General
Review and verify the following for
the custom schematic design:
- The sections above, including relevant
application notes and FAQ links.
- Pin attributes, signal description, and
electrical specifications.
- Electrical characteristics, timing parameters,
and any additional available information.
- Reset signal is asserted (low) while the
processor supplies are ramping up or down.
- MCU_PORz POR input is 3.3V tolerant and
fail-safe. The threshold follows the VDDS_OSC0
levels.
- Level of warm reset for MCU and main domains
RESET_REQz (VDDSHV0), MCU_RESETz (VDDSHV_MCU)
matches the IO supply group supply (1.8V or
3.3V).
- Reset inputs follow the slew rate requirements
(FS RESET, LVCMOS).
- Input slew rate when open-collector output is
connected (connecting through discrete push pull is
recommended) directly to the reset input.
- Follow reset requirements including slew rate and
POR hold time when a non-TI power design is
used.
Schematic Review
Follow the steps below for the custom schematic
design:
- Cold and warm
reset input signals slew rate requirements are
considered.
- Cold reset input
(MCU_PORz) deassertion hold time (MCU_PORz input, 9.5ms
minimum) after all supplies ramps are provided as per the
data sheet requirement.
- Provision for
filter capacitor is provided at the input of the reset
inputs (add 22pF (ball park for place holder) capacitor as a
filter option and DNI).
- Connection of
reset inputs when not used as per pin connectivity
requirements.
- Connection of
push button warm reset inputs through debouncing circuit
(Schmitt trigger buffer based).
Additional
- MCU_PORz input has a maximum rise and fall time
requirement when PMIC_POWERGOOD (open-drain) is connected to
the MCU_PORz. Adjust the pullup to minimize the rise time
(<200ns).
- MCU_PORz is fail-safe and 3.3V tolerant.
- Connect the output from a push pull discrete
buffer (with fast rise time) as the MCU_PORz input is a slow
rising open-drain output.
- Not connecting a valid MCU_PORz causes
unpredictable and random behavior, because the device is not
getting a valid reset, internal circuits are in random
states. Slow rising reset signal causes glitches internal to
the processor reset circuit.
- LVCMOS inputs have slew rate requirements. A
schmitt trigger circuit is recommended for the slow ramp
push button RC connected to the processor warm reset inputs.
Schmitt trigger circuit is recommended when using a push
button or an RC reset.
- A provision for external ESD protection for
manual reset input added near to the reset signal.
- Fail-safe operation when connected to external
reset input signals. Applying an external input before
supply ramps causes voltage feed and affects the processor
performance.
- Reviewed MCU_RESETz related errata.