 |
数据搜索系统，热门电子元器件搜索 |
|
|
数据搜索系统，热门电子元器件搜索 |
|
LTC3803 数据表(PDF) 13 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LTC3803 数据表(HTML) 13 Page - Linear Technology |
|
|
13 / 24 page  LT8300 13 8300f Typically, choose the transformer turns ratio to maximize available output power. For low output voltages (3.3V or 5V), a larger N:1 turns ratio can be used with multiple primarywindingsrelativetothesecondarytomaximizethe transformer’s current gain (and output power). However, remember that the SW pin sees a voltage that is equal to the maximum input supply voltage plus the output voltage multiplied by the turns ratio. In addition, leakage inductance will cause a voltage spike (VLEAKAGE) on top of this reflected voltage. This total quantity needs to remain below the 150V absolute maximum rating of the SW pin to prevent breakdown of the internal power switch. To- gether these conditions place an upper limit on the turns ratio, NPS, for a given application. Choose a turns ratio low enough to ensure: NPS < 150V − VIN(MAX) − VLEAKAGE VOUT + VF For lower output power levels, choose a smaller N:1 turns ratio to alleviate the SW pin voltage stress. Although a 1:N turns ratio makes it possible to have very high output voltages without exceeding the breakdown voltage of the internal power switch, the multiplied parasitic capacitance through turns ratio coupled with the relatively resistive 150V internal power switch may cause the switch turn-on currentspikeringingbeyond160nsleading-edgeblanking, thereby producing light load instability in certain applica- tions. So any 1:N turns ratio should be fully evaluated before its use with the LT8300. The turns ratio is an important element in the isolated feedback scheme, and directly affects the output voltage accuracy. Make sure the transformer manufacturer speci- fies turns ratio accuracy within ±1%. applicaTions inForMaTion Saturation Current Thecurrentinthetransformerwindingsshouldnotexceed itsratedsaturationcurrent.Energyinjectedoncethecoreis saturated will not be transferred to the secondary and will instead be dissipated in the core. When designing custom transformers to be used with the LT8300, the saturation current should always be specified by the transformer manufacturers. Winding Resistance Resistance in either the primary or secondary windings will reduce overall power efficiency. Good output voltage regulation will be maintained independent of winding re- sistance due to the boundary/discontinuous conduction mode operation of the LT8300. Leakage Inductance and Snubbers Transformer leakage inductance on either the primary or secondary causes a voltage spike to appear on the primary after the power switch turns off. This spike is increasingly prominent at higher load currents where more stored en- ergy must be dissipated. It is very important to minimize transformer leakage inductance. When designing an application, adequate margin should be kept for the worst-case leakage voltage spikes even under overload conditions. In most cases shown in Figure 5, the reflected output voltage on the primary plus VIN should be kept below 120V. This leaves at least 30V margin for the leakage spike across line and load conditions. A larger voltage margin will be required for poorly wound transformers or for excessive leakage inductance. In addition to the voltage spikes, the leakage inductance also causes the SW pin ringing for a while after the power switch turns off. To prevent the voltage ringing falsely trig- ger boundary mode detector, the LT8300 internally blanks theboundarymodedetectorforapproximately250ns.Any remaining voltage ringing after 250ns may turn the power switch back on again before the secondary current falls to zero. So the leakage inductance spike ringing should be limited to less than 250ns. |
类似零件编号 - LTC3803 |
|
类似说明 - LTC3803 |
|
|
|
链接网址 |
| 隐私政策 |
| ALLDATASHEETCN.COM |
| ALLDATASHEET是否为您带来帮助? [ DONATE ] |
关于 Alldatasheet | 广告服务 | 联系我们 | 隐私政策 | 链接交换 | 制造商名单 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 |
Chinese ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
