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Initial function IO and power architecture

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This commit contains the inital functional IO (engine controls and
general digital and analog IO excluding digital IO) and the initial
power architecture for the project
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h3cx
2026-08-29 21:18:45 +02:00
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Architecture/IO_MODULES/DIGITAL_OUTPUTS.md
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# General-Purpose Digital Output Module
## Purpose
This module defines the generic harness-connected digital-output classes for
NeoECU V1. It does not cover the dedicated ignition and injector power stages.
Connector positions, channel count, and the assignment of vehicle functions
remain open until packaging and connector design.
Two non-interchangeable output classes are provided:
- protected 5 V high-side logic outputs for external electronic-control inputs;
- protected battery-domain low-side outputs for relays, solenoids, and other
inductive loads.
Firmware assigns a compatible vehicle role and reported polarity to a channel;
it cannot turn one electrical class into the other. A starter-enable function
may use either class only when the external starter interface accepts it.
## Protected 5 V logic outputs
Use the automotive-qualified TI `TPS4H000-Q1` quad smart high-side switch.
It is supplied from `+5V_AUX`, not directly from `+5V_MAIN`.
```text
+5V_MAIN --> +5V_AUX eFuse / load switch --> TPS4H000-Q1 VBB
|
MCU GPIO --> TPS4H000-Q1 INx OUTx --> LOGIC_OUTx --> connector
| |
R_IN_PD R_OUT_PD
| |
GND GND
```
- `+5V_AUX` isolates an external logic-output fault from `+5V_MAIN`, the MCU,
and the sensor-excitation rail.
- Each channel is active high: when commanded on, it sources `+5V_AUX`.
`R_OUT_PD` holds the connector output low when the channel is off or the ECU
is unpowered. This is a protected high-side output with a passive low state,
not a true push-pull stage.
- `R_IN_PD` is an external pull-down at the IC input. It holds the output off
while the MCU is reset, booting, unpowered, or has not deliberately taken
control. MCU internal pulls are not a substitute.
- Set each channel's current limit to the TPS4H000-Q1 minimum configured value
of 100 mA. This is the intended maximum output current for this logic-output
class; the `+5V_AUX` eFuse limit must be selected consistently with the
populated channel count and simultaneous-fault policy.
- Use the IC's diagnostic/current-sense variant as appropriate for the MCU
interface. Per-channel fault reporting is useful but open-load reporting is
optional for generic logic commands.
### Logic-output connector protection
Place `TVS_LOGIC_OUTx` at the connector side of each output, with a short,
low-inductance return to the protected output-ground reference. Select its
working standoff above the maximum `+5V_AUX` voltage and its worst-case dynamic
clamp below the TPS4H000-Q1 output-pin limit with margin.
The TVS absorbs transient events. It is not sized to dissipate a sustained
misconnection to `VBAT_PROT`; the TPS4H000-Q1's off-state short-to-battery
detection and fault behaviour must handle that case. Confirm its unpowered
output behaviour and the completed TVS network against the actual connector
fault and transient specification before schematic freeze.
## Protected low-side outputs
Use the automotive-qualified Infineon `TLE9104SH` smart quad low-side switch.
It drives battery-domain loads supplied from `VBAT_PROT`.
```text
VBAT_PROT --> external load --> SINK_OUTx --> TLE9104SH OUTx
|
internal low-side MOSFET
|
OUT_PGND --> power-entry ground star
VBAT_PROT --> TLE9104SH VS +5V_MAIN --> TLE9104SH VDD
+3V3_MAIN --> TLE9104SH VIO
MCU GPIO --> TLE9104SH INx MCU SPI <--> TLE9104SH SPI
| |
R_IN_PD diagnostics
|
TLE9104SH local ground reference
MCU enable --> TLE9104SH EN
|
R_EN_PD
|
TLE9104SH local ground reference
```
- The TLE9104SH supplies active inductive-load clamping, configurable
overcurrent protection, short-circuit and thermal protection, direct channel
inputs, and SPI diagnostics.
- `VS` is supplied from `VBAT_PROT`; use the documented logic supplies so the
MCU-facing interface is referenced to `+3V3_MAIN` while the driver itself is
supplied from the internal 5 V rail. Decouple both supply domains locally at
the IC.
- `R_EN_PD` holds `EN` inactive through power-up and MCU reset. `R_IN_PD` on
every direct input holds its channel off. Firmware may enable outputs only
after the required reset, SPI configuration, and diagnostic checks have
completed.
- Use the diagnostic interface to identify overcurrent, overtemperature,
short-to-battery, short-to-ground, and—where useful—open-load faults. The
final retry, latching, reporting, and output-inhibit policy is firmware work
and remains open.
- Define `OUT_PGND` as a high-current return domain. It must remain separate
from `DGND`, sensor return, injector return, and ignition return until the
deliberate power-entry star connection.
### Sink-output connector protection
The TLE9104SH's internal active clamp is the primary turn-off path for
inductive loads. Provide a connector-side transient-protection footprint for
each sink output, but select and place any external TVS only after calculating
the load energy, harness transient environment, and desired release time. An
incorrect low-voltage clamp can bypass the driver's intended inductive clamp,
increase TVS dissipation, or slow a relay/solenoid release.
The final protection network shall keep the output pin within its validated
limit for connector transients and for an externally powered load while the
ECU is off. It shall not back-power the TLE9104SH logic supply, `+3V3_MAIN`,
or `+5V_AUX`.
## Default state and fault behaviour
| Condition | Logic output (`TPS4H000-Q1`) | Sink output (`TLE9104SH`) |
| --- | --- | --- |
| MCU reset or boot | `R_IN_PD` holds the channel off; `R_OUT_PD` holds the connector low. | `R_EN_PD` and `R_IN_PD` keep every channel open. |
| ECU unpowered | Output is not actively driven; connector protection and the IC must tolerate the assigned external-fault case without rail back-power. | Output is open; externally powered loads and connector faults must not back-power ECU logic. |
| Output short/overload | Per-channel current limit and thermal protection act; `+5V_AUX` eFuse limits the aggregate branch. | Per-channel overcurrent/thermal protection acts and status is reported through SPI. |
| Inductive turn-off | Not an intended load class. | Internal active clamp controls load-current decay; any external TVS is coordinated with it. |
## Validation and open items before schematic freeze
1. Confirm the output connector transient/ESD and sustained miswiring cases,
including externally applied battery voltage while the ECU is off.
2. Select `TVS_LOGIC_OUTx` by worst-case dynamic clamp and pulse rating, not
nominal voltage marking. Confirm it does not conduct at the maximum
`+5V_AUX` voltage.
3. Select `R_OUT_PD` from the external logic-input leakage, required low level,
and permitted static current when the output is high.
4. Select the `+5V_AUX` eFuse threshold and TPS4H000-Q1 channel-limit setting
together; 100 mA per active channel is the maximum intended logic-output
current.
5. For each sink load, establish steady current, inrush, inductance, stored
energy, required release time, PWM requirement, and thermal/copper limits.
6. Calculate whether an external sink-output TVS is required and verify that it
complements rather than overrides the TLE9104SH active clamp.
7. Define the firmware diagnostic and recovery policy, and identify any output
assignment that needs an additional hardware permit gate.
## References
- [TPS4H000-Q1 product page and datasheet](https://www.ti.com/product/TPS4H000-Q1)
- [TLE9104SH product page and datasheet](https://www.infineon.com/cms/de/product/power/smart-power-switches/multichannel-spi-switches-controller/flex-multichannel-spi-low-side-power-switch/tle9104sh/)