ISL6316_06 Datasheet, PDF (21/29 Pages) Intersil Corporation – Enhanced 4-Phase PWM Controller with 6-Bit VID Code Capable of Precision rDS(ON) or DCR Differential Current Sensing for VR10 Application

VCC
ISL6316
VR_FAN
The NTC resistance at the set point T2 and release point T1
of VR_FAN signal can be calculated as:
R_NTC(T2) = 1.267xR_NTC(T3)
(EQ. 17)
R_NTC(T1) = 1.644xR_NTC(T3)
(EQ. 18)
R_TM1
TM
o_c
R_NTC
0.33V_CC
0.28V_CC
VR_HOT
FIGURE 14. BLOCK DIAGRAM OF THERMAL MONITORING
FUNCTION
V_TM/V_CC vs TEMPERATURE
100
90
80
70
60
50
40
30
20
0 20 40 60 80 100 120 140
TEMPERATURE (°)
FIGURE 15. THE RATIO OF TM VOLTAGE TO NTC
TEMPERATURE WITH RECOMMENDED PARTS
TM
0.39*VCC
0.33*VCC
0.28*VCC
VR_FAN
VR_HOT
TEMPERATURE
T1 T2 T3
FIGURE 16. VR_HOT AND VR_FAN SIGNAL vs TM VOLTAGE
With the NTC resistance value obtained from Equations17
and 18, the temperature value T2 and T1 can be found from
the NTC datasheet.
Temperature Compensation
ISL6316 supports inductor DCR sensing, MOSFET r_DS(ON)
sensing, or resistive sensing techniques. Both inductor DCR
and MSOFET r_DS(ON) have the positive temperature
coefficient, which is about +0.38%/°C. Because the voltage
across inductor or MOSFET is sensed for the output current
information, the sensed current has the same positive
temperature coefficient as the inductor DCR or MOSFET
r_DS(ON).
In order to obtain the correct current information, there should
be a way to correct the temperature impact on the current
sense component. ISL6316 provides two methods: integrated
temperature compensation and external temperature
compensation.
Integrated Temperature Compensation
When TCOMP voltage is equal or greater than VCC/15,
ISL6316 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 17.
V_CC
RTM1
TM
°C _RNTC
V_CC
NON-LINEAR
A/D
CHANNEL CURRENT
SENSE
I4
I3
I2
I1
I_SEN4
I_SEN3
I_SEN2
I_SEN1
D/A
KI
R _TC1
TCOMP
RTC2
4-BIT
A/D
DROOP AND OVERCURRENT
PROTECTION
FIGURE 17. BLOCK DIAGRAM OF INTEGRATED
TEMPERATURE COMPENSATION
21
FN9227.1
December 12, 2006