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LM3409 demonstration board

Posted: 08 Apr 2010 ?? ?Print Version ?Bookmark and Share

Keywords:demonstration board? LM3409 PFET controller? buck current regulator?

This demonstration board showcases the LM3409 PFET controller for a buck current regulator. It is designed to drive 4 LEDs (VO = 15V) at a maximum average LED current (ILED = 1A) from a DC input voltage (VIN = 24V). The switching frequency (fSW = 525kHz) is targeted for the nominal operating point. However, fSW varies across the entire operating range. The circuit can accept an input voltage of 6V-42V. However, if the input voltage drops below the regulated LED string voltage, the converter goes into dropout and VO = VIN ideally.

The PCB is made using 2 layers of 2 oz. copper with FR4 dielectric. The board showcases several features of the LM3409 including both analog dimming using a potentiometer (R5) tied to the IADJ pin and internal PWM dimming using the EN pin. There is a header (J1) with a removable jumper, which is used to select PWM dimming or low power shutdown.

The board has a right angle connector (J2) which can mate with an external LED load board allowing for the LEDs to be mounted close to the driver. This reduces potential ringing when there is no output capacitor. Alternatively, the LED+ and LED- turrets can be used to connect the LED load.

View the PDF document for more information.

Click here to view related datasheets.

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