Datenblatt-Suchmaschine für elektronische Bauteile |
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LM3242 Datenblatt(PDF) 15 Page - Texas Instruments |
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LM3242 Datenblatt(HTML) 15 Page - Texas Instruments |
15 / 28 page ISAT > IOUT_MAX + IRIPPLE VOUT VIN © § VIN - VOUT 2 x L © § x IRIPPLE = x 1 f © § where LM3242 www.ti.com SNOSB48D – OCTOBER 2011 – REVISED MARCH 2013 APPLICATION INFORMATION Setting the Output Voltage The LM3242 features a pin-controlled adjustable output voltage to eliminate the need for external feedback resistors. It can be programmed for an output voltage from 0.4V to 3.6V by setting the voltage on the VCON pin, as in the following formula: VOUT = 2.5 x VCON (1) When VCON is between 0.16V and 1.44V, the output voltage will follow proportionally by 2.5 times of VCON. If VCON is less than 0.16V (VOUT = 0.4V), the output voltage may not be well regulated. Refer to datasheet curve “Low VCON Voltage vs. Output Voltage” for details. This curve exhibits the characteristics of a typical part, and the performance cannot be ensured as there could be a part-to-part variation for output voltages less than 0.4V. For VOUT lower than 0.4V, the converter might suffer from larger output ripple voltage and higher current limit operation. FB Typically the FB pin is connected to VOUT for regulating the output voltage maximum of 3.6V. Inductor Selection There are two main considerations when choosing an inductor; the inductor should not saturate, and the inductor current ripple is small enough to achieve the desired output voltage ripple. Different manufacturers follow different saturation current rating specifications, so attention must be given to details. Saturation current ratings are typically specified at 25°C so ratings over the ambient temperature of application should be requested from manufacturer. Minimum value of inductance to guarantee good performance is 0.3 µH at bias current (ILIM (typ.)) over the ambient temperature range. Shielded inductors radiate less noise and should be preferred. There are two methods to choose the inductor saturation current rating. Method 1: The saturation current should be greater than the sum of the maximum load current and the worst case average to peak inductor current. This can be written as: where • IRIPPLE: average-to-peak inductor current • IOUT_MAX: maximum load current (750 mA) • VIN: maximum input voltage in application • L minimum inductor value including worst-case tolerances (30% drop can be considered for Method 1) • F: minimum switching frequency (5.7 MHz) • VOUT: output voltage (2) Copyright © 2011–2013, Texas Instruments Incorporated Submit Documentation Feedback 15 Product Folder Links: LM3242 |
Ähnliche Teilenummer - LM3242_14 |
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Ähnliche Beschreibung - LM3242_14 |
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