A6211 High-Current LED Driver Evaluation Board Notes Allegro Microsystems, January 23, 2012 The A6211 is a single IC switching regulator that provides constant-current output to drive high-power LEDs. It integrates a high-side N-channel DMOS switch for DC-to-DC step- down (buck) conversion. The A6211 EVB (evaluation board) accepts input voltage from 6V to 48V to drive a single LED string. LED current can be from several hundred mA up to 3A, selected by jumper combination on the EVB. Switching frequency is fixed at 1MHz for the EVB, but it can be easily changed by changing a resistor (see data sheet for details). Allegro offers Gerber files for this evaluation board on the following website (click on the tab labeled “Technical Docs”): http://www.allegromicro.com/en/Products/Regulators-And-Lighting/LED-Drivers-For-Lighting/A6211.aspx Figure 1 A6211 Evaluation Board Quick Startup Guide: 1. Connect a LED string between LED+ (anode) and LED- (cathode) 2. Insert or remove jumpers from P1 to select the appropriate LED current (see table below) 3. Connect input power between VIN and GND. For LED current regulation, the minimum input voltage should be at least 20% higher than the LED string’s operating voltage. 4. Connect EN (enable) to a logic high signal, or connect it to VIN. This will turn on the LED string. 5. For LED dimming: connect EN to a suitable PWM signal (such as 0-3V, 200Hz 50%). Vary the PWM duty cycle between 1% and 100% to control the brightness of LED string. A6211 High-Current LED Driver Evaluation Board Notes 1 Jumper Settings vs. LED Current: Jumper 1-2 Jumper 3-4 Jumper 5-6 Jumper 7-8 Approximate LED current (A) ON 0.3 ON 0.5 ON 1.0 ON 1.5 ON ON 2.0 ON ON 2.5 ON ON ON 3.0 Note that due to contact resistance introduced by connectors and jumpers, the above current settings are approximate. Schematics: Figure 2 A6211 EVB schematic A6211 High-Current LED Driver Evaluation Board Notes 2 Bill of Material: Ref Qty Description Footprint Part Number Remarks Cap Radial 8mm surface mount 565-2568-1-ND Vin filter electrolytic cap (exactly value not critical) Capacitor_1210 587-2225-1-ND Capacitor_1206 587-1962-1-ND Resistor_Capacitor_0603 399-1095-1-ND Vin filter ceramic cap Optional, use in case of noisy sense line Resistor_Capacitor_0603 445-5095-1-ND BOOT cap Resistor_Capacitor_0603 399-1095-1-ND C2 1 C3 0 C4 1 C5 1 CAP 47UF 50V ELECT MZA SMD CAP CER 10UF 50V X5R 1210 CAP CER 4.7UF 50V X5R 1206 0.1uF 10V X7R ceramic 0.047UF 50V X7R 0603 0.1uF 10V X7R ceramic C6 0 10nF 50V X7R Resistor_Capacitor_0603 490-1511-1-ND C7 0 Capacitor_1206 587-2402-1-ND Diode_SMA B350A-FDICTND for LED current up to ~2A Diode_SMC B560C-FDICTND for LED current up to 3A 445-3595-1-ND Use larger inductance for lower frequency and lower current 1 2.2uF 50V X5R B350A-13-F DIODE SCHOTTKY 3A 50V SMA B560C-13-F DIODE SCHOTTKY 5A 60V SMC VLF12060T220M4R1 (22UH 4A 36mOhm, 12*11.7*6mm) B82464G4103M (10uH 3.4A 10x10x5mm) NR8040T100M (10uH 3.4A 20% 44mohm, 8*8*4mm Header, 4-Pin, Dual row Vcc filter cap optional input cap for EN (can be used for 10K pulldown resistor instead) Optional filter cap across LED string. Try 0.47uF to 4.7uF 1 R1 C1 1 0 D1 0 1 0 L1 1 0 12x12mm 10.4x10.4mm 5-1796-1-ND 8x8mm 587-2001-1-ND 63.4K 0.1W 1% 603 P63.4KHDKRND 0 27.4K 0.1W 1% 603 R2 1 0.13 ohm 0.5W 1% Resistor_1206 R3 1 0.20 ohm 0.5W 1% Resistor_1206 R4 1 0.39 ohm 0.5W 1% Resistor_1206 R5 1 0.75 ohm 0.5W 1% Resistor_1206 P27.4KHCT-ND RL16R.13FCTND RL16R.20FCTND RL16R.39FCTND RL16R.75FCTND R7 EN, LEDLED+, VIN GND, GND1 1 1K 0.1W 1% Resistor_Capacitor_0603 P1.0KDBCT-ND 2 Test Point, Yellow Test_Point 5014K-ND 2 Test Point, Red Test_Point 5010K-ND 2 Test Point, Black Test_Point 5011K-ND U1 1 A6211/A6213 SOICN 8 P1 Use smaller inductance for higher frequency and current This 8mm inductor is only good for up to ~2A LED current! HDR2X4 A6211 High-Current LED Driver Evaluation Board Notes Ron=63.4K gives F_sw = 1MHz Ron=27.4K gives F_sw = 2MHz ~1.35A (due to jumper resistance) ~0.9A ~0.45A ~0.24A Limits the input current in case EN > Vin Narrow SOIC-8 with exposed pad 3