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LM4140ACM-1.0 Datasheet(PDF) 9 Page - National Semiconductor (TI) |
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LM4140ACM-1.0 Datasheet(HTML) 9 Page - National Semiconductor (TI) |
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9 / 15 page  Application Hints Input Capacitors Although not always required, an input capacitor is recom- mended. A supply bypass capacitor on the input assures that the reference is working from a source with low impedance, which improves stability. A bypass capacitor can also im- prove transient response by providing a reservoir of stored energy that the reference can utilize in case where the load current demand suddenly increases. The value used for C IN may be used without limit. Refer to the typical application section for examples of input capacitors. Output Capacitors The LM4140 requires a 1µF (nominally) output capacitor for loop stability (compensation) as well as transient response. During the sudden changes in load current demand, the out- put capacitor must source or sink current during the time it takes the control loop of the LM4140 to respond. This capacitor must be selected to meet the requirements of minimum capacitance and equivalent series resistance (ESR) range. In general, the capacitor value must be at least 0.2µF (over the actual ambient operating temperature), and the ESR must be within the range indicated in Figure 1, Figure 2 and Figure 3. 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 for by the LM4140. The results of testing the LM4140 stability with surface mount solid tan- talum capacitors show good stability with values in the range of 0.1µF. However, optimum performance is achieved with a 1µF capacitor. Tantalum capacitors that have been verified as suitable for use with the LM4140 are shown in Table 1. TABLE 1. Surface-Mount Tantalum Capacitor Selection Guide 1µF Surface-Mount Tantalums Manufacturer Part Number Kemet T491A105M010AS NEC NRU105N10 Siemens B45196-E3105-K Nichicon F931C105MA Sprague 293D105X0016A2T 2.2µF Surface-Mount Tantalums Kemet T491A225M010AS NEC NRU225M06 Siemens B45196/2.2/10/10 Nichicon F930J225MA Sprague 293D225X0010A2T Aluminum Electrolytic Capacitors Although probably not a good choice for a production design, because of relatively large physical size, an aluminium elec- trolytic capacitor can be used in the design prototype for an LM4140 reference. A 1µF capacitor meeting the ESR condi- tions can be used. If the operating temperature drops below 0˚C, the reference may not remain stable, as the ESR of the aluminium electrolytic capacitor will increase, and may ex- ceed the limits indicated in the figures. Multilayer Ceramic Capacitors Surface-mountable multilayer ceramic capacitors may be an attractive choice because of their relatively small physical size and excellent RF characteristics. DS101079-28 FIGURE 1. 0.22 µF ESR Range DS101079-29 FIGURE 2. 1 µF ESR Range DS101079-30 FIGURE 3. 10 µF ESR Range www.national.com 9 |
Similar Part No. - LM4140ACM-1.0 |
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Similar Description - LM4140ACM-1.0 |
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