LM3409HVEVAL/NOPB

User's Guide SNVA390D – May 2009 – Revised May 2013 AN-1953 LM3409HV Evaluation Board 1 Introduction This evaluation board showcases the LM3409HV PFET controller for a buck current regulator. It is designed to drive 12 LEDs (VO = 42V) at a maximum average LED current (ILED = 1.5A) from a DC input voltage (V = 48V). The switching frequency (fSW = 400 kHz) is targeted for the nominal operating point, however fSWIN varies across the entire operating range. The circuit can accept an input voltage of 6V-75V. 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 4 layers of 2 oz. copper with FR4 dieletric. The evaluation board showcases all features of the LM3409HV including analog dimming using the IADJ pin and internal PWM dimming using the EN pin. High frequency external parallel FET shunt PWM dimming can also be evaluated. The board has a header (J1) with a removable jumper, which is used to select the PWM dimming method. The evaluation 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. This board can be easily modified to demonstrate other operating points as shown in Section 9. The Design Procedure section of the LM3409/3409HV/3409Q/3409QHV PFET Buck Controller for High Power LED Drivers (SNVS602) data sheet can be used to design for any set of specifications. 100 EFFICIENCY (%) 95 90 85 80 75 40 45 50 55 60 65 70 75 INPUT VOLTAGE (V) Figure 1. Efficiency with 12 Series LEDS AT 1.5A Since the board contains a buck regulator designed for 48V input, the efficiency is very high at input voltages near or less than 48V. The switching frequency increases as input voltage increases, yielding lower efficiency at higher input voltages. Note that increasing the off-time resistor (R6) will increase the efficiency at high input voltage. All trademarks are the property of their respective owners. SNVA390D – May 2009 – Revised May 2013 Submit Documentation Feedback AN-1953 LM3409HV Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 1 Schematic 2 www.ti.com Schematic R8 R10 R7 1 VADJ VIN UVLO 10 VIN C4 C6 2 VCC IADJ C1 C2 C3 9 GND 8 LED+ J1 1 3 EN COFF C7 CSN 7 J2 D2 DAP 5 C5 CSP R9 4 R6 5V LM3409HV R11 3 R4 EN GND PGATE 6 Q1 L1 R5 C9 U1 C8 D1 1 14 2 13 3 12 5 10 6 9 7 8 R3 R2 PWM2 Q2 Q3 R1 GND2 LED3 2 Pin Descriptions Pin(s) Name Description Application Information 1 UVLO Input under-voltage lockout Connect to a resistor divider from VIN and GND. Turn-on threshold is 1.24V and hysteresis for turn-off is provided by a 22µA current source. 2 IADJ Analog LED current adjust Apply a voltage between 0 - 1.24V, connect a resistor to GND, or leave open to set the current sense threshold voltage. 3 EN Logic level enable / PWM dimming 4 COFF Off-time programming Apply a voltage >1.74V to enable device, a PWM signal to dim, or a voltage