EM260-RTR datasheet(20/50 Pages) SILICONIMAGE

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EM260

120-0260-000M Rev 1.1

Page 20

Table 12 lists the specifications for the high-frequency crystal.

Table 12. High-Frequency Crystal Specifications

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Frequency

MHz

Duty cycle

Phase noise from 1kHz to 100kHz

120

dBc/Hz

Accuracy

Initial, temperature, and aging

- 40

+ 40

ppm

Crystal ESR

Load capacitance of 10pF

100



Crystal ESR

Load capacitance of 18pF



Start-up time to stable clock

(max. bias)

Start-up time to stable clock

(optimum bias)

Current consumption

Good crystal: 20 ESR, 10pF

load

0.2

0.3

Current consumption

Worst-case crystals (60, 18pF

or 100, 10pF)

0.5

Current consumption

At maximum bias

4.11.2 Internal RC Oscillator

The EM260 has a low-power, low-frequency RC oscillator that runs all the time. Its nominal frequency is

10kHz.

The RC oscillator has a coarse analog trim control, which is first adjusted to get the frequency as close to

10kHz as possible. This raw clock is used by the chip management block. It is also divided down to 1kHz using

a variable divider to allow software to accurately calibrate it. This calibrated clock is used by the sleep timer.

Timekeeping accuracy depends on temperature fluctuations the chip is exposed to, power supply impedance,

and the calibration interval, but in general it will be better than 150ppm (including crystal error of 40ppm).

Table 13 lists the specifications of the RC oscillator.

Table 13. RC Oscillator Specifications

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Frequency

kHz

Analog trim steps

kHz

Frequency variation with supply

For a voltage drop from 3.6V to

3.1V or 2.6V to 2.1V

0.75

1.5

4.12 Random Number Generator

The EM260 allows for the generation of random numbers by exposing a randomly generated bit from the RX

ADC. Analog noise current is passed through the RX path, sampled by the receive ADC, and stored in a

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