STM32W108CBU6 STMICROELECTRONICS [STMicroelectronics], STM32W108CBU6 Datasheet - Page 134

• Manufacturer Part Number: STM32W108CBU6
• Description: High-performance, IEEE 802.15.4 wireless system-on-chip
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Analog-to-digital converter
134/179
Table 17.
Input range
ADC inputs can be routed through input buffers to expand the input voltage range. The input
buffers have a fixed 0.25 gain and the converted data is scaled by that factor.
With the input buffers disabled the single-ended input range is 0 to VREF and the differential
input range is -VREF to +VREF. With the input buffers enabled the single-ended range is 0
to VDD_PADS and the differential range is -VDD_PADS to +VDD_PADS.
The input buffers are enabled for the ADC P and N inputs by setting the ADC_HVSELP and
ADC_HVSELN bits respectively, in the ADC_CFG register. The ADC accuracy is reduced
when the input buffer is selected.
Sample time
ADC sample time is programmed by selecting the sampling clock and the clocks per
sample.
●
●
Table 18
results.
Table 18.
VREF
VDD_PADSA/2
ADC_PERIOD
ADC P input
The sampling clock may be either 1 MHz or 6 MHz. If the ADC_1MHZCLK bit in the
ADC_CFG register is clear, the 6 MHz clock is used; if it is set, the 1 MHz clock is
selected. The 6 MHz sample clock offers faster conversion times but the ADC
resolution is lower than that achieved with the 1 MHz clock.
The number of clocks per sample is determined by the ADC_PERIOD bits in the
ADC_CFG register. ADC_PERIOD values select from 32 to 4096 sampling clocks in
powers of two. Longer sample times produce more significant bits. Regardless of the
sample time, converted samples are always 16-bits in size with the significant bits left-
aligned within the value.
0
1
2
3
4
5
6
7
shows the options for ADC sample times and the significant bits in the conversion
Typical ADC input configurations (continued)
ADC sample times
Sample
Clocks
1024
2048
4096
128
256
512
32
64
VREF/2
VREF/2
ADC N input
1 MHz clock 6 MHz clock 1 MHz clock 6 MHz clock
1024
2048
4096
Sample Time (µs)
128
256
512
32
64
Doc ID 16252 Rev 2
5.33
10.7
21.3
42.7
85.3
ADC_MUXP
170
341
682
10
11
Sample Frequency (kHz)
0.977
0.488
0.244
31.3
15.6
7.81
3.91
1.95
STM32W108CB, STM32W108HB
ADC_MUXN
9
9
93.8
46.9
23.4
11.7
5.86
2.93
1.47
188
Calibration
Calibration
Purpose
Significant
Bits
10
11
12
5
6
7
8
9