DEMO CIRCUIT 1187 LTC3212 QUICK START GUIDE LTC3212 RGB LED Driver and Charge Pump DESCRIPTION ing a single wire interface. White mode optimizes WARNING the red, green, and blue current settings to provide the best white color. Do not look directly at operating LED. This circuit produces light that can damage eyes. LED currents are regulated using internal low dropout current sources. Automatic mode switch- ing optimizes efficiency by switching modes only Demonstration circuit 1187 is an RGB LED Driver when a dropout is detected. Refer to the LTC3212 and Charge Pump featuring the LTC3212. datasheet for more information on this device. The LTC3212 is a low noise charge pump capable Design files for this circuit board are available. of driving three LEDs up to 25mA each. This de- Call the LTC factory. vice requires only one flying capacitor, two by-pass capacitors, and one to three programming resis- L, LTC, LTM, and LT are registered trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the tors. Each LED may be turned on individually, in products. combination with each other, or in white mode us- PERFORMANCE SUMMARY Specifications are at T = 25C A PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supply Range 2.7 5.5 V I Shutdown Current LEDEN = LOW 3 8 A VIN I Operating Current I = 0mA, 1X Mode 0.4 mA VIN CPO I = 0mA, 2X Mode 2.0 mA CPO I R = 33.87KW (Not in White Mode) 5.24 mA LED ISET R = 58.87KW (Not in White Mode) 3.0 mA ISET R = 8.87KW (Not in White Mode) 20.0 mA ISET I (WHITE MODE) R = 33.87KW 5.24 mA LEDG ISETG R = 58.87KW 3.0 mA ISETG R = 8.87KW 20.0 mA ISETG I (WHITE MODE) R = 33.87KW 3.93 mA LEDB ISETG R = 58.87KW 2.62 mA ISETG R = 8.87KW 15.0 mA ISETG I (WHITE MODE) R = 33.87KW 4.72 mA LEDR ISETG R = 58.87KW 2.71 mA ISETG R = 8.87KW 18.0 mA ISETG I Dropout Voltage (V ) Mode Switching Threshold, I = 15mA 150 mV LED ILED LED Charge Pump Output Clamp Voltage 5.1 V I 0 75 mA CPO 1 LTC3212 OPERATING PRINCIPLES The DC1187 has a programmable IC on board that color variations and intensities. The current for 2 communicates to the DC590 USB to I C board LEDG is set by the RSETG potentiometer, R4. The and drives the LTC3212 via a single wire interface. currents for LEDR and/or LEDB are also set by the The current in each LED output is set by adjusting RSETG potentiometer when in white mode and the resistance at the associated ISET pin. Each when ISETR and/or ISETB are tied to VIN via JP2 ISET pin is connected to an 8.87KW resistor in se- and JP3 respectively. Otherwise, the LEDR and ries with a 50KW potentiometer. This allows the LEDB output currents are set by the RSETR po- user to adjust each ISET resistance between tentiometer, R6, and RSETB potentiometer, R5, 8.87KW and 58.87KW to experiment with different respectively. QUICK START PROCEDURE Demonstration circuit 1187 is easy to set up to 6. Connect DC1187 to the DC590 USB Serial Con- evaluate the performance of the LTC3212. Refer to troller using the supplied 14-conductor ribbon Figure 1 for proper measurement equipment setup cable as shown in Figure 1. and follow the procedure below: 7. With power off, connect the input power supply NOTE. When measuring the input or output voltage ripple, care to VIN and GND with a series ammeter and a must be taken to avoid a long ground lead on the oscilloscope voltmeter as shown in Figure 1. probe. Measure the input or output voltage ripple by touching the probe tip directly across the VIN or CPO and GND terminals. See 8. Turn on the input power supply and set the VIN Figure 2 for proper scope probe technique. voltage to 3.6V. 1. Place jumpers in the following positions: NOTE. Make sure that the input voltage does not exceed 6V. JP1 LEDEN: Up, DC590 position. 9. Run the QuikEval program. The program de- tects the DC1187 and displays the LTC3212 JP2 ISETR: Down, RSETR position. control window (shown in Figure 3). JP3 ISETB: Down, RSETB position. 10. Select the Green/Red option button on the 2. Make sure that the RSETG, RSETR, and LTC3212 control window and observe that the RSETB potentiometers are set approximately to RGB LED illuminates light greenish. the center position (adjustment slot is 11. Adjust RSETG fully counterclockwise and ob- perpendicular to top of board). serve that the RGB LED changes to a yellowish 3. Refer to the DC590 Quick Start Guide for green color. TM QuikEval setup and software installation 12. Adjust RSETR fully clockwise and observe that details. the RGB LED color changes to light orange. 4. If using the DC590B board, make sure the 13. Move the ISETR jumper from the RSETR posi- VCCIO jumper, JP6, on the DC590B board is tion to the RSETG position and observe that the set to the 5V position. The microcontroller on RGB LED color changes to light green. the DC1187 board needs 5V to operate properly. 14. Select the Blue/Green option button on the LTC3212 control window and observe that the 5. Make sure the USB cable is connected between RGB LED illuminates light blue. the computer and the DC590 controller board. 2