Schematic Review and Fixes
Thought for 1 min 41 sec
Short answer
- TPS259531DSGT is an appropriate eFuse for your 6 V input. Use it at J6 input for inrush control, current limit, and fault protection.
- Keep D1 in series unless the TPS259531 variant you have explicitly specifies reverse-polarity tolerance/reverse blocking at IN. Most TPS25953x parts block reverse current OUT->IN but do not survive a reversed adapter on IN without an external diode.
How to wire and use TPS259531 correctly in your design
- Power path
- J6 tip (+6 V) -> U1 (TPS259531) IN
- U1 OUT -> series Schottky [D1] anode
- D1 cathode -> PiVIN (the 6 V rail feeding the buck and the spotlight loads)
- J6 sleeve -> GND
- Control and set pins (check the datasheet’s pin table for exact names)
- ILIM: add a resistor to GND to set the current limit to your target. For Pi ~3 A + motors up to 2 A, set ILIM ≈ 4.5–5.0 A. Use the datasheet’s ILIM vs RILIM equation to choose the resistor.
- dVdt: add a capacitor from dVdt to GND to slow the U1 OUT slew and tame inrush into your bulk and the buck. Pick CdVdt per the datasheet’s rise-time equation; start with a few nF to tens of nF and adjust as needed.
- EN/UVLO: tie EN so the device turns on at your intended VIN; you can use simple enable or add a divider to set UVLO above brownout if desired.
- FLT/PG (if present): optional; leave NC or pull up to a logic rail for fault indication.
- Exposed pad: tie to GND with ample copper for thermal relief.
- Keep D1 unless the datasheet for your exact TPS259531 device states input reverse polarity protection. If it does, you can remove D1 and wire U1 OUT directly to PiVIN.
Everything else looks consistent with your goals
- Pi 5 V path: Buck set to ~5.2 V -> PTC [F2] (sized for your intended Pi draw; use ~3 A hold if you truly need 3 A) -> H1 Pin 1 and Pin 3 (bottom-mounted header). Good.
- Pi-side TVS: SMF6.0A with K on the fused Pi 5 V, A to GND, placed right at the header with a very short ground via. Good.
- Spotlight loads: JST connectors should be wired VIN (6 V) on one pin and the MOSFET drain on the other; gates driven from GPIO via 100 Ω with 100 kΩ pulldowns, flyback diodes to PiVIN. Good.
- Brownout avoidance
- Set U1 ILIM to ~5 A and add dVdt capacitance.
- Use bulk capacitance:
- At PiVIN (6 V): add 47–100 µF (electrolytic or multiple ceramics) near the buck input caps.
- At the fused Pi 5 V after F2: add 47–100 µF low-ESR bulk to help step loads.
- Keep VIN, BUCK_5V, and PI_5V copper wide (see prior guidance: VIN 2.0–3.0 mm trunk, PI_5V 1.5–2.0 mm) and use via arrays at layer changes.
Action checklist to finalize
- Confirm TPS259531’s datasheet for:
- ILIM resistor equation and set RILIM for ~5 A.
- dVdt rise-time equation and choose CdVdt.
- Whether your exact device supports input reverse polarity; if not, keep D1.
- Ensure D1 is a 5 A class Schottky (e.g., MBRS540) and is placed as: U1 OUT -> D1 A, D1 K -> PiVIN.
- Verify F2’s hold current aligns with your Pi current target (≈3 A hold if you truly want up to 3 A).
- Add/confirm bulk caps as above and re-run ERC/DRC.
If you want, tell me your chosen ILIM and I’ll compute a starting RILIM and CdVdt target from the datasheet equations, plus review the U1 pin wiring against your schematic one-to-one.
Share load specs
Ask ILIM resistor
Clarify reverse polarity
dVdt capacitor sizing
Confirm pin wiring
