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Description
LM317D2TR4G is an adjustable 3-terminal positive voltage regulator Able to provide more than 1.5 A current within the output voltage range 1.2 V to 37V. This regulator is very easy to use and Only two external resistors are required to set the output voltage. In addition, it Adopt internal current limit, thermal shutdown and safe area Compensation, making it essentially a proof of blowout prevention.
LM317 can be used in various applications, including local, Card gauge. The device can also be used for programmable Output voltage regulator, or through the Adjustment and output, LM317D2TR4G can be used as precision current Regulator.
Features
1. Output Current in Excess of 1.5 A
2. Output Adjustable between 1.2 V and 37 V
3. Internal Thermal Overload Protection
4. Internal Short Circuit Current Limiting Constant with Temperature
5. Output Transistor Safe−Area Compensation
6. Floating Operation for High Voltage Applications
7. Eliminates Stocking many Fixed Voltages
8. Available in Surface Mount D2PAK−3, and Standard 3−Lead Transistor Package
9. NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC−Q100 Qualified and PPAP Capable
10. These are Pb−Free Devices
Basic Circuit Operation
The LM317D2TR4G is a 3−terminal floating regulator. In operation, the LM317D2TR4G develops and maintains a nominal 1.25 V reference (Vref) between its output and adjustment terminals. This reference voltage is converted to a programming current (IPROG) by R1 , and this constant current flows through R2 to ground. The regulated output voltage is given by:
Basic Circuit Configuration
Since the current from the adjustment terminal (IAdj) represents an error term in the equation, the LM317D2TR4G was designed to control IAdj to less than 100 A and keep it constant. To do this, all quiescent operating current is returned to the output terminal. This imposes the requirement for a minimum load current. If the load current is less than this minimum, the output voltage will rise. Since the LM317D2TR4G is a floating regulator, it is only the voltage differential across the circuit which is important to performance, and operation at high voltages with respect to ground is possible.
External Capacitors
A 0.1 F disc or 1.0 F tantalum input bypass capacitor (Cin) is recommended to reduce the sensitivity to input line impedance.
The adjustment terminal may be bypassed to ground to improve ripple rejection. This capacitor (CAdj) prevents ripple from being amplified as the output voltage is increased. A 10 F capacitor should improve ripple rejection about 15 dB at 120 Hz in a 10 V application.
Although the LM317 is stable with no output capacitance, like any feedback circuit, certain values of external capacitance can cause excessive ringing. An output capacitance (CO) in the form of a 1.0 F tantalum or 25 F aluminum electrolytic capacitor on the output swamps this effect and insures stability。
