EV0035 Monolithic Power Systems MP1523 Precision Driver for Single String of 6 White LEDs EVALUATION BOARD General Description Absolute Maximum Ratings The EV0035 evaluation board uses the MP1523 to drive up to six (6) series white LEDs from a single cell Lithium Ion battery. The MP1523 uses a current limited, variable frequency architecture to regulate the LED current, which is measured through an external current sense resistor. It's low 0.4V feedback threshold reduces power loss and improves efficiency. To prevent damage due to an open circuit condition, the BIAS pin can measure the output voltage and turns off the converter if an overvoltage condition is present. Supply Voltage VIN Switch Voltage SW to GND VEN, VFB Storage Temperature The MP1523 includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. The MP1523 is available in a tiny 5 lead SOT23 package. Ordering Information Board Number MPS IC Number EV0035 MP1523DT 28V -0.5V to 28V -0.3V to 6V -55C to +150C Recommended Operating Conditions Supply Voltage VIN 2.7 V to 25V Features On board power MOSFET Drives 6 White LEDs Up to 90% efficiency Over 80mA output current capacity Open Load Shut Down Low 0.4V Feedback Threshold UVLO, Thermal shutdown Soft Start Internal Current Limit MP1523 in Tiny SOT23 package Applications Cell Phones Handheld Computers and PDAs Digital Still and Video Cameras Small LCD Displays Figure 1: EV0035 Evaluation Board Actual Size: 2"X x 1.4"Y EV0035 Rev 1.1_03/19/03 www.monolithicpower.com 1 EV0035 Monolithic Power Systems MP1523 Precision Driver for Single String of 6 White LEDs EVALUATION BOARD Figure 2: EV0035 Schematic EV0035 Rev 1.1_03/19/03 www.monolithicpower.com 2 EV0035 Monolithic Power Systems MP1523 Precision Driver for Single String of 6 White LEDs EVALUATION BOARD Table 1: EV0035 Bill of Materials Designator Component Package Qty U1 C1, C2 C3 R1 R2 D1 L1 MP1523DT 1F 10nF 100K 20 MBR0540 15H SOT23-5 1206 0603 0603 0603 1810 CDRH127 1 2 1 1 1 1 1 Total 8 Operating Instructions 1. Connect VIN to the power source's positive output. 2. Connect GND to supply ground. 3. Remove the jumper J1 to allow the MP1523 to automatically start when power is applied. Place the shorting clip across J1 to disable the MP1523. A logic signal may be applied to EN to enable/disable the MP1523, provided the shorting clip is not installed across J1. 4. To dim the LEDs remove the shorting clip from J1 and apply a PWM signal to the EN pin. Adjusting the duty cycle of the PWM signal determines the brightness of the LEDs. Figure 3: EV0035 Top Silk Layer EV0035 Rev 1.1_03/19/03 www.monolithicpower.com 3 EV0035 Monolithic Power Systems MP1523 Precision Driver for Single String of 6 White LEDs EVALUATION BOARD Figure 4: EV0035 Top Layer Figure 5: EV0035 Bottom Layer NOTICE: MPS believes the information in this document to be accurate and reliable. However, it is subject to change without notice. Please contact the factory for current specifications. No responsibility is assumed by MPS for its use or fit to any application, nor for infringement of patent or other rights of third parties. EV0035 Rev 1.1 03/19/03 (c) 2003 MPS, Inc. Monolithic Power Systems, Inc. 3777 Stevens Creek Blvd, Suite 400, Santa Clara, CA 95051-7364 USA Tel: (408) 243-0088, Fax: (408) 243-0099, Web: www.monolithicpower.com 4