When the display boots, the LX1692 allows a deliberate time window for the high-voltage transformer to strike the lamps.
If the inverter stays on with the bypass in place, the technician can quickly identify the faulty lamp or transformer, power down, and replace the broken component. Circuit Design Best Practices
If a critical fault is detected on any of these pins, the controller enters a latched fault state, shutting down the outputs to protect the circuit. Often, the system must be power-cycled to reset.
In repair scenarios where a technician needs to troubleshoot a "backlight on then off" issue, the protection is often bypassed to keep the lamps lit for testing. For many similar CCFL controllers, this is done by: (typically between lx1692 protection pin
Before assuming the IC itself is bad, technicians must rule out external component failures: Target Component Failure Mode Impact on LX1692 Aged cathode, low emission, or broken glass. Triggers Open/Short Lamp protection loop. Inverter Transformer Shorted internal secondary windings.
When the display powers on, the IC allows a brief initialization window for the lamps to ignite ("strike"). If the feedback current pins—such as the pin—do not receive a stable, expected signal within the timeframe set by the external capacitor on the C_TO pin, the IC presumes a severe fault exists. The internal latch trips, immediately shutting down the gate drive outputs ( AOUT , BOUT , COUT , DOUT ) to kill power to the external MOSFETs. 2. Diagnosing a Backlight "Two-Second Shutdown"
In RUN mode, if the current level at ISNS drops below 0.3V for 256 consecutive clock counts, a fault latch is set, and the IC shuts down. When the display boots, the LX1692 allows a
Set your multimeter to DC volts. Place the black probe on ground and the red probe on Pin 11 of the LX1692. Power on the monitor. Observe the voltage. If it ramps from 0V to 1.5V and then the backlight dies, you have a false trigger.
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
| 引脚号 | 引脚名称 | 功能说明 | 实测电压参考值（例） | | :--- | :--- | :--- | :--- | | | | | | | 20 | VDDP | 工作电压输入端，标称5V供电，最大耐压5.5V | 5.07V | | 6 | ENABLE | 点灯延时/使能控制脚，高电平有效 | 3.99V | | 1 | VDDA | 模拟电压调节器输出（4V LDO），可外接滤波电容 | 3.99V | | 17 | GND | 芯片地 | 0V | | 5 | IR | 内部偏置电流设定电阻输入端 | 理论值由R_IR决定 | | 故障检测与保护类 | | | | | 11 | OC_SNS | 过电流感测输入 ，接外部电阻采样变压器初级电流，超2V阈值即触发保护 | 0V（保护未被触发） | | 13 | OV_SNS | 过电压检测输入 ，监视灯管两端电压分压信号，配合1000:1分压网络 | 0.2V（灯管正常点燃） | | 14 | ISNS | 电流检测输入 ，采CCFL灯管回路电流，用于点火判定与稳流控制 | 0.14V（正常运行） | | 12 | ICOMP | 电流误差放大器输出端，外接RC补偿网络 | 3.99V | | 10 | VCOMP | 电压误差放大器补偿端 | 2.96V | | 亮度控制类 | | | | | 7 | BRITE_A | 模拟调光控制输入端（0–2.5V模拟电压） | 5.07V | | 9 | BRITE_D | 数字PWM调光控制输入端 | 0V | | 3 | C_BST | Burst调光模式频率设定电容引脚 | 0V | | 振荡与时序类 | | | | | 2 | C_R | 灯管工作频率设定电容引脚 | 0V | | 4 | C_TO | 外部定时电容，设定点火超时保护时长 | 0V | | 8 | VIN_SNS | 工作电压感测（配合输入电压前馈补偿） | 0V | | 驱动输出类 | | | | | 15 | DOUT | 缓冲器N-FET激励输出D（全桥逆变器下管驱动） | 0V | | 16 | COUT | 缓冲器N-FET激励输出C（全桥逆变器上管驱动） | 0V | | 18 | BOUT | 缓冲器N-FET激励输出B（副半桥下管驱动） | 56V（峰值） | | 19 | AOUT | 缓冲器N-FET激励输出A（副半桥上管驱动） | 0.058V（静默状态） | Often, the system must be power-cycled to reset
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Alternatively, forcing a steady DC voltage that simulates a "good lamp" status onto the sensing pin can keep the IC from shutting down. 4. Troubleshooting Checklist
