STA330 datasheet(21/55 Pages) STMICROELECTRONICS

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STA330

Analog-digital converter (ADC)

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Analog-digital converter (ADC)

7.1

Functional description

The STA330 analog input is provided through a low-power, low-voltage, stereo, audio-ADC

front end designed for audio applications. It includes a programmable gain amplifier, anti-

aliasing filter, a low-noise microphone biasing circuit, a third-order, MASH2-1, delta-sigma

modulator, a digital decimating filter and a first-order DC-removal filter. This device is

fabricated using a 0.18 µm CMOS process, where high-speed precision analog circuits are

combined with high-density logic circuits.

The ADC works in a microphone-input (mic-in) mode and in a line-input mode.

If the line-input mode is selected, the ADC is configured in stereo and all conversion

channels are active.

If the microphone-input mode is selected, the ADC is configured in mono. The mono

channel is routed through the left conversion path, and the right conversion path is kept in

power-down mode to minimize power consumption. A programmable gain amplifier (PGA) is

available in mic-in mode, giving the possibility to amplify the signal from 0 to +42 dB in steps

of 6 dB.

7.1.1

Digital anti-aliasing filter characteristics

The digital filter characteristics are shown in Table 12.

Table 12.

Digital filter characteristics

Parameter

Typical

Pass band

0.4535 * fS

Pass band ripple:

Fs mode

Fs_by_2 mode

Fs_by_4 mode

0.08 dB at 44.1 kHz

0.08 dB at 22.05 kHz

0.08 dB at 11.025 kHz

Stop band attenuation:

Fs mode

Fs_by_2 mode

Fs_by_4 mode

45 dB at 44.1 kHz

45 dB at 22.05 kHz

45 dB at 11.025 kHz

Group delay:

Fs mode

Fs_by_2 mode

Fs_by_4 mode

0.4 ms at 32 kHz

0.7 ms at 16 kHz

1.4 ms at 8 kHz

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