BLUENRG-2 datasheet(32/190 Pages) STMICROELECTRONICS

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Functional details

BlueNRG-2

32/190

DocID030675 Rev 2

Several channels are available for conversion, the CHSEL selects the channel according to

Table 27: "ADC channels".

Table 27: ADC channels

CHSEL

Channels description

All switch open. No input

Single ended through ADC2 pin. InP = Vbias (internal), InN = ADC2 pin

Single ended through ADC1 pin. InP = ADC1 pin, InN = Vbias (internal)

Differential ADC1 pin

– ADC2 pin. InP = ADC1 pin, InN = ADC2 pin

Temperature sensor. InN=TEMP, InP = 0.6 V (internal)

Battery level detector. InN = BLD, InP = 0.6 V (internal)

Short. InP = InN = 0.6 V (internal)

The conversion can be single (CONT = 0) or continuous (CONT = 1). In continuous mode,

the conversion runs with a preprogrammed sampling rate, while in single step mode the

ADC performs a conversion and then stops.

The output data rate depends on the setting of OSR according to the following table.

Table 28: ADC data rate

OSR

Output data rate [Ksample/s]

0 (200)

1 (100)

2 (64)

15.625

3 (32)

31.25

The setting of the oversampling ratio (OSR) must be done according to the frequency of

the input signal (AC), while for DC signals, the best performance is with OSR = 200. In

order to achieve the best performance within the selected input voltage range, the

associated Vbias and attenuation value must be set through the corresponding registers

PGASEL and REFSEL values, as per the following table.

Table 29: ADC parameters settings

Vin range [V]

Vbias [V]

Attenuation [dB]

REFSEL value

PGASEL value

[0, 1.2]

0.6

[0, 2.4]

0.6

6.02

[0, 3.6]

0.6

9.54

[0.6, 1.8]

1.2

[1.2, 3.6]

1.2

6.02

The system can work in conjunction with an external MEMS microphone by setting

MIC_SEL. In this mode, an IO configured as PDM_CLK provides the clock to the external

microphone, while an IO configured as PDM_DATA received the PDM stream from the

external microphone. The external clock is 1.6 MHz (DIG_FILT_CLK = 0) or 0.8 MHz

(DIG_FILT_CLK = 1).

The output data rate changes with the OSR according to Table 30: "Output data rate with

microphone".

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