ST92163 - A/D CONVERTER (A/D)
8.6 A/D CONVERTER (A/D)
8.6.1 Introduction
The 8 bit Analog to Digital Converter uses a fully
differential analog configuration for the best noise
immunity and precision performance. The analog
voltage references of the converter are connected
to the internal AVDD & AVSS analog supply pins of
the chip if they are available, otherwise to the ordi-
nary VDD and VSS supply pins of the chip. The
guaranteed accuracy depends on the device (see
Electrical Characteristics). A fast Sample/Hold al-
lows quick signal sampling for minimum warping
effect and conversion error.
8.6.2 Main Features
s 8-bit resolution A/D Converter
s Single Conversion Time (including Sampling
Time):
– 138 internal system clock periods in slow
mode (~5.6 µs @25Mhz internal system
clock);
– 78 INTCLK periods in fast mode (~6.5 µs @
12MHZ internal system clock)
s Sample/Hold: Tsample=
– 84 INTCLK periods in slow mode (~3.4 µs
@25Mhz internal system clock)
– 48 INTCLK periods in fast mode (~4 µs
@12Mhz internal system clock)
s Up to 8 Analog Inputs (the number of inputs is
device dependent, see device pinout)
Figure 86. A/D Converter Block Diagram
n
SUCCE SSIVE
APPROXI MATION
REGI STER
s Single/Continuous Conversion Mode
s External/Internal source Trigger (Alternate
synchronization)
s Power Down mode (Zero Power Consumption)
s 1 Control Logic Register
s 1 Data Register
8.6.3 General Description
Depending on the device, up to 8 analog inputs
can be selected by software.
Different conversion modes are provided: single,
continuous, or triggered. The continuous mode
performs a continuous conversion flow of the se-
lected channel, while in the single mode the se-
lected channel is converted once and then the log-
ic waits for a new hardware or software restart.
A data register (ADDTR) is available, mapped in
page 62, allowing data storage (in single or contin-
uous mode).
The start conversion event can be managed by
software, writing the START/STOP bit of the Con-
trol Logic Register or by hardware using either:
– An external signal on the EXTRG triggered input
(negative edge sensitive) connected as an Alter-
nate Function to an I/O port bit
– An On Chip Event generated by another periph-
eral, such as the MFT (Multifunction Timer).
DATA
REGIST ER
Ain0
Ain1
S/H
ANA LOG
MUX
Ainx
CONTROL LOGIC
EXT RG
INTRG
(On Chip Event)
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