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MIC69153YME Datasheet(PDF) 7 Page - Micrel Semiconductor |
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MIC69153YME Datasheet(HTML) 7 Page - Micrel Semiconductor |
7 / 9 page Micrel, Inc. MIC69151/153 July 2010 7 M9999-071210-D Application Information The MIC69151/153 is an ultra-high performance low dropout linear regulator designed for high current applications requiring a fast transient response. It utilizes a single input supply, perfect for low-voltage DC-to-DC conversion. The MIC69151/153 requires a minimum number of external components. The MIC69151/153 regulator is fully protected from damage due to fault conditions offering constant current limiting and thermal shutdown. Input Supply Voltage VIN provides high current to the collector of the pass transistor. The minimum input voltage is 1.65V allowing conversion from low voltage supplies. Output Capacitor The MIC69151/153 requires a minimum of output capacitance to maintain stability. However, proper capacitor selection is important to ensure desired transient response. The MIC69151/153 is specifically designed to be stable with low ESR ceramic chip capacitors. A 10µF ceramic chip capacitor should satisfy most applications. Output capacitor can be increased without bound. See typical characteristics for examples of load transient response. X7R dielectric ceramic capacitors are recommended because of their temperature performance. X7R-type capacitors change capacitance by only 15% over their operating temperature range and are the most stable type of ceramic capacitors. Z5U and Y5V dielectric capacitors change value by as much as 50% and 60%, respectively over their operating temperature ranges. To use a ceramic chip capacitor with Y5V dielectric the value must be much higher than an X7R ceramic or a tantalum capacitor to ensure the same capacitance value over the operating temperature range. Tantalum capacitors have a very stable dielectric (10% over their operating temperature range) and can also be used with this device. Input Capacitor An input capacitor of 1µF or greater is recommended when the device is more than 4 inches away from the bulk supply capacitance or when the supply is a battery. Small, surface mount, ceramic chip capacitors can be used for the bypassing. The capacitor should be placed within 1 inch of the device for optimal performance. Larger values will help to improve ripple rejection by bypassing the input to the regulator further improving the integrity of the output voltage. Minimum Load Current The MIC69151/153 regulator is specified between finite loads. If the output current is too small, leakage currents dominate and the output voltage rises. A 10mA minimum load current is necessary for proper operation. Adjustable Regulator Design The MIC69153 adjustable version allows programming the output voltage anywhere between 0.5V and 5.5V with two resistors. The resistor value between VOUT and the adjust pin should not exceed 10kΩ. Larger values can cause instability. The resistor values are calculated by: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + ∗ = 1 R R 0.5 V 2 1 OUT Where VOUT is the desired output voltage. Enable The fixed output voltage versions of the MIC69151 feature an active high enable input (EN) that allows on- off control of the regulator. Current drain reduces to near “zero” when the device is shutdown, with only microamperes of leakage current. EN may be directly tied to VIN and pulled up to the maximum supply voltage. Thermal Design Linear regulators are simple to use. The most complicated design parameters to consider are thermal characteristics. Thermal design requires the following application-specific parameters: • Maximum ambient temperature (TA) • Output current (IOUT) • Output voltage (VOUT) • Input voltage (VIN) • Ground current (IGND) First, calculate the power dissipation of the regulator from these numbers and the device parameters from this data sheet. PD = (VIN – VOUT) IOUT + VIN IGND where the ground current is approximated by using numbers from the “Electrical Characteristics” or “Typical Characteristics” sections. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) – TA) / θJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature and the regulator will go into thermal shutdown. Refer to “Application Note 9” for further details and examples on thermal design and heat sink applications. |
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