isl6307b Intersil Corporation, isl6307b Datasheet - Page 24

• 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

Thermal monitoring (VR_HOT/VR_FAN)
There are two thermal signals to indicate the temperature
status of the voltage regulator: VR_HOT and VR_FAN. Both
VR_FAN and VR_HOT are open-drain output, and external
pull-up resistors are required.
VR_FAN signal indicates that the temperature of the voltage
regulator is high and more cooling airflow is needed.
VR_HOT signal can be used to inform the system that the
temperature of the voltage regulator is too high and the CPU
should reduce its power consumption. VR_HOT signal may
be tied to the CPU’s PROCHOT# signal.
The diagram of thermal monitoring function block is shown in
Figure 15. One NTC resistor should be placed close to the
power stage of the voltage regulator to sense the operational
temperature, and one pull-up resistor is needed to form the
voltage divider for TM pin. As the temperature of the power
stage increases, the resistance of the NTC will reduce,
resulting in the reduced voltage at TM pin. Figure 16 shows
the TM voltage over the temperature for a typical design with
a recommended 6.8kΩ NTC (P/N: NTHS0805N02N6801
from Vishay) and 1kΩ resistor RTM1. We recommend using
those resistors for the accurate temperature compensation.
There are two comparators with hysteresis to compare the
TM pin voltage to the fixed thresholds for VR_FAN and
VR_HOT signals respectively. VR_FAN signal is set to high
when TM voltage is lower than 33% of Vcc voltage, and is
pulled to GND when TM voltage increases to above 39% of
Vcc voltage. VR_HOT is set to high when TM voltage goes
below 28% of Vcc voltage, and is pulled to GND when TM
voltage goes back to above 33% of Vcc voltage. Figure 17
shows the operation of those signals.
FIGURE 14. VOLTAGE AT IOUT PIN WITH A NTC NETWORK
0A
PLACED BETWEEN IOUT TO GROUND WHEN
LOAD CURRENT CHANGES
V_IOUT, 200mV/DIV
24
50A
100A
ISL6307B
FIGURE 15. BLOCK DIAGRAM OF THERMAL MONITORING
FIGURE 16. THE RATIO OF TM VOLTAGE TO NTC
FIGURE 17. VR_HOTAND VR_FAN SIGNAL vs TM VOLTAGE
o
VR_HOT
VR_FAN
c
0.39*Vcc
0.33*Vcc
0.28*Vcc
100%
90%
80%
70%
60%
50%
40%
30%
20%
TM
VCC
R
R
TM
TM1
NTC
0
FUNCTION
TEMPERATURE WITH RECOMMENDED PARTS
20
0.33V
0.28V
V
40
TM
Tem perature (
/ V
CC
CC
CC
60
T1
vs. Tem perature
T2
80
o
T3
C)
100
Temperature
120
VR_FAN
VR_HOT
March 9, 2006
FN9225.0
140