ISL6266AHRZ Datasheet, PDF (23/30 Pages) Intersil Corporation – Two-phase Core Controllers (Montevina, IMVP-6+)

ISL6266, ISL6266A
ISEN1
ISEN2
ISEN1
ISEN2
10µA
-
OC
+
INTERNAL TO
ISL6266
+
1
+
-
+
1
+
-
RTN
OCSET
R_OCSET
VO'
VSUM
+
DROOP_{- DFB}
DROOP
R_drp2
VSUM
R_SERIES
Cn
R_PAR
VSEN
R_NTC
I_PHASE1
RS
VSUM
I_PHASE2
RS
VSUM
VDIFF
0.018µF
82nF
0.018µF
R_OPN2
VO'
R_drp1
VO'
10
R_opn1
TO V_OUT
V_{CC_SENSE}
V_{SS_SENSE}
TO PROCESSOR
SOCKET KELVIN
CONNECTIONS
L1
R_L1
Vdcr₁
+-
DCR
CL1
RO1
ISEN1
L₂
R_L2
ISEN2
VO'
DCR
+
-
Vdcr₂
R_O2
C_L2
VO'
V_OUT
C_BULK
ESR
FIGURE 37. SIMPLIFIED SCHEMATIC FOR DROOP AND DIE SENSING WITH INDUCTOR DCR CURRENT SENSING
Static Mode of Operation - Processor Die Sensing
Die sensing is the ability of the controller to regulate the core
output voltage at a remotely sensed point. This allows the
voltage regulator to compensate for various resistive drops
in the power path and ensure that the voltage seen at the
CPU die is the correct level independent of load current.
The VSEN and RTN pins of the ISL6266A are connected to
Kelvin sense leads at the die of the processor through the
processor socket. These signal names are V_{CC_SENSE} and
V_{SS_SENSE} respectively. This allows the voltage regulator to
tightly control the processor voltage at the die, independent
of layout inconsistencies and voltage drops. This Kelvin
sense technique provides for extremely tight load line
regulation.
These traces should be treated as noise sensitive traces.
For optimum load line regulation performance, the traces
connecting these two pins to the Kelvin sense leads of the
processor must be laid out away from rapidly rising/falling
voltage nodes (switching nodes) and other noisy traces. To
achieve optimum performance, place common mode and
differential mode RC filters to analog ground on VSEN and
RTN as shown in Figure 37. The filter resistors should be
10Ω so that they do not interact with the 50kΩ input
resistance of the differential amplifier. The filter resistor may
be inserted between V_{CC_SENSE} and the VSEN pin.
Another option is to place to the filter resistor between
Vcc_sense and VSEN pin and between V_{SS_SENSE} and
RTN pin. The need for RC filters really depends on the
actual board layout and noise environment.
Intersil recommends the use of the R_OPN1 and R_OPN2
connected to V_OUT and ground as shown in Figure 37.
These resistors provide voltage feedback in the event that
the system is powered up without a processor installed.
These resistors typically range from 20Ω to 100Ω.
Setting the Switching Frequency - FSET
The R³ modulator scheme is not a fixed frequency PWM
architecture. The switching frequency can increase during
the application of a load to improve transient performance.
It also varies slightly due to changes in input and output
voltage and output current, but this variation is normally less
than 10% in continuous conduction mode.
See Figure 32. The resistor connected between the VW and
COMP pins of the ISL6266A adjusts the switching window,
and therefore adjusts the switching frequency. The R_FSET
resistor that sets up the switching frequency of the converter
operating in CCM can be determined using Equation 7,
where R_FSET is in kΩ and the switching frequency is in kHz.
R_FSET(kΩ)
=
⎛
⎝
F_{----S----W2----2--}(_-3-k_--2--H_----z_----)⎠⎞
–1.1202
(EQ. 7)
Equation 7 is only a rough estimate of actual frequency. It
should be used to choose an R_FSET value in the vicinity of
the desired switching frequency. Empirical fine tuning may
be necessary to achieve the actual frequency target. In
addition, droop amplifier gain may slightly affect the
switching frequency. Equation 7 is derived using the droop
gain seen on the ISL6266AEVAL1Z REV A evaluation
board.
23
FN6398.3
June 14, 2010