BIT3368 LED Driver Protection Removal: OVP, OCP, Pinout, Safe Diagnostic Methods

User question

Bit3368 protection remove

Artificial Intelligence Response

Direct answer to the question

• Do not remove/disable the BIT3368 protections in normal use; many are intrinsic to the IC. If protection is tripping, diagnose and correct the root cause (typically an open/short LED string, bad diode/inductor, or a wrong sense/divider value). The only protection you can practically “relax” for brief diagnostic purposes is the external OVP/OCP sensing, via the OVP (pin 5) divider and the OCP (pin 7) sense resistor—not pin 3. Pin 3 is EA (error‑amp node), not a “protection latch” pin. (datasheet4u.com)
• The BIT3368 integrates many protections (OVP, OCP, LSP, LCSP, OTP, UVLO, etc.); these are key to safe operation. (bitek.com.tw)

Key points

• Pinout (SOP‑8): 1‑CMP, 2‑INN, 3‑EA, 4‑VDD, 5‑OVP, 6‑GND, 7‑OCP (CS), 8‑OUT. Therefore any advice that says “ground pin 3 to remove protection” is incorrect for BIT3368. (datasheet4u.com)
• OCP comparator (CS at pin 7) trips around 0.3 V; peak current limit ≈ 0.3 V/RSENSE. (datasheet4u.com)
• Permanent defeat of protection can overheat LEDs, blow the MOSFET/diode/inductor, or start a fire. Keep any bypass strictly temporary and current‑limited.

Detailed problem analysis

• What usually triggers shutdown in LED backlight boost drivers:
  • Open LED segment: Output voltage rises until OVP trips; backlight flashes then goes dark.
  • Shorted LED(s) or wiring: Current spikes; OCP/short‑load protection trips.
  • Bad Schottky diode or inductor: Abnormal switch node, large ripple, OVP/OCP trips.
  • Wrong/aged feedback parts: OVP divider drift or CS sense resistor drift.
• How BIT3368 enforces protection:
  • OVP (pin 5) monitors VOUT via a resistor divider; if the divider node exceeds the internal OVP reference, PWM is stopped.
  • OCP (pin 7, “CS”) monitors the current sense resistor; when CS ≈ 0.3 V the cycle is terminated and, if persistent, protection asserts. (datasheet4u.com)
  • Additional protections (LSP, LCSP, OTP, UVLO, Schottky/inductor fault monitors) are integrated and not meant to be disabled. (bitek.com.tw)
• Why “pin‑3 LED clamp” is wrong here:
  • On BIT3368, pin 3 is EA (error‑amplifier node). Clamping EA does not specifically defeat OVP/OCP and can drive uncontrolled duty cycles, overshoot, and destruction. The correct protection‑related pins are OVP (5) and OCP/CS (7). (datasheet4u.com)

Current information and trends

• The manufacturer’s current product page (last crawled recently) lists expanded protection features (LSP, LCSP, OTP, UVLO) beyond legacy one‑page summaries. These protections reflect industry practice: modern LED boost controllers integrate multiple fault detectors to prevent over‑voltage, over‑current, and wiring faults in TV backlights and light engines. (bitek.com.tw)

Supporting explanations and details

• OCP sizing:
  • Ipk_limit ≈ 0.3 V / RSENSE. Example: RSENSE = 0.30 Ω → Ipk_limit ≈ 1.0 A. Reducing RSENSE raises the current limit and device stress; increasing it lowers the limit. (datasheet4u.com)
• OVP divider:
  • The OVP divider sets the trip voltage: VOUT_OVP ≈ VREF_OVP × (1 + Rtop/Rbot). Raising Rbot or lowering Rtop raises the trip point; the exact internal VREF_OVP is in the datasheet; do not guess—verify on your board.
• Typical failure signatures:
  • OVP trip: VOUT ramps high at startup; OVP pin crosses threshold; PWM halts.
  • OCP trip: CS pin (OCP) hits ~0.3 V near each cycle’s peak; sustained hits cause shutdown. (datasheet4u.com)

Ethical and legal aspects

• Defeating safety functions can violate product safety requirements (e.g., UL/IEC for consumer electronics) and local fire safety codes. It also risks user injury and property damage. Use only for controlled bench diagnostics, never for shipped products.

Practical guidelines

If you must keep the supply alive briefly to locate a bad LED strip or wiring fault:

• Preparation
  • Power from a current‑limited bench supply and set a conservative current limit.
  • Add a series fuse in VIN and keep a thermal camera or finger‑safe IR thermometer handy.
• Temporary, reversible diagnostic methods
  • OVP side (pin 5):
  • Slightly raise the OVP trip point by temporarily paralleling a high‑value resistor (e.g., +10–20% change) on the divider bottom leg to ground, or momentarily clamp OVP below threshold with a diode to GND during start to see if the rail stays up. Remove after seconds of testing. Monitor VOUT carefully to avoid runaway. Target the OVP pin only—do not touch pin 3 (EA). Pin mapping verified above. (datasheet4u.com)
  • OCP side (pin 7, CS):
  • For testing only, you can temporarily increase the current limit slightly by shunting a small additional resistor in parallel with RSENSE (net RSENSE↓). Compute the new Ipk from 0.3 V/RSENSE and stay within safe limits for the MOSFET, diode, and inductor. Restore original RSENSE after diagnosis. (datasheet4u.com)
• Prefer safer diagnostics
  • Substitute a known‑good LED load or add a “dummy” load string to keep VOUT within the normal range while you probe.
  • Scope the OVP (pin 5), CS (pin 7), OUT (pin 8), and VOUT during the fault to identify which protection trips first.
  • Check the Schottky diode, inductor DCR, and LED harness/connectors for opens/shorts.
• What not to do
  • Do not tie EA (pin 3) to ground or clamp it with an LED expecting to disable protection; this can remove loop control and cause destructive overdrive. (datasheet4u.com)

Possible disclaimers or additional notes

• Exact OVP reference and behavior can vary by silicon revision (BIT3368 vs. BIT3368O). Always verify with the specific datasheet for your board version. (bitek.com.tw)
• Some protections (OTP, UVLO, certain fault monitors) are hard‑wired and cannot be “removed.”

Suggestions for further research

• Obtain the full BIT3368/BIT3368O datasheet used on your board to get the exact OVP reference voltage and timing behavior, and confirm the pinout silk/revision. (bitek.com.tw)
• If available, consult your TV/monitor chassis service manual for the backlight section to see the intended OVP divider values and LED string configuration.

Brief summary

• For the BIT3368, target protection‑related pins correctly: OVP = pin 5 and OCP/CS = pin 7. Do not modify pin 3 (EA). Protections are there for safety; only make minimal, temporary adjustments for diagnostics under strict current limiting and monitoring. Then fix the real fault (usually in the LED string or power stage) and restore the original protection settings. (datasheet4u.com)

If you can share your board model, measured voltages at pins 5 and 7 during shutdown, RSENSE value, and the OVP divider values, I can calculate safe diagnostic adjustments and a concrete repair path.

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.