EM260-RTR datasheet(19/50 Pages) SILICONIMAGE

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EM260

Page 19

120-0260-000M Rev 1.1

The 1.8V POR cell holds the main digital core in reset until the regulator output voltage rises above a

threshold.

Additionally, the digital domain counts 1,024 clock edges on the 24MHz crystal before releasing the reset to

the main digital core.

Table 11 lists the features of the EM260 POR circuitry.

Table 11. POR Specifications

Parameter

Min.

Typ.

Max.

Unit

VDD_PADS POR release

1.0

1.2

1.4

VDD_PADS POR assert

0.5

0.6

0.7

1.8V POR release

1.35

1.5

1.65

1.8V POR hysteresis

0.08

0.1

0.12

4.11 Clock Sources

The EM260 integrates two oscillators: a high-frequency 24MHz crystal oscillator and a low-frequency internal

10kHz RC oscillator.

4.11.1 High-Frequency Crystal Oscillator

The integrated high-frequency crystal oscillator requires an external 24MHz crystal with an accuracy of

±40ppm. Based upon the application Bill of Materials and current consumption requirements, the external

crystal can cover a range of ESR requirements. For a lower ESR, the cost of the crystal increases but the

overall current consumption decreases. Likewise, for higher ESR, the cost decreases but the current

consumption increases. Therefore, the designer can choose a crystal to fit the needs of the application.

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