FDA803U datasheet(49/76 Pages) STMICROELECTRONICS

部件名	FDA803U

功能描述	1 x 45 W class D digital input automotive power amplifier with diagnostics, wide voltage operation range for car audio and telematic

PDF	76 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

49 / 76 page

DS12497 Rev 2

49/76

FDA803U

Additional features

Please note that, by limiting the PWM duty cycle, a limitation of the output power occurs: the

output power in case of usage of LRF function decreases about 10 % @ 1 % THD.

11.2

Noise gating

Noise gating is an automatic noise reduction feature that activates when output signal

reaches not audible levels.

When input signal levels falls below -109 dBFs, the system activity is automatically

optimized in order to exploit very low noise level on the output speakers.

The noise gating process has a 500 ms watching time before turning on, in order to avoid

spurious activations.

The feature is enabled by default and can be disabled selecting IB3[1].

11.3

Dither PWM

The device implements a function, Dither PWM, which can be enabled through I2C bus by

setting IB1[2].

The main target of this feature is to improve the EMC performances in the range [10 –

30 MHz], especially in MUTE condition.

The function consists in modulating the period of the output PWM. The function doesn’t

affect the average PWM frequency.

The modulation pattern is repeated every 8 PWM clock cycles, in order to avoid introducing

significant noise in the audio bandwidth.

A qualitative example of the function operation is depicted in Figure 62.

Figure 62. Dither PWM effect on output PWM

FDA803U 数据表(PDF) 49 Page - STMicroelectronics