ISL6307A Datasheet, PDF (24/33 Pages) Intersil Corporation – Ultra-high bandwidth 6-Phase PWM Controller with 8 Bit VID Code Capable of Precision RDS(ON) or DCR Differential Current Sensing

ISL6307A
Current Sense Output
The ISL6307A has two current sense output pins, IDROOP
and IOUT and they are identical. In a typical application
where load-line is required, the IDROOP pin is connected to
the FB pin. The IOUT pin was designed for load current
measurement. As shown in typical application schematics
on pages 4 to 7, load current information can be obtained by
measuring the voltage at IOUT pin with a resistor connected
to ground. When the programmable temperature
compensation function of ISL6307A is properly used, the
output current at IOUT pin is proportional to load current, as
shown in Figure 17.
Those numbers are recommended for 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 is set high when TM
is lower than 33% of Vcc, and is pulled to GND when TM
increases to above 39% of Vcc. VR_HOT is set high when
TM goes below 28% of Vcc, and is pulled to GND when TM
goes back to above 33% of Vcc. Figure 20 shows operation
of thermal monitoring and indication.
VCC
VR_FAN
V_IOUT, 200mV/DIV
R_TM1
TM
o_c
R_NTC
0.33V_CC
0.28V_CC
VR_HOT
0A
50A
100A
FIGURE 17. VOLTAGE AT IOUT PIN WITH ARESISTOR TO
GND WHEN LOAD CURRENT CHANGES
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 outputs, and external
pull-up resistors are required.
VR_FAN indicates that the temperature of the voltage
regulator is high and more cooling airflow is needed.
VR_HOT 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 may be tied
to the CPU’s PROCHOT# signal.
The diagram of thermal monitoring function block is shown in
Figure 18. 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 the TM pin. As the temperature of the
power stage increases, the resistance of the NTC will
reduce, resulting in the reduced voltage at the TM pin.
Figure 19 shows the TM voltage over temperature for a
typical design with a recommended 6.8kΩ NTC (P/N:
NTHS0805N02N6801 from Vishay) and 1kΩ resistor RTM1.
FIGURE 18. BLOCK DIAGRAM OF THERMAL MONITORING
FUNCTION
100%
90%
80%
70%
60%
50%
40%
30%
20%
0
V_TM / V_CC vs . Te m pe rature
20 40 60 80 100 120 140
Te m pe rature (^oC)
FIGURE 19. THE RATIO OF TM VOLTAGE TO NTC
TEMPERATURE WITH RECOMMENDED PARTS
24
FN9236.0
February 6, 2006