SAB80C515A-5 Datasheet, PDF (77/108 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller Family

SAB 80C515A/83C515A-5
A/D Converter
In the SAB 80C515A a new high performance / high-speed 8-channel 10-bit A/D-Converter
(ADC) is implemented. Its successive approximation technique provides 7 µs conversion time
(f_OSC = 16 MHz). The conversion principle is upward compatible to the one used in the
SAB 80C515. The main functional blocks are shown in figure 3.
The comparator is a fully differential comparator for a high power supply rejection ratio and very
low offset voltages. The capacitor network is binary weighted providing genuine10-bit
resolution.
The table below shows the sample time T _S and the conversion time T _C, which are dependend
on f _OSC and a new prescaler.
f _OSC [MHz]
Prescaler
12
÷8
÷ 16
16
÷8
÷ 16
18
÷8
÷ 16
f _ADC [MHz]
1.5
0.75
2.0
1.0
–
1.125
Sample Time
T_S [µs]
2.67
5.33
2.0
1.0
–
3.55
Conversion Time
(incl. sample time)
T_C [µs]
9.3
18.66
7.0
14.0
–
12.4
The ADC is clocked (f _ADC) with f _OSC/8. Because of the ADC's maximum clock frequency of
2 MHz the prescaler (divide-by-2) has to be enabled (set Bit ADCL in SFR ADCON 1) when the
oscillator frequency (f _OSC) is higher than 16 MHz.
Semiconductor Group
6-25