C515C Datasheet, PDF (43/69 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C515C
10-Bit A/D Converter
The C515C includes a high performance / high speed 10-bit A/D-Converter (ADC) with 8 analog
input channels. It operates with a successive approximation technique and uses self calibration
mechanisms for reduction and compensation of offset and linearity errors. The A/D converter
provides the following features:
– 8 multiplexed input channels (port 6), which can also be used as digital inputs
– 10-bit resolution
– Single or continuous conversion mode
– Internal or external start-of-conversion trigger capability
– Interrupt request generation after each conversion
– Using successive approximation conversion technique via a capacitor array
– Built-in hidden calibration of offset and linearity errors
The main functional blocks of the A/D converter are shown in figure 19.
The A/D converter uses basically two clock signals for operation : the input clock f_IN (=1/t_IN) and the
conversion clock f_ADC (=1/t_ADC). These clock signals are derived from the C515C system clock
f_OSC which is applied at the XTAL pins. The input clock f_IN is equal to f_OSC. The conversion clock
is limited to a maximum frequency of 2 MHz and therefore must be adapted to f_OSC by
programming the conversion clock prescaler. The table in figure 18 shows the prescaler ratios and
the resulting A/D conversion times which must be selected for typical system clock rates.
MCU System Clock ADCL
Rate (f_OSC)
2 MHz
0
4 MHz
0
6 MHz
0
8 MHz
0
10 MHz
1
Figure 18
A/D Converter Clock Selection
Conversion Clock
f_ADC [MHz]
.5
1
1.5
2
1.25
Semiconductor Group
43
1997-07-01