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AN265

EP93xx RTC Oscillator Circuit

Note: This application note is applicable to all revisions of the EP93xx device.

1. BACKGROUND

Cirrus Logic has found that the Real Time Clock (RTC) circuit in the current EP93xx devices is susceptible

to on-chip noise, which can generate an inaccurate clock count and possibly cause the IC to boot into an

improper state during power-up.

To correct this issue, customers need to provide a clean square wave input to the RTCXTALI pin. This

may be accomplished several ways, such as by using an external clock oscillator or a dedicated RTC chip

like the DS1337. This application note, however, shows the use of an external Pierce oscillator circuit to

replace the existing internal RTC circuit.

Please note that an external RTC oscillator circuit is required for the EP93xx family on both existing and

future revision parts.

2. IMPLEMENTATION

Figure 1. Implementation Using a Pierce Oscillator Circuit and Schmitt-trigger Inverter

DEC ‘05

AN265REV2

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Página 1 - EP93xx RTC Oscillator Circuit

Página 2 - 2 AN265REV2

AN2652 AN265REV2The NC7SPU04 is an unbuffered inverter that is powered from the 1.8 VDC rail. The output of theNC7SPU04 connects to the RTCXTALI input

Página 3

AN265AN265REV2 33. Determining the Silicon Revision of the Integrated CircuitOn the front of the integrated circuit, directly under the part number, i

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Cirrus-logic AN265 Manual do Utilizador

Consulte online ou descarregue Manual do Utilizador para Hardware Cirrus-logic AN265. Cirrus Logic AN265 User Manual Manual do Utilizador

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