I’m reconciling the completed schematic/ERC work against the live project now. If the schematic gate is genuinely clear, I’ll continue through placement cleanup and pre-routing checks without pausing.
Thought for 11 sec — Considering execution processes
Awaiting 1 background task
"PCB Placement Repair" completed.
Thought for 7 sec
flux
8 days ago
The schematic executor reduced ERC from 218 floating pins and 8 single-pin nets to 2 floating pins and 1 single-pin net. It completed most supply, ground, ADC, connector, CAN, protection, and unused-pin wiring.
Two electrical decisions remain before routing:
Select the MAX9926 crank/cam threshold mode for U10.
Remap VSS_GPIO; the current Teensy symbol exposes GPIO0–41, so the planned GPIO42 assignment is unavailable.
The placement-repair executor also completed, but I could not retrieve and reconcile its final report. Therefore the four overlap/access repairs, mounting-hole keepouts, CMC clearance, and Teensy service access are not yet independently accepted.
Routing has not started. Next session should reconcile placement, resolve the two schematic items, rerun ERC/DRC, remove stale traces, and then begin routing. Execution stopped because your ACUs ran out.
This selection targets a socketed Teensy 4.1 ECU for eight confirmed high-impedance port injectors, eight smart coils with internal igniters, one external fuel-pump relay, and two external cooling-fan relays. Stepper idle-air control is not included. All outputs must default OFF during reset and loss of synchronization.
Selected parts
Table
Function
Selected device
Quantity
Reason
Injector drivers
Infineon TLE9104SHXUMA1
2
Four automotive powertrain low-side channels per IC; explicitly supports gasoline multiport injection; 3 A continuous per channel, 50-60 V active clamp, SPI diagnostics, configurable overcurrent protection, and direct PWM inputs
Smart-coil trigger buffer
TI SN74AHCT244QPWRQ1
1
Eight non-inverting 5 V push-pull outputs; TTL-compatible 2 V input-high threshold accepts Teensy 3.3 V logic; dual active-low output-enable pins provide hardware shutdown
Relay drivers
Infineon TLE8108EMXUMA1
1
Eight protected low-side channels; 400 mA continuous per channel, 41-50 V clamp, overload and thermal shutdown, and SPI open/short diagnostics
| Main surge suppressor | Littelfuse SM8S33A | 1 | AEC-Q101 6.6 kW TVS; 33 V standoff and 53.3 V maximum clamp for a protected 12 V automotive front end |
| Reverse-battery and power-path controller | TI LM74930QRGERQ1 | 1 | AEC-Q100 dual external-NMOS controller with reverse battery, overvoltage, undervoltage, overcurrent and load-dump support |
| Coil-trigger ESD arrays | Nexperia PESD5V0L4UG | 2 | Four protected 5 V signal lines per device; two devices cover all eight smart-coil triggers |
1. Injector channels 1-8
Driver
Use two TLE9104SH devices, one channel per high-impedance injector.
Datasheet-supported characteristics:
Intended for automotive injectors, solenoids, and relays
Direct parallel inputs support time-critical gasoline multiport injection PWM
3.0-5.5 V logic supply and 4.5-5.5 V analog supply
3 A nominal continuous load current per channel
150 milliohm typical on-resistance at 25 C
50-60 V integrated output clamp for fast injector closing
Configurable 1 A, 2 A, 3 A, or 4 A overcurrent thresholds
Per-channel overtemperature and open/short diagnostics through SPI
Channel protection and support
47 ohm series resistor from each Teensy timing output to TLE9104 parallel input
47 kohm pull-down on each parallel input so every injector remains OFF if the Teensy is absent or resetting
100 nF ceramic at each VIO and VDD pin group, plus 4.7 uF local bulk capacitance per IC
EN held low by 10 kohm and asserted only by a hardware-qualified ECU-enable signal
RESN held low during power-up; connect to the reset supervisor rather than firmware alone
Place 100 nF, 100 V ceramic from each injector output to power ground only as an optional EMI tuning footprint; do not populate until emissions testing shows it is needed
Do not add ordinary flyback diodes across injectors because they slow closing. The TLE9104's 50-60 V active clamp is the intended energy path
Constraint
The design requirement is saturated, high-impedance port injectors, normally about 10-16 ohm. Low-impedance peak-and-hold or gasoline direct-injection injectors are explicitly outside this ECU version's scope.
2. Smart-coil trigger channels 1-8
Driver
Use one SN74AHCT244-Q1 powered from the protected 5 V rail.
4.5-5.5 V supply
2.0 V minimum input-high threshold, so Teensy 3.3 V outputs are valid
Eight push-pull outputs arranged as two independently enabled groups of four
Automotive Q-temperature range to 125 C
OE high forces high impedance; both OE pins must have 10 kohm pull-ups to 5 V for default disable
Per-channel protection
Use this connector-side network on each trigger:
Buffer output
1 kohm series resistor
Connector-side trigger node
10 kohm pull-down from trigger node to sensor/logic ground
One channel of a 5 V ESD array from trigger node to ground, placed immediately beside the main connector
Optional 100 pF C0G capacitor from trigger node to ground for RF control; leave unpopulated initially
The 1 kohm resistor limits fault and clamp current while remaining suitable for normal high-impedance smart-coil inputs. Confirm trigger polarity, input resistance, and maximum input voltage for every supported coil family before connecting a vehicle harness.
Hardware shutdown
Drive both OE pins from a hardware COIL_ENABLE_N signal. A watchdog/reset supervisor must release the buffer only after firmware initialization and valid crank synchronization. Loss of watchdog, reset, or power-good must disable the outputs without firmware action.
400 mA continuous per channel with all channels active
0.8 ohm typical on-resistance at 25 C
41-50 V active clamp
20 mJ single-pulse clamp rating under the datasheet condition
Overload, short-circuit, overtemperature, open-load and short-to-ground diagnostics
Protection
Fit a diode directly across each external relay coil in the vehicle harness whenever possible: automotive-qualified 1 A diode, cathode to relay +12 V and anode to ECU low-side output
If relay release speed matters, use a diode plus 24-33 V TVS or Zener clamp instead of a plain diode, after checking TLE8108 output limits
10 kohm pull-down on each direct input and reset pin arrangement that leaves all outputs OFF at startup
100 nF plus 4.7 uF local supply decoupling
Do not drive pump or fan motor current through the ECU; these outputs drive relay coils only
4. Shared automotive power protection
Use LM74930-Q1 with two external automotive N-channel MOSFETs as the main reverse-battery and disconnect stage. Place SM8S33A at the connector after the input fuse and before sensitive regulators.
Recommended sequence:
BATTERY -> fuse -> SM8S33A -> EMI filter -> LM74930-Q1 and external MOSFETs -> protected 12 V rail
The LM74930-Q1 surrounding resistor values, current shunt, MOSFET voltage rating, and overvoltage thresholds must be calculated from the final ECU current budget. Use at least 80 V automotive MOSFETs unless a complete ISO 7637-2 and ISO 16750-2 analysis justifies a lower rating.
5. Grounding and connector protection
Use separate connector pins for power ground, injector/stepper power returns, logic ground, and sensor ground
Join grounds at a controlled star region near the power entry and ADC reference return; do not route injector current through sensor ground
Place all connector-facing ESD parts at the connector, before traces enter the logic area
Keep injector and stepper output copper away from crank/cam and analog sensor inputs
Use at least two power-ground connector contacts if the connector contact rating or temperature rise requires it
Final validation required before schematic freeze
Measure or obtain injector resistance, inductance, maximum current, and expected repetition rate.
Identify the smart-coil families and verify trigger polarity and allowed 0-5 V input network.
Obtain relay-coil resistance and inductance for the selected fuel-pump and fan relays.
Complete a power and thermal budget at 85 C ambient and maximum battery voltage.
Validate pulse immunity and load dump against the intended vehicle class; this is an engineering prototype and is not automatically road or safety certified.