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Using the EL7516 Demo Board
Technical Brief May 13, 2005 TB435.0
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. 1. VIN = 2.5V-5.5V. Can be higher with higher voltage rated C1
2. VO = 12V. Can be set according to the following formula:
R 1 V O = V FB x 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) 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 R5 C4 27nF C2 R4 10k + C1 22F 10k
C5
R3 3.9k C6 4.7nF
1 COMP R1 85.2k R2 10k 2 FB 3 SHDN 4 GND
SS 8 FSEL 7 VDD 6 LX 5
2.7V TO 5.5V L1 10H D1 + C3 22F 12V
0.1F
FIGURE 1. 3.3V TO 12V CONVERTER TABLE 1. EL7516 BILL OF MATERIALS FOR VO = 12V REFERENCE DESIGNATOR R1 R2 R3 R4, R5 C1, C3 C2 C4 C5 C6 L1 D1 VALUE 85.2k/1%, 0603 10k/1%, 0603 3.9k, 0603 10k/1%, 0603 22F, 16V, 1812 0.1F, 16V, 0805 27nF, 0603 OPEN 4.7nF, 0603 10H MBR0520 Any Coilcraft On Semiconductor 847-639-6400 800-282-9855 DO1608C-103 MBR0520 MANUFACTURER Any Any Any Any TDK Any Any C4532X5R1C226M MANUFACTURER'S PHONE NUMBER MANUFACTURER'S PART NUMBER
1
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
1500 mil
1.5 in
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. 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.
1500 mil
FIGURE 3. BOTTOM LAYER
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

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