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ACE77LE9GM+H データシート(PDF) 6 Page - ACE Technology Co., LTD. |
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ACE77LE9GM+H データシート(HTML) 6 Page - ACE Technology Co., LTD. |
6 / 8 page ACE77LE9 High Efficiency Low Noise PFM Step-Up DC/DC Converter VER 1.1 6 Application Information LED Current Control The ACE77LE9 regulates the LED current by setting the current sense resistor (R1) connecting to feedback and ground. The ACE77LE9 feedback voltage (VFB) is 0.20V. The LED current (ILED) can be set by a resistor R1. ILED=0.20/R1. In order to have an accurate LED current, a precision resistor is preferred (1% is recommended). PWM Dimming Control When adding the PWM signal to CE pin, the ACE77LE9 is turned on or off by the PWM signal, so the LEDs operate at either zero or full current. The average LED current increase proportionally with the duty cycle of the PWM signal. The magnitude of the PWM signal should be higher than the maximum enable voltage of EN pin, in order to let the dimming control perform correctly. The recommended frequency range of the PWM signal is from 100Hz to 100 kHz. Inductor Selection The recommended val ue of inductor is 2.2μH to 10μH. Small size and better efficiency are the major concerns for portable device, such as ACE77LE9 used for mobile phone. The inductor should have low core loss at 2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered. Capacitor Selection Input and output ceramic capacitors of 4.7μF are recommended for ACE77LE9 applications. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges. Diode Selection Schottky diode is a good choice for ACE77LE9 because of its low forward voltage drop and fast reverses recovery. Using Schottky diode can get better efficiency. The high speed rectification is also a good characteristic of Schottky diode for high switching frequency. Current rating of the diode must meet the root mean square of the peak current and output average current multiplication as following: ID(RMS) ≈(IOUT×IPEAK )1/2 The diode’s reverse breakdown voltage should be larger than the output voltage. SS0520 is recommended Schottky diode for rectifier. Layout Guide A full GND plane without gap break. Minimized LX node copper area to reduce EMI. Minimized FB node copper area and keep far away from noise sources. |
同様の部品番号 - ACE77LE9GM+H |
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同様の説明 - ACE77LE9GM+H |
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