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LP2980AIM5X-2.5 Datasheet(PDF) 10 Page - Texas Instruments |
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LP2980AIM5X-2.5 Datasheet(HTML) 10 Page - Texas Instruments |
10 / 24 page LP2980-N SNOS733M – APRIL 2000 – REVISED JUNE 2013 www.ti.com APPLICATION HINTS OUTPUT CAPACITOR Like any low-dropout regulator, the LP2980-N requires an output capacitor to maintain regulator loop stability. This capacitor must be selected to meet the requirements of minimum capacitance and equivalent series resistance (ESR) range. It is not difficult to find capacitors which meet the criteria of the LP2980-N, as the acceptable capacitance and ESR ranges are wider than for most other LDOs. In general, the capacitor value must be at least 1 μF (over the actual ambient operating temperature), and the ESR must be within the range indicated in Figure 34, Figure 35 and Figure 36. It should be noted that, although a maximum ESR is shown in these Figures, it is very unlikely to find a capacitor with ESR that high. Tantalum Capacitors Surface-mountable solid tantalum capacitors offer a good combination of small physical size for the capacitance value, and ESR in the range needed by the LP2980-N. The results of testing the LP2980-N stability with surface-mount solid tantalum capacitors show good stability with values of at least 1 μF. The value can be increased to 2.2 μF (or more) for even better performance, including transient response and noise. Small value tantalum capacitors that have been verified as suitable for use with the LP2980-N are shown in Table 1. Capacitance values can be increased without limit. Aluminum Electrolytic Capacitors Although probably not a good choice for a production design, because of relatively large physical size, an aluminum electrolytic capacitor can be used in the design prototype for an LP2980-N regulator. A value of at least 1 μF should be used, and the ESR must meet the conditions of Figure 34, Figure 35 and Figure 36. If the operating temperature drops below 0°C, the regulator may not remain stable, as the ESR of the aluminum electrolytic capacitor will increase, and may exceed the limits indicated in the Figures. Table 1. Surface-Mount Tantalum Capacitor Selection Guide 1 μF Surface-Mount Tantalums Manufacturer Part Number Kemet T491A105M010AS NEC NRU105M10 Siemens B45196-E3105-K Nichicon F931C105MA Sprague 293D105X0016A2T 2.2 μF Surface-Mount Tantalums Manufacturer Part Number Kemet T491A225M010AS NEC NRU225M06 Siemens B45196/2.2/10/10 Nichicon F930J225MA Sprague 293D225X0010A2T Multilayer Ceramic Capacitors Surface-mountable multilayer ceramic capacitors may be an attractive choice because of their relatively small physical size and excellent RF characteristics. However, they sometimes have ESR values lower than the minimum required by the LP2980-N, and relatively large capacitance change with temperature. The manufacturer's datasheet for the capacitor should be consulted before selecting a value. Test results of LP2980-N stability using multilayer ceramic capacitors show that a minimum value of 2.2 μF is usually needed for the 5V regulator. For the lower output voltages, or for better performance, a higher value should be used, such as 4.7 μF. 10 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LP2980-N |
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