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MIC5216-2.5BMM Datasheet(PDF) 8 Page - Micrel Semiconductor |
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MIC5216-2.5BMM Datasheet(HTML) 8 Page - Micrel Semiconductor |
8 / 13 page Micrel, Inc. MIC5216 March 2007 8 M9999-032307 Application Information The MIC5216 is designed for 150mA to 200mA output current applications where a high current spike (500mA) is needed for short, startup conditions. Basic application of the device will be discussed initially followed by a more detailed discussion of higher current applications. Enable/Shutdown Forcing EN (enable/shutdown) high (> 2V) enables the regulator. EN is compatible with CMOS logic. If the enable/shutdown feature is not required, connect EN to IN (supply input). See Figure 5. Input Capacitor A 1µF capacitor should be placed from IN to GND if there is more than 10 inches of wire between the input and the ac filter capacitor or if a battery is used as the input. Output Capacitor An output capacitor is required between OUT and GND to prevent oscillation. 1µF minimum is recommended. Larger values improve the regulator’s transient response. The output capacitor value may be increased without limit. The output capacitor should have an ESR (equivalent series resistance) of about 5Ω or less and a resonant frequency above 1MHz. Ultralow-ESR capacitors could cause oscillation and/or underdamped transient response. Most tantalum or aluminum electrolytic capacitors are adequate; film types will work, but more expensive. Many aluminum electrolytics have electrolytes that freeze at about –30°C, so solid tantalums are recommended for operation below –25°C. At lower values of output current, less output capacitance is needed for stability. The capacitor can be reduced to 0.47µF for current below 10mA or 0.33µF for currents below 1mA. No-Load Stability The MIC5216 will remain stable and in regulation with no load (other than the internal voltage divider) unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. Error Flag Output The error flag is an open-collector output and is active (low) when an undervoltage of approximately 5% below the nominal output voltage is detected. A pull-up resistor from IN to FLAG is shown in all schematics. If an error indication is not required, FLAG may be left open and the pull-up resistor may be omitted. Thermal Considerations The MIC5216 is designed to provide 200mA of continuous current in two very small profile packages. Maximum power dissipation can be calculated based on the output current and the voltage drop across the part. To determine the maximum power dissipation of the package, use the thermal resistance, junction-to- ambient, of the device and the following basic equation. ( ) JA A J(MAX) D(MAX) θ T T P − = TJ(MAX) is the maximum junction temperature of the die, 125°C, and TA is the ambient operating temperature. θJA is layout dependent; table 1 shows examples of thermal resistance, junction-to-ambient, for the MIC5216. Package θ JA Recommended Minimum Footprint θ JA 1” Square Copper Clad θ JC MM8™ (MM) 160°C/W 70°C/W 30°C/W SOT-23-5 (M5) 220°C/W 170°C/W 130°C/W Table 1. MIC5216 Thermal Resistance The actual power dissipation of the regulator circuit can be determined using one simple equation. PD = (VIN – VOUT) IOUT + VIN IGND Substituting PD(MAX) for PD and solving for the operating conditions that are critical to the application will give the maximum operating conditions for the regulator circuit. For example, if we are operating the MIC5216-3.3BM5 at room temperature, with a minimum footprint layout, we can determine the maximum input voltage for a set output current. ( ) C/W 220 C 25 C 125 PD(MAX) ° ° − ° = PD(MAX) = 455mW The thermal resistance, junction-to-ambient, for the minimum footprint is 220°C/W, taken from table 1. The maximum power dissipation number cannot be exceeded for proper operation of the device. Using the output voltage of 3.3V, and an output current of 150mA, we can determine the maximum input voltage. Ground current, maximum of 3mA for 150mA of output current, can be taken from the Electrical Characteristics section of the data sheet. 455mW = (VIN – 3.3V) 150mA + VIN × 3mA () ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + + 3mA 150mA 150mA 3.3V 455mW VIN |
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