 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
SP6136 Datasheet(PDF) 12 Page - Sipex Corporation |
|
|
|||||||||||||||||||||||||||||
SP6136 Datasheet(HTML) 12 Page - Sipex Corporation |
|
|
12 / 18 page  2 Oct 3-06 Rev L SP636 Synchronous Buck Controller © 2006 Sipex Corporation IL(rms) = Iout(max) X √+ •{ Ipp }2 3 Iout(max) Output Capacitor Selection The required ESR (Equivalent Series Re- sistance) and capacitance drive the selec- tion of the type and quantity of the output capacitors. The ESR must be small enough that both the resistive voltage deviation due to a step change in the load current and the output ripple voltage do not exceed the tolerance limits expected on the output voltage. During an output load transient, the output capacitor must supply all the ad- ditional current demanded by the load until the SP636 adjusts the inductor current to the new value. Therefore, the capacitance must be large enough so that the output voltage is held up while the inductor current ramps up or down to the value corresponding to the new load current. Additionally, the ESR in the output capacitor causes a step in the output voltage equaltothecurrent. Becauseofthefasttran- sient response and inherent 00% and 0% duty cycle capability provided by the SP636 when exposed to output load transients, the output capacitor is typically chosen for ESR, not for capacitance value. The output capacitor’s ESR, combined with the inductor ripple current, is typically the main contributor to output voltage ripple. The maximum allowable ESR required to maintain a specified output voltage ripple can be calculated by: RESR < ΔVout ipk-pk where: ΔVout = Peak to Peak Output Voltage Ripple ipk-pk = Peak to Peak Inductor Ripple Current The total output ripple is a combination of the ESR and the output capacitance value and can be calculated as follows: ΔVout = . . √ (Ipp•REsr) 2 + { Ipp • (1-d) } 2 Cout • Fs where: Fs = Switching Frequency D = Duty Cycle Cout = Output Capacitance Value Input Capacitor Selection The input capacitor should be selected for ripple current rating, capacitance and voltage rating. The input capacitor must meet the ripple current requirement imposed by the switching current. In continuous conduction mode, the source current of the high-side MOSFET is approximately a square wave of duty cycle Vout/VIN. Most of this current is supplied by the input bypass capacitors. The RMS value of input capacitor current is determined at the maximum output current and under the assumption that the peak to peak inductor ripple current is low, it is given by: . Icin (rms) = Iout(max) X √ D • (-D) Schottky Diode Selection When paralleled with the bottom MOSFET, an optional Schottky diode can improve efficiency and reduce noise. Without this Schottky diode, the body diode of the bot- tom MOSFET conducts the current during the non-overlap time when both MOSFETs are turned off. Unfortunately, the body di- APPLICATION INFORMATION |
|
|
Link URL |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link to Datasheet | 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
