Hi NXP,
Reference design : KIT6UL-3000EVM (SPF-29105)
The i.MX reset input (POR_B) will be driven by RESET_MCU_B of PMIC PF3000.
Why do we need U501(UM803RS) on page 8 for this design? Could we remove it without any side effect?
And how about is the i.MX reset sequence or requirement (just one RTC clock is needed, right? )
BRs
Mark
Hi Mark
POR duration requirements (which are provided by UM803RS on schematic) are given
in sect.4.2.1 Power-Up Sequence i.MX6UL Datasheet
http://cache.freescale.com/files/32bit/doc/data_sheet/IMX6ULCEC.pdf
The POR_B input (if used) must be immediately asserted at power-up and
remain asserted until after the last power rail reaches its working voltage.
Also clocks should be stable at time of POR deassertion.
Best regards
igor
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Hi igor,
Thanks for your quick reply for question 2. Would you answer me first question?
"The i.MX reset input (POR_B) will be driven by RESET_MCU_B of PMIC PF3000.
Why do we need U501(UM803RS) on page 8 for this design? Could we remove it without any side effect?"
BRs
Mark
>Why do we need U501(UM803RS) on page 8 for this design?
to guarantee that all board power supplies are stable when POR will release.
RESET_MCU_B of PMIC PF3000 guarantee only PMIC PF3000 output voltages, which are input
to i.MX6. Some time is needed to charge for example _CAP voltages and other board capacitors.
>Could we remove it without any side effect?"
yes, if you guarantee that all board power supplies are stable when POR will release.
Best regards
igor
Hi igor,
I don't understand what you mean.
For reference design, U501 only can guarantee "DCDC_3V3" to reach threshold voltage and generate reset signal. And DCDC_3V3 is came from PMIC. As you said, RESET_MCU_B guarantee PMIC's output and it include DCDC_3V3 indeed. I can't understand what's different w/ or w/o reset IC (U501). Could you explain it more?
BRs
Mark
Hi Mark
>U501 only can guarantee "DCDC_3V3" to reach threshold voltage
this is not fully correct. It additionally holds _RESET during 140-560mS.
There are other capacitors which should be charged, so U501
adds additional delay. In custom design you can remove it if
all power supplies, including processor _CAP voltages are stable
at deassertion time RESET_MCU_B of PMIC PF3000.
Best regards
igor
Hi igor,
OK, so R511 and C503 are reserved for this requirement.
Thanks for your reply.
BRs
Mark