ISD91200 Series Technical Reference Manual
Release Date: Sep 16, 2019
- 373 -
Revision 2.4
7
ANALOG SIGNAL PATH BLOCKS
This section describes the functional blocks that perform analog signal functions on the ISD91200. This
includes the ADC, DPWM Speaker Driver, PGA Gain Amplifier, Automatic Gain Control and a variety of
auxiliary analog functional blocks.
7.1
Sigma- Delta Analog-to-Digital Converter (SDADC)
7.1.1
Functional Description
The ISD91200 includes a Sigma-Delta Audio Analog-to-Digital converter. The converter can run at
sampling rates up to 6.144MHz while a configurable decimation filter allows oversampling ratios of
64/128/192 and 384. The decimation input is 6.144 MHz oversample rate. The SINC filter and low pass
filter can down sample up to 64000. Low pass filter is IIR filter implemented by BIQ filter.
7.1.2
Features
Programmable volume control from -108dB to36dB in 0.5dB steps.
Support Automatic Level Controller (ALC) function.
Configurable down-sampling to support sample rate 64KHz.
Programmable Bi-quad filter to support multiple sample rate 64KHz.
DMA support for minimal CPU intervention.
7.1.3
Block Diagram
SINC
ALC
VOL
APB Bus
PDMA
Interface
SDADC->EN.SDADCEN
VOLCTRL->EN.SDADCVOLEN
BIQ->CTL.BIQEN
FIFO
SD ADC
BIQ
ALC->CTL.ALCEN
Figure 7-1 ADC Signal Path Block Diagram