ISL6326 Intersil Corporation, ISL6326 Datasheet - Page 22

• Manufacturer Part Number: ISL6326
• Description: 4-Phase PWM Controller
• Manufacturer: Intersil Corporation

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VR_HOT signals respectively. The VR_FAN signal is set to
high when the TM voltage is lower than 33% of VCC voltage,
and is pulled to GND when the TM voltage increases to
above 39% of VCC voltage. The VR_FAN signal is set to
high when the TM voltage goes below 28% of VCC voltage,
and is pulled to GND when the TM voltage goes back to
above 33% of VCC voltage. Figure 13 shows the operation
of those signals.
FIGURE 11. BLOCK DIAGRAM OF THERMAL MONITORING
FIGURE 12. THE RATIO OF TM VOLTAGE TO NTC
o
c
100%
90%
80%
70%
60%
50%
40%
30%
20%
VCC
R
R
TM
TM1
NTC
0
FUNCTION
TEMPERATURE WITH RECOMMENDED PARTS
20
0.33V
V
0.28V
40
TM
Tem perature (
/ V
CC
CC
CC
22
60
vs. Tem perature
80
o
C)
100
120
VR_FAN
VR_HOT
140
ISL6326
Based on the NTC temperature characteristics and the
desired threshold of the VR_HOT signal, the pull-up resistor
RTM1 of TM pin is given by:
R
temperature T3.
The NTC resistance at the set point T2 and release point T1
of VR_FAN signal can be calculated as:
With the NTC resistance value obtained from Equations 17
and 18, the temperature value T2 and T1 can be found from
the NTC datasheet.
Temperature Compensation
ISL6326 supports inductor DCR sensing, or resistive
sensing techniques. The inductor DCR has a positive
temperature coefficient, which is about +0.38%/°C. Since the
voltage across inductor is sensed for the output current
information, the sensed current has the same positive
temperature coefficient as the inductor DCR.
In order to obtain the correct current information, there
should be a way to correct the temperature impact on the
current sense component. ISL6326 provides two methods:
integrated temperature compensation and external
temperature compensation.
Integrated Temperature Compensation
When the TCOMP voltage is equal or greater than VCC/15,
ISL6326 will utilize the voltage at TM and TCOMP pins to
compensate the temperature impact on the sensed current.
The block diagram of this function is shown in Figure 14.
R
R
R
FIGURE 13. VR_HOT AND VR_FAN SIGNAL vs TM VOLTAGE
NTC(T3)
TM1
NTC T2
NTC T1
VR_FAN
VR_HOT
0.39*Vcc
0.33*Vcc
0.28*Vcc
(
(
TM
=
2.75xR
)
)
is the NTC resistance at the VR_HOT threshold
=
=
1.267xR
1.644xR
NTC T3
(
NTC T3
NTC T3
)
(
(
)
)
T1
T2
T3
Temperature
April 21, 2006
(EQ. 17)
(EQ. 18)
(EQ. 19)
FN9262.0