General
Review and verify the following for
the custom schematic design:
- Above sections, 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 using a non-TI power
solution
Schematic Review
Follow the below list 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 have 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 MCU_PORz input rather that
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.
- 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.