 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LM2991T Datasheet(PDF) 5 Page - National Semiconductor (TI) |
|
|
||||||||||||||||||||||||||||||
LM2991T Datasheet(HTML) 5 Page - National Semiconductor (TI) |
|
|
5 / 12 page  Typical Performance Characteristics (Continued) Application Hints External Capacitors Like any low-dropout regulator, external capacitors are re- qired to stabilize the control loop. These capacitors must be correctly selected for proper performance. INPUT CAPACITOR: An input capacitor is reqiuired if the regulator is located more than 6 ″ from the input power supply filter capacitor (or if no other input capaciotr is present). A solid Tantalum or ceramic capacitor whose value is at least 1 µF is recommended, but an aluminum electrolytic ( ≥ 10 µF) may be used. However, aluminum electrolytics should not be used in applications where the ambient temperature can drop below 0˚C because their internal impedance increases significantly at cold temperatures. OUTPUT CAPACITOR: The output capacitor must meet the ESR limits shown in the graph, which means it must have an ESR between about 25 m Ω and 10Ω. A solid Tantalum (value ≥ 1 µF) is the best choice for the out- put capacitor. An aluminum electrolytic ( ≥ 10 µF) may be used if the ESR is in the stable range. It should be noted that the ESR of a typical aluminum elec- trolytic will increase by as much as 50X as the temperature is reduced from 25˚C down to −40˚C, while a Tantalum will exhibit an ESR increase of about 2X over the same range. For this and other reasons, aluminum electrolytics should not be used in applications where low operating tempera- tures occur. The lower stable ESR limit of 25 m Ω means that ceramic ca- pacitors can not be used directly on the output of an LDO. A ceramic ( ≥ 2.2 µF) can be used on the output if some exter- nal resistance is placed in series with it (1 Ω recommended). Dielectric types X7R or X5R must be used if the temperature range of the application varies more than ± 25˚ from ambient to assure the amount of capacitance is sufficient. CERAMIC BYPASS CAPACITORS:Many designers place distributed ceramic capacitors whose value is in the range of 1000 pF to 0.1 µF at the power input pins of the IC’s across a circuit board. These can cause reduced phase margin or oscillations in LDO regulators. The advent of multi-layer boards with dedicated power and ground planes has removed the trace inductance that (previ- ously) provided the necessary ″decoupling″ to shield the out- put of the LDO from the effects of bypass capacitors. These capacitors should be avoided if possible, and kept as far far away from the LDO output as is practical. Adjust Pin Current DS011260-25 Low Voltage Behavior DS011260-26 Maximum Power Dissipation (TO-220) DS011260-27 Maximum Power Dissipation (TO-263) (See Note 3) DS011260-28 www.national.com 5 |
Similar Part No. - LM2991T |
|
Similar Description - LM2991T |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
