Datenblatt-Suchmaschine für elektronische Bauteile |
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NCP5608 Datenblatt(PDF) 7 Page - ON Semiconductor |
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NCP5608 Datenblatt(HTML) 7 Page - ON Semiconductor |
7 / 16 page NCP5608 http://onsemi.com 7 APPLICATIONS INFORMATION DC−DC OPERATION The converter is based on a charge pump technique to generate a DC voltage capable to supply the white LED load. The system regulates the current flowing into each LED by means of internal current mirrors associated with the white diodes. Consequently, the output voltage will be equal to the Vf of the LED, plus the 300 mV (typical) developed across the internal NMOS mirror. Typically, assuming a standard white LED forward biased at 10 mA, the output voltage will be 3.2 V. The third external capacitor makes possible the 1.33X extra mode of operation, with a significant efficiency improvement of the converter over the normal battery voltage span. The threshold levels have been defined to optimize this range of operating voltages, assuming a high efficiency is not relevant when the system is connected to a battery charger (i.e. Vbat > 4.5 V). The built−in OVP circuit continuously monitors each output and stops the converter when the voltage is above 5.0 V. The converter resumes normal operation when the voltage drops below 5.0 V (no latch−up mechanism). Consequently, the chip can operate with no load during any test procedures, but in the case of special applications, it is recommended to connect the unused LED driver either to the VOUT supply to avoid any uncontrolled operation. The structure is built with power MOS devices to accommodate the modes selected by the analog functions. The current flowing into each LED is continuously regulated according to the value defined by the programming message. The total current is limited to 500 mA DC. The system runs with two cycles: − Cycle#1 Fly capacitors are charged from the battery. − Cycle#2 Energy accumulated into the fly capacitors is transferred to the load. PIN 16 GND VOUT PWRGND Q2 PIN 19 C1 C1N C1P PIN 17 Q8 C2 C2P PIN 21 Q12 C3 C3P PIN 22 Q1 Q6 Q10 Q11 Q3 Q7 Q4 Q5 Q9 PIN 23 PIN 20 CURRENT CONTROL PIN 18 PIN 13 LEDx GND C2N C3N Li−Ion 2.90 V − 4.10 V Figure 3. Basic DC−DC NCP5608 Converter Structure GND |
Ähnliche Teilenummer - NCP5608 |
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Ähnliche Beschreibung - NCP5608 |
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