ISL6565 Intersil Corporation, ISL6565 Datasheet - Page 22

• Manufacturer Part Number: ISL6565
• Description: Multi-Phase PWM Controller with Precision rDS(ON) or DCR Current Sensing for VR10.X Application
• Manufacturer: Intersil Corporation

important to note that when using Equations 33 and 34 the
resistor divider ratio of the corresponding phase RC network
is being changed. In the phase being adjusted, this new ratio,
K
If this occurs, the current in the hot phase can not be reduced
any more. Instead of decreasing the current in the hot phase,
the current must be increased in the colder phases. To
accomplish this use Equations 33 and 34 to get the desired
temperature rise in the cold phases.
While a single adjustment, according to Equations 33 and 34,
is usually sufficient, it may occasionally be necessary to adjust
R
to achieve optimal thermal balance between all phases.
Load-Line Regulation Resistor
The load-line regulation resistor is labeled R
Its value depends on the desired full-load droop voltage
(V
chosen, the load-line regulation resistor can be calculated
using Equation 36.
If one or more of the ISEN resistors is adjusted for thermal
balance, as in Equation 26, the load-line regulation resistor
should be selected according to Equation 37 where I
full-load operating current and R
connected to the n
Temperature Compensation Resistor
By combining Equations 17 and 18 found in the
Temperature Compensation section, the value of the Tcomp
resistor can be determined using Equation 38.
In Equation 38, K
between the ISL6565A and the closest lower MOSFET, or
the ISL6565B and the output inductor. It represents how
closely the controller temperature tracks the lower MOSFET
or inductor temperature. The value of K
75% and100%. K
transconductance of the internal compensation circuit. Its
value is designed as 2µA/V/°C. The temperature coefficient
of MOSFET r
the ratio of the change in resistance to the change in
R
K
R
R
new
1
FB
new
FB
TCOMP
DROOP
and R
=
=
(described in Equation 32), can not exceed 1.0.
=
--------------------------------
I
V
------------------------ -
70 10
FL
K
V
DROOP
2
=
DROOP
∆T
----------
∆T
in Figure 7). Once the ISEN resistor has been
×
r
in the corresponding channels two or more times
DS ON
--------------------- -
K
1
2
DS(ON)
–
T
(
6
α
K
TC
T
TC
)
th
is the temperature coupling coefficient
∑
n
is the temperature dependant
ISEN pin.
or inductor DCR is given by α. This is
R
ISEN n ( )
22
ISEN(n)
T
is the ISEN resistor
is typically between
FB
in Figure 7.
ISL6565A, ISL6565B
(EQ. 35)
(EQ. 36)
FL
(EQ. 37)
(EQ. 38)
is the
temperature. Resistance is normalized to the value at 25°C
and the value of
0.50%/°C.
According to Equation 38, a voltage regulator with 80%
thermal coupling coefficient between the controller and lower
MOSFET and 0.4%/°C temperature coefficient of MOSFET
r
If the exact value for K
can give an incorrect value for R
follow the steps below to obtain an accurate value for
R
voltage measurements. The first is made by using too much
temperature compensation, and the second with too little.
Each of the measurements produces an error and a linear
interpolation is used to find a TCOMP resistor value to
produce zero error. Make all measurements using a digital
multimeter accurate to 100µV or better.
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
R
DS(ON)
1. Install a 5kΩ resistor (R
2. Start the regulator at room temperature and apply full
3. Allow the board to heat until the output voltage stabilizes
4. Install a 1kΩ resistor (R
5. Start the regulator at room temperature and apply full
6. Allow the board to heat until the output voltage stabilizes
7. Calculate the correct value for R
TCOMP
TCOMP
load current. Record the output voltage, V
after loading the regulator.
(usually several minutes). Record the output voltage, V
load current. Record the output voltage, V
after loading the regulator.
(usually several minutes). Record the output voltage, V
Equation 39.
requires a 2.5kΩ TCOMP resistor.
. This procedure works by making two output
=
R
1
–
(
α
R
is typically between 0.35%/°C and
1
–
R
T
2
and α are not known, Equation 38
)
------------------------------------------------------- -
(
V
1
2
2
) for R
) for R
–
C
V
(
V
1
and C
TCOMP
2
)
+
–
TCOMP
TCOMP
V
(
TCOMP
V
1
C
3
)
.
–
. If this is the case,
V
.
.
4
)
using
1
3
, immediately
, immediately
(EQ. 39)
2
4
.
.