ST TDA7468 User Manual

TDA7468

Fi

TWO BANDS DIGITALLY CONTROLLED

AUDIO PROCESSOR WITH BASS ALC SURROUND

1 FEATURES

 INPUT MULTIPLEXER

– 4 STEREO INPUTS – SELECTABLE INPUT GAIN FOR OPTIMAL

ADAPTATION TO DIFFERENT SOURCES

 ONE STEREO OUTPUT  BASS ALC  TREBLE AND BASS CONTROL IN 2.0dB  STEPS  VOLUME CONTROL IN 1.0dB STEPS  TWO SPEAKER ATTENUATORS:

– TWO INDEPENDENT SPEAKER CONTROL

IN 1.0dB STEPS FOR BALANCE FACILITY

– INDEPENDENT MUTE FUNCTION

 ALL FUNCTION ARE PROGRAMMABLE VIA  SERIAL BUS  EXTERNALLY ADJUSTABLE SURROUND

2 DESCRIPTION

The TDA7468D is a volume tone (bass and treble) balance (Left/Right) processor for quality audio

Figure 2. PIN CONNECTION (Top view)

gure 1. Package

SO28

Table 1. Order Codes

Part Number Package

TDA7468D SO28

TDA7468D13TR Tape & Reel

applications in Hi-Fi systems.

Selectable input gain is provided. Control of all the functions is accomplished by serial bus.

The AC signal setting is obtained by resistor networks and switches combined with operational amplifiers.

Thanks to the used BIPOLAR/CMOS Technology, Low Distortion, Low Noise and DC stepping are obtained

April 2010

V

1

S

MIC

IN1_L

IN2_L

IN3_L IN3_R

IN4_L

MUX_L

IS_L

TREBLE_L

BASSI_L

BASSO_L

OUT_L

DGND

SCL

2

3

4

5

6

7

8

9

10

11

12

13

14

D99AU1057

28

27

26

25

24

22

21

20

19

18

17

16

15

GND

CREF

IN1_R

IN2_R

IN4_R23

MUX_R

IS_R

TREBLE_R

BASSI_R

BASSO_R

OUT_R

ALC

SDA

Rev. 4

1/23

TDA7468

Figure 3. BLOCK DIAGRAM

18

BASSO-R

192021

BASSI-R

TREBLE-R

gm

63dB att.

OUT-R

17

-24 att. /8dB step

BASS

/2dB step

-14 to +14dB

TREBLE

/2dB step

-14 to +14dB

/1dB step

+ 6dB gain

+

DGND

SCL

SDA

131215

14

C BUS DECODER + LATCHES

2

I

+

OUT-L

-24 att.

BASS

-14 to +14dB

TREBLE

-14 to +14dB

63dB att.

+

/8dB step

/2dB step

/1dB step

+ 6dB gain

S

1

SUPPLY V

REF

V

gm

GND CREFTREBLE-LMUX-L IS-L

BASSO-LBASSI-L

IS-R

22

MUX-R

23

IN-R4

50K

inverting

non-inverting

/ 2dB step

buffer gain:

0 to 14dB gain

INPUT

SELECT

24

IN-R3

50K

MIX

VARIABLE

0dB

6dB

9dB

12dB

25

IN-R2

+

50K

26

IN-R1

BASS_ALC

50K

CONTROL

0dB, 6dB

10dB, 14dB

2

50K

MIC-MIX

RECTIFIER

HALF_WAVE

16

ALC

3

IN-L1

INPUT

50K

inverting

non-inverting

/ 2dB step

buffer gain:

0 to 14dB gain

SELECT

50K

4

IN-L2

VARIABLE

0dB

+

5

MIX

6dB

IN-L3

9dB

12dB

50K

6

50K

78 9 10 11 2827

50K

D99AU1058A

IN-L4

2/23

TDA7468

Table 2. ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

T

V

amb

stg

Operating Supply Voltage 10.5 V

S

Operating Ambient Temperature 0 to 70 °C

Storage Temperature Range -55 to 150 °C

Table 3. THERMAL DATA

Symbol Parameter Value Unit

R

th j-pin

Thermal Resistance Junction-pins 85 °C/W

Table 4. QUICK REFERENCE DATA

Symbol Parameter Min. Typ. Max. Unit

V

THD

Supply Voltage 5 9 10 V

S

Max. input signal handling 2 Vrms

CL

Total Harmonic Distortion V

= 1Vrms; f = 1KHz

I

= 0.1Vrms; f = 1KHz

I

0.01 % %

0.1 %

S/N

S

Signal to Noise Ratio V

Channel Separation f = 1KHz 90 dB

C

= 1Vrms (0dB)

out

100 dB

Input Gain (2dB step) 0 14 dB

Volume Control (1dB step) -87 0 dB

Treble Control (2dB step) -14 +14 dB

Bass Control (2dB step) -14 +14 dB

Mute Attenuation 86 dB

3/23

TDA7468

ELECTRICAL CHARACTERISTICS

(refer to the test circuit T specified)

Symbol Parameter Test Condition Min. Typ. Max. Unit

SUPPLY

V

SVR Ripple Rejection 60 90 dB

INPUT STAGE

R

V

S

G

inmin

G

inmax

G

MIC

R

G

MIX

SURROUND

R

G

inmin

G

inmax

G

M

ixmax

CrosstalkCrosstalk of Mux Output to 100%

G

buffer

VOLUME CONTROL

C

RANGE1

A

VMAX1

A

STEP1

Match1 Matching TBD dB

C

RANGE2

A

VMAX2

A

STEP2

Match2 Matching TBD dB

A

VMAX1

A

VMAX2

Supply Voltage 5 9 10 V

S

Supply Current 9 mA

I

S

Input Resistance 35 50 65 KΩ

IN

Clipping Level THD = 0.3% 2 2.5

CL

Input Separation 80 100 dB

IN

Minimum Input Gain -1 0 1 dB

Maximum Input Gain 14 dB

Step Resolution 2 dB

step

Input Resistance 35 50 65 KΩ

IN

Mic Input Gain 1 14 dB

mic1

Mic Input Gain 2 10 dB

mic2

Mic Input Gain 3 6 dB

mic3

Mic Input Gain 4 0 dB

min4

Mixing Rate 50 %

mic

Input Resistance 35 50 65 KΩ

in

Minimum Input Gain -1 0 1 dB

Maximum Input Gain 12 dB

Inverting Gain -1

inV

Minimum Mixing Rate 0 %

ixmin

Maximum Mixing Rate 100 %

IS

Buffer Gain 6dB

Vol 1 Control Range 63 dB

Vol 1 Max. Attenuation 61 63 65 dB

Vol 1 Step Resolution 0.5 1 1.5 dB

Vol 2 Control Range 24 dB

Vol 2 Max. Attenuation 22 24 26 dB

Vol 2 Step Resolution 7 8 9 dB

+

Vol 1 + Vol 2 Max Attenuation 84 dB

= 25°C, VS = 9V, f = 1KHz all controls flat (G = 0dB), unless otherwise

amb

40 dB

Vrms

4/23

TDA7468

ELECTRICAL CHARACTERISTICS (continua)

(refer to the test circuit T specified)

Symbol Parameter Test Condition Min. Typ. Max. Unit

BASS CONTROL

Gb Control Range Max. Boost/cut ±12.0 ±14.0 ±16.0 dB

B

STEP

R

BASS ALC CONTROL

R

attack1

R

attack2

R

attack3

R

attack4

Thresh1 Threshold 1 700 mVrms

Thresh2 Threshold 2 485 mVrms

Thresh3 Threshold 3 320 mVrms

Thresh4 Threshold 4 170 mVrms

TREBLE CONTROL

Gt Control Range Max. Boost/cut +13.0 +14.0 +15.0 dB

T

STEP

AUDIO OUTPUTS

V

R

VO

GENERAL

E

S/N Signal to Noise Ratio

S

BUS INPUT

V

I

V

Step Resolution 1 2 3 dB

Internal Feedback Resistance 33 44 55 KΩ

B

Attack Time Resistor 1 12.5 KΩ

Attack Time Resistor 2 25 KΩ

Attack Time Resistor 3 50 KΩ

Attack Time Resistor 4 100 KΩ

Step Resolution 1 2 3 dB

R

Internal Resistance 25 KΩ

t

Clipping Level THD = 0.3% 2 2.5

OCL

Output Load Resistance 2 KΩ

L

DC Voltage Level 4.5 V

UT

Output Noise BW = 20Hz to 20KHz;

NO

Channel Separation Left/Right 90 dB

C

dDistortion A

Channel Separation left/right 90 dB

C

Total Tracking Error 0 1 dB

Input Low Voltage 1V

IL

Input High Voltage 2.5 V

IH

Input Current VIN = 0.4V -5 5 µA

IN

Output Voltage (ACK) IO = 1.6mA 0.4 0.8 V

O

= 25°C, VS = 9V, f = 1KHz all controls flat (G = 0dB), unless otherwise

amb

All gains 0dB;

output muted 5 µV

flat 10 15 µV

All gains 0dB

= 0; VI = 0.1V

V

A

= 0; VI = 1V

V

; V

O

rms

= 1V

rms

;

rms

; 0.1 %

; 0.01 %

100 dB

Vrms

5/23

TDA7468

Figure 4. TEST CIRCUIT

-24 att.

BASSO-R

18192021

5.6K

100nF 100nF

BASSI-R

-14 to +14dB

OUT-R

17

/8dB step

BASS

/2dB step

S

-24 att. /8dB step

/2dB step

-14 to +14dB

V

1

SUPPLY

10µF

REF

V

GND CREFTREBLE-L

BASSO-LBASSI-L

DGND

SCL

SDA

131215

14

OUT-L

BASS

3.3nF

TREBLE-R

IS-R

22

MUX-R

50K

gm

63dB att.

buffer gain:

INPUT

SELECT

TREBLE

/2dB step

-14 to +14dB

/1dB step

+ 6dB gain

+

MIX

VARIABLE

inverting

non-inverting

/ 2dB step

0 to 14dB gain

0dB

6dB

9dB

12dB

+

C BUS DECODER + LATCHES

2

I

+

0dB, 6dB

10dB, 14dB

HALF_WAVE

CONTROL

BASS_ALC

RECTIFIER

inverting

non-inverting

/ 2dB step

buffer gain:

0 to 14dB gain

INPUT

SELECT

TREBLE

+

VARIABLE

0dB

+

/2dB step

-14 to +14dB

63dB att.

/1dB step

+ 6dB gain

MIX

6dB

9dB

12dB

gm

50K

78 9 10 11 2827

MUX-L IS-L

6/23

0.47µF

23

IN-R4

50K

0.47µF

24

IN-R3

50K

0.47µF

25

IN-R2

50K

0.47µF

26

IN-R1

50K

2

MIC-MIX

0.47µF

50K

16

ALC

0.47µF

3

IN-L1

1M

0.47µF

50K

4

IN-L2

0.47µF

5

IN-L3

50K

0.47µF

6

IN-L4

50K

D99AU1059A

TDA7468

3 APPLICATION SUGGESTIONS

The first and the last stages are volume control blocks. The control range is 0 to -63dB (mute) with 1dB step resolution for this first one, 0 to 24dB (mute) with 8dB step resolution for the last one.

The very high resolution allows the implementation of systems free from any noisy acoustical effect.

The TDA7468D audioprocessor provides 2 bands tones control.

3.1 Bass, Stages

The Bass cell has an internal resistor R

Several filter types can be implemented, connecting external components to the Bass IN and OUT pins.

The fig.5 refers to basic T Type Bandpass Filter R2,C1,C2 external) the centre frequency Fc, the gain Av at max. boost and the filter Q factor are computed as follows:

= 44KΩ typical.

i

F

-----------------------------------------------------------------=

C

2 π R1 R2 C1 C2⋅⋅⋅⋅⋅

R2 C2 R2 C1 Ri C1++

A

----------------------------------------------------------------=

V

starting from the filter component values (R1 internal and

1

R2 C1 R2 C2+

R1 R2 C1 C2⋅⋅⋅

------------------------------------------------- -=

R2 C1 R2 C2+

1–

V

CRi

Q⋅⋅ ⋅ ⋅

---------------------------------------------------------------------- -=

2 π C1 F

C2

1– Q2–

A

V

CAV

2

C1⋅

Q

----------------------------- -==

1– Q2–

A

V

1–()Q⋅⋅ ⋅⋅⋅

Viceversa, once F

Q

, AV, and Ri internal value are fixed, the external components values will be:

C

A

----------------------------------------- -

C1

2 π F

R2

3.2 Treble Stage

The treble stage is a high pass filter whose time constant is fixed by an internal resistor (25KΩ typical) and an external capacitor connected between treble pins and ground.

3.3 CREF

The suggested 10µF reference capacitor (CREF) value can be reduced to 4.7µF if the application requires faster power ON.

Figure 5.

Ri internal

OUTIN

C

1

C

2

R

2

D95AU313

7/23