Automotive PCB · Reference Sheet

Thermo

Resistive temp sending unit input + NEMA14 stepper driver, on one AEC-Q100 board. This sheet covers physical wiring — connector pinouts and the real parts on each end of the harness.

Board: 67.7 × 48.9 mm
Layers: 4
MCU: S32K144
ADC: ADS1118-Q1
Driver: DRV8434A-Q1
Connectors: 4

Thermo PCB, isometric render, top side populated

Thermo PCB, second isometric angle — Populated top side, low angle

Thermo PCB, straight top-down view with silkscreen references visible — Top-down — reference designators visible

Back side — mounting holes, no components

Wiring the harness

Every off-board connection on Thermo is a short pigtail: a sealed Deutsch DTM06 connector on the outboard (engine-bay) end, wired to one of the four board-mount connectors below. None of the DTM06 housings mount to the PCB directly — they live on the free end of the wire.

J6Power Input

Board side: Phoenix Contact MKDS 1,5/2-5,08 (ord. 1715721), 5.08 mm screw terminal · Outboard end: Deutsch DTM06-2S, nickel contacts

Pin	Net	Function
1	VIN	+12V, engine-bay battery rail (fused & reverse-battery protected on-board)
2	GND	Chassis / battery return

Protected by F1, a 2A Littelfuse 297-series MINI blade fuse (SAE J2077 / ISO 8820-3) in a standard replaceable holder — swap it with any auto-parts-store blade fuse. Reverse-battery protection is a real ideal-diode stage (TI LM74700-Q1), not just a series diode, so there's no forward-voltage drop to budget for.

J4Temperature Sensor Input

Board side: Molex KK-254 22-27-2021, 2.54 mm friction-lock · Outboard end: Deutsch DTM06-2S, nickel contacts

Pin	Net	Function
1	TSENSE	Sensor signal lead — resistive divider node (R12 pull-up to +3V3)
2	GND	Sensor return lead

Real automotive resistive temp sending unit (GM-style closed-element NTC, via DIYAutoTune, 3/8" NPT, 2-wire isolated, −40°F–210°F). No polarity to worry about — it's a plain 2-terminal resistor, so the two leads are interchangeable, unlike the K-type thermocouple this input used to carry. Feeds U5 (ADS1118-Q1) AIN0 as a simple resistive divider (R12 = 1.00kΩ, chosen to center ADC resolution on the sensor's real 86–210°F operating range) — firmware needs a resistance-to-temperature lookup against the sensor's published curve (−40°F=100.7kΩ, 86°F=2.24kΩ, 210.2°F=177Ω), not a linear formula.

J5Stepper Output

Board side: Molex KK-254 22-27-2041, 2.54 mm friction-lock · Outboard end: Deutsch DTM06-4S, nickel contacts

Pin	Net	Function
1	AOUT1	Motor coil A, terminal 1
2	AOUT2	Motor coil A, terminal 2
3	BOUT2	Motor coil B, terminal 2
4	BOUT1	Motor coil B, terminal 1

Driven by U6 (DRV8434A-Q1), current-limited to 1.50 A/phase by an on-board VREF divider (R4 = 1.00kΩ, R5 = 1.50kΩ), matched to the specified motor (StepperOnline 14C19S1504GF5-025RS, 1.5 A/phase) rather than the driver's own 2.5A ceiling. Identify your motor's two coil pairs with a multimeter continuity check before wiring — each coil reads as a low-resistance loop; two leads from different coils read open. Within a coil, lead order only flips that phase's direction (harmless); mixing leads between coils will make the motor stall instead of step. Note the B pair runs 2-then-1: J5's order follows the driver's own physical pad order (U6 pins 3-6 are AOUT1, AOUT2, BOUT2, BOUT1 along its edge), so the four phase traces stay straight and non-crossing. Both pins are still coil B — only that coil's direction flips.

J2SWD Programming

Tag-Connect TC2030-IDC-NL, 6-pin pogo, no header to solder

Pin	Net	Function
1	SWDIO	Serial wire data
2	VCC	+3V3 target reference (not a supply pin)
3	SWCLK	Serial wire clock
4	NC	Spare — was BOOT0 on this footprint's original STM32 use, no S32K1 equivalent
5	RESET	MCU reset, active low
6	GND	Ground reference

Programmed via NXP's S32 Design Studio + SDK over SWD — the "Arduino-style" heritage of this board family is physical footprint only, there's no Arduino IDE / sketch flow on this MCU.

Bill of Materials

Every part that actually populates the board — 44 placements across 30 orderable line items. Passives are grouped by real value; each semiconductor and connector is a distinct real part, not a placeholder.

30Line items

44Placements

8Semiconductors

28Passives

4Connectors

Ref	Qty	Part	Description	Mfr / Pkg	Qualification
Semiconductors
U1	1	NXP S32K144	Arm Cortex-M4F MCU, LQFP-64, 10×10mm, 0.5mm pitch	—	AEC-Q100
U2	1	TI LMR33630-Q1	5V synchronous buck converter, VQFN-HR-12 (RNX0012C)	—	AEC-Q100 G1
U3	1	TI LM74700-Q1	Ideal-diode reverse-battery controller, SOT-23-6	—	AEC-Q100 G1
U4	1	TI TLV733P-Q1	3.3V LDO, SOT-23-5	—	AEC-Q100 G1
U5	1	TI ADS1118-Q1	16-bit SPI ADC w/ PGA, resistive temp-sensor front-end, VSSOP-10 (DGS0010A)	—	AEC-Q100 G1
U6	1	TI DRV8434A-Q1	Stepper motor driver, integrated current sense, VQFN-24 (RGE0024N)	—	AEC-Q100
Q1	1	Nexperia PMV37ENEA	N-channel MOSFET, reverse-battery protection, SOT-23	—	AEC-Q101
D1	1	SMCJ33A	TVS diode, 33V, transient protection, SMC	—	AEC-Q101
Resistors — 0603
R4, R12	2	1.00kΩ	Motor VREF divider upper (R4) & TSENSE pull-up (R12) — same value, unrelated circuits	—	AEC-Q200
R5	1	1.50kΩ	VREF divider, lower — self-calculated, sets IFS=1.50A for the real motor	—	AEC-Q200
R1, R2, R6, R11	4	10kΩ	Pull-ups (RESET, buck FB reference, U6 nFAULT, U5 SPI_CS)	—	AEC-Q200
R3	1	2.49kΩ	Buck feedback divider, lower	—	AEC-Q200
Capacitors — 0603, X7R
C6, C7, C10, C11, C13, C24	6	100nF	Decoupling / charge-pump / TSENSE smoothing	—	AEC-Q200
C17, C18	2	10nF	U6 VM decoupling	—	AEC-Q200
C1, C19	2	10µF	Input protection bulk / U6 VM bulk (self-selected)	—	AEC-Q200
C4, C5	2	18pF	Y1 crystal load caps	—	AEC-Q200
C23	1	1nF	U6 TRQ_CNT/STL_TH, required regardless of mode	—	AEC-Q200
C3, C8, C12	3	1µF	LDO output / VDDA / VCC decoupling	—	AEC-Q200
C21	1	220nF	U6 charge pump, VCP–VM	—	AEC-Q200
C20	1	22nF	U6 charge pump, CPH–CPL	—	AEC-Q200
C2	1	22µF	Buck output bulk	—	AEC-Q200
C22	1	470nF	U6 DVDD bypass	—	AEC-Q200
Inductors
L1	1	10µH	Buck power inductor, 1210	—	AEC-Q200
L2	1	Ferrite bead	VDDA filter, 1210	—	AEC-Q200
Electromechanical
F1	1	Keystone 3568 + Littelfuse 297	Mini blade fuse holder (THT) + 2A replaceable fuse, SAE J2077 / ISO 8820-3	—	—
Y1	1	8MHz crystal	SMD, 3225 4-pin	—	AEC-Q200
Connectors — board side
J2	1	Tag-Connect TC2030-IDC-NL	SWD programming, 6-pin pogo	—	—
J4	1	Molex 22-27-2021	KK-254, 2-pos — temp sensor pigtail landing	—	—
J5	1	Molex 22-27-2041	KK-254, 4-pos — stepper pigtail landing	—	—
J6	1	Phoenix Contact 1715721	MKDS 1,5/2-5,08 screw terminal — power pigtail landing	—	—

Not included above (see the connector cards higher up this page): the real automotive temp sending unit itself (GM-style closed-element NTC via DIYAutoTune) and the outboard Deutsch DTM06 housings/contacts that complete each pigtail (all nickel now — J4 downgraded from gold once the sensor stopped being a raw mV thermocouple signal), and the 4× M3 mounting-hole hardware (MH1–MH4, unpopulated NPTH). Y1's 8MHz value and F1's holder/fuse split are generic-part placeholders, not vendor-locked — substitute freely as long as ratings match.