UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
266 of 362
1.
Features
•
Two 16-bit Analog to Digital converters with decimation filters
•
Digital values can be read as 16 or 24 bits
•
Ancillary modules for A-to-D include:
–
Dual Programmable Gain Amplifiers
–
Dual Single-to-Differential Converters
•
Simple Analog In (SAI) module provides FIFO buffering
•
DMA or processor handling of SAI
2.
Description
The ADC circuitry consists of two identical 16-bit Sigma-Delta converters. In order to allow
use for synchronized sampling applications, such as I-V measurements for power factor
calculations or stereo audio, the converters are synchronized so that the two channels
operate on “left” and “right” data which are sampled at the same time.
Each ADC input has a programmable gain amplifier stage (PGA) which has a range from
0 to +24 dB. The output of each PGA is fed to a single to differential converter (SD), the
output of which goes to an ADC.
The output of each ADC is a bitstream at 128*fs (where fs is the Nyquist sample
frequency). Decimators then converts these bitstreams to 24 bit parallel format clocked at
the sample rate. Each decimator block also includes DC blocking digital filters in its input
and output stages as well as a digital gain control that can be used as a volume control in
audio applications.
Because the ARM7 microcontroller typically services a variety of tasks in an interleaved
fashion that involves worst-case event-arrival considerations, a FIFO buffer called an SAI
smooths the transfer of the digital values into memory. This transfer can be performed by
the processor, or by one or two GPDMA channel(s).
3.
Dual ADC pins
The Dual ADC has two dedicated analog input pins, as shown in
UM10208
Chapter 21: Dual-channel 16-bit Analog-to-Digital Converter
(DADC)
Rev. 02 — 1 June 2007
User manual
Table 300. Analog input pins
Name
Description
AINL
Input to L Programmable Gain Amplifier (LPGA)
AINR
Input to R Programmable Gain Amplifier (RPGA)