Using the EL7516 Demo Board ® Technical Brief May 13, 2005 The complete schematic of EL7516 demo board is shown in Figure 1. With different components stuffed, this demo board can easily be configured into the applications shown in this technical brief. The standard demo board being sent out is the complete 5V to 12V converter shown in Table 1, which occupies less than 0.4 in2 area with components on top side only. Layout diagrams are given at the end of this document. TB435.0 2. VO = 12V. Can be set according to the following formula: R V O = V FB × 1 + ------1- R 2 where VFB is 1.294V. 3. IO - up to 750mA depending on input voltage, provided that diode and inductor can handle the corresponding currents (refer to data sheet for the chart) 1. VIN = 2.5V-5.5V. Can be higher with higher voltage rated C1 4. Switching frequency - can be selected between 620KHz (FSEL <0.6V) or 12.5MHz (FSEL >2.7V) 5. R3 and C5 are the compensation network. SW C5 1 COMP R3 3.9kΩ C6 R1 85.2kΩ R2 10kΩ 4.7nF 2 FB FSEL 7 3 SHDN 4 GND SS 8 VDD 6 LX 5 R5 C4 R4 27nF 10kΩ C2 2.7V TO 5.5V + C1 0.1µF 10kΩ 22µF L1 10µH D1 + C3 12V 22µF FIGURE 1. 3.3V TO 12V CONVERTER TABLE 1. EL7516 BILL OF MATERIALS FOR VO = 12V REFERENCE DESIGNATOR VALUE MANUFACTURER R1 85.2kΩ/1%, 0603 Any R2 10kΩ/1%, 0603 Any R3 3.9kΩ, 0603 Any R4, R5 10kΩ/1%, 0603 Any C1, C3 22µF, 16V, 1812 TDK C2 0.1µF, 16V, 0805 Any C4 27nF, 0603 Any C5 OPEN C6 4.7nF, 0603 Any L1 10µH Coilcraft 847-639-6400 DO1608C-103 D1 MBR0520 On Semiconductor 800-282-9855 MBR0520 1 MANUFACTURER’S PHONE NUMBER MANUFACTURER’S PART NUMBER C4532X5R1C226M CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-352-6832 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2005. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Technical Brief 435 Demo Board Layout 1.5 in 1500 mil 1500 mil 1.5 in FIGURE 2. TOP LAYER FIGURE 4. TOP SILKSCREEN Layout Guidelines To achieve highest efficiency, best regulation and most stable operation, a good printed circuit board layout is essential. It is strongly recommended that the demo board layout to be followed as closely as possible. Use the following general guidelines when laying out the print circuit board: 1500 mil 1. Place C4 as close to the VDD pin as possible. C4 is the supply bypass capacitor of the device. 2. Keep the C1 ground, GND pin and C2 ground as close as possible. 3. Keep the two high current paths a) from C1 through L1, to the LX pin and GND and b) from C1 through L1, D1, and C2 as short as possible. 1500 mil FIGURE 3. BOTTOM LAYER 4. High current traces should be short and as wide as possible. 5. Place feedback resistor close to the FB pin to avoid noise pickup. 6. Place the compensation network close to the COMP pin. The demo board is a good example of layout based on these principles; it is available upon request. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 2 TB435.0