Conventional flash LED drivers use current recovery to drive current recovery from high current LEDs. That is, all current is returned to the driver, causing the drive to generate a large amount of thermal energy, which in turn affects the reliability of the system. The LM3554 uses a dual LED high-side current drive architecture to provide a stable drive current for the two LEDs, but the cathode of the LED is directly connected to the ground. This grounding cable design not only enhances heat dissipation, but also simplifies wiring and protects the sensitivity of the circuit. Since the LED light output has a nonlinear relationship with the LED current, even with the same amount of light output, the power consumption of the dual LED architecture is still lower than that of the one LED. In addition, this chip is equipped with a monitoring pin, which can detect whether other circuits of the system are consuming a large amount of current, and flexibly adjust the LED current when needed to avoid the system being faulty or affected by the excessive power consumption of the battery. damage.
The LM3554 is available in a 16-pin micro SMD package. The entire LED flash boost converter solution with National's LM3554 chip is very small and does not exceed 23mm2.
National's LM3554 flash LED driver is a fixed-frequency step-up DC/DC converter featuring two stable current sources that can drive up to 1.2A with a single Li-Ion battery. The LM3554 chip can be used in a high-power flash mode to support camera functions. In addition, the drive can also use a low-power flashlight mode to support the video function. System designers can use the I2C-compatible interface to set the drive configuration, adjust the amount of flash current and timer time. In addition, the LM3554 chip also has a built-in timeout protection function to avoid damage to the flash LED due to overheating.
National's LM3554 chip features an adjustable switching current limit function that allows the system to use small inductors with low saturation current. In addition, the chip's 5V power supply can drive LED backlights and power the audio amplifier. The chip features a high-power flash mode and a low-power flashlight mode. When using the flash mode, it can drive two high-current LEDs; in the low-power mode, it can drive a high-current LED, and the built-in register or strobe circuit and TX pin are responsible for switching the control mode. In addition, the system can independently control the associated hardware through the general-purpose input/output (GPIO) pins, so that the hardware reset pin can fully control the operation of the chip once communication problems occur on the I2C interface. This chip also has internal soft start
Price and availability
National's LM3554 chip is available in volume quantities and is priced at $2.32 each in 1,000-unit quantities.
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