Electronic Components Datasheet Search |
|
AHP2812D Datasheet(PDF) 9 Page - International Rectifier |
|
AHP2812D Datasheet(HTML) 9 Page - International Rectifier |
9 / 11 page www.irf.com 9 AHP28XXD Series General Application Information Table 2. Nominal Resistance of Cu Wire The AHP28XXD series of converters are capable of providing large transient currents to user loads on demand. Because the nominal input voltage range in this series is relatively low, the resulting input current demands will be correspondingly large. It is important therefore, that the line impedance be kept very low to prevent steady state and transient input currents from degrading the supply voltage between the voltage source and the converter input. Wire Size, AWG Resistance per ft 24 Ga 25.7 m Ω 22 Ga 16.2 m Ω 20 Ga 10.1 m Ω 18 Ga 6.4 m Ω 16 Ga 4.0 m Ω 14 Ga 2.5 m Ω 12 Ga 1.6 m Ω Incorporation of a 100 µfd capacitor at the input terminals is recommended as compensation for the dynamic effects of the parasitic resistance of the input cable reacting with the complex impedance of the converter input, and to provide an energy reservoir for transient input current requirements. Figure VI. Problems of Parasitic Resistance in input Leads Vin Rtn Case Enable 1 Sync Out Sync In R p R p I Rtn I in e source System Ground e Rtn 100 µfd Another potential problem resulting from parasitically induced voltage drop on the input lines is with regard to the operation of the enable 1 port. The minimum and maximum operating levels required to operate this port are specified with respect to the input common return line at the converter. If a logic signal is generated with respect to a ‘common’ that is distant from the converter, the effects of the voltage drop over the return line must be considered when establishing the worst case TTL switching levels. These drops will effectively impart a shift to the logic levels. In Figure VI, it can be seen that referred to system ground, the voltage on the input return pin is given by e Rtn = IRtn • RP Therefore, the logic signal level generated in the system must be capable of a TTL logic high plus sufficient additional amplitude to overcome e Rtn. When the converter is inhibited, I Rtn diminishes to near zero and eRtn will then be at system ground. In applications requiring high static currents and large transients, it is recommended that the input leads be made of adequate size to minimize resistive losses, and that a good quality capacitor of approximately100 µfd be connected directly across the input terminals to assure an adequately low impedance at the input terminals. Table 2 relates nominal resistance values and selected wire sizes. As an example of the effects of parasitic resistance, consider an AHP2815D operating at full power of 100 W. From the specification sheet, this device has a minimum efficiency of 83% which represents an input power of more than 120 W. If we consider the case where line voltage is at its’ minimum of 16 volts, the steady state input current necessary for this example will be slightly greater than 7.5 Amps. If this device were connected to a voltage source with 10 feet of 20 gauge wire, the round trip (input and return) would result in 0.2 Ω of resistance and 1.5 volts of drop from the source to the converter. To assure 16 volts at the input, a source closer to 18 volts would be required. In applications using the paralleling option, this drop will be multiplied by the number of paralleled devices. By choosing 14 or 16 gauge wire in this example, the parasitic resistance and resulting voltage drop will be reduced to 25% or 31% of that with 20 gauge wire. |
Similar Part No. - AHP2812D |
|
Similar Description - AHP2812D |
|
|
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 |