User's Manual

TiWi-uB1 Module

DATASHEET

The information in this document is subject to change without notice.

SLOW CLOCK (32 KHZ) SOURCE REQUIREMENTS

Two 32-kHz oscillators are available in the device as clock sources for the 32-kHz clock:

• 32-kHz XOSC – External Crystal Oscillator

• 32-kHz RCOSC – Internal RC Oscillator

By default, after a reset, the 32-kHz RCOSC is enabled and selected as the 32-kHz clock source. The

RCOSC consumes less power, but is less accurate compared to the 32-kHz XOSC. The chosen 32-kHz

clock source drives the Sleep Timer, generates the tick for the Watchdog Timer, and is used as a strobe in Timer

2 to calculate the Sleep Timer sleep time.

The crystal is required for accurate sleep timing, so it is only needed to for the module be BLE certified when

using low power modes.

32.768-kHz EXTERNAL CRYSTAL OSCILLATOR

Characteristic

Condition

Min

Typ

Max

Unit

Crystal frequency

32768

Crystal frequency accuracy

requirement

-40

ppm

ESR Equivalent series

Resistance

C0 Crystal shunt

Capacitance

CL Crystal load capacitance

Start-up time

0.25

Power-down guard time

The crystal oscillator must be in power

down for a guard time before it is used

again. This requirement is valid for all

modes of operation. The need for power-

down guard time can vary with crystal

type and load.

Table 10 32 kHz External Clock Requirements