NXP Semiconductors i.MX8 QM - Checking for Clock Pitfalls; Avoiding Reset Pitfalls; Sample Board Bring-up Checklist

Table 40. Sample voltage report (continued)
Source Net Name
Expected
(V)
Measured
(V)
Measure
point
Comment
i.MX8 LDO VDD_HDMI_RX0_ LDO0_1P0_CAP 1.0 V C308-1
Internal LDO sourced
by i.MX8
i.MX8 LDO VDD_HDMI_RX0_ LDO1_1P0_CAP 1.0 V C310-1
Internal LDO sourced
by i.MX8
Enet PHY VCC_ENET0_1V8 1.8 V C412-1
Software sets up Phy for
1.8 V output
5.4 Checking for clock pitfalls
Problems with the external clocks are another common source of board bring-up issues. Ensure that all of the clock sources run
as expected.
The XTALI/XTALO and the RTC_XTALI/RTC_XTALO clocks are the main clock sources for the 24 MHz and 32.768 kHz reference
clocks respectively.
When checking crystal frequencies, use an active probe to avoid excessive loading. A passive probe typically inhibits the 32.768
kHz and 24 MHz oscillators from starting up. Use the following guidelines:
• The RTC_XTALI clock is running at 32.768 kHz.
• XTALI/XTALO is running at 24 MHz (used for the PLL reference).
5.5 Avoiding reset pitfalls
Follow the following guidelines to ensure that you are booting using the correct boot mode.
• Follow the recommended power-up sequence specified in the i.MX8 data sheet.
• Ensure that the POR_B signal remains asserted (low) until all voltage rails associated with the bootup are on.
The SCU_BOOT_MODE balls and internal fuses control the boot. For a more detailed description of the different boot modes, see
the system boot chapter of the chip reference manual.
5.6 Sample board bring-up checklist
Note that the checklist incorporates the recommendations described in the previous sections. Blank cells should be filled in during
bring-up, as appropriate.
Table 41. Board bring-up checklist
Checklist Item Details Owner
Findings
and Status
Note: The following items must be completed serially.
1. Perform a visual
inspection.
Check the major components to make sure nothing is misplaced or
rotated before applying power.
2. Verify all i.MX8 voltage
rails.
Confirm that the voltages match the data sheet requirements. Be sure
to check the voltages as close to the i.MX8 as possible
Table continues on the next page...
NXP Semiconductors
Avoiding board bring-up problems
i.MX8 QM / i.MX8 QXP Hardware Developer’s Guide, Rev. 2.4p, 06/2021
User's Guide 83 / 89