Electronic Components Datasheet Search |
|
IRU3038CF Datasheet(PDF) 5 Page - International Rectifier |
|
IRU3038CF Datasheet(HTML) 5 Page - International Rectifier |
5 / 18 page IRU3038 5 Rev. 2.0 09/12/02 www.irf.com APPLICATION INFORMATION Design Example: The following example is a typical application for IRU3038, the schematic is Figure 11 on page 12. Output Voltage Programming Output voltage is programmed by reference voltage and external voltage divider. The Fb pin is the inverting input of the error amplifier, which is referenced to the voltage on non-inverting pin of error amplifier. For this applica- tion, this pin (VP) is connected to reference voltage (VREF). The output voltage is defined by using the following equa- tion: When an external resistor divider is connected to the output as shown in Figure 3. Figure 3 - Typical application of the IRU3038 for programming the output voltage. Equation (1) can be rewritten as: Choose R5 = 1K V This will result to R6 = 1K V If the high value feedback resistors are used, the input bias current of the Fb pin could cause a slight increase in output voltage. The output voltage set point can be more accurate by using precision resistor. Soft-Start Programming The soft-start timing can be programmed by selecting the soft-start capacitance value. The start-up time of the converter can be calculated by using: Where CSS is the soft-start capacitor ( mF) For a start-up time of 7.5ms, the soft-start capacitor will be 0.1 mF. Choose a ceramic capacitor at 0.1mF. Shutdown The converter can be shutdown by pulling the soft-start pin below 0.5V. The control MOSFET turns off and the synchronous MOSFET turns on during shutdown. Boost Supply Vc To drive the high-side switch it is necessary to supply a gate voltage at least 4V greater than the bus voltage. This is achieved by using a charge pump configuration as shown in Figure 11. The capacitor is charged up to approximately twice the bus voltage. A capacitor in the range of 0.1 mF to 1mF is generally adequate for most applications. In application, when a separate voltage source is available the boost circuit can be avoided as shown in Figure 1. Input Capacitor Selection The input filter capacitor should be based on how much ripple the supply can tolerate on the DC input line. The ripple current generated during the on time of control MOSFET should be provided by input capacitor. The RMS value of this ripple is expressed by: Where: D is the Duty Cycle, D=VOUT/VIN. IRMS is the RMS value of the input capacitor current. IOUT is the output current for each channel. For higher efficiency, a low ESR capacitor is recom- mended. Choose two Poscap from Sanyo 10TPB100ML (10V, 100 mF, 55mV) with a maximum allowable ripple current of 1.9A. tSTART = 753Css (ms) ---(2) VIN = 5V VOUT = 2.5V IOUT = 8A DVOUT = 100mV fS = 200KHz Fb IRU3038 VOUT R5 R6 VREF VP For VIN=5V, IOUT=8A and D=0.5, the IRMS=4A VOUT = VP 3 1 + ---(1) R6 R5 VP = VREF = 1.25V ( ) R6 = R5 3 - 1 VOUT VP ( ) IRMS = IOUT D 3(1-D) ---(3) |
Similar Part No. - IRU3038CF |
|
Similar Description - IRU3038CF |
|
|
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 |