Current capability and current balance are critical

　　(1) Regarding the IC Thermal issue required by the system, the IC Package temperature can be lower than the customer's specification.

　　(2) It can be flexibly applied to 4 Channel LED light bar including the following drivers. It also provides parallel connection function for applications of 4 Channel LED light bar or above.

　　(3) The LED Short Protection Threshold is adjustable and flexible. It only needs to use resistors and is not limited by the controller process.

　　(4) Single CH Fault detection can be used for single CH LED Open/Short protection, while other CHs maintain operation, and the use is flexible.

　　LD7890 backlight protection mechanism

　　LD7890 focuses on larger-sized LED TVs and can provide LED short-circuit and open-circuit protection mechanisms, as well as output protection signals for LED malfunction signal detection, allowing the system to determine the usage status of the LED light bar.

　　When using LED as the backlight source of the LCD panel, because the area of the LCD panel is quite large, a large number of LEDs are needed, and these LEDs are often connected into several strings, and each string of LEDs is driven by a controllable current source. For example, the current flowing through each string of LEDs is controlled to be the same, so that each LED emits the same brightness. As long as the light emitted by each LED is properly conducted, the LCD panel can obtain approximately uniform backlight brightness. Among all LEDs, no matter which LED is short-circuited or open-circuited, it will affect the brightness uniformity of the LCD panel. Therefore, the LD7890 has a good LED string driver circuit and an appropriate protection detection circuit to detect whether the LED is short-circuited or open-circuited and take corresponding protective measures.

　　Easy to set LED short circuit protection function

　　The LED string is short-circuited due to poor contact between the wiring or poor LED quality. When the LED short-circuit occurs, excess voltage will cross the external steady-current NMOS of the LED Driver; PD=ILEDx VLED-Short. When there are too many LED Shorts, the LED Driver and NMOS will become high-temperature. The advantage of LD7890 is that it can be set using only an external resistor. When the LED string is short-circuited, if the condition VD–ISP×RSP > VLEDSP is met, the STATUS Pin will be Pull low and the short-circuited LED string will be turned off. If a short circuit occurs at the beginning and end of the LED string, you only need to consider the energy during the short circuit to select the appropriate resistor wattage. For the calculation method, refer to the block description.

　　Easy to set LED open circuit protection function

　　When the LED is open-circuited due to poor quality or poor connection between the LED string connection systems, the VD voltage will be close to 0V. At this time, the Boost converter will increase the output voltage Vout because no feedback signal is detected. If there is no feedback signal, the VD voltage will be close to 0V. LED open circuit protection isolates the abnormal loop from the feedback control of the boost converter, and the excess voltage will cross the external steady-current NMOS of the normally operating LED driver; PD=ILED×VD. This will cause the component to overheat.

　　When any LED string of the LD7890 is open-circuited, the Boost converter does not detect the feedback signal and increases the output voltage Vout until the OVP Pin reaches 2.5V. If the IC detects that the VSENSE Pin is lower than 0.2V, it means that this LED If there is an abnormality in the string, the LED Driver will turn off the faulty LED string and pull the STATUS Pin Low.

　　VOUT short circuit protection function description

　　When the LED string driving circuit is just connected to the power supply, it is likely that the driving power supply is not ready yet, causing the LED string driving circuit to determine that the LED strings cannot be driven, and thus misjudge the LED string open circuit or short circuit event. This should also be prevented. LD7890 provides VOUT short circuit protection. When VSCP < SCPSET, LD7890 will turn off the LED Driver and PWM Controller to avoid irreparable damage to the entire system.

　　Easy to use multiple chips in parallel application

　　The number of LED strings required for LED Backlight is not fixed in different applications or designs. There are many combinations according to the specifications of the Panel module manufacturer. The LD7890 is flexible in use and can be used in parallel with more than 4 strings. String or more, use the LD7890 PARL Pin to connect multiple LD7890 ICs. The PARL Pin has the function of selecting the best feedback potential when connecting multiple LD7890 ICs in parallel, providing the correct feedback potential for the boost topology. The PARL Pin has the function of selecting the optimal feedback potential when multiple LD7890 ICs are connected in parallel. Correct protection mechanism for short circuit and open circuit without malfunction.

　　in conclusion

　　When LED replaces CCFL as its backlight source for large-size panels of 10 inches or more, such as laptops, desktop monitors, and TVs, the integration of the Backlight Driver IC (Power Topology + LED Current Balance) protection function of the LED backlight module becomes particularly important. Importantly, looking at the above description, it provides a complete and comprehensive protection for the input, output and LED Backlight of the topology, and it is an LED solution that highly integrates the Boost architecture and Current Balance, providing high current for each LED string. Precision current balance (<3%), high LED current driving capability, and instantaneous high current LED driving capability for 3D applications. Considering its comprehensive fail-safe function and taking into account the high LED driving current capability and high accuracy of current balance, the LD7890 is indeed an excellent LED Backlight driver solution.

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