Hardware design

SPBT2632C2A

20/27

Doc ID 022833 Rev 4

7.6

External LPO input circuit

An optional low power oscillator input may be added to allow Deep sleep and Sniff modes.

●

LPO parameters:

–

Frequency: 32.768 kHz

–

Tolerance: 150 ppm

–

Voltage levels

–Low: 0.5 V

–

High: 1.8 V

–

Input capacitance: 2.5 pF maximum

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Configurations:

–

Use two configuration variables: UseExtLPO and AllowSniff.

Figure 11.

External LPO circuit

Table 9.

System configuration variables

Variable

Name

Default

Description

Var37

UseExtLPO

True

True when a 32.768 kHz low power oscillator is present, and false

if not present

Var43

AllowSniff

True

Enables Sniff mode.