General
Review and verify the following for the custom
schematic design:
- Reviewed above "Common checklist for all sections" section of the
user's guide.
- Connection of IO supply for IO groups.
- ROC, voltage sequence and
slew rate requirements for processor IO supply for IO groups.
- Connection of recommended external capacitor for IO groups pins.
Selection of CAP_VDDSn capacitor voltage rating.
Schematic Review
Follow the list below for the custom schematic design:
- The recommendation is to compare
the implementation of bulk and decoupling capacitor for the supply rails with SK
schematic implementation.
- A valid fixed 1.8V/3.3V supply
source is connected to (VDDSHV_CANUART, VDDSHV_MCU, VDDSHV0, VDDSHV1, VDDSHV2,
VDDSHV3) all the IO supply for IO groups as per the ROC.
- A valid supply 1.8V/3.3V (that
can be dynamically switched) source is connected to VDDSHV4, VDDSHV5, VDDSHV6 as
per the ROC.
- All IO supply for IO groups
VDDSHVx have a valid supply connected irrespective of the use of IOs referenced
to the IO supply for IO group.
- Supply rails connected to the IO supply for IO group VDDSHVx follow the
ROC.
- Slew rate requirements followed
for processor IO supply for IO groups. Refer processor-specific data
sheet.
- Connection of the recommended capacitor to CAP_VDDSn pin and VSS. Each CAP_VDDSn
pin requires a separate 1μF capacitor connected with respect to VSS (ground)
(for internal LDO, across CAP_VDDSn pin and VSS).
- CAP_VDDSn capacitor package (recommend using the smallest possible (0201 or
package size closest to 0201) package to minimize loop inductance).
- Voltage rating of the CAP_VDDSn
capacitor selected for the capacitance value to be in the range 0.8μF to 1.5μF
including aging, temperature and effect of DC bias. Use 10V or above.
- Select CAP_VDDSn capacitor with < 1Ω ESR, keep the trace loop inductance <
2.5nH.
- IO supply voltage sequence follow
the power-up and power-down sequence as per processor-specific data sheet.
Additional
- The recommendation is to add a 0Ω
resistor or jumper for isolation or current measurement at the PMIC DC/DC or LDO
output for the IO supply rails. The recommendation is to add TPs for
measurement. The recommendation is to follow kelvin current sense connection to
connect the TPs. Choose the resistor package based on the supply rail current
and the resistor current carrying capacity.
- In use case where the VDDSHVx IO supply rails are sourced from the 3.3V supply,
all IOs referenced to (powered by) the VDDSHVx are required to operate at 3.3V
IO level. If a VDDSHVx power rail is sourced from a 1.8V supply, all IOs
referenced to (powered by) the VDDSHVx are required to operate at 1.8V IO
level.
- Some interfaces span multiple VDDSHVx, for example MMC2 and GPMC0. When using
any of the interface, all VDDSHVx domains supporting a specific interface
(peripheral) needs to be powered from the same power source.
- A number of processor IOs are not fail-safe. Applying input voltage to the IOs
while the corresponding VDDSHVx supply is off is not recommended or
allowed.
- The recommendation is to verify all IO pins on each VDDSHVx (or VDDSHV_MCU)
connects to a single voltage level.
- Leaving VDDSHVx rails unconnected is not recommended. The recommendation is to
connect IO supply for IO group pins to either 1.8V or 3.3V, depending on the use
case.