STMicroelectronics TDA7478D Schematic [ru]

TDA7478

Fi

SINGLE CHIP RDS DEMODULATOR

1 FEATURES

■ VERY HIGH RDS DEMODULATION QUALITY

WITH IMPROVED DIGITAL SIGNAL
PROCESSING

■ HIGH PERFORMANCE, 57KHz BANDPASS

FILTER (8th ORDER)

■ FILTER ADJUSTMENT FREE AND WITHOUT

EXTERNAL COMPONENTS

■ PURELY DIGITAL RDS DEMODULATION

WITHOUT EXTERNAL COMPONENTS

■ RDS SIGNAL QUALITY OUTPUT

■ 4.332MHz CRYSTAL OSCILLATOR(8.664MHz

OPTIONAL)

■ LOW NOISE CMOS TECHNOLOGY

■ LOW RADIATION

2 DESCRIPTION

The TDA7478 recovers the additional inaudible RDS
information which is transmitted by FM radio broad­casting stations and operates in accordance with the

Figure 2. Block Diagram

gure 1. Packages

SO16

TSSOP16

Table 1. Order Codes

Part Number Package

TDA7478D SO16

E-TDA7478AD TSSOP16

EBU (European Broadcasting Union) specifications.

The device is made up of two sections: a cascaded
antialiasing + switched capacitors 8th bandpass filter
for precise RDS band selection and a demodulating
section that performs the extraction od RDS data
stream (RDDA) and clock (RDCL), to be further pro­cessed by a suitable RDS decoder.

Output for RDS signal quality is also present.

4.332MHz C2 47pFC1 27pF

MPX

270pF

FILOUT

V

S

100nF

10µF

November 2004

4

8

12

3VREF

GND

T57

15

2nd ORDER

ANTIALIASING

FILTER

8th ORDER

SC-BANDPASS

FILTER

-

+

6

BIPHASE DEC.

BIPHASE DEC.

57KHz PLL

POLARITY

INTEGRAL

OSCILLATOR &

DIVIDER

OSCOUTOSCIN

1413

5

OSEL

9

FSEL

16

1187.5Hz
PLL

QUAL DET.

0

MUX

EXTRES

DIFF. DECODER

TEST LOGIC

11

D03AU1490

1

RDCL

7

N.U.

1

QUAL

2

RDDA

10

TM

Rev. 2

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TDA7478

Table 2. Pin Description

No pin Name Description

1 QUAL Output for signal quality indication (High = good)

2 RDDA RDS data output

3 VREF Reference voltage

4 MPX RDS input signal

5 OSEL Oscillator selector pin:

6 GND Ground

7 N.U. Not Used (to be left open)

8 FILOUT Filter output

9 FSEL Frequency selector pin:

10 TM Test mode pin: - open = normal operation - closed to VS = testmode

11 EXTRES Reset pin: - open=run mode - closed to VS = reset condition

12 V

13 OSCIN Oscillator input

14 OSCOUT Oscillator output

15 T57 Testing output pin: 57kHz clock output

16 RDCL RDS clock output 1187.5Hz

S

- open, closed to V

- closed to GND=external driven

- open = 4.332MHz

- closed to VS = 8.664MHz

Supply voltage

= quartz oscillator

S

Figure 3. Pin Connection (Top view)

QUAL

RDDA

VREF

MPX

OSEL

GND

N.U.

1

2

3

4

5

6

7TM

15

14

13

12

11

10

RDCL16

T57

OSCOUT

OSCIN

V

S

EXTRES

FILOUT 8 FSEL9

D97AU752A

Table 3. Thermal Data

Symbol Description Value Unit

R

th j-case

Thermal Resistance Junction-case Max. 200 °C/W

2/8

TDA7478

Table 4. Absolute Maximum Ratings

Symbol Parameter Value Unit

V

S

T

op

T

stg

Table 5. Electrical Characteristcs
(T

= 25°C, VS = 5V, unless otherwise specified)

amb

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

S

I

S

FILTER

f

C

BW 3dB Bandwidth 2.5 3 3.5 kHz

G Gain f = 57kHz 17 20 23 dB

A Attenuation ∆f ± 4kHz 22 dB

R

I

R

L

S/N Signal to noise ratio V

V

IN

S

RDS

S

ARI

V

REF

DEMODULATOR

Input pins (EXTRES, FSEL, TM) all with internal pull down resistor
Input pin (OSEL) with internal pull up resistor

I

PD

I

PU

V

IH

VIL Input voltage low

Output pins (RDCL, RDDA, QUAL, T57)

V

OH

V

OL

OSCILLATOR

CLL

V

VCLH Input level OSCIN pin OSEL = open circuit 4 V

V

PP

(1) The 3rd harmonic (57kHz) must be less than -40dB with respect to the input signal plus gain.

Supply Voltage -0.3 to 7 V

Operating Temperature Range -40 to 85 °C

Storage Temperature -55 to 150 °C

Supply voltage 4.5 5 5.5 V

Supply current 7.5 12.0 mA

Center frequency 56.6 57 57.4 kHz

f = 38kHz 60 dB

f = 67kHz 45 dB

Input impedance of MPX 120 KΩ

Load impedance on FILOUT 1 MΩ

= 3mVRMS 30 40 dB

IN

MPX input signal

f = 19kHz; T3 ≤ 40dB
f = 57kHz (RDS)

(1)

100050mV

mV

RDS Detection Sensitivity 1 mVrms

ARI Detection Sensitivity 3 mVrms

Reference VS/2 V

Input Current VIN = 5V (pull-down input) 15 30 µA

Input Current VIN = 0V (pull-up input) -25 -10 µA

Input voltage high

0.7 · VS0.8 · V

0.2 · VS0.3 · V

S

V

V

S

Ouput voltage high IL = 0.5mA 4 4.6 V

Output voltage low IL = 0.5mA 0.4 1 V

Input level OSCIN pin OSEL = open circuit 1 V

Amplitude OSCOUT OSEL = open circuit 4.5 V

Amplitude OSCIN
(for external drive)

OSEL = GND, f = 4.332MHz
OSEL = GND, f = 8.664MHz

100
120

mVpp
mVpp

RMS

RMS

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