TDA7501 Datasheet TDA7501 | P13-P15

TDA7501 Description of the output part

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4 Description of the output part

The TDA7501 has 6 independent outputstage with volume control. The first 4 (main) outputs

have an input selector which allows to select besides the DAC outputs CD direct or

Phone/Navigation-mix. In addition one can mix the SPKR1 with Phone/Navigation so that

traffic or navigation announcements can bypass the DSP (see figure 8).

The TDA7500 CODEC outputs have a maximum output voltage of 0.5Vrms . To obtain

4Vrms , (in the dual supply mode only) the signal is first amplified to have a reference

amplitude of 2V rms. The following volume stage offers up to 15dB gain which gives along

with the programmable 6dB gain in the output-stage enough overdrive capability. To achieve

the maximum output swing of 4Vrms the device must be supplied with an additional supply

of 12V. With a single supply (V

= V

= 8.3V) 2.8Vrms are obtained at the output at

maximum.

Figure 10. Output part.

4.1 Overall gain structure

The overall gain structure of the TDA7501 can be shown in its target application together

with the V225.

The output part in level select (D6/4) offers an additional adaption to the DSP's output level

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Description of the output part TDA7501

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Figure 11. Level diagram.

4.2 Speaker (linedriver) outputs

The Speaker outputs can be configured in three different operating modes:

1. - Internal reference mode with 0dB output gain,

2. - External reference mode with 0dB output gain

3. - External reference mode with 6dB output gain

Basically, in the internalreference mode the linedriver amplifier acts as a buffer with 0dB gain

regardless of the output gain programmed by bit D0. Since the buffer tracks the internal

generated reference, the OUTPUTREF pin may be left floating.

In the external reference mode the linedriver amplifiers reference tracks the voltage present

at the OUTPUTREF pin. This reference does not necessary have to be external to the

device, it can also be generated by invoking the VCC/2 divider inside the TDA7501 (bit

D1/6). In practice, the term external reference implied that the OUTPUTREF pin at least has

to connect to an external capacitor. In the external reference mode, an additional gain of

6dB can be added by assessing bit D0. This provides a nominal 4V

RMS

output level in case

the TDA7501 is powered from a dual supply (V

= 8.3V). When fed from a single supply,

only 2.8V

RMS

output level can be acheived.

For the programming of output gain and reference selection see the programming section.

Figure 12. Speaker (Linedriver) outputs simplified

INPUT GAIN

0..15dB

1dB STEP

CODEC

INTERFACE

TDA7500

VOLUME

+15

LEVEL

SELECT

-79dB

OUTPUT

LINEDRIVERS

0/+6dB STEP

INPUT PART TDA7501 OUTPUT PART

IN OUT

2Vrms

4.15Vdc

2Vrms

4.15Vdc

0.8Vrms

1.65Vdc

0.9Vrms

1.65Vdc

2Vrms

4.15Vdc

+6dB or

+12dB

GAIN

2Vrms (typ)

4.15Vdc

2Vrms

4.15Vdc

4Vrms

6Vdc

D00AU1205

D0/60dB

buffer

6dB 6dB

REF

OUTPUTREF

SPKROUT

from VOLUME-STAGE

2Vrms

4.15Vdc

2RR3R

D0/6

D1/6

REF

D00AU1207

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TDA7501 Reference concept

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5 Reference concept

For the input section the TDA7501 generates the internal reference voltage by multiplying

the V33 voltage by 1.2575.

The V33 voltage is also buffered and fed back to the CODEC where it is used to generate all

necessary references. For best performance it is recommended to filter the V33 reference

pin by means of a passive second order lowpass as shown in Figure 13. This concept allows

a direct DC coupling between the TDA7501 and the DSP because of the accurate matching

of DC levels. On the output side the TDA7501 offers two main modes: a single supply and a

dual supply mode.

5.1 Dual supply mode

In this mode the outputs are able to provide up to 4V rms with a minimum supply V

of 12V

as well as a output reference voltage set to half of V

(bit D0 of the mode select byte set to

'1').

If the switch D1/byte mode select is open the output reference voltage must be defined

externally e.g. a zener diode with RC lowpass.

If the switch is closed the reference voltage will be half of V

and only an external capacitor

has to be added.

5.2 Single supply mode

If V

and V

are connected to a single supply the maximum possible output swing is about

2.8V rms .

The output reference voltage pin can be left open or otherwise the internal voltage divider

can be used to generate for the outputs a V

/2 reference.

Figure 13. Reference voltage generation

TDA7500

TDA7501

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TDA7501

Mfr. #:

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