STM32W108CB datasheet(223/278 Pages) STMICROELECTRONICS

223 / 278 page

STM32W108HB STM32W108CC STM32W108CB STM32W108CZ

Analog-to-digital converter

Doc ID 16252 Rev 14

223/278

Table 40 shows the options for ADC sample times and the significant bits in the conversion

results.

Note:

ADC sample timing is the same whether the STM32W108 is using the 24 MHz HSE OSC or

the 12 MHz HSI RC oscillator. This facilitates using the ADC soon after the CPU wakes from

deep sleep, before switching to the crystal oscillator.

11.1.7

Operation

Setting the ADC_EN bit in the ADC_CR register enables the ADC; once enabled, it performs

conversions continuously until it is disabled. If the ADC had previously been disabled, a 21

µs analog startup delay is imposed before the ADC starts conversions. The delay timing is

performed in hardware and is simply added to the time until the first conversion result is

output.

When the ADC is first enabled, and or if any change is made to ADC_CR after it is enabled,

the time until a result is output is double the normal sample time. This is because the ADC’s

internal design requires it to discard the first conversion after startup or a configuration

change. This is done automatically and is hidden from software except for the longer timing.

Switching the processor clock between the RC and crystal oscillator also causes the ADC to

go through this startup cycle. If the ADC was newly enabled, the analog delay time is added

to the doubled sample time.

If the DMA is running when ADC_CR is modified, the DMA does not stop, so the DMA buffer

may contain conversion results from both the old and new configurations.

Table 40.

ADC sample times

SMP[2:0]

Sample

clocks

Sample time (µs)

Sample frequency (kHz)

Significant

bits

1 MHz clock 6 MHz clock 1 MHz clock 6 MHz clock

032

325.33

31.3

188

10.7

15.6

93.8

128

21.3

7.81

46.9

256

42.7

3.91

23.4

512

85.3

1.95

11.7

1024

170

0.977

5.86

2048

341

0.488

2.93

4096

682

0.244

1.47

STM32W108CB Datasheet(PDF) 223 Page - STMicroelectronics

STM32W108CB Datasheet(HTML) 223 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL