FDA903D-EHT datasheet(34/82 Pages) STMICROELECTRONICS

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Power limiter function

FDA903D

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Power limiter function

An adjustable power limiting function has been integrated to protect "small speakers"

applications: thanks to this feature, it's possible to limit by configuration the max power

delivered to the load.

Taking advantage of digital input architecture, the output power limitation is obtained through

the management of the input signal. It's important to underline that the limitation is

implemented independently of the supply voltage value.

The intervention thresholds, configurable through I2C are listed in the table below

The limitation is gradual in order to have no impact on the acoustic performance. Depending

on the signal amplitude and the desired attenuation, different gains are applied to the signal

itself.

Here an example of the response obtained with a limitation corresponding to 80% of the full-

scale: the blue line represents the signal when the power limiter is not employed, while the

red line is the result of the applied attenuation.

Table 8. Power limiter function

I2C IB2[3-0]

Full-Scale Voltage limit

Output Voltage limit [V]

Standard gain

setting

Low gain setting

0000

100% (Disabled)

19 (1)

1. 19 V is only a reference level, coherently with "standard gain" value in Section 5.3, to deduce the power

limiter thresholds. The reference level is unreachable due to the maximum supply voltage range, equal to

18 V.

11.4

1011

80%

15.2

9.12

1010

70%

13.3

7.98

1001

60%

11.4

6.84

1000

50%

9.5

5.7

0111

45%

8.55

5.13

0110

40%

7.6

4.56

0101

35%

6.65

3.99

0100

30%

5.7

3.42

0011

25%

4.75

2.85

0010

20%

3.8

2.28

0001

15%

2.85

1.71

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