LSC409091FN IC Identification in Ford EEC-V ECU, Motorola/Freescale PLCC Driver

User question

lsc409091fn

Artificial Intelligence Response

DIRECT ANSWER TO THE QUESTION

• I cannot find any authoritative public datasheet or manufacturer record for “LSC409091FN.” It is most likely a house‑coded/proprietary ASIC (very common in automotive ECUs) or a misread/mistyped code.
• If this marking comes from a Ford EEC‑V/ECU board, community reports suggest similar LSCxxxxxx devices are coil/low‑side driver ASICs, but this cannot be verified from primary sources. Treat the identification as unconfirmed.
• The “FN” suffix in legacy Motorola/Freescale/NXP part codes denotes a PLCC (Plastic Leaded Chip Carrier) package; if your device is PLCC, that aligns with the suffix usage. (nxp.com)

KEY POINTS

• No official listing found; likely custom/obsoleted ASIC or incorrect part number.
• If from an ECU, probable function is high‑current low‑side switching (ignition/injector/solenoid), but verify on your PCB.
• Request: please share a clear photo of the IC topmark, package, and surrounding circuit, plus vehicle/ECU context.

DETAILED PROBLEM ANALYSIS

• Why it’s hard to find: Automotive Tier‑1/Tier‑2 suppliers (Motorola/Freescale/NXP, Siemens/Continental, Bosch, etc.) often delivered custom ASICs with customer-specific topmarks. Such parts seldom appear in public catalogs and are supported only via OEM documentation. Broker listings sometimes echo the code but don’t prove identity or function.
• Interpreting the suffix: In Motorola/Freescale nomenclature, “FN” maps to PLCC. If your device is a 20/28/32/44/52‑pin PLCC mounted in an ECU, that strengthens the hypothesis you’re dealing with an older automotive ASIC made under a customer code. (nxp.com)
• Plausible role on an ECU board:
  • Low‑side drivers (ignition coils, injectors, purge/EGR solenoids, relays). Look for:
  • Thick copper pours to a few output pins leading to ECU connector pins.
  • Flyback paths: clamp diodes, TVS, or snubbers to battery/ground near the outputs.
  • Thermal spreading (larger copper around the package) and nearby sense resistors.
  • Interface pins: several inputs from the MCU (5 V logic), Vbat and/or 5 V bias, multiple grounds.
• How to confirm function without a datasheet:
  1. Board‑level forensics
     • Trace outputs from the suspect IC to the harness connector; map them to the vehicle pinout (ignition coil/injector/solenoid circuits).
     • Note supply pins by continuity to 5 V regulator and to Vbat nets; note multiple ground pins to the ground plane.
  2. Comparative measurements (power off)
     • If you have two identical boards, compare pin‑to‑pin diode/resistance readings between the unknown chip and a known‑good one.
  3. In‑circuit checks (current‑limited bench supply)
     • Power the ECU on the bench with current limit (e.g., 13.5 V, 200–400 mA limit). Verify the ASIC’s supply pins (5 V bias, possibly Vbat).
     • Scope suspected outputs while commanding actuators via a scan tool/simulator; observe low‑side switching waveforms and inductive kick behavior at the connector with a x10 probe.
  4. Failure signatures of low‑side drivers
     • Permanently shorted outputs (near 0–10 Ω to GND/Vbat), burnt epoxy, localized charring, or cracked package.
     • Board TVS or snubbers shorted after driver failure.

CURRENT INFORMATION AND TRENDS

• Public databases and mainstream distributors do not show “LSC409091FN” today; obsolete/custom ECU ASICs increasingly disappear from public listings as ECU integration shifts toward mixed‑signal SoCs and smart drivers from Infineon, ST, onsemi, and NXP.
• Naming convention trend: legacy Freescale/Motorola packaging suffixes (like FN=PLCC) remain documented in NXP literature and programmer databases, which is a reliable clue about package style but not device function. (nxp.com)
• Industry practice has moved to integrated smart high‑side/low‑side drivers (diagnostics, current sense, thermal/OC protection), making one‑off ASIC replacements harder. Engineers often repair by donor‑ECUs or redesigning a daughterboard that replicates the function.

SUPPORTING EXPLANATIONS AND DETAILS

• Differentiating ignition vs injector driver roles:
  • Ignition coil drivers switch larger peak currents with fast di/dt; expect robust clamp networks and often fewer channels per IC.
  • Injector/solenoid drivers may be multi‑channel with shared supply pins and per‑channel flyback.
• If the ECU logs DTCs P035x (coil primary/secondary), that often implicates the coil circuit. But DTCs alone cannot prove the driver IC is bad; shorted coils or harness faults can cascade into ECU driver failure.

ETHICAL AND LEGAL ASPECTS

• ECU/ignition driver rework affects safety and emissions. In the United States (as of December 24, 2025), tampering with emissions controls is prohibited; ensure any repair restores OEM behavior and complies with federal/state law.
• Beware counterfeit parts. Unobtainable ASICs offered online may be pulls/remarked devices; validate provenance if you must source from brokers.

PRACTICAL GUIDELINES

• Verification checklist before replacing the IC:
  • Confirm coil(s)/injector(s) and wiring are not shorted; measure coil primary resistance and check for rubbed‑through harness sections.
  • Replace any suspect coil pack before powering a repaired ECU to avoid immediate re‑failure (common field pitfall).
• Rework tips (PLCC “FN” package):
  • Use quality hot‑air with preheat; shield nearby components; apply flux generously.
  • Lift straight up once all leads are liquid; clean pads with wick; inspect for lifted pads/vias.
  • Align Pin‑1; reflow and inspect all gullwing leads under microscope; continuity‑check ground and supply pins after reflow.
• If the ASIC is unobtainable:
  • Donor ECU harvesting is often the only practical route.
  • As a last resort, a small daughterboard with discrete MOSFETs/smart drivers can emulate low‑side channels, but you must carefully replicate protection (flyback clamps, SOA, thermal) and timings; this is non‑trivial and vehicle‑specific.

POSSIBLE DISCLAIMERS OR ADDITIONAL NOTES

• The strongly specific claim that LSC409091FN is a Ford ignition‑coil driver from Motorola in a 20‑pin PLCC appears online in forums, but I could not corroborate it with primary documentation; treat that mapping as unverified until you confirm by tracing the board.
• The earlier suggestion that it is a Linear Technology/Analog Devices PMIC is unlikely based on LT/ADI part‑numbering conventions.

SUGGESTIONS FOR FURTHER RESEARCH

• Provide high‑resolution photos (topmark, all sides, board context), ECU model (sticker numbers), vehicle year/model/engine, and any DTCs. With that, I can help reverse‑engineer the pinout and function.
• Search OEM service literature or enthusiast communities specific to your ECU family (e.g., Ford EEC‑V wiring/pinout guides) to correlate connector pins to the suspect IC channels.
• If you can share continuity maps from the IC pins to the ECU connector, we can infer function and propose safe test procedures.

BRIEF SUMMARY

• “LSC409091FN” has no publicly verifiable datasheet; it likely denotes a proprietary ASIC, commonly seen in automotive ECUs. If it’s on a PLCC package, the “FN” suffix lines up with Motorola/Freescale’s PLCC code. Identify its role by tracing PCB nets and observing in‑circuit behavior; do not assume coil/driver function until confirmed. If failed and unobtainable, consider donor ECU parts; ensure coils/harness are healthy before powering a repaired unit. (nxp.com)

Quick questions to move forward:

• Where exactly is this part installed (device/board/vehicle)?
• Can you share clear photos of the IC topmark and the surrounding circuitry?
• What symptoms or DTCs are you chasing, and what measurements have you already taken?

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.