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AMS317-X Datasheet(PDF) 3 Page - Advanced Monolithic Systems |
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AMS317-X Datasheet(HTML) 3 Page - Advanced Monolithic Systems |
3 / 8 page Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS317 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications and test conditions, see the Electrical Characteristics . The guaranteed specifications apply only for the test conditions listed. Parameters identified with boldface type apply over the full operating temperature range. Note 2: Line and Load regulation are guaranteed up to the maximum power dissipation of 1.2 W. Power dissipation is determined by the input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output range. Note 3: See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constant junction temperature by low duty cycle pulse testing. Load regulation is measured at the output lead ~1/8” from the package. Note 4: Minimum load current is defined as the minimum output current required to maintain regulation. When 3V ≤ (V IN - VOUT) ≤ 25V the device is guaranteed to regulate if the output current is greater than 10mA. APPLICATION HINTS The AMS317 series of adjustable and fixed regulators are easy to use and are protected against short circuit and thermal overloads. Thermal protection circuitry will shut-down the regulator should the junction temperature exceed 165 °C at the sense point. Pin compatible with older three terminal adjustable regulators, these devices offer the advantage of a lower dropout voltage, more precise reference tolerance and improved reference stability with temperature. Stability The circuit design used in the AMS317 series requires the use of an output capacitor as part of the device frequency compensation. The addition of 150 µF aluminum electrolytic or a 22µF solid tantalum on the output will ensure stability for all operating conditions. When the adjustment terminal is bypassed with a capacitor to improve the ripple rejection, the requirement for an output capacitor increases. The value of 22 µF tantalum or 150µF aluminum covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal smaller capacitors can be used with equally good results. To ensure good transient response with heavy load current changes capacitor values on the order of 100 µF are used in the output of many regulators. To further improve stability and transient response of these devices larger values of output capacitor can be used. Protection Diodes Unlike older regulators, the AMS317 family does not need any protection diodes between the adjustment pin and the output and from the output to the input to prevent over-stressing the die. Internal resistors are limiting the internal current paths on the AMS317 adjustment pin, therefore even with capacitors on the adjustment pin no protection diode is needed to ensure device safety under short-circuit conditions. Diodes between the input and output are not usually needed. Microsecond surge currents of 50A to 100A can be handled by the internal diode between the input and output pins of the device. In normal operations it is difficult to get those values of surge currents even with the use of large output capacitances. If high value output capacitors are used, such as 1000 µF to 5000µF and the input pin is instantaneously shorted to ground, damage can occur. A diode from output to input is recommended, when a crowbar circuit at the input of the AMS317 is used (Figure 1). AMS317 IN OUT ADJ + C OUT 150 µF V OUT R 1 R 2 C ADJ 10 µF D1 V IN Figure 1. Output Voltage The AMS317 series develops a 1.25V reference voltage between the output and the adjust terminal. Placing a resistor between these two terminals causes a constant current to flow through R1 and down through R2 to set the overall output voltage. This current is normally the specified minimum load current of 10mA. Because IADJ is very small and constant it represents a small error and it can usually be ignored. AMS317 IN OUT ADJ R1 R2 V OUT V REF V IN I ADJ 50 µA VOUT = VREF (1+ R2/R1)+I ADJR2 Figure 2. Basic Adjustable Regulator |
Número de pieza similar - AMS317-X |
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Descripción similar - AMS317-X |
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