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LM3501 датащи(PDF) 1 Page - National Semiconductor (TI) |
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LM3501 датащи(HTML) 1 Page - National Semiconductor (TI) |
1 / 18 page LM3501 Synchronous Step-up DC/DC Converter for White LED Applications General Description The LM3501 is a fixed-frequency step-up DC/DC converter that is ideal for driving white LEDs for display backlighting and other lighting functions. With fully intergrated synchro- nous switching (no external schottky diode required) and a low feedback voltage (515 mV), power efficiency of the LM3501 circuit has been optimized for lighting applications in wireless phones and other portable products (single cell Li-Ion or 3-cell NiMH battery supplies). The LM3501 oper- ates with a fixed 1 MHz switching frequency. When used with ceramic input and output capacitors, the LM3501 provides a small, low-noise, low-cost solution. Two LM3501 options are available with different output volt- age capabilities. The LM3501-21 has a maximum output voltage of 21V and is typically suited for driving 4 or 5 white LEDs in series. The LM3501-16 has a maximum output voltage of 16V and is typically suited for driving 3 or 4 white LEDs in series (maximum number of series LEDs dependent on LED forward voltage). If the primary white LED network should be disconnected, the LM3501 uses internal protec- tion circuitry on the output to prevent a destructive overvolt- age event. A single external resistor is used to set the maximum LED current in LED-drive applications. The LED current can eas- ily be adjusted by varying the analog control voltage on the control pin or by using a pulse width modulated (PWM) signal on the shutdown pin. In shutdown, the LM3501 com- pletely disconnects the input from output, creating total iso- lation and preventing any leakage currents from trickling into the LEDs. Features n Synchronous rectification, high efficiency and no external schottky diode required n Uses small surface mount components n Can drive 2-5 white LEDs in series (may function with more low V F LEDs) n 2.7V to 7V input range n True shutdown isolation, no LED leakage current n DC voltage LED current control n Input undervoltage lockout n Internal output over-voltage protection (OVP) circuitry, with no external zener diode required LM3501-16: 15.5V OVP; LM3501-21: 20.5V OVP. n Requires only a small 16V (LM3501-16) or 25V (LM3501-21) ceramic capacitor at the input and output n Thermal Shutdown n 0.1µA shutdown current n Small 8-bump thin micro SMD package Applications n LCD Bias Supplies n White LED Back-Lighting n Handheld Devices n Digital Cameras n Portable Applications Typical Application Circuit 20065301 FIGURE 1. Typical 3 LED Application May 2005 © 2005 National Semiconductor Corporation DS200653 www.national.com |
Аналогичный номер детали - LM3501 |
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Аналогичное описание - LM3501 |
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