isl6262a Intersil Corporation, isl6262a Datasheet - Page 23

• Manufacturer Part Number: isl6262a
• Description: Two-phase Core Controller Santa Rosa, Imvp-6+
• Manufacturer: Intersil Corporation

thermistor should be placed in the spot which gives the best
indication of the temperature of voltage regulator circuit.
Static Mode of Operation - Static Droop Using DCR
Sensing
As previously mentioned, the ISL6262A has an internal
differential amplifier which provides for very accurate voltage
regulation at the die of the processor. The load line
regulation is also accurate for both two-phase and
single-phase operation. The process of selecting the
components for the appropriate load line droop is explained
here.
For DCR sensing, the process of compensation for DCR
resistance variation to achieve the desired load line droop
has several steps and is somewhat iterative.
The two-phase solution using DCR sensing is shown in
Figure 37. There are two resistors connecting to the terminals
of inductor of each phase. These are labeled R
These resistors are used to obtain the DC voltage drop across
each inductor. Each inductor will have a certain level of DC
current flowing through it, and this current, when multiplied by
the DCR of the inductor, creates a small DC voltage drop
across the inductor terminal. When this voltage is summed with
the other channels DC voltages, the total DC load current can
be derived.
R
outputs of all channels together and thus create a summed
average of the local CORE voltage output. R
through an understanding of both the DC and transient load
currents. This value will be covered in the next section.
However, it is important to keep in mind that the output of
each of these R
VSUM voltage node. With both the outputs of R
together, the simplified model for the droop circuit can be
derived. This is presented in Figure 40.
O
is typically 1Ω to 10Ω. This resistor is used to tie the
OC
VDIFF
INTERNAL TO
ISL6262A
S
-
+
resistors are tied together to create the
+
+
10µA
FIGURE 40. EQUIVALENT MODEL FOR DROOP AND DIE SENSING USING DCR SENSING
1
1
+
+
-
-
23
RTN
VSEN
DROOP
-
+
DROOP
OCSET
S
VSUM
DFB
S
is determined
O
and R
VO'
and R
O
.
S
tied
ISL6262A
Cn
VSUM
Figure 40 shows the simplified model of the droop circuitry.
Essentially one resistor can replace the R
phase and one R
each phase. The total DCR drop due to load current can be
replaced by a DC source, the value of which is given by:
Equation 16.
For the convenience of analysis, the NTC network
comprised of R
labeled as a single resistor R
The first step in droop load line compensation is to adjust
R
exists even at light loads between the VSUM and VO' nodes.
As a rule of thumb, we start with the voltage drop across the
R
provides for a fairly reasonable amount of light load signal
from which to arrive at droop.
The resultant NTC network resistor value is dependent on
the temperature and given by Equation 17.
For simplicity, the gain of Vn to the V
G1, also dependent on the temperature of the NTC
thermistor.
Therefore, the output of the droop amplifier divided by the
total load current can be expressed as shown in
Equation 20, where R
and 0.00393 is the temperature coefficient of the copper.
V
R
G
DCR T ( )
VN
VO'
DCR_EQU
n
n
n
+
1
-
, RO
T ( )
T ( )
network, VN, to be 0.5 to 0.8 times V
=
EQV
Δ
=
(
--------------------------------------------------------------
=
R
R
------------------------------------------ -
R
DCR
series
series
Rn
=
n
and RS
T ( )
I
-------------------------------- -
OUT
=
ntc
R
25°C
+
n
(
-----------------------------------------------------------------------
(
+
+
S
Rntc
Rntc
, R
T ( )
RS
R
R
resistor can replace the R
•
2
RS
EQV
ntc
ntc
•
DCR
series
EQV
droop
(
EQV
+
+
1
) R
Vdcr
+
Rseries
Rseries
•
RO
+
such that sufficient droop voltage
R
0.00393*(T-25)
par
and R
=
EQV
par
is the realized load line slope
EQV
n
RS
--------
2
in Figure 40.
)
)
=
×
+
=
par
Rpar
Rpar
RO
-------- -
I
OUT
2
, given in Figure 37, is
dcr_equ
×
DCR_EQU
)
DCR
-------------
O
2
resistors of each
is defined by
S
December 23, 2008
resistors of
. This ratio
(EQ. 16)
(EQ. 17)
(EQ. 18)
(EQ. 19)
FN6343.1