Electronic Components Datasheet Search 

ISL6322 Datasheet(PDF) 36 Page  Intersil Corporation 

ISL6322 Datasheet(HTML) 36 Page  Intersil Corporation 
36 / 41 page 36 FN6328.0 August 21, 2006 type III controller, as shown in Figure 24, provides the necessary compensation. The first step is to choose the desired bandwidth, f0, of the compensated system. Choose a frequency high enough to assure adequate transient performance but not higher than 1/3 of the switching frequency. The typeIII compensator has an extra highfrequency pole, fHF. This pole can be used for added noise rejection or to assure adequate attenuation at the erroramplifier highorder pole and zero frequencies. A good general rule is to choose fHF = 10f0, but it can be higher if desired. Choosing fHF to be lower than 10f0 can cause problems with too much phase shift below the system bandwidth. In the solutions to the compensation equations, there is a single degree of freedom. For the solutions presented in Equation 42, RFB is selected arbitrarily. The remaining compensation components are then selected according to Equation 42. In Equation 42, L is the perchannel filter inductance divided by the number of active channels; C is the sum total of all output capacitors; ESR is the equivalentseries resistance of the bulk outputfilter capacitance; and VPP is the peaktopeak sawtooth signal amplitude as described in Electrical Specifications on page 7. Output Filter Design The output inductors and the output capacitor bank together to form a lowpass filter responsible for smoothing the pulsating voltage at the phase nodes. The output filter also must provide the transient energy until the regulator can respond. Because it has a low bandwidth compared to the switching frequency, the output filter limits the system transient response. The output capacitors must supply or sink load current while the current in the output inductors increases or decreases to meet the demand. In highspeed converters, the output capacitor bank is usually the most costly (and often the largest) part of the circuit. Output filter design begins with minimizing the cost of this part of the circuit. The critical load parameters in choosing the output capacitors are the maximum size of the load step, ΔI, the loadcurrent slew rate, di/dt, and the maximum allowable outputvoltage deviation under transient loading, ΔV MAX. Capacitors are characterized according to their capacitance, ESR, and ESL (equivalent series inductance). At the beginning of the load transient, the output capacitors supply all of the transient current. The output voltage will initially deviate by an amount approximated by the voltage drop across the ESL. As the load current increases, the voltage drop across the ESR increases linearly until the load current reaches its final value. The capacitors selected must have sufficiently low ESL and ESR so that the total outputvoltage deviation is less than the allowable maximum. Neglecting the contribution of inductor current and regulator response, the output voltage initially deviates by the amount specified in Equation 43. FIGURE 24. COMPENSATION CIRCUIT WITHOUT LOADLINE REGULATION ISL6322 COMP CC RC RFB FB IDROOP VDIFF C2 C1 R1 C C 0.75 V IN 2 π f HF LC ⋅ 1 – ⋅⋅ ⋅ () ⋅⋅ 2 π ⋅ ()2 f 0 fHF LC ⋅ () R FB VPP ⋅⋅ ⋅ ⋅ ⋅  = R C V PP 2 π ⎝⎠ ⎛⎞ ⋅ 2 f 0 fHF LCRFB ⋅⋅ ⋅ ⋅ ⋅ 0.75 V IN 2 π f HF LC ⋅ 1 – ⋅⋅ ⋅ () ⋅⋅  = R 1 R FB CESR ⋅ LC ⋅ C ESR ⋅ –  ⋅ = C 1 LC ⋅ C ESR ⋅ – R FB  = C 2 0.75 V IN ⋅ 2 π ⋅ ()2 f 0 fHF LC ⋅ () R FB VPP ⋅⋅ ⋅ ⋅ ⋅  = (EQ. 42) ΔVESL di dt  ⋅ ESR ΔI ⋅ + ≈ (EQ. 43) ISL6322 
Link URL 
Privacy Policy 
ALLDATASHEET.COM 
Does ALLDATASHEET help your business so far? [ DONATE ] 
About Alldatasheet  Advertisement  Datasheet Upload  Contact us  Privacy Policy  Alldatasheet API  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 