 |
Motore di ricerca datesheet componenti elettronici |
|
|
Motore di ricerca datesheet componenti elettronici |
|
ACT4911QW Scheda tecnica(PDF) 22 Page - Active-Semi, Inc |
|
||||||||||||||||||||||||||||||
ACT4911QW Scheda tecnica(HTML) 22 Page - Active-Semi, Inc |
|
|
22 / 33 page  ACT4911QW Rev 1.0, 15-Sept-2017 Innovative PowerTM www.active-semi.com ActiveSwitcherTM is a trademark of Active-Semi Copyright © 2017 Active-Semi, Inc. 22 Table 3: Buck Current Limit BK_CLIM[1:0] ILIMSET (A) 00 5.0 01 6.0 10 7.0 11 9.0 A short circuit condition that results in the peak switch current being 122.5% of BK_CLIM immediately shuts down the supply and asserts nIRQ low. A buck overcurrent, undervoltage, or overvoltage condition moves the IC into the UV/POR state. Compensation The Buck regulator utilizes type 2 external compensation placed on the COMP pin. Contact the factory for compensation details. Input Capacitor Selection The STR pin is the input voltage to the buck converter. It requires a dedicated high quality, low-ESR, ceramic input capacitor that is optimally placed to minimize the power routing. For optimal PCB layout considerations, 1206 or 1210 sized input capacitors are recommended. A 22uF capacitor is typically suitable, but the actual value is application dependent. The input capacitor can be increased without limit. Choose the input capacitor value to keep the input voltage ripple less than 50mV ∗ ∗ ∗ Equation 5 Where Iout is the maximum eFuse load current in Amperes, VSTR is the maximum storage voltage, FSW is the switching frequency, and Vripple is the maximum allowable ripple voltage on the input of the buck converter. Note that the storage capacitor values should not be considered when calculating the input voltage ripple because they are not typically designed for high frequency functionality. Be sure to consider the input capacitor’s DC bias effects. A capacitor’s actual capacitance is strongly affected by its DC bias characteristics. The input capacitor is typically an X5R, X7R, or similar dielectric. Use of Y5U, Z5U, or similar dielectrics is not recommended. Input capacitor placement is critical for proper operation. The buck’s input capacitor must be placed as close to the IC as possible. The traces from STR to the capacitor and from the capacitor to PGND should as short and wide as possible. Inductor Selection The Buck regulator utilizes current-mode control and a proprietary internal compensation scheme to simultaneously simplify external component selection and optimize transient performance over their full operating range. These ACT4911 is optimized for operation with 1uH to 3.3uH inductors. Choose an inductor with a low DC-resistance, and avoid inductor saturation by choosing inductors with DC ratings that exceed the maximum output current by at least 30%. Due to the requirement for the buck converter to start up as quickly as possible, the inductor should be designed to give a maximum ripple current, ΔIL, of 50% to 60% of the maximum output current. The following equation calculates the recommended inductor value. ∗ ∗∆ Equation 6 Where L is the inductor value in µH, VOUT is the output voltage, VSTR is the maximum storage voltage, FSW is the switching frequency in Hz, and ΔIL is the desired ripple current in Amperes. Output Capacitor Selection The buck converter is designed to take advantage of the benefits of ceramic capacitors, namely small size and very-low ESR. The buck converter is designed to operate with 44µF output capacitor over most of its operating ranges, although more capacitance may be desired depending on the duty cycle and load step requirements. Choose a ripple voltage that is approximately 1% of the output voltage setpoint. Note that the output capacitance must be placed at the output of the buck converter. Additional downstream capacitance will be placed at the loads, but this capacitance should not be considered when calculating the buck output capacitance. However, the downstream capacitance should be considered when compensating the power supply. The following equation calculates the output voltage ripple as a function of output capacitance. Note that the worst case ripple voltage occurs at the beginning of supplement mode when the storage capacitors are fully charged. COUT ∆ ∗ ∗ Equation 7 |
Codice articolo simile - ACT4911QW |
|
Descrizione simile - ACT4911QW |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEETIT.COM |
| Lei ha avuto il aiuto da alldatasheet? [ DONATE ] |
Di alldatasheet | Richest di pubblicita | contatti | Privacy Policy | scambio Link | Ricerca produttore 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 |
Italian ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
