 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LMS8117AMP-3.3 Datasheet(PDF) 7 Page - National Semiconductor (TI) |
|
|
||||||||||||||||||||||||||||||
LMS8117AMP-3.3 Datasheet(HTML) 7 Page - National Semiconductor (TI) |
|
|
7 / 16 page  Application Note 1.0 EXTERNAL CAPACITORS/STABILITY 1.1 Input Bypass Capacitor An input capacitor is recommended. A 10µF tantalum on the input is a suitable input bypassing for almost all applications. 1.2 Adjust Terminal Bypass Capacitor The adjust terminal can be bypassed to ground with a by- pass capacitor (C ADJ) to improve ripple rejection. This by- pass capacitor prevents ripple from being amplified as the output voltage is increased. At any ripple frequency, the impedance of the C ADJ should be less than R1 to prevent the ripple from being amplified: 1/(2 π*f RIPPLE*CADJ) < R1 The R1 is the resistor between the output and the adjust pin. Its value is normally in the range of 100-200 Ω. For example, with R1 = 124 Ω and f RIPPLE = 120Hz, the CADJ should be > 11µF. 1.3 Output Capacitor The output capacitor is critical in maintaining regulator sta- bility, and must meet the required conditions for both mini- mum amount of capacitance and ESR (Equivalent Series Resistance). The minimum output capacitance required by the LMS8117A is 10µF, if a tantalum capacitor is used. Any increase of the output capacitance will merely improve the loop stability and transient response. The ESR of the output capacitor should be greater than 0.5 Ω and less than 5Ω.In the case of the adjustable regulator, when the C ADJ is used, a larger output capacitance (22µf tantalum) is required. 2.0 OUTPUT VOLTAGE The LMS8117A adjustable version develops a 1.25V refer- ence voltage, V REF, between the output and the adjust ter- minal. As shown in Figure 1 , this voltage is applied across resistor R1 to generate a constant current I1. The current I ADJ from the adjust terminal could introduce error to the output. But since it is very small (60µA) compared with the I1 and very constant with line and load changes, the error can be ignored. The constant current I1 then flows through the output set resistor R2 and sets the output voltage to the desired level. For fixed voltage devices, R1 and R2 are integrated inside the devices. For fixed voltage devices, R1 and R2 are integrated inside the devices. 3.0 LOAD REGULATION The LMS8117A regulates the voltage that appears between its output and ground pins, or between its output and adjust pins. In some cases, line resistances can introduce errors to the voltage across the load. To obtain the best load regula- tion, a few precautions are needed. Figure 2, shows a typical application using a fixed output regulator. The Rt1 and Rt2 are the line resistances. It is obvious that the V LOAD is less than the VOUT by the sum of the voltage drops along the line resistances. In this case, the load regulation seen at the R LOAD would be degraded from the data sheet specification. To improve this, the load should be tied directly to the output terminal on the positive side and directly tied to the ground terminal on the negative side. 10119617 FIGURE 1. Basic Adjustable Regulator 10119618 FIGURE 2. Typical Application using Fixed Output Regulator www.national.com 7 |
Similar Part No. - LMS8117AMP-3.3 |
|
Similar Description - LMS8117AMP-3.3 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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
