Part Details for LM3445 by National Semiconductor Corporation

The TIDA-01004 reference design is a remote automotive camera module that connects over a high speed serial video interface to a display or machine vision processing system. It uses TIs FPD-Link III SerDes technology to transmit uncompressed MegaPixel video data, bidirectional control signals and power either over shielded twisted pair or coax cable.

The main purpose of the power supply is to convert the rectified AC Input to DC regulated current for 6 LEDs.  The power supply provides protection for the LEDs: limits the transient input voltage and protect against inrush current at plug in.  The overall power supply conformity (e.g. mains harmonics (EN): mains interference: international safety standards etc.) are not approved for all the applicable European Norms (EN).The principle of this power supply is a step down. It is regulated by the 350ma average current with a fixed Toff time.  At the heart of the power supply is the controller LM3445 current mode control from National Semiconductor.  The LM3445 switching frequency is set at a nominal 45 kHz.With the LM3445 National Semiconductor provides a device that avoids visible flickering caused by a TRIAC forward or reverse phase dimmer.   The LM3445 overcomes this challenge by translating the TRIAC-chopped waveform to a DIM signal and decoding it to a DC signal.  In fact: the LED current is linearly regulated according to the dimming signal.

It is a TRAIC dimmable offline flyback LED driver using LM3445. It has an adaptive constant off-time AC/DC constant current controller feature. It can be used with input supply of 230V AC and can light 7 LEDs in string supplying 420mA of current.

This reference design demonstrates a high efficiency non-isolated dimmable LED driver solution using LM3445. With additional feed-forward circuit: improved line regulation <+/-2% performance is achieved. The input range is 90~132Vac and output is 40V310mA.

It is an offline AC-DC LED driver. It has TRIAC dimming capability. It is basically a low sidebuck which has valley filled PFC. It takes an input voltage of 120V AC. This circuit usesLM3445 which is an adaptive constant off-time AC/DC buck (step-down) constant current controller designed to be compatible with Traic dimmers.

This demonstration board highlights the performance of a LM3445 based Flyback LED driver solution that can be used to power a single LED string consisting of 6 / 7 series connected LEDs from an 198 VRMS to 264 VRMS: 50 Hz input power supply. This is a two-layer board using the bottom and top layer for component placement. The demonstration board can be modified to adjust the LED forward current: the number of series connected LEDs that are driven and the switching frequency. Refer to the LM3445 datasheet for detailed instructions. A bill of materials is included that describes the parts used on this demonstration board.