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REG1117A Datasheet(PDF) 8 Page - Burr-Brown (TI) |
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REG1117A Datasheet(HTML) 8 Page - Burr-Brown (TI) |
8 / 23 page REG1117 REG1117A SBVS001D − OCTOBER 1992 − REVISED JULY 2004 www.ti.com 8 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, all models, unless otherwise noted. LOAD TRANSIENT RESPONSE 0.1 0 −0.1 0.5 0 −0.5 0 2040 6080 100 Time ( µs) C IN =10µF COUT =10µF Tantalum V IN =4.25V Preload = 0.1A LINE TRANSIENT RESPONSE 60 40 20 0 −20 −40 5.25 4.25 3.25 0 20 40 60 80 100 120 140 160 180 200 Time ( µs) C IN =1µF C OUT =10µFTantalum I OUT =0.1A APPLICATIONS INFORMATION Figure 1 shows the basic hookup diagram for fixed-voltage models. All models require an output capacitor for proper operation, and for improving high-frequency load regulation; a 10 µF tantalum capacitor is recommended. Aluminum electrolytic types of 50 µF or greater can also be used. A high-quality capacitor should be used to assure that the ESR (Effective Series Resistance) is less than 0.5 Ω. REG1117 V O V IN 10 µF Tantalum 10 µF Tantalum ++ Figure 1. Fixed-Voltage Model—Basic Connections Figure 2 shows a hookup diagram for the adjustable voltage model. Resistor values are shown for some commonly-used output voltages. Values for other voltages can be calculated from the equation shown in Figure 2. For best load regulation, connect R1 close to the output pin and R2 close to the ground side of the load as shown. THERMAL CONSIDERATIONS The REG1117 has current limit and thermal shutdown circuits that protect it from overload. The thermal shutdown activates at approximately TJ = 165°C. For continuous operation, however, the junction temperature should not be allowed to exceed 125 °C. Any tendency to activate the thermal shutdown in normal use is an indication of an inadequate heat sink or excessive power dissipation. The power dissipation is equal to: PD = (VIN – VOUT) IOUT The junction temperature can be calculated by: TJ = TA + PD ( qJA) where TA is the ambient temperature, and qJA is the junction-to-ambient thermal resistance. REG1117 (Adj) V IN V O C 2 10 µF C 1 10 µF C 3 (1) 10 µF + + + R 1 R 2 Load 32 1 NOTES: (1) C 3 optional. Improves high−frequency line rejection. (2) Resistors are standard 1% values. V O = x (1.25V) + (50 µA) (R 2) R 1 R 1 +R2 This term is negligible with proper choice of values −see table at right. V OUT R 1 R 2 (V)( Ω)(2) ( Ω)(2) 1.25 Open Short 1.5 750 147 2.1 158 107 2.85 169 215 3 137 191 3.3 115 187 5 113 340 10 113 787 Figure 2. Adjustable-Voltage Model—Basic Connections |
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Similar Description - REG1117A |
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