 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ISL6563IRZ Datasheet(PDF) 16 Page - Intersil Corporation |
|
||||||||||||||||||||||||||||||
ISL6563IRZ Datasheet(HTML) 16 Page - Intersil Corporation |
|
|
16 / 19 page  16 FN9126.6 April 13, 2005 The ESR of the bulk capacitors is also responsible for the majority of the output-voltage ripple. As the bulk capacitors sink and source the inductor ac ripple current, a voltage develops across the bulk-capacitor ESR equal to IPP. Thus, once the output capacitors are selected and a maximum allowable ripple voltage, VPP(MAX), is determined from an analysis of the available output voltage budget, the following equation can be used to determine a lower limit on the output inductance. Since the capacitors are supplying a decreasing portion of the load current while the regulator recovers from the transient, the capacitor voltage becomes slightly depleted. The output inductors must be capable of assuming the entire load current before the output voltage decreases more than ∆VMAX. This places an upper limit on inductance. While the previous equation addresses the leading edge, the following equation gives the upper limit on L for cases where the trailing edge of the current transient causes a greater output voltage deviation than the leading edge. Normally, the trailing edge dictates the selection of L, since duty cycles are usually less than 50%. Nevertheless, both inequalities should be evaluated, and L should be selected based on the lower of the two results. In all equations in this paragraph, L is the per-channel inductance and C is the total output bulk capacitance. Layout Considerations MOSFETs switch very fast and efficiently. The speed with which the current transitions from one device to another causes voltage spikes across the interconnecting impedances and parasitic circuit elements. These voltage spikes can degrade efficiency, radiate noise into the circuit and lead to device overvoltage stress. Careful component layout and printed circuit design minimizes the voltage spikes in the converter. Consider, as an example, the turnoff transition of the upper PWM MOSFET. Prior to turnoff, the upper MOSFET was carrying channel current. During the turnoff, current stops flowing in the upper MOSFET and is picked up by the lower MOSFET. Any inductance in the switched current path generates a large voltage spike during the switching interval. Careful component selection, tight layout of the critical components, and short, wide circuit traces minimize the magnitude of voltage spikes. There are two sets of critical components in a DC-DC converter using an ISL6563 controller. The power components are the most critical because they switch large amounts of energy. Next are small signal components that connect to sensitive nodes or supply critical bypassing current and signal coupling. Note that as the ISL6563 does not allow external adjustment of the channel-to-channel current balancing (current information is multiplexed across a single RISEN resistor), it is important to have a symmetrical layout, preferably with the controller equidistantly located from the two power trains it controls. Equally important are the gate drive lines (UGATE, LGATE, PHASE): since they drive the power train MOSFETs using short, high current pulses, it is important to size them accordingly and reduce their overall impedance. Equidistant placement of the controller to the two power trains also helps keeping these traces equally long (equal impedances, resulting in similar driving of both sets of MOSFETs). The power components should be placed first. Locate the input capacitors close to the power switches. Minimize the length of the connections between the input capacitors, CIN, and the power switches. Locate the output inductors and output capacitors between the MOSFETs and the load. Locate the high-frequency decoupling capacitors (ceramic) as close as practicable to the decoupling target, making use of the shortest connection paths to any internal planes, such as vias to GND immediately next, or even onto the capacitor solder pad. The critical small components include the bypass capacitors for VCC and PVCC. Locate the bypass capacitors, CBP, close to the device. It is especially important to locate the components associated with the feedback circuit close to their respective controller pins, since they belong to a high- impedance circuit loop, sensitive to EMI pick-up. It is important to place the RISEN resistor close to the respective terminal of the ISL6563. A multi-layer printed circuit board is recommended. Figure 9 shows the connections of the critical components for one output channel of the converter. Note that capacitors CxxIN and CxxOUT could each represent numerous physical capacitors. Dedicate one solid layer, usually the one underneath the component side of the board, for a ground plane and make all critical component ground connections with vias to this layer. Dedicate another solid layer as a power plane and break this plane into smaller islands of common voltage levels. Keep the metal runs from the PHASE terminal to inductor LOUT short. The power plane should support the input power and output power nodes. Use copper filled polygons on the top and bottom circuit layers for the phase nodes. Use the remaining printed circuit layers for small signal wiring. The wiring traces from the IC to the MOSFETs’ gates and sources should be sized to carry at least one ampere of current (0.02” to 0.05”). LESR VIN 2VOUT ⋅ – () V OUT ⋅ fS VIN VPP MAX () ⋅⋅ ----------------------------------------------------------------- ⋅ ≥ L 4CVOUT ⋅⋅ ∆I () 2 -------------------------------- ∆V MAX ∆I ESR ⋅ – () ⋅ ≤ L 2.5 C ⋅ ∆I () 2 ----------------- ∆V MAX ∆I ESR ⋅ – () V IN VO – () ⋅⋅ ≤ ISL6563 |
Similar Part No. - ISL6563IRZ |
|
Similar Description - ISL6563IRZ |
|
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
