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ISL97702 Datasheet(PDF) 11 Page - Renesas Technology Corp |
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ISL97702 Datasheet(HTML) 11 Page - Renesas Technology Corp |
11 / 13 page ISL97702 FN7462 Rev 0.00 Page 11 of 13 October 13, 2005 Typical Application Typical applications are passive- or active-matrix organic light emitting diode displays (PMOLED, AMOLED) in handheld devices. Applications with low power or screen saver/ reduced brightness modes are also directly supported. Motivation: In the low power mode the OLED display brightness (~pixel current) is reduced so that the display drivers can operate with equally reduced power. Usually the supply voltage is kept at the same level, although the pixel voltage drops by several volts when the pixel current levels are reduced. Here a further power reduction can be achieved if the supply voltage for the display drivers is reduced according to the pixel diode characteristic. The ISL97702 allows selection between a nominal and a reduced output voltage level in order to supply more effectively OLED display drivers. Components Selection The input capacitance is normally 10µf~15µF and the output capacitor is 3.3µf to 6.6µF. X5R or X7R type of ceramic capacitor with correct voltage rating is recommended. The output capacitor value will affect the output voltage ripple. Higher value of the output capacitor, lower ripple of the output voltage. When choosing an inductor, make sure the inductor can handle the average and peak currents given by following formulas (80% efficiency assumed): Where: • IL is the peak-to-peak inductor current ripple in Amperes • L inductance in H •fOSC switching frequency, typically 1.0MHz Optimal combination of the boost inductor L and the output capacitor Cout are listed in table: Recommended Inductor and Ceramic capacitor manufactures are listed in the following table: PCB layout Considerations The layout is very important for the converter to function properly. To ensure the high pulse current in the power ground does not interfere with the sensitive feedback signals, the current loops (VIN-L1-LX-GND, and VIN-L1-VOUT-COUT-GND) should be as short as possible. For the DFN package, there is FIGURE 20. ISL97702 APPLICATION BOARD GND 1 VDDOUT 2 VDD 3 NSYNC 4 FB0 5 FB1 6 SEL 7 NEN 8 VOUT 9 LX 10 U1 L1 6.8µH C1 100n C2 10µ J1 VDD_IN J2 GND_IN J3 GND_OUT J4 NSYNC J5 J6 J7 VOUT R1 390K R2 OPEN R3 OPEN R4 OPEN R5 26.1K R6 39K C3 OPEN C4 OPEN C5 OPEN C8 100n 2 J1 2 J2 VDD VDD VDD JP3 VDD C6 1nF/50V C7 3.3µF/50V C9 4.7µ/10V ISL97702 SEL NEN ILAVG IOUT VOUT 0.8 VIN ---------------------------------- = (EQ. 1) ILPK ILAVG 1 2 --- + IL = (EQ. 2) INDUCTOR (µH) CAPACITOR (µF) MIN MAX 4.7 2.2 10 6.8 3.3 10 10 4.7 10 15 6.8 10 INDUCTOR CERAMIC CAPACITOR Sumida: www.sumida.com Taiyo Yuden: www.t-yuden.com TDK: www.tdk.co.jp AVX: www.avxcorp.com Toko: www.tokoam.com Murata: www.murata.com IL VIN VOUT VIN – LVOUT fOSC --------------------------------------------------- = (EQ. 3) |
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