Specifications

ST72104Gx, ST72215Gx, ST72216Gx, ST72254Gx
86/141
11.5 8-BIT A/D CONVERTER (ADC)
11.5.1 Introduction
The on-chip Analog to Digital Converter (ADC) pe-
ripheral is a 8-bit, successive approximation con-
verter with internal sample and hold circuitry. This
peripheral has up to 16 multiplexed analog input
channels (refer to device pin out description) that
allow the peripheral to convert the analog voltage
levels from up to 16 different sources.
The result of the conversion is stored in a 8-bit
Data Register. The A/D converter is controlled
through a Control/Status Register.
11.5.2 Main Features
■ 8-bit conversion
■ Up to 16 channels with multiplexed input
■ Linear successive approximation
■ Data register (DR) which contains the results
■ Conversion complete status flag
■ On/off bit (to reduce consumption)
The block diagram is shown in Figure 1.
11.5.3 Functional Description
11.5.3.1 Analog Power Supply
V
DDA
and V
SSA
are the high and low level refer-
ence voltage pins. In some devices (refer to device
pin out description) they are internally connected
to the V
DD
and V
SS
pins.
Conversion accuracy may therefore be impacted
by voltage drops and noise in the event of heavily
loaded or badly decoupled power supply lines.
See electrical characteristics section for more de-
tails.
Figure 47. ADC Block Diagram
CH2 CH1CH3COCO 0 ADON 0 CH0
ADCCSR
AIN0
AIN1
ANALOG TO DIGITAL
CONVERTER
AINx
ANALOG
MUX
R
ADC
C
ADC
D2 D1D3D7 D6 D5 D4 D0
ADCDR
4
DIV 2
f
ADC
f
CPU
HOLD CONTROL