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UC621XX Datasheet(PDF) 6 Page - E-Tech Electronics LTD |
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UC621XX Datasheet(HTML) 6 Page - E-Tech Electronics LTD |
6 / 14 page UC621XX CMOS IC UNISONICTECHNOLOGIESCO.,LTD 6 of 14 www.unisonic.com.tw QW-R502-028,B TYPICAL APPLICATION CIRCUIT PNP Tr RBE RB EXT VIN VOUT Vss CE VIN RL CL (Tantalum) CIN (Tantalum) + + Peripherals: PNP Tr:2SA1213 RBE : 20KΩ~ 47KΩ RB: Please refer to Note2 on the directions for use . CIN :10µF(Tantalum) CL:47µF(Tantalum)10µF minimum OPERATIONAL EXPLANATION Functional Description Output voltage (VOUT) can be fixed by revising the external transistor's base current. This can be done by comparing the detected voltage level and the set voltage power supply level. DIRECTIONS FOR USE Suggestions for External Comporients 1. PNP Transistor The selection of a transistor should take into account output current, input voltage and power dissipation for each specific application. It is recommended that a transistor that has a low output saturated voltage (VCE) and high hFE characteristics be used. 2. RB Resistor Although the IC unit is protected by a base current remitter circuit, it is recommended that a resistor (RB) be connected between the transistor's base and the IC's EXT pin to protect the transistor. Required output current can be calculated using the following equation although characteristic variations and conditions of use should be carefully checked before use. The following equation also indicates the conditions needed to obtain IOUT (max.) at VIN (min.). However, the larger the input current, the larger the output current (IOUT) that can be obtained. VIN(min) -1.2(V) 0.7(V) IOUT(max) RB RBE hFE 3. RBE Resistor, CL Capacitor To prevent oscillation due to output load variation, use of a phase compensation capacitor CL is recommended. Please use a Tantalum capacitor of at least 10µF. Please also use an RBE resistor of less than 47kΩ. An RBE resistor of between 20kΩ and 47kΩ is recommended for less power consumption. 4. Input Impedance In order to control oscillation brought about as a result of impedance at the power supply line, connect a capacitor of 10µF or more (Tantalum) between the external transistor's emitter and the ground pin. Special Note 1. Protection Circuit The built-in protect circuit is to protect the IC only. Therefore to prevent output shorts and overshoot current through the transistor, use of a resistor RB or an overshoot current protection circuit is recommended. Care should also be taken with the transistor's power dissipation. |
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