isl6307b Intersil Corporation, isl6307b Datasheet - Page 26

• Manufacturer Part Number: isl6307b
• Description: 6-phase Vr11 Pwm Controller With 8-bit Vid Code Capable Of Precision Rds On Or Dcr Differential Current Sensing For Applications In Which Supply Voltage Is Higher Than 5v
• Manufacturer: Intersil Corporation

ISL6307B multiplexes the TCOMP factor N with the TM
digital signal to obtain the adjustment gain to compensate
the temperature impact on the sensed channel current. The
compensated channel current signal is used for droop and
overcurrent protection functions.
Design Procedure:
10. Record the output voltage as V1 immediately after the
11. If the output voltage increases over 2mV as the
The design spreadsheet is available for those calculations.
External Temperature Compensation
By setting the voltage of TCOMP pin to 0, the integrated
temperature compensation function is disabled. And one
external temperature compensation network, shown in
Figure 18, can be used to cancel the temperature impact on
the droop (i.e. load line).
1. Properly choose the voltage divider for TM pin to match
2. Run the actual board under the full load and the desired
3. After the board reaches the thermal steady state, record
4. Use the following equation to calculate the resistance of
5. Use the following equation to calculate the TCOMP factor
6. Choose an integral number close to the above result for
7. Choose the pull-up resistor R
8. If N = 15, do not need the pull-down resistor R
9. Run the actual board under full load again with the proper
the TM voltage Vs temperature curve with the
recommended curve in Figure 16.
cooling condition.
the temperature (T
(inductor or MOSFET) and the voltage at TM and Vcc
pins.
the TM NTC, and find out the corresponding NTC
temperature T
R
N:
N
the TCOMP factor. If this factor is higher than 15, use
N=15. If it is less than 1, use N = 1.
otherwise obtain R
R
resistors to TCOMP pin.
output voltage is stable with the full load; Record the
output voltage as V2 after the VR reaches the thermal
steady state.
temperature increases, i.e. V2-V1 > 2mV, reduce N and
redesign R
as the temperature increases, i.e. V1-V2 > 2mV, increase
N and redesign R
NTC T
TC2
=
209x T
------------------------------------------------------- -
(
=
NTC
3xT
NxR
---------------------- -
(
15 N
TC2
NTC
)
CSC
–
TC1
=
NTC
; if the output voltage decreases over 2mV
V
------------------------------- -
V
+
–
TM
CC
400
T
TC2
CSC
TC2
NTC
from the NTC datasheet.
xR
–
.
V
TM1
)
) of the current sense component
TM
by the following equation:
+
26
4
TC1
(typical 10kΩ).
TC2
(EQ. 21)
(EQ. 22)
(EQ. 23)
,
ISL6307B
The sensed current will flow out of IDROOP pin and develop
the droop voltage across the resistor (R
VDIFF pins. If RFB resistance reduces as the temperature
increases, the temperature impact on the droop can be
compensated. A NTC resistor can be placed close to the
power stage and used to form R
temperature characteristics of the NTC, a resistor network is
needed to make the equivalent resistance between FB and
VDIFF pin is reverse proportional to the temperature.
The external temperature compensation network can only
compensate the temperature impact on the droop, while it
has no impact to the sensed current inside ISL6307B.
Therefore this network cannot compensate for the
temperature impact on the overcurrent protection function.
General Design Guide
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multiphase
power converter. It is assumed that the reader is familiar with
many of the basic skills and techniques referenced below. In
addition to this guide, Intersil provides complete reference
designs that include schematics, bills of materials, and
example board layouts for all common microprocessor
applications.
Power Stages
The first step in designing a multiphase converter is to
determine the number of phases. This determination
depends heavily on the cost analysis which in turn depends
on system constraints that differ from one design to the next.
Principally, the designer will be concerned with whether
components can be mounted on both sides of the circuit
board; whether through-hole components are permitted; and
the total board space available for power-supply circuitry.
Generally speaking, the most economical solutions are
those in which each phase handles between 15 and 20A. All
surface-mount designs will tend toward the lower end of this
current range. If through-hole MOSFETs and inductors can
FIGURE 19. VOLTAGE AT IDROOP PIN WITH A RESISTOR
PLACED FROM IDROOP PIN TO GND WHEN
LOAD CURRENT CHANGES
IDROOP
COMP
VDIFF
FB
FB
. Due to the non-linear
o
FB
c
) between FB and
March 9, 2006
FN9225.0