ISL6262 Datasheet, PDF (20/27 Pages) Intersil Corporation – Two-Phase Core Regulator for IMVP-6 Mobile CPUs

ISL6262
ISEN1
ISEN2
ISEN1
OC
ISEN2
10µA
-
+
INTERNAL TO
ISL6262
+
1
+
-
+
1
+
-
RTN
OCSET
R_OCSET
VO'
VSUM
+
DROOP_{- DFB}
DROOP
R_drp2
VSEN
VSUM
R_SERIES
Cn
R_PAR
R_NTC
VDIFF
0.018µF
82nF
0.018µF
R_OPN2
VO'
R_drp1
VO'
10
R_opn1
TO V_OUT
VCC_SENSE
VSS_SENSE
TO PROCESSOR
SOCKET KELVIN
CONNECTIONS
I_PHASE1
RS
VSUM
I_PHASE2
RS
VSUM
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 31. SIMPLIFIED SCHEMATIC FOR DROOP AND DIE SENSING WITH INDUCTOR DCR CURRENT SENSING
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 changes in input and output voltage
and output current, but this variation is normally less than
10% in continuous conduction mode.
Refer to Figure 26, the resistor connected between the VW
and COMP pins of the ISL6262 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 the
following relationship, where R_FSET is in kΩ and the
switching period is in µs. Place a 47pF capacitor in parallel
with the frequency set resistor for better noise immunity.
R_FSET(kΩ) ≅ (period(μs) – 0.5) • 1.56
(EQ. 4)
In discontinuous conduction mode (DCM), the ISL6262 runs
in period stretching mode. The switching frequency is
dependent on the load current level. In general, the lighter
load, the slower switching frequency. Therefore, the
switching loss is much reduced for the light load operation,
which is important for conserving the battery power in the
portable application.
Voltage Regulator Thermal Throttling
lntel® IMVP-6 technology supports thermal throttling of the
processor to prevent catastrophic thermal damage to the
voltage regulator. The ISL6262 features a thermal monitor
which senses the voltage change across an externally
placed negative temperature coefficient (NTC) thermistor.
Proper selection and placement of the NTC thermistor
allows for detection of a designated temperature rise by the
system.
Figure 32 shows the thermal throttling feature with
hysteresis. At low temperature, SW1 is on and SW2
connects to the 1.18V side. The total current going into NTC
pin is 60µA. The voltage on NTC pin is higher than threshold
voltage of 1.18V and the comparator output is low. VR_TT#
is pulling up high by the external resistor.
54µA 6µA
NTC
+
V_{NTC RNTC}
-
R_s
1.20V
SW1
VR_TT#
-
+
SW2
1.18V
INTERNAL TO
ISL6262
FIGURE 32. CIRCUITRY ASSOCIATED WITH THE THERMAL
THROTTLING FEATURE IN ISL6262
20
FN9199.2
May 15, 2006