SGS Thomson Microelectronics TDA7420 Datasheet



MULTIFUNCTIONAUDIO PROCESSOR

CASSETTEPREAMPLIFIER:

FORWARD/REVERSE INPUTS GROUND
COMPATIBLE

INTERNALSWITCHES FOR EQUALIZATION
INTERNALADJUSTMENTFOR TRAKING
INTERNALADJUSTMENTFOR OUTPUT

AMS:

INPUTGAINCONTROL
ADJUSTABLEGAINVERSUSFREQUENCY

TDA7420

TQFP 64(14x14)

AUDIOPROCESSOR:

INPUTS:1 FULLYDIFFERENTIAL, 1 DIFFER­ENTIAL, 1 STEREOAND 1 MONO

INPUTGAINFROM 0 TO 15dB(1dB STEP)
VOLUME CONTROL FROM +16 TO -63dB

(1dB STEP)
BASS AND TREBLE CONTROL FROM -18

TO 18dB (1dB STEP)
DIRECT MUTE, SOFT MUTE AND RADIO

MUTE
FOURINDEPENDENT OUTPUTSTAGES:

- ATTENUATIONCONTROL FROM
0 TO -79dB (1dB STEP)

- BEEPCONTROL (ON/OFF, FRONT/REAR)

STEREO DECODER:

ROLL-OFFADJUSTMENT
SELECTABLEDEEMPHASIS
19KHzCANCELLATION
HIGHCUT CONTROL
STEREOBLEND

NOISE BLANKER

AUTOMATIC THRESHOLD CONTROL AND
PROGRAMMABLE TRIGGERTHRESHOLD

INTEGRATEDHIGHPASSFILTER
PACKAGE:TQFP64(14x14)

ORDERING NUMBER: TDA7420

DESCRIPTION

The TDA7420 I
audio processor contains all signal processing
blocks of a high performance car radio, including
audioprocessor, stereodecoder, noise blanker,
differentmute functions,cassettepreamplifierand
AMS function.

The use of BICMOS technologyallows the imple­mentation of several filter functions with switched
capacitor techniques like fully integrated, adjust­ment free PLL Loop filter, pilot detector with inte­grator.

This minimizes the number of external compo­nents.

Due to a highly linear signal processing, using
CMOS-switching techniques instead of standard
bipolar multipliers, very low distortion and very
low noise are obtained also in the stereodecoder
part.

Very low DC stepping is obtained by use of the
BICMOStechnology.

2

C bus controlled multifunction

May 1998

1/29

TDA7420

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

S

T

amb

T

stg

PIN CONNECTION

Operating Supply Voltage 10 V
Operating Temperature Range -40 to 85 °C
Storage Temperature Range -55 to 150 °C

AC_IN1_R

AC_OUT1_R

AC_OUT1_L

TREBLE_L

TREBLE_R

AC_OUT2_R

AC_OUT2_L

AC_IN2_L

AC_IN2_R

BASS2_R
BASS1_R

BASS2_L
BASS1_L

V

CC

SDA

SCL

AC_IN1_L

CSM

1
2
3
4
5
6
7
8
9

10

12
13
14

15
16

17 18 19 20 21

AGND

DIGGND

CREF

VHCC

AM_RR1L1

COMPOSIT

AM_L

59 58 57 56 5455 53 52 51 50 49

6061626364

22 23 24 25 26

VR

HCL

VSB AM_C

HCR

TRIGGER OUT

CD_L+

PEAK

TBLANK

CD_L-

CD_R-

CD_R+

VCC_PRE

PREOUT_R

271128 29 30 31 32

VCO

AMS_IN

AMS_LF

INTP

AMS_GAIN

EQRO

48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33

INTS

EQRI
INR2(FR)
INR1(RR)
GND_PRE
INL1(RL)
INL2(FL)
EQLI
EQLO
PREOUT_L
EQSW
BEEP
OUT_RL
OUT_FL
OUT_RR
OUT_FR
AMS_OUT

D94AU182

THERMALDATA

Symbol Parameter Value Unit

R

th j-pins

Thermal ResistanceJunction-pins max 85 °C/W

2/29

BLOCK DIAGRAM

TDA7420

LR_OUT

LF_OUT

RR_OUT

RF_OUT

34

35

36

37

-79

-79

-79

MUTE

1dB

-63

+16 ÷

-79

1dB

1dB

0 ÷

0 ÷

&

RADIO MUTE

+18

1dB

BASS

-18 ÷

+

1dB

MUTE

(IN, OUT)

100K

-6dB

0.5dB

0÷

-6dB

0.5dB

0÷

1dB

1dB

0 ÷

0 ÷

CS4

AC_IN2_R

9863765410121311

AC_IN2_L

AC_OUT2_L
AC_OUT2_R

TR_R

TR_L

BASS2_R

BASS2_L

BASS1_L

BASS1_R

100KΩ

S

AMS OUT

V

CC

V

DOLBY B/C

INTS
INTP

AMS_GAIN

AC_IN1_L

AC_IN1_R

AMS_IN

AC_OUT1R

AC_OUT1L

AMS_LF

L1 R1

33313064 32

129

2

32850404941

PREOUT_RPREOUT_L

-23dB/

0/-20dB/

-23dB/

0/-20dB/

MUTE

MUTE

+

SOFT

+18

TREBLE

-18 ÷

VOLUME

BEEP

DIG GND

SCL

SDA

38

C BUS

2

I

DECODER

BUS LATCHES

AMS

GAIN 0÷28dB 1dB

G

L

HCL

21

171516

CUT

HIGH

50 - 75

NOISE

19KHz

&

DEMODULATOR

FM/AM

15dB

1dB step

0 ÷

R

+

MUTE

MULTIPLEXER

HCR

20

-5dB

CONTROL

µsec

DEEMPH

BLANKER

25KHz

CANCELLATION

AMPLITUDE ADJ

VHCCVRVSB

LEVEL

CONTROL

THRESHOLD

9dB

2.5dB

1.5 ÷

221923

CONTROL

PLL

MUTE

TRIGGER_

24

PEAK DETECTOR +

RECTIFIER

COMP

OUT

PULSE FORMER

SUPPLY

D94AU106I

14 - November - 1995

TBLANKPEAK

27 25

456KHz

AGND CREF VCO

1814 62 26

VCC

RADIO MUTE

EQROEQLO

CC_PRE

V

51

(Nom)

5% step

3.8K

45

GND_PRE

RM
RM

42434439464748

INL1

INL2

EQLI

EQSW

INR1

INR2

EQRI

53

CD_R-

0dB

0dB

20K

20K

20K

20K

50K

52

CD_R+

55

50K

CD_L+

545657

L1

CD_L-

100K

100K

R1

25K

25K

25K

25K

58

59

AM_R GAIN

AM_C

25K

25K

25K

60

61

AM_L

COMPOSIT

3/29

TDA7420

ELECTRICALCHARACTERISTICS (VS= 8.5V; T

amb

=25°C; RL= 10KΩ; all gains = 0dB; f = 1KHz;

unless otherwise specified, refer to the Test Circuit.)

Symbol Parameter Test Condition Min. Typ. Max. Unit

INPUT SECTION

DifferentialInput Pins 52,53, 54, 55

R

V

CL

CMRR Common Mode Rejection Ratio 45 55 dB

DIFF Differential Gain -1 0 1 dB

G

Input Resistance 37 50 63 KΩ

I

Clipping Level THD = 0.3% 2.0 2.5 Vrms

StereoInput Pins56, 57

R

V

CL

Input Resistance 75 100 125 KΩ

I

Clipping Level 2.0 2.5 Vrms

QuasiDifferentialInput Pins58, 59,60

R

V

CL

Input Resistance 18 25 32 KΩ

I

Clipping Level 2.0 2.5 Vrms

CompositeInput Pin 61

R

V

CL

Input Resistance 18 25 32 K

I

Clipping Level 2.0 2.5 Vrms

MULTIPLEXER

G

G
G

R

IMIN
IMAX
STEP

V

DC

O

Output Resistance(pin 2,3) 100 200 300
Minimum Gain -1 0 1 dB
Maximum Gain 14 15 16 dB
Step Resolution 0.5 1 1.5 dB
Dc Steps Adjacent Gain Step -5 1 5 mV

MINto GMAX 2mV

G

Ω

Ω

VOLUME CONTROL

R

C

MAX

A

MAX

STEPC Step Resolution Coarse

A

E

A

E

T

V

DC

Input Resistance (1, 64) 24 33 42 KΩ

I

Max Gain 15 16 17 dB
Max Attenuation 63 dB

Attenuation
Attenuation Set Error G =16 to -40dB -1.5 0 1.5 dB
Tracking Error 2dB
DC Steps Adjacent Attenuation Steps -3 0.1 3 mV

SOFTMUTE

A

MUTE

t

D

Mute Attenuation 40 50 dB
Delay Time C

BASS CONTROL

C

RANGE

A

STEP

R

B

Control Range +15 +18 +20 dB
Step Resolution 0.5 1 1.5 dB
Internal Feedback Resistance 48 65 82 KΩ

AV= 16to -40dB 0.5 1.0 1.5 dB

from 0dB to A

= 22nF; I= I

EXT

MAX

0 to -20dB; I = I

MAX

MIN

0.5 5 mV

1.0 ms
23 ms

4/29

TDA7420

ELECTRICALCHARACTERISTICS (continued.)

Symbol Parameter Test Condition Min. Typ. Max. Unit

TREBLE CONTROL

C

RANGE

A

STEP

T Internal Feedback Resistance 37 50 63 KΩ

R

SPEAKERATTENUATORS

C

RANGE

A

STEP

A

MUTE

E

A

V

DC

AUDIO OUTPUTS

V

CLIP

R

L

R

OUT

V

DC

GENERAL

E

NO

S/N Signal toNoise Ratio All gains 0dB; V

d Distortion V

S

C

E

T

Control Range +17 +18 +19 dB
Step Resolution 0.5 1 1.5 dB

Control Range 79 dB
Step Resolution AV= 0to -40dB 0.5 1 1.5 dB
Output MuteAttenuation 80 100 dB
Attenuation Set Error AV= 0to -40dB 1.50 dB
DC Step Adjacent Attenuation Steps 0.1 3 mV

Clipping Level d = 0.3% 2.0 2.5 V
Output LoadResistance 2 KΩ
Output Impedance 100 200 300 Ω
DC VoltageLevel 3.35 3.6 3.85 V

Output Noise BW = 20Hz to 20KHz, flat

Output Muted
All gains = 0dB

=1V

I

; 0.01 0.08 %

RMS

O =1VRMS ; 106 dB

4.0

5.0 15

Channel Separation Left/Right 80 95 dB
Total Tracking Error AV= 0to -20dB; 0 1 dB

A

= -20to -40dB; 0 2 dB

V

RMS

µ
µV

V

BUS INPUT

V

IL

V

IH

I

IN Input Current VIN = 0.4V -5 5 µA

V

O

Input Low Voltage 1V
Input High Voltage 3 V

Output VoltageSDA

IO= 1.6mA 0.1 0.4 V

Acknowledge

SUPPLY

V

IL

I

S

SVR Ripple Rejection

Supply Voltage 6.5 8.5 10.0 V
Supply Current Stereo Decoder = ON 25 33 41 mA

Stereo Decoder = OFF 20 28 35 mA
Audioprocessor 80 dB

C

=22µF

ref

StereoDecoder + Audioprocessor 60 dB

5/29

TDA7420

PREAMPLIFIER(VS=8.5V; T

amb

=25°C; RIN= 600Ω; unlessotherwisespecified(see testcircuit)

Symbol Parameter Test Condition Min. Typ. Max. Unit

R

V

out DC

R

O

I

I

VO Open Loop Gain f = 400Hz 110 dB

G

G

V
N Resistance Normal Position 50 250 500 Ω

R

R

MLR

Input Resistance 100 KΩ

I

Output VoltageDC (pin 40, 50) 3.2 3.5 3.9 V
Output Resistance(pins 40,50) 100 200 300 Ω
Input BiasCurrent 10

Closed LoopGain NAB short 31 32.5 34 dB

Resistance Metal Position

2.85 3.8 4.75 KΩ

(left ,right)

R

MR

R

Mmax

R

Mmin

Step Resolution (versus RM)5%
Maximum Value for R

M

3.42 4.56 5.7 KΩ
Minimum Valuefor RM 2.28 3.04 3.8 KΩ
Dolby LevelControl Control Range 5.5 6.0 6.5 dB

Step Resolution 0.25 0.5 0.75 dB

S

R

e

N

Slew Rate NAB Short 1 V/µs
Total Input Noise RIN=600Ω; unweighte d 0.8 µV

R

=600Ω;CCIR warn 0.5

IN
IN=0;unweighted 0.45 µV

R

Output AttenuationControl D1, D0 = 00 -0.75 0 0.75 dB

D1, D0 = 01 -20 dB
D1, D0 = 10 -23 dB
D1, D0 = 11 -80 dB

THD Total Harmonic Distortion V

SVR

C

S Channel Separation(L to R) 45 60 dB

C

CT

Ripple Rejection 75 dB

1

Channel Cross talk (F to R) 60 80 dB

S/N Signal to Noise V

= 1V; f = 1KHz metal 0.02 %

O

V

= 1V; f = 1KHz normal 0.02 0.1 %

O

V

= 1V; f = 10KHz metal 0.05 %

O

V

= 1V; f = 10KHz normal 0.04 %

O
O = 2V; f = 1KHz %

V

= 388mV; metal; CCIR arm 65 dB

O

A

µ

V

µ

AUDIO MUSIC SENSOR

IAMSOUT AMS Output Current 5 mA

VAMS

6/29

R

i-29

V

TH1

V

TH2

AMS

V

INTP

V

INTS

S

R

i-30

G

AMS Output Low Level IAM

OUT

= 2mA 500 800 mV

OUT

Input Resistance AMS Gain (pin 23) 75 100 125 KΩ
Interprogram Threshold Voltage 1.2 1.45 1.7 V
Interspace Threshold Voltage 4.8 5.2 5.6 V
AMS ThresholdLevel 2.0 2.8 3.6 V

th

INTP Output Voltage I
INTS Output Voltage I

= 2mA 0.2 0.8 mV

OUT

= 2mA 0.2 0.8 mV

OUT

INTP Charge Current 50 70 150
INTS Charge Current 50 70 150 µA
Gain Sensitivity min Gain V30vs V

max Gain V

30

vs V

29
29

11 dB
42 dB

AMS Gain Resistance D6, D5 = 00 13 17.5 22 KΩ

D6, D5 = 01 16.5 22 27.5 K
D6, D5 = 11 75 100 125 KΩ

A

µ

Ω

TDA7420

STEREO DECODER PART
ELECTRICAL CHARACTERISTICS (V

age on pin 61 (composite):V

I = 1.5dB;T

G

Symbol Parameter Test Condition Min. Typ. Max. Unit

SVRR Supply Voltage Ripple Rejection V

V

O

α ChannelSeparation V

THD Total Harmonic Distortion 0.02 0.3 %

S + N

=27°C;unless otherwise specified)

amb

DC Output Voltage(HCL, HCR) 3.95 4.25 4.55 V

Signal Plus Noise toNoise Ratio f = 20Hz to 16KHz;

MPX

=0.5V

N

MONO/STEREOSWITCH

V

V

INTH

INTH

Pilot Threshold Voltage for stereo ”ON” Pth=1

Pilot Threshold Voltage for stereo ”OFF” Pth =1

STEREOBLEND

V

SB-VR

Control Voltage for Channel
Separation

HIGH CUT CONTROL

τ

deemp

R

HCC

De-Emphasis Time Constant CL,CR=1nF;STDDS= 0

High Cut Control Resistance V

VCO

f

OSC

∆f/f Capture and Hold Range 0.5 1 %

Oscillator Frequency 456 KHz

= 8.5V; de-emphasis time: T = 50µs; nominal MPX input volt-

S

(75KHzdeviation);modulation frequency= 1KHz;

RMS

= 100mV; f =1KHz 50 65 dB

RIPPLE

SB-VR

=100mV

DC

50 dB

91 dB

S=2V

RMS

P

th =0

19

8

P

12

=0

th

= 6dB; (note 5) -300 -250 -200 mV

α

16

16
26

14
22

2234mV

2028mV

α = 26dB; -80 mV

43 50 57

V

HCC-VR

C

L,CR

V

HCC-VR
HCC-VR

V

HCC-VR

= 100mV

=1nF;STDDS= 1

64 75 86 µs

=100mV
=100mV;STDDS=0 43 50 57 K
=-0.5V(note5) 115 150 185 KΩ

mV

mV

µ

RMS
RMS

RMS
RMS

s

Ω

CARRIERAND HARMONIC SUPPRESSIONAT THE OUTPUT

α19 Pilot Signal f= 19KHz 40 55 dB
α38 Subcarrier f =38KHz 75 dB
α57 Subcarrier f =57KHz 62 dB

76 Subcarrier f = 76KHz 90 dB

α

INTERMODULATION (note1)

2f

α

3f

α

= 10KHz; f

mod

= 13KHz; f

mod

= 1KHz 65 dB

spur

= 1KHz 75 dB

spur

TRAFFIC RADIO (note 2)

57 Signal f = 57KHz 70 dB

α

SCA - SUBSIDIARY COMMUNICATIONS AUTHORIZATION (note3)

67 Signal f = 67KHz 75 dB

α

ACI - ADJACENTCHANNEL INTERFERENCE(note4)

α114 Signal f = 114KHz 95 dB

190 Signal f = 190KHz 84 dB

α

7/29

TDA7420

NOTES TO THE CHARACTERISTICS

1 INTERMODULATION SUPPRESSION

α2 =

α3 =

(

V

signal)(at1KHz

O

V

(spurious)(at1KHZ)

O

(signal)(at1KHz)

V

O

(

V

spurious)(at1KHZ

O

)

;f

= (2x 10KHz) - 19KHz

s

;f

= (3x 13KHz) - 38KHz

s

)

measuredwith : 91% monosignal; 9% pilot signal; fm=10KHzor 13KHz.

2. TRAFFICRADIO(V.F.) suppression

α57 (V.W.F.)=

V

O(signal)

(spurious)(at1KHZ ±23Hz)

V

O

(at1KHz)

measuredwith : 91% stereosignal; 9% pilotsignal; fm=1KHz; 5% subcarrier

(f=57KHz,fm = 23Hz AM,m = 60%)

3. SCA (SUBSIDIARYCOMMUNICATIONS AUTHORIZATION)

α67 =

V

O(signal)

V

(spurious)(at9KHZ)

O

(at1KHz)

;f

= (2 x 38KHz) - 67KHz

s

measuredwith : 81% monosignal; 9% pilot signal; fm=1KHz;

10% SCA - subcarrier(f

= 67KHz, unmodulated).

s

4. ACI (ADJACENTCHANNEL INTERFERENCE)

α114 =

α190 =

V

O(signal)

(spurious)(at4KHZ)

V

O

V

O(signal)

(spurious)(at4KHZ)

V

O

(at1KHz)

(at1KHz)

;f

= 110KHz- (3x 38KHz)

s

;f

= 186KHz- (5x 38KHz)-

s

measuredwith 90%mono signal; 9% pilot signal;fm = 1KHz; 1%spurioussignal

= 110KHzor 186KHz,unmodulated).

(f

s

5: Controlrange for HighCut Controland StereoBlend is V
Figure : High CutControl

f

8/29

c

(KHz)

3

2

1

0

-500 -400 -300 -200 -100 0 V

D94AU183

HCC-VR

- 400mV ≤ VSB,V

R

Figure: StereoBlend

SEP
(dB)

40

30

20

10

0

-400 -300 -200 -100 VSB-V

HCC≤VR

D94AU184

R

TDA7420

NOISE BLANKERPART
FEATURES:

INTERNAL 2nd ORDER 140KHz HIGH-PASS
FILTER

NOISE RECTIFIER OUTPUT FOR SIGNAL
QUALITYDETECTION

PROGRAMMABLETRIGGERTHRESHOLD

ADDITIONAL CIRCUITS FOR DEVIATION
AND FIELD STRENGTH -DEPENDENT TRIG­GER ADJUSTMENT

BLANKING TIME PROGRAMMABLE BY EX­TERNALCAPACITOR

VERY LOW OFFSET CURRENT DURING
HOLD TIME DUE TO OPAMPS WITH MOS
INPUTS

TRIGGER THRESHOLD DEPENDENT ON
HIGH FREQUENCY NOISE WITH PRO­GRAMMABLEGAIN

ELECTRICALCHARACTERISTICS (continued)

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

TRMIN

V

TRMIN

V

TRSTEP

V

TRNOISE

V

PEAK

V

RECTDEV

V

RECTFS

T

I

OS

Trigger Threshold (*)1)minimum Measured with

NBT =000
V

= 1.2V

PEAK

D2onbyte2=1
D2onbyte2=0

100 15030200 mVp

Trigger Threshold1)maximum Measured with

NBT =111
V

= 1.2V

PEAK

D2onbyte2=1
D2onbyte2=0

130 18565250 mVp

Trigger Threshold Step Size 5 mVp
Noise Adjusted Trigger Threshold

Rectifier Voltage
D2onbyte2 =1

2)

Measured with
V

PEAK

D2 on byte 2 = 0

= 1.4V

NAT = 00
NAT = 01
NAT = 10
NAT = 11

VMPX = 0mV 0.9 V

= 50mV

V

MPX

140
180
240
280

1.5 V

f = 200KHz
V

MPX

= 100mV

2.0 V

f = 200KHz

Deviation Dependent Rectifier
Voltage

3)

Measured with
V

=500mV

MPX

(75KHzdev.)

OVD = 00(off)
OVD = 01
OVD = 10
OVD = 11

Field Strength Controlled Rectifier
Voltage

4)

Measured with
V

=0mV

MPX

V

=-500mV

SB-VR

(fullymono.)

Suppression PulseDuration CBLANK = 330pF 40

S

FSC = 00(off)
FSC = 01
FSC = 10
FSC = 11

Input Offset Current During

0.9

1.2

2.0

2.8

0.9

1.3

1.9

2.4

10 pA

Suppression Time

mVp
mVp
mVp
mVp

V
V
V
V

V
V
V
V

s

µ

(*) All thresholds are measured by using a pulse withTR=2µs, T

The repetition rate must notincrease the PEAK voltage.

1) NTB representsbits D0 - D2 of NB byte 1

2) NAT representsbits D3 - D4 of NB byte 1

3) OVD represents bits D5 -D6 of NB byte 1

4) FSC representsbits D0 - D1 of NB byte 2

=2µs and TF=10µs.

HIGH

V

DC-LEVEL

MPX

D94AU185

V

TH

TRT

HIGH

T

F

Time

9/29

TDA7420

DESCRIPTION

DESCRIPTIONOFTHE NOISEBLANKER
In the normal automotive environment the MPX

signal is disturbed by ignition spikes, motors and
high frequencyswitches etc.

The aim of the noiseblanker part is to cancel the
influence of the spikes produced by these compo­nents.
Therefore the output of the stereodecoder is
switched off for a time of 40µs (averagespike du­ration).

In a first stage the spikes must be detected but to
avoid a wrong triggering on high frequency noise
a complextriggercontrol is implemented.

Behind the triggerstage a pulse former generates
the40µs ”blanking” pulse.

In the following section all of these circuits are de­scribed in their function and their programming,
too (see fig.1).

1.1 NormalTriggerPath (RECT-PEAK, ACT,
PEAK-COMP,BLANK-COMP, BIAS-MONO)

The Incoming MPX signal is highpass-filtered,
amplifiedand rectified(block RECT-PEAK).

The second order highpass-filterhas a corner-fre­quency of 140KHz.

The gain of the rectifier can be controlled by the
bit D2 of the noiseblankerbyte2.

If programmingbit D2 to zero the gain is only half
of the nominal value.

All trigger thresholds must be roughly doubled in
this case. The rectified signal, RECT, is used to
generate by peak-rectification a signal called
PEAK,which isavailable at the PEAK pin.

Also noise with a frequency >100KHz increases
the PEAK voltage. The value of the PEAK voltage
influences the trigger threshold voltage Vth (block
ATC).

Both signals, RECT and PEAK+Vth are fed to a
comparator (block PEAK-COMP) which outputs a
sawtooth-sharped waveform at the TBLANK pin,
it is triggered.

A second comparator (block BLANK-COMP)
formsthe internal blanking duration of 40µs.

The noiseblanker is supplied by his own biasing
circuit (block BIAS-MONO).

1.2 Automatic Threshold Control (ATC)

There are two independent possibilities for pro­grammingthe triggerthreshold:

a)the minimum threshold in 8 steps (bits D0-D2,

NB-byte1)

b)the maximum threshold in 4 steps (bits D3-

D4, NB-byte 1) (see fig.2)

The low threshold is used in combination with a
good MPX signalwithout any noise.
The sensitivity in thisoperationis high, depending
only on the programmed”Low Trigger Threshold”,
bits D0-D2 of the noiseblankerbyte 1.

It isindependentof the PEAK voltage.
The MPX signal is noisy (low fieldstrength) the

PEAK signal increases due to the higher noise,
whichis also rectified (see part 1.1).

With increasing of the PEAK voltage the trigger
threshold voltage increases, too. This particular
gain is programmablein4 steps (see fig.2).

1.3 AutomaticThreshold Control by the
Stereoblendvoltage (ATC-SB)

Besides the noise controlled thresholdadjustment
there is an additional possibility for influencingthe
trigger.

It is controlledby the differencebetween Vsb and
Vr, similar to the Stereoblend.

The reason for implementing such a second con­trol will be explainedinthe following:

The point where the MPX signal starts to become
noisyis fixedby the RF part.

Therefore also the starting point of the normal
noise controlled trigger adjustment is fixed (fig.3).

But in some cases the behaviour of the noise­blanker can be improved by increasing the
threshold even in a region of higher fieldstrength,
for the MPX signal often shows distortion in this
range.

Because of the overlap of this range and the
range of the stereo/mono transitionit can be con­trolledby Vsband Vr.

This threshold increase is programmable in 3
steps or switchedoff (see fig.3).

1.4 Over Deviation Detector(MPX-RECT)

Sometimes when listening to stations with a
higher deviation than 75KHz the noiseblanker
triggerson thehigh frequencymodulation.

To avoid this blanking, which causes noise in the
output signal, the noiseblankeroffers a deviation­dependentthresholdadjustment.

By rectifying the MPX signal a further signal rep­resentingthe actualdeviationis obtained.

It isused to increase the PEAK voltage.
Offset and gainof this circuit are programmablein

3 steps (the first step turns off the detector, see
fig.4).

10/29

Figure 1: BlockDiagram of the Noise Blanker

TDA7420

MPX IN

V

R

V

SB

80KHz LP

I2C-BUS

SIGNAL PATH

AMP

1

ADDITIONAL THRESHOLD

(ATC-SB, MPX_RECT)

D94AU189A

Figure 2: TriggerThresholdvs. V

CONTROL

peak

BUF

RECT-PEAK

4

R

PEAK

82KΩ

RECT

PEAK

AUTOMATIC

THRESHOLD

CONTROL

C

PEAK

47nF

ATC

5

PEAK COMP

+

-

PEAK+VTH

C

BLANK

330pF

BLANK COMP

REF.

40µs

LEFT

RIGHT

CMOS OUTPUT

to INPUT

STAGE

SELECTOR

of AUDIOPROC.

TRIGGER

OUT

40µs

8 STEPS

VTH

65mV

30mV

TRIG. THRESHOLD

0.9V

D94AU186B

NOISE

ADJUSTED

TRIG. THRESHOLD

1.4V

V

PEAK(V)

280mV
240mV
180mV
140mV

11/29

TDA7420

Figure 3: Behaviourof the Field Strength Controlled Threshold Adjustment

V

PEAK

MONO STEREO

3G

TRIG. THRESHOLD

NOISE

noisy signal good signal

D94AU187B

ATC_SB OFF (00)

2.4V(11)

1.9V(10)

1.3V(01)

0.9V

E’

Figure 4: Behaviourof the DeviationDependent Threshold Adjust (Over Deviation Detector)

V

PEAK

(V)

=11

OVM

=10

OVM

=01

OVM

DEVIATION(KHz)

2

C BUS INTERFACE

I

2.8

2.0

1.2

0.9

D94AU188

20

32.5 45 75

DETECTOR OFF (00)

Interface Protocol

The interfaceprotocol comprises:

A startcondition (s)
A chipaddressbyte, (the LSB bit determines

read/writetransmission).

A subaddressbyte
A sequenceof data (N-bytes + acknowledge)
A stopcondition (P)

CHIP ADDRESS

SUB ADDRESS

LSBMSB

MSB LSBMSB

LSB

DATA 1...DATA n

S1000100R/WACKXXTIA3A2A1A0ACK DATA ACK P

ACK = Acknowledge
S = Start
P = Stop
I = Autoincrement
MAX CLOCK SPEED500kbits/s

Autoincrement

If bit I in the subaddressbyte is set to ”1”,the autoincrementof subaddressis enabled.

12/29

TRANSMITTED DATA(SENDMODE)

MSB LSB

X X X X X ST SM AMS HIGH = Active

AMS = True BlankDetected
SM = Soft mute activated
ST = Stereo (HIGH = active)

SUBADDRESS (RECEIVE MODE)

TDA7420

MSB LSB

XXX ID

3

0000Mux
0001Volume
0010Treble
0011Bass
0100Speaker Attenuator LF
0101Speaker Attenuator RF
0110Speaker Attenuator LR
0111Speaker Attenuator RR
1000Mute & Beep
1001Stereodecoder
1010Noise Blanker1
1011Noise Blanker2
1100AMS
1101Dolby LevelControl
1110Metal ResistanceControl
1111Preamplifier Attenuation

D

2

D

1

D

0

FUNCTION

If bit in the subaddressbyte is set to ” 1”, the autoincrementof subaddressis enabled

13/29

TDA7420

INPUT SELECTOR

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

00000dB
00011dB
00102dB
00113dB
01004dB
01015dB
01106dB
01117dB
10008dB
10019dB
101010dB
101111dB
110012dB
110113dB
111014dB
111115dB

FUNCTION

Input Gain

0 0 0 Full diff CD
0 0 1 Stereo
0 1 0 Stereo Decoder
0 1 1 AM quasi diff input
1 0 0 Quasi diff CD
1 0 1 Not allowed
1 1 0 Not allowed
1 1 1 AM Mono (AM R input)

14/29

VOLUME

TDA7420

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 -0dB
0 0 1 -1dB
0 1 0 -2dB
0 1 1 -3dB
1 0 0 -4dB
1 0 1 -5dB
1 1 0 -6dB
1 1 1 -7dB

0000 16dB
0001 8dB

010 0dB
0 1 1 -8dB
1 0 0 -16dB
1 0 1 -24dB
1 1 0 -32dB

1 1 1 -40dB
1000 -48dB
1001 -56dB

1 Mute

FUNCTION

-1 dB STEPS

-8 dB STEPS

15/29

TDA7420

TREBLE

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

110010-18dB

110001-17dB

110000-16dB

101111-15dB

101110-14dB

101101-13dB

101100-12dB

101011-11dB

101010-10dB

101001-9dB

101000-8dB

100111-7dB

100110-6dB

100101-5dB

100100-4dB

100011-3dB

100010-2dB

100001-1dB

1000000dB

0000000dB

0000011dB

0000102dB

0000113dB

0001004dB

0001015dB

0001106dB

0001117dB

0010008dB

0010019dB

00101010dB

00101111dB

00110012dB

00110113dB

00111014dB

00111115dB

01000016dB

01000117dB

01001018dB

FUNCTION

16/29

BASS

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

110010-18dB

110001-17dB

110000-16dB

101111-15dB

101110-14dB

101101-13dB

101100-12dB

101011-11dB

101010-10dB

101001-9dB

101000-8dB

100111-7dB

100110-6dB

100101-5dB

100100-4dB

100011-3dB

100010-2dB

100001-1dB

1000000dB

0000000dB

0000011dB

0000102dB

0000113dB

0001004dB

0001015dB

0001106dB

0001117dB

0010008dB

0010019dB

00101010dB

00101111dB

00110012dB

00110113dB

00111014dB

00111115dB

01000016dB

01000117dB

01001018dB

TDA7420

FUNCTION

1 Non DC extended bass
0 DC extended bass

17/29

TDA7420

SPEAKERSATTENUATORS

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

0000dB
0 0 1 -1dB
0 1 0 -2dB
0 1 1 -3dB
100-4B
1 0 1 -5dB
1 1 0 -6dB
1 1 1 -7dB

0000 0dB
0001 -8dB
0010 -16dB
0011 -24dB
0100 -32dB
0101 -40dB
0110 -48dB
0111 -56dB
1000 -64dB
1001 -72dB
110
101
111

LF, LR, RF, RR

-1dB STEPS

8dB STEPS

Mute

MUTE & BEEP

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

1 Soft Mute - FAST SLOPE

0 Soft Mute - Slow Slope
1 Soft Mute OFF
0 Soft Mute ON

0 0 Direct InputMute ON

1 0 Direct InputMute OFF
0 0 Radio Mute ON
1 0 Radio Mute OFF

1 Composit Input Enabled
0 Composit Mute Enabled

1 Beep ON - Front

1 Beep ON - Rear
1 VCO OFF
0 VCO ON

18/29

FUNCTION

STEREO DECODER

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

Input Gain

0 0 1.5dB InputGain
0 1 4.0dB InputGain
1 0 6.5dB InputGain
1 1 9dB InputGain

Roll Off Adjustement

0 0 1 20.2%
0 1 0 21.9%
0 1 1 23.7%
1 0 0 25.5%
1 0 1 27.3%
1 1 0 29.2%
111 31%

0 Deemph. Time Constant 75µs

1 Deemph. Time Constant 50µs
1 Forced Mono
0 Stereo Enabled

0 Pilot Threshold High
1 Pilot Threshold Low

TDA7420

FUNCTION

NOISE BLANKER1

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

000V
001V
010V
011V
100V
101V
110V
111V

Noise Blanker Noise Adjusted Threshold Vpeak = 1.4V

00 V
01 V
10 V
11 V

Gain of Overdeviation Detector Vpeak with MPX of 75KHz Deviation

0 0 Detector Off
0 1 Vpeak = 1.2Vop
1 0 Vpeak = 2.0Vop
1 1 Vpeak = 2.8Vop

FUNCTION

Noise Blanker Threshold Vpeak = 0.9V

= 30mV

th

= 35mV

th

= 40mV

th

= 45mV

th

= 50mV

th

= 55mV

th

= 60mV

th

= 65mV

th

= 140mV

th

= 180mV

th

= 240mV

th

= 280mV

th

19/29

TDA7420

NOISE BLANKER2

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

Field Strenght Controlled Rectifier Voltage (control by Vsb-Vr) Vpeak at Vsb-Vr = -500mV (fully Mono)

0 0 Control Off
0 1 Vpeak = 1.3V
1 0 Vpeak = 1.9V
1 1 Vpeak = 2.4V

Noise Blanker Gain

1 Low
0 High

AMS

FUNCTION

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

Att. Sensitivity Tuning

0 0 0dB
0 1 -1dB
1 0 -2dB
1 1 -3dB

Gain Sensitivity Tuning

000 0dB
0 0 1 10dB
0 1 0 14dB
0 1 1 18dB
1 0 0 22dB
1 0 1 26dB
1 1 0 30dB
1 1 1 34dB

AC Sensitivity Tuning

0 0 22dB f = 1.1KHz SW1 = SW2 = SW3
0 1 34dB f = 1.1KHz
1 0 not allowed
1 1 21dB f = 160Hz

0AMSON
1 AMS OFF

FUNCTION

20/29

DOLBY LEVEL CONTROL

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

00000dB
0001-0.5dB
0010-1.0dB
0011-1.5dB
0100-2.0dB
0101-2.5dB
0110-3.0dB
0111-3.5dB
1000-4.0dB
1001-4.5dB
1010-5.0dB
1011-5.5dB
1 1 X X -6.0dB

0000 -0dB
0001 -0.5dB
0010 -1.0dB
0011 -1.5dB
0100 -2.0dB
0101 -2.5dB
0110 -3.0dB
0111 -3.5dB
1000 -4.0dB
1001 -4.5dB
1010 -5.0dB
1011 -5.5dB
1 1 X X -6.0dB

TDA7420

FUNCTION

Right Channel

Left Channel

21/29

TDA7420

METAL RESISTANCECONTROL

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

Right Channel

1000Rmetal +20%
0000Rmetal +15%
0001Rmetal +10%
0010Rmetal +5%
0011Rmetal =3.8KΩ Typical
0100Rmetal - 5%
0101Rmetal - 10%
0110Rmetal - 15%
0111Rmetal - 20%

Left Channel

1000 Rmetal +20%
0000 Rmetal +15%
0001 Rmetal +10%
0010 Rmetal +5%
0011 Rmetal =3.8KΩ Typical
0100 Rmetal - 5%
0101 Rmetal - 10%
0110 Rmetal - 15%
0111 Rmetal - 20%

FUNCTION

PREAMPLIFIER

MSB LSB

D7 D6 D5 D4 D3 D2 D1 D0

0 0 0dB
0 1 -20dB
1 0 -23dB
1 1 Mute

0 Reverse Mode On
1 Forward ModeOn

FUNCTION

Attenuation control

22/29

TDA7420

PINS: 1, 64

V

CC

GND

PINS: 40, 50

V

CC

Vcc/2

33K

PINS: 2,3,6,7,

20µA

D95AU267

V

CC

GND GND

V

CC

20µA

50K

D95AU268

V

CC/2

PINS: 8, 9

V

CC

V

CC

205

GND GND

PINS: 10, 12

V

CC

GND GND

PIN 11
PIN 13

65K

D95AU269

D95AU271A

20µA

20µA

GND

PINS: 11, 13

BASS-LB

BASS-RB

20µA

33K

Vcc/2

V

S

D95AU270

20µA

65K

D95AU272

23/29

TDA7420

PIN: 15

GND GND

PIN: 19

V

CC

20µA

20µA

D95AU273

40µA

PIN: 16

GND

PINS: 20, 21

V

CC

20µA

D95AU274

GND

D95AU275

PIN: 22

CC

GND

205

205

16K

20µA

V

CC

GND

GND GND

GND

V

CC

4K

V

CC

25K 75K

GND

D95AU276

GND

PIN: 23

40µAV

V

CC

20µA

40µA

205

24/29

D95AU277

GND

GND

D95AU278

GND

TDA7420

PIN: 24

PIN: 26

V

CC

V

CC

GND

205

D95AU279

V

CC

V

CC

GND

VCCV

CC

PIN: 25

PIN: 27

V

CC

35µA

40µA

205

V

GND

CC

V

GND

CC

D95AU280

PIN: 28

GND

GND

V

CC

280

12K

12K

6K4K

100µA

56K

D95AU282

500

500

40µA

D95AU281

GND

50µA2K

GND

PINS: 29, 56, 57

V

CC

20µA

V

CC

20µA

GND

V

CC

20µA

100K

D95AU283

GND

GND

V

CC

/2

D95AU284

25/29

TDA7420

PIN: 30

V

CC

10K

GND GND

100K

PIN: 32

V

CC

V

CC

D95AU285

PIN: 31

V

CC

GND GNDGND

D95AU286

PIN: 33

V

CC

V

CC

GND

GND

PINS: 34, 35, 36, 37

V

CC

GND

D95AU289

205 24

20µA

GND

D95AU287

GND

GND

GND

GND

PINS: 38

V

GND

CC

50K

V

GND

CC

50K

/2

29K

GND

D95AU288

20µA

D95AU290

26/29

TDA7420

PINS: 39

GND GND

PINS: 42, 48

V

CC

V

CC

D95AU291

205

PINS: 41,49

V

V

CC

CC

V

CC

4.56K

224K

GND

GND

D95AU292

PINS: 43, 44, 46, 47

V

CC

205

GND GND

PINS: 52, 53

V

CC

GND

PIN 52
PIN 53

50K V

20K

CC/2

20K

D95AU295

20µA

D95AU293

20µA

GND
PIN 43, 44
PIN 46, 47

PINS: 54, 55

V

CC

GND

PIN 54
PIN 55

D95AU296

50K

20K

20K

D95AU294

V

CC/2

27/29

TDA7420

PINS: 58, 60

V

CC

25K

GND GND

25K

PIN: 61

V

CC

20µA

V

CC

D95AU297

20µA

PIN: 59

GND

PIN: 62

V

CC

25K

D95AU298

V

CC

20µA

25K

V

CC/2

20µA

V

CC

20K

GND

PIN: 63

25K

V

CC/2

V

CC

20µA

10K

1.7K

GND GND

GND GND

D95AU301

D95AU299

GND

GND

20K

D95AU300

28/29

TDA7420

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are
subject to change withoutnotice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products
are not authorized for use as critical components in lifesupport devices or systems without express written approval of STMicroelectronics.

The ST logois a trademark of STMicroelectronics

 1998 STMicroelectronics – Printed in Italy – All Rights Reserved

STMicroelectronics GROUP OF COMPANIES

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Singapore - Spain - Sweden - Switzerland- Taiwan- Thailand- United Kingdom- U.S.A.

29/29