BLUENRG-332VT datasheet(44/67 Pages) STMICROELECTRONICS

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6.3.8

Wake-up time from low power modes

The wake-up times reported are the latency between the event and the execution of the instruction. The device

goes to low-power mode after WFI (wait for interrupt) instructions.

Table 26. Low power mode wake-up timing

Symbol

Parameter

Conditions

Typ. Unit

TWUDEEPSTOP

Wake-up time from DEEPSTOP mode to RUN

mode

Wake-up from GPIO VDD = 3.3 V flash memory 170

µs

6.3.9

High speed crystal requirements

The high speed external oscillator must be supplied with an external 32 MHz crystal that is specified for a 6 to 8

pF loading capacitor. The BlueNRG-LPS includes internal programmable capacitances that can be used to tune

the crystal frequency in order to compensate the PCB parasitic one. These internal load capacitors are made by

a fixed one, in parallel with a 6-bit binary weighted capacitor bank. Thanks to low CL step size (1-bit is typically

0.07 pF), very fine crystal tuning is possible. With a typical XTAL sensitivity of -14 ppm/pF, it is possible to trim a

32 MHz crystal, with a resolution of 1 ppm.

The requirements for the external 32 MHz crystal are reported in the table below.

Table 27. HSE crystal requirements

Symbol

Parameter

Conditions

Min. Typ. Max. Unit

fNOM

Oscillator frequency

MHz

fTOL

Frequency tolerance

Includes initial accuracy, stability over temperature,

aging and frequency pulling due to incorrect load

capacitance

±50

ppm

ESR

Equivalent series resistance

100

Ω

Drive level

100

µW

HSE crystal load capacitance

27 °C, typical corner

GMCONF = 3

5 (1)

7(2) 9.2(3)

CLstep

HSE crystal load capacitance 1-bit

value

27 °C,

GMCONF = 3

XOTUNE code between 32 and 33

0.07

1. XOTUNE programed at minimum code = 0

2. XOTUNE programed at center code = 32

3. XOTUNE programed at maximum code = 63

6.3.10

Low speed crystal requirements

Low speed clock can be supplied with an external 32.768 kHz crystal oscillator. Requirements for the external

32.768 kHz crystal are reported in the table below.

Table 28. LSE crystal requirements

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Unit

fNOM

Nominal frequency

32.768

kHz

ESR

Equivalent series resistance

kΩ

Drive level

0.1

µW

BlueNRG-LPS

Operating conditions

DS13819 - Rev 4

page 44/67

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