Control pin SYNC
S
Output QUAL indicates the safety of the regenerated RDS
data (HIGH = ‘good’ data; LOW = ‘unsafe’ data).
Oscillator and system clock generator
For good performance of the bandpass and demodulator
stages, the demodulator requires a crystal oscillator with a
frequency of 4.332 or 8.664 MHz. The demodulator can
operate with either frequency (see Table 2), so that a radio
set with a microcontroller can run, in this case, with one
crystal only. The demodulator oscillator can drive the
microcontroller, or vice versa.
Table 2 Control pins TCON and MODE
The clock generator generates the internal 4.332 MHz
system clock and timing signal derivatives.
Power supply and internal reset
The demodulator has separate power supply inputs for the
digital and analog parts of the device. For the analog
functions an additional reference voltage (
internally generated and available via the output pin V
The demodulator requires a defined reset condition. The
demodulator generates automatically a reset signal after
the power supply V
IGNAL QUALITY DETECTION
TCON
SYNC
HIGH
HIGH
HIGH
LOW
internal ARI clamping disabled
ARI clamping allowed to be logged
MODE
HIGH
LOW
DDA
is switched on, or at a voltage-drop.
OSCILLATOR FREQUENCY
ARI CLAMPING
Product specification
4.332 MHz
8.664 MHz
SAA6581
1
2
V
DDA
) is
ref
.