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CS5205A-1 데이터시트(PDF) 4 Page - Cherry Semiconductor Corporation |
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CS5205A-1 데이터시트(HTML) 4 Page - Cherry Semiconductor Corporation |
4 / 6 page 4 The CS5205A-1 linear regulator provides an adjustable voltage at currents up to 5A. The regulator is protected against short circuit, and include thermal shutdown and safe area protection (SOA) circuitry. The SOA protection circuitry decreases the maximum available output current as the input-output differential voltage increases. The CS5205A-1 has a composite PNP-NPN output transis- tor and requires an output capacitor for stability. A detailed procedure for selecting this capacitor is included in the Stability Considerations section. The adjustable regulator (CS5205A-1) has an output volt- age range of 1.25V to 13V. An external resistor divider sets the output voltage as shown in Figure 1. The regulator maintains a fixed 1.25V (typical) reference between the output pin and the adjust pin. A resistor divider network R1 and R2 causes a fixed cur- rent to flow to ground. This current creates a voltage across R2 that adds to the 1.25V across R1 and sets the overall output voltage. The adjust pin current (typically 50µA) also flows through R2 and adds a small error that should be taken into account if precise adjustment of VOUT is necessary. The output voltage is set according to the formula: VOUT = VREF ´ () + IAdj ´ R2 The term IAdj ´ R2 represents the error added by the adjust pin current. R1 is chosen so that the minimum load current is at least 10mA. R1 and R2 should be the same type, e.g. metal film for best tracking over temperature. The adjust pin is bypassed to improve the transient response and ripple rejection of the regulator. Figure 1. Resistor divider scheme for the adjustable version. The output or compensation capacitor helps determine three main characteristics of a linear regulator: start-up delay, load transient response and loop stability. The capacitor value and type is based on cost, availability, size and temperature constraints. A tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capaci- tor with almost zero ESR, can cause instability. The alu- minum electrolytic capacitor is the least expensive solu- tion. However, when the circuit operates at low tempera- tures, both the value and ESR of the capacitor will vary considerably. The capacitor manufacturers data sheet pro- vides this information. A 22µF tantalum capacitor will work for most applications, but with high current regulators such as the CS5205A-1 the transient response and stability improve with higher val- ues of capacitor. The majority of applications for this regu- lator involve large changes in load current so the output capacitor must supply the instantaneous load current. The ESR of the output capacitor causes an immediate drop in output voltage given by: ÆV = ÆI ´ ESR For microprocessor applications it is customary to use an output capacitor network consisting of several tantalum and ceramic capacitors in parallel. This reduces the overall ESR and reduces the instantaneous output voltage drop under load transient conditions. The output capacitor net- work should be as close as possible to the load for the best results. When large external capacitors are used with a linear regu- lator it is sometimes necessary to add protection diodes. If the input voltage of the regulator gets shorted, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of the capaci- tor, the output voltage and the rate at which VIN drops. In the CS5205A-1 linear regulator, the discharge path is through a large junction and protection diodes are not usu- ally needed. If the regulator is used with large values of output capacitance and the input voltage is instantaneous- ly shorted to ground, damage can occur. In this case, a diode connected as shown in Figure2 is recommended. Figure 2. Protection diode scheme for adjustable output regulator. Since the CS5205A-1 is a three terminal regulator, it is not possible to provide true remote load sensing. Load regula- tion is limited by the resistance of the conductors connect- ing the regulator to the load. Output Voltage Sensing VOUT VIN CS5205A-1 VIN Adj R1 R2 C1 VOUT C2 CAdj IN4002 (optional) Protection Diodes Stability Considerations VOUT VIN CS5205A-1 VIN Adj R1 R2 C1 VOUT C2 VREF IAdj CAdj R1 + R2 R1 Adjustable Operation Applications Information |
유사한 부품 번호 - CS5205A-1 |
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유사한 설명 - CS5205A-1 |
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