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MIC4832 Datasheet(PDF) 6 Page - Micrel Semiconductor |
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MIC4832 Datasheet(HTML) 6 Page - Micrel Semiconductor |
6 / 11 page ![]() Micrel MIC4832 March 2009 6 M9999-033109-C VIN = 3.6V IIN = 17mA L = 220µH COUT = 2.7nF LAMP = 2 in2 RSW = 300k REL = 2.82M Time (2ms/div) Figure 2. 100Hz Output Waveform Switching Frequency The switching frequency of the converter is controlled via an external resistor between RSW pin and VDD pin of the device. The switching frequency increases as the resistor value decreases. For resistor value selections, see the “Typical Characteristics: Switching Frequency vs. SW Resistor” or use the equation below. The switching frequency range is 65kHz to 250kHz, with an accuracy of ±20%. In general, the lower the switching frequency, the greater the input current is drawn to deliver more power to the output. However, the switching frequency should not be so low as to allow the voltage at the switch node or the CS pin to go beyond the absolute maximum voltage of those pins. () Ω = M R 36 (kHz) f SW SW EL Frequency The EL lamp frequency is controlled via an external resistor connected between REL pin and VDD pin of the device. The lamp frequency increases as the resistor value decreases. For resistor value selections, see the “Typical Characteristics: EL Frequency vs. EL Resistor” graph on page 4 or use the equation below. The EL lamp frequency range is 60Hz to 1000Hz, with an accuracy of ±20%. () () Ω = M R 360 Hz f EL EL VIN = 3.6V IIN = 27mA L = 220µH COUT = 2.7nF LAMP = 2 in2 RSW = 332k REL = 1.78M Time (2ms/div) Figure 3. 200Hz Output Waveform In general, as the EL lamp frequency increases, the amount of current drawn from the battery will increase. The color of the EL lamp and the intensity are dependent upon its frequency. VIN = 3.6V IIN = 21mA L = 220µH COUT = 2.7nF LAMP = 1 in2 RSW = 353k REL = 1.1M Time (2ms/div) Figure 4. 300Hz Output Waveform Enable Function The MIC4832 is disabled by connecting the external resistor (Rsw) to GND. This turns off the switch oscillator of the boost converter. Connecting the external resistor (Rsw) to VDD enables the oscillator and turns on the device. The enable voltage should rise or fall monotonically without interruption. |
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