ISL6323A Datasheet, PDF (30/35 Pages) Intersil Corporation – Monolithic Dual PWM Hybrid Controller Powering AMD SVI Split-Plane and PVI Uniplane Processors

ISL6323A
Case 1:
---------------1----------------
2⋅π⋅ L⋅C
>
f₀
R_C
=
R_FB
⋅
2-----⋅_---π_-----⋅_---f--0----⋅_{---V-----P------P-----}⋅_{-------L-----}⋅_---C---
0.66 ⋅ V_IN
C_C
=
--------------0---.--6---6-----^â‹---V----^I--^N----------------
2 ⋅ π ⋅ V_PP ⋅ R_FB ⋅ f₀
Case 2:
---------------1----------------
2⋅π⋅ L⋅C
≤
f₀
<
2-----⋅^---π^-----⋅^---C--1----⋅^{---E----S-----R---}
R_C = R_FB ⋅ -V----^P----^P-----^â‹---⁽--20----.-^â‹_6---^π-6---⁾--_⋲----V^â‹----_I-f-_N0--²-----^â‹---L-----^â‹---C---
C_C
=
------------------------------0----.-6----6-----^â‹---V----^I--^N--------------------------------
(2 ⋅ π)² ⋅ f₀₂ ⋅ V_PP ⋅ R_FB ⋅ L ⋅ C
(EQ. 51)
Case 3:
f₀
>
------------------1-------------------
2 ⋅ π ⋅ C ⋅ ESR
R_C = R_FB ⋅ ^2-0----.â‹-6--^π--6----^â‹-_â‹--f--V⁰----_I^â‹--_N-V----_â‹^P---E-^---^P-S----^â‹-R--L-
C_C
=
-----0---.--6---6-----^â‹---V----^I--^N-----^â‹---E-----S----R------^â‹-------C-------
2 ⋅ π ⋅ V_PP ⋅ R_FB ⋅ f₀ ⋅ L
Compensation Without Loadline Regulation
The non load-line regulated converter is accurately modeled
as a voltage-mode regulator with two poles at the L-C
resonant frequency and a zero at the ESR frequency. A
type III controller, as shown in Figure 23, provides the
necessary compensation.
C₂
R_C ^CC
COMP
C₁
R₁
R_FB
FB
ISL6323A
VSEN
FIGURE 23. COMPENSATION CIRCUIT WITHOUT LOAD-LINE
REGULATION
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 type-III compensator has
an extra high-frequency pole, f_HF. This pole can be used for
added noise rejection or to assure adequate attenuation at the
error-amplifier high-order pole and zero frequencies. A good
general rule is to choose f_HF = 10f₀, but it can be higher if
desired. Choosing f_HF to be lower than 10f₀ can cause
problems with too much phase shift below the system
bandwidth,
.
R₁
=
R_FB
⋅ ------------C------^â‹---E----S-----R-------------
L ⋅ C – C ⋅ ESR
C₁
=
-----L-----^â‹---C-----^–-----C------^â‹---E----S-----R--
R_FB
C₂
=
--------------------------------------0----.-7----5-----^â‹---V----^I--^N----------------------------------------
(2 ⋅ π)² ⋅ f₀ ⋅ f_HF ⋅ ( L ⋅ C) ⋅ R_FB ⋅ V_P-P
R_C
=
-V----^P----^---^P-----^â‹---^⎝⎛--2----^π---^⎠⎞----²----^â‹---f--⁰----^â‹---f--^H----^F-----^â‹---L-----^â‹---C------^â‹---R----^F----^B--
0.75 ^⋠V_IN ^{⋅ (2 ⋅ π ⋅ f}_HF ^{⋅ L ⋅ C–1)}
(EQ. 52)
C_C
=
-------0----.-7----5----^â‹----V----^I--^N-----^â‹---⁽--2-----^â‹---^π-----^â‹---f--^H----^F-----^â‹-------L-----^â‹---C-----^–---1----⁾-------
(2 ⋅ π)² ⋅ f₀ ⋅ f_HF ⋅ ( L ⋅ C) ⋅ R_FB ⋅ V_P-P
In the solutions to the compensation equations, there is a
single degree of freedom. For the solutions presented in
Equation 53, R_FB is selected arbitrarily. The remaining
compensation components are then selected according to
Equation 53.
In Equation 53, L is the per-channel filter inductance divided
by the number of active channels; C is the sum total of all
output capacitors; ESR is the equivalent-series resistance of
the bulk output-filter capacitance; and V_PP is the peak-to-
peak sawtooth signal amplitude as described in Electrical
Specifications on page 6.
Case 1:
---------------1----------------
2⋅π⋅ L⋅C
>
f₀
R_C = R_FB ⋅ ^2-----â‹---^π-----^â‹---f-0-⁰--.--6^â‹---6V-----^P_â‹---V^---^P--_I--_N-^â‹-------L-----^â‹---C---
C_C
=
--------------0---.--6---6-----^â‹---V----^I--^N----------------
2 ⋅ π ⋅ V_PP ⋅ R_FB ⋅ f₀
Case 2:
---------------1----------------
2⋅π⋅ L⋅C
≤
f₀
<
------------------1-------------------
2 ⋅ π ⋅ C ⋅ ESR
R_C
=
R_FB
⋅
-V----^P----^P-----^â‹---⁽--2-----^â‹---^π----⁾--²----^â‹-----f-⁰--²-----^â‹---L-----^â‹---C---
0.66 ⋅ V_IN
C_C
=
-------------------------------0---.--6---6-----^â‹---V-----^I-^N---------------------------------
(2 ⋅ π)² ⋅ f₀₂ ⋅ V_P-P ⋅ R_FB ⋅ L ⋅ C
(EQ. 53)
Case 3:
f₀ > _2-----â‹---_π-----_â‹---C--1----_â‹---E----S-----R---
R_C
=
R_FB
⋅
2-----⋅_---π_------⋅_---f--0----⋅_{---V----P-------P-----}⋅_---L-
0.66 ⋅ V_IN ⋅ ESR
C_C
=
-----0----.-6----6----^â‹---V-----^I-^N------^â‹---E----S-----R-----^â‹--------C-------
2 ⋅ π ⋅ V_P-P ⋅ R_FB ⋅ f₀ ⋅ L
30
FN6878.0