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docs: Update the amplitude constraints for external 32 kHz oscillator

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Shen Mengjing
2025-09-02 17:56:46 +08:00
committed by morris
parent f4c40f7e69
commit 7943b1ff58
4 changed files with 4 additions and 8 deletions
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docs/en/api-reference/system/system_time.rst
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@@ -35,7 +35,7 @@ The RTC timer has the following clock sources:
:not esp32c2: - ``External 32 kHz crystal``: Requires a 32 kHz crystal to be connected to the external crystal pins. This source provides a better frequency stability at the expense of a slightly higher (by 1 μA) Deep-sleep current consumption. Refer to the `datasheet <{IDF_TARGET_DATASHEET_EN_URL}>`__ for information on which pins to connect to.
- ``External 32 kHz oscillator``: Allows using 32 kHz clock generated by an external circuit. The external clock signal must be connected to the external oscillator pin. The amplitude should be less than 1.2 V for sine wave signal and less than 1 V for square wave signal. Common mode voltage should be in the range of 0.1 < Vcm < 0.5xVamp, where Vamp stands for signal amplitude. Refer to the `datasheet <{IDF_TARGET_DATASHEET_EN_URL}>`__ for information on which pin to connect to.
- ``External 32 kHz oscillator``: Allows using a 32 kHz clock generated by an external circuit. The external clock signal must be connected to the external oscillator pin. The input amplitude must ensure that the digital circuit can correctly distinguish between logic high and low levels. Test results show that 1.7 V is the threshold between high and low levels. Therefore, make sure the input waveform has a peak value greater than 1.7 V and a minimum value lower than 1.7 V. For details on pin connections, please refer to the `datasheet <{IDF_TARGET_DATASHEET_EN_URL}>`__.
:esp32 or esp32s2 or esp32s3 or esp32c2 or esp32c3: - ``Internal 8.5–17.5 MHz oscillator (depending on chip), divided by 256``: Provides better frequency stability than the ``Internal 90–150 kHz RC oscillator`` at the expense of a higher (by 5 μA) Deep-sleep current consumption. It also does not require external components.