ISL6566CR-T Intersil, ISL6566CR-T Datasheet - Page 23

• Manufacturer Part Number: ISL6566CR-T
• Description: IC CTRLR PWM BUCK 3PHASE 40-QFN
• Manufacturer: Intersil

Specifications of ISL6566CR-T

• Applications: Controller, Intel VRM9, VRM10, and AMD Hammer Applications
• Voltage - Input: 3 ~ 12 V
• Number Of Outputs: 1
• Voltage - Output: 0.84 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 40-VFQFN, 40-VFQFPN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Then the resistor R
sense network gain, obtaining the desired full load droop
voltage. Follow the steps below to choose the component
values for this R-C network.
Due to errors in the inductance or DCR it may be necessary
to adjust the value of R
correctly. The effects of time constant mismatch can be seen
in the form of droop overshoot or undershoot during the
initial load transient spike, as shown in Figure 19. Follow the
steps below to ensure the R-C and inductor L/DCR time
constants are matched accurately.
1. Choose an arbitrary value for C
2. Plug the inductor L and DCR component values, and the
3. Use the new value for R
1. Capture a transient event with the oscilloscope set to
2. Record ∆V1 and ∆V2 as shown in Figure 19.
value is 0.01µF.
values for C
calculate the value for R
26, as well as the desired full load current, I
droop voltage, V
27 to calculate the value for R
about L/DCR/2 (sec/div). For example, with L = 1µH and
DCR = 1mΩ, set the oscilloscope to 500µs/div.
R
R
COMP
S
V
DROOP
=
ISL6566
FIGURE 18. DCR SENSING CONFIGURATION
+
-
------------------------ - R
V
PHASE1
PHASE2
PHASE3
DROOP
=
I
ICOMP
FL
ISUM
IREF
---------------------------------------
DCR C
COMP
⋅
S
⋅
DROOP
L
must be chosen to set the current
COMP
COMP
chosen in steps 1, into Equation 26 to
COMP
(optional)
R
S
, and inductor DCR in Equation
⋅
C
COMP
COMP
DCR
23
R
COMP
to match the time constants
S
S
R
.
COMP
obtained from Equation
S
.
R
I
I L3
I
L2
COMP
L1
INDUCTOR
INDUCTOR
INDUCTOR
L
L
L
. The recommended
V
L
(s)
DCR
DCR
DCR
-
FL
, full load
(EQ. 26)
(EQ. 27)
C
I
OUT
OUT
ISL6566
After choosing a new value for R
necessary to adjust the value of R
load droop voltage. Use Equation 27 to obtain the new value
for R
Compensation
The two opposing goals of compensating the voltage
regulator are stability and speed.
The load-line regulated converter behaves in a similar
manner to a peak current mode controller because the two
poles at the output filter L-C resonant frequency split with the
introduction of current information into the control loop. The
final location of these poles is determined by the system
function, the gain of the current signal, and the value of the
compensation components, R
Since the system poles and zero are affected by the values of
the components that are meant to compensate them, the
solution to the system equation becomes fairly complicated.
3. Select a new value, R
4. Replace R
FIGURE 20. COMPENSATION CONFIGURATION FOR
resistor based on the original value, R
following equation.
the error is corrected. Repeat the procedure if necessary.
R
S
FIGURE 19. TIME CONSTANT MISMATCH BEHAVIOR
COMP 2
.
∆V
1
,
R
LOAD-LINE REGULATED ISL6566 CIRCUIT
=
COMP
FB
R
COMP 1
with the new value and check to see that
R
C
,
C
2
COMP,2
⋅
C
(OPTIONAL)
∆
----------
∆
C
V
V
1
2
C
COMP
and C
S
, for the time constant
COMP
VDIFF
to obtain the desired full
FB
, it will most likely be
C
.
COMP,1
∆V
∆I
2
ISL6566
, using the
March 9, 2006
V
I
TRAN
OUT
(EQ. 28)
FN9178.4