i.MX RT1050 internal oscillator's accuracy

[masahirokiniwa]

I checked the data sheet of i.MX RT1050, but I couldn't find the internal oscillator's specification.

Could you tell me the internal oscillator's accuracy both 24MHz and 32kHz?

Best regards,

M.Kiniwa

[masahirokiniwa]

I see that the internal 24MHz oscillator is stated when the power on sequence.

But the external oscillator is started by the software initialize sequence as below.

I see the frequency of the internal 24MHz oscillator is not as accurate, but I need its accuracy for consideration.

<initialize sequence by MCUXpresso Config Tools>

void BOARD_BootClockRUN(void)
{
    /* Enable 1MHz clock output. */
    XTALOSC24M->OSC_CONFIG2 |= XTALOSC24M_OSC_CONFIG2_ENABLE_1M_MASK;
    /* Use free 1MHz clock output. */
    XTALOSC24M->OSC_CONFIG2 &= ~XTALOSC24M_OSC_CONFIG2_MUX_1M_MASK;
    /* Set XTAL 24MHz clock frequency. */
    CLOCK_SetXtalFreq(24000000U);
    /* Enable XTAL 24MHz clock source. */
    CLOCK_InitExternalClk(0);
    /* Enable internal RC. */
    CLOCK_InitRcOsc24M();
    /* Switch clock source to external OSC. */
    CLOCK_SwitchOsc(kCLOCK_XtalOsc);

Best regards,

M.Kiniwa

[masahirokiniwa]

Hi Artur,

OK, I will consider to use external xtal oscillator.

But I think the 24MHz internal oscillator is used for boot sequence before turning-on the external xtal oscillator.

So, I need the specification of 24MHz internal oscillator.

Could you tell me the accuracy of it?

Best regards,

M.Kiniwa

[art]

The internal 24MHz quartz oscillation circuit starts up immediately when the VDD_HIGH_IN rail is powered on. The hardware power-up sequence must be designed so as the POR_B signal is released only when the external 24MHz crystal is up and running stable.

[masahirokiniwa]

Hi Artur,

Thank you for you answer.

I see the accuracy of 32kHz internal ring oscillator.

In the reference manual P.1116, XTALOOSC_24M_LOWPWR_CTRn has RC_OSC_EN bit.

I can configure to use the internal RC oscillator by MCUXpresso Config Tools.

I think the RC OSC is a 24MHz internal oscillator.

Is it a miss definition?

Best regards,

M.Kiniwa

[art]

Initially, the 24MHz ring oscillator was planned to be implemented. However, finally, its actual accuracy and stability appeared to be very weak, so, it has been considered as not practically usable.

Artur

[art]

Do you mean the internal ring oscillator of the low-frequency (32kHz) clock source? If so, its accuracy is very weak and its frequency dispersion can be up to +/- 50%.

The 24MHz clock source doesn't have an internal oscillator, so, its accuracy is equal to the accuracy of an external crystal or oscillator used.

Have a great day,
Artur

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