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LT1763IS8-3.3-TRPBF 数据表(PDF) 16 Page - Linear Technology |
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LT1763IS8-3.3-TRPBF 数据表(HTML) 16 Page - Linear Technology |
16 / 22 page LT1763 Series 16 1763fg Output Capacitance and Transient Response The LT1763 regulators are designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capaci- tors. A minimum output capacitor of 3.3μF with an ESR of 3Ω, or less, is recommended to prevent oscillations. The LT1763-X is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT1763-X, will increase the effective output capacitor value. With larger capacitors used to bypass the reference (for low noise operation), larger values of output capacitors are needed. For 100pF of bypass capacitance, 4.7μF of output capaci- tor is recommended. With a 1000pF bypass capacitor or larger, a 6.8μF output capacitor is recommended. The shaded region of Figure 3 defines the range over which the LT1763 regulators are stable. The minimum ESR needed is defined by the amount of bypass capacitance used, while the maximum ESR is 3Ω. Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are specified with EIA temperature characteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but they tend to have strong voltage and temperature coefficients, as shown in Figures 4 and 5. When used with a 5V regulator, a 16V 10μF Y5V capacitor can exhibit an effective value as low as 1μF to 2μF for the DC bias voltage applied and over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values. Care still must be exercised when using X5R and X7R capacitors; the X5R and X7R codes only specify operating temperature range and maximum capacitance change over temperature. Capacitance change due to DC bias with X5R and X7R capacitors is better than APPLICATIONS INFORMATION OUTPUT CAPACITANCE (μF) 1 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 310 1763 F03 24 5 6 78 9 STABLE REGION CBYP = 330pF CBYP 1000pF CBYP = 100pF CBYP = 0 Figure 3. Stability DC BIAS VOLTAGE (V) 1763 F04 20 0 –20 –40 –60 –80 –100 0 4 8 10 26 12 14 X5R Y5V 16 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF TEMPERATURE (°C) –50 40 20 0 –20 –40 –60 –80 –100 25 75 1763 F05 –25 0 50 100 125 Y5V X5R BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF Figure 4. Ceramic Capacitor DC Bias Characteristics Figure 5. Ceramic Capacitor Temperature Characteristics |
类似零件编号 - LT1763IS8-3.3-TRPBF |
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类似说明 - LT1763IS8-3.3-TRPBF |
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