ISL6323A Datasheet, PDF (27/35 Pages) Intersil Corporation – Monolithic Dual PWM Hybrid Controller Powering AMD SVI Split-Plane and PVI Uniplane Processors

ISL6323A
power dissipation in the controller itself, P_DR, can be roughly
estimated as Equation 30:
P_DR = P_{DR_UP} + P_{DR_LOW} + P_BOOT + (I_Q ⋅ VCC)
P_BOOT
=
-^P----^Q----^g----^_--^Q-----¹-
3
(EQ. 30)
P _{D R _UP}
=
⎛
⎜
⎝
-------------^R-----^H----^I--¹--------------
R_HI1 + R_EXT1
+
R^-----_L^---_O^-----₁^{R----+-L---O-}R^----1-_E^----_X^----_T^---₁^- _{⎠⎟⎞}
⋅ ^P-----^Q----^g----^_--^Q-----¹-
3
P _{D R _LOW}
=
⎛
⎜
⎝
-------------^R-----^H----^I--²--------------
R_HI2 + R_EXT2
+
R^-----_L^---_O^-----₂^{R----+-L---O-}R^----2-_E^----_X^----_T^---₂^- _{⎠⎟⎞}
⋅
P_{-----Q----g----_---Q----2-}
2
R_EXT1
=
R_G
1
+
R_{-----G-----I-1--}
N_Q1
R_EXT2
=
R_G2
+
R_{-----G-----I-2--}
N_Q2
Inductor DCR Current Sensing Component
Selection and R_SET Value Calculation
With the single R_SET resistor setting the value of the
effective internal sense resistors for both the North Bridge
and Core regulators, it is important to set the R_SET value
and the inductor RC filter gain, K, properly. See “Continuous
Current Sampling” on page 13 and “Channel-Current
Balance” on page 14 for more details on the application of
the R_SET resistor and the RC filter gain.
There are 3 separate cases to consider when calculating
these component values. If the system under design will
never utilize the North Bridge regulator and the ISL6323 will
always be in parallel mode, then follow the instructions for
Case 3 and only calculate values for Core regulator
components.
For all three cases, use the expected VID voltage that would
be used at TDC for Core and North Bridge for the V_CORE
and V_NB variables, respectively.
CASE 1
I_NBM
A
X
⋅
D
C
R_NB
<
I_{--C-----o---r--e---M-----A----X--}
N
⋅
D
C
R_C
o
r
e
(EQ. 31)
In Case 1, the DC voltage across the North Bridge inductor
at full load is less than the DC voltage across a single phase
of the Core regulator while at full load. Here, the DC voltage
across the Core inductors must be scaled down to match the
DC voltage across the North Bridge inductor, which will be
impressed across the ISEN_NB pins without any gain. So,
the R₂ resistor for the North Bridge inductor RC filter is left
unpopulated and K = 1.
1. Choose a capacitor value for the North Bridge RC filter. A
0.1µF capacitor is a recommended starting point.
2. Calculate the value for resistor R₁ using Equation 32:
R_1NB
=
--------------^L----^N----^B---------------
DCR_NB ⋅ C_NB
(EQ. 32)
3. Calculate the value for the R_SET resistor using
Equation 33: (Derived from Equation 20).
R_SET
=
4_----0_---0_--
3
⋅
D_-----C_{--1---0R---0--N--μ--B--A---}⋅_---K_--
⋅
⎛
⎝⎜ ^{I O}
C
PN
B
+
2^----V-⋅^---IL^--N--_N^---–-_B^----V-⋅^---Nf^--_S^--B--_W^---
⋅
-^V-_V---^N-_I--_N-^B--_{⎠⎟⎞}
Where: K = 1
(EQ. 33)
4. Using Equation 34 (also derived from Equation 20),
calculate the value of K for the Core regulator.
K
=
----³-----
400
⋅
R_SET
⋅
--------------^N---------------
DCR_CORE
⋅
-_I-_O-----_C----_P----_C----_O----_R-----_E-----+------_V--₂------_I----_⋅N--¹---_L----⁰_-–--C----⁰---_N-O----^μ------_Râ‹--^A----_V--_E--------_C--_â‹------_Of----_S----_R----_W-----_E-------â‹----_V--------_C--_V------_O--_I----_N---_R---------E----
(EQ. 34)
5. Choose a capacitor value for the Core RC filters. A 0.1µF
capacitor is a recommended starting point.
6. Calculate the values for R₁ and R₂ for Core.
Equations 35 and 36 will allow for their computation.
K
=
--------------^R----²----^C----^o---^r--^e---------------
R_1Core + R_2Core
(EQ. 35)
------^L---^C-----^o---^r--^e-------
DCR_Core
=
-^R-----¹---^C----^o----^r--^e----^â‹---^R-----²---^C----^o---^r---^e--
R_1Core + R_2Core
⋅
C_Core
(EQ. 36)
CASE 2
I_NBM
A
X
⋅
D
C
R
N
B
>
I_{--C-----o---r--e---M-----A----X--}
N
⋅
DC
R_Co
r
e
(EQ. 37)
In Case 2, the DC voltage across the North Bridge inductor
at full load is greater than the DC voltage across a single
phase of the Core regulator while at full load. Here, the DC
voltage across the North Bridge inductor must be scaled
down to match the DC voltage across the Core inductors,
which will be impressed across the ISEN pins without any
gain. So, the R₂ resistor for the Core inductor RC filters is
left unpopulated and K = 1.
1. Choose a capacitor value for the Core RC filter. A 0.1µF
capacitor is a recommended starting point.
2. Calculate the value for resistor R₁:
R_1Core = -_D----_C-----_R-----_C--^L--_o-^C--_r--_eo----^r-_â‹-^e--_C----_C----_o----_r--_e-
(EQ. 38)
3. Calculate the value for the R_SET resistor using Equation 39
(Derived from Equation 20).:
R_SET
=
4_----0_---0_--
3
⋅
D_-----C_-----R_{-----C----O----R-----E-----}⋅_---K_--
100 μ A
⋅
⎛
⎜
⎝
I_O
C
PC
O
R
E
+
----^V----^I--^N-----–-----^V----^C----^O-----^R----^E-----
2 ⋅ L_CORE ⋅ f_SW
⋅
V_{-----C-V---O-I--N-R-----E--⎠⎟⎞}
Where: K = 1
(EQ. 39)
4. Using Equation 40 (also derived from Equation 20),
calculate the value of K for the North bridge regulator.
K
=
----³-----
400
⋅
R_SET
⋅
----------¹-----------
DCR_NB
⋅
-------------------------------¹----⁰---⁰----^μ----^A---------------------------------
I_O
C
PN
B
+
----^V----^I--^N-----–-----^V----^N----^B-----
2 ⋅ L_NB ⋅ f_SW
⋅
-^V----^N----^B--
V_IN
(EQ. 40)
27
FN6878.0