EM357-RTR datasheet(43/241 Pages) SILABS

43 / 241 page

Rev 1.3

6.3.3. Low-Frequency Internal RC Oscillator (OSCRC)

A low-frequency RC oscillator (OSCRC) is provided as an internal timing reference. The nominal frequency coming

out of reset is 10 kHz, and Ember software calibrates this clock to 10 kHz. From the tuned 10 kHz oscillator

(OSCRC) Ember software calibrates a fractional-N divider to produce a 1 kHz reference clock, CLK1K. Table 6.8

contains the specification for the low frequency RC oscillator.

Table 6.7. High-Frequency Crystal Oscillator Specification

Parameter

Test Conditions

Min

Typ

Max

Unit

Frequency

—

MHz

Accuracy

–40

—

+40

ppm

Duty cycle

—

Start-up time at max bias

—

Start up time at optimal bias

—

Current consumption

—

200

300

μA

Current consumption at max bias

—

Crystal with high ESR

—

100

Ω

Load capacitance

—

Crystal capacitance

—

Crystal power dissipation

—

200

µW

Crystal with low ESR

—

Ω

Load capacitance

—

Crystal capacitance

—

Crystal power dissipation

—

Table 6.8. Low-Frequency RC Oscillator Specification

Parameter

Test Condition

Min

Typ

Max

Unit

Nominal frequency

After trimming

kHz

Analog trim step size

—

0.5

—

kHz

Supply dependence

For a voltage drop from 3.6 V to 3.1 V or 2.6 V to 2.1 V

(without re-calibration)

—

Temperature



dependence

Frequency variation with temperature for a change

from –40 to +85 oC

(without re-calibration)

—

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