Lx1692 Protection Pin !!hot!! 🆕 Newest
A logic low (< 0.8V) disconnects internal power, disabling all functions immediately. Fault Stop Threshold
Senses electrical arcing in the high-voltage section. 🔍 How the Protection Works
PROT pin (LX1692) ---+--- To other LX1692 PROT pins | +--- 10kΩ pull-up to 5V (optional if internal current source is sufficient) | +--- Drain of external N-MOSFET (source to GND) | Gate of N-MOSFET from microcontroller (active high shutdown command)
While most technicians focus on the PWM input or the high-voltage transformer outputs, there is a tiny, often overlooked conductor orchestrating the safety of the entire system: lx1692 protection pin
Upon validating a fault via the PROT pin, the LX1692 enters a latched shutdown mode. It immediately ceases the Pulse Width Modulation (PWM) drive signals to the external power MOSFETs, cutting off power to the high-voltage transformer. This prevents component overheating, fire hazards, or electrical arcing. The IC will remain locked in this safe state until the main power input ( VDDcap V sub cap D cap D end-sub ) or the Enable (ENA) signal is cycled off and on. Typical Circuit Interfacing with the PROT Pin
Broken Lamp / High Voltage Arc
I can provide targeted troubleshooting steps for your exact setup. Share public link A logic low ( Senses electrical arcing in
The LX1692 is a third-generation Cold Cathode Fluorescent Lamp (CCFL) controller designed for full-bridge inverter topologies. It is widely used in legacy LCD TVs and computer monitors. The IC uses a precise feedback loop to handle high-voltage striking and lamp illumination.
This pin monitors the output voltage of the transformer via a capacitive or resistive voltage divider. If the voltage exceeds a preset threshold, the IC limits the duty cycle or initiates a shutdown timer.
If an LX1692 keeps shutting down, it means the controller is correctly doing its job by detecting a genuine hardware failure. Disabling the protection might , such as a transformer arc-over or damage to the power supply. Share public link The LX1692 is a third-generation
The LX1692's protection pins represent a sophisticated and crucial safety network for CCFL-based displays. Understanding their function is helpful for diagnostics, but any repair should always focus on identifying and replacing the root cause of the fault—not merely disabling the warning system.
| State | PROT Pin Voltage | IC Outputs (PWM) | |---|---|---| | Normal | ~5V | Switching | | Fault detected (first few cycles) | ~5V (no change) | Switching | | Fault confirmed | 0V | Hi-Z (off) | | After ( V_CC ) reset | ~5V (rising edge) | Switching resumes |
On specific chassis variations utilizing the LX1692 configuration, the open-lamp protection threshold can be cheated using a dedicated pull-down resistor to mimic a stable current load.
The IC monitors voltage levels on specific sensing pins (like for over-voltage and ISNS for current). If these values exceed preset thresholds, the internal logic triggers the protection pin to stop the gate drivers. Common Shutdown Causes:
