ISL6336D Datasheet, PDF (23/30 Pages) Intersil Corporation – VR11.1, 6-Phase PWM Controller with Phase Dropping,Droop Disabled and Load Current Monitoring Features

ISL6336D
signals respectively. The VR_FAN signal is set to high when the
TM voltage is lower than 39.1% of VCC voltage, and is pulled to
GND when the TM voltage increases to above 45.1% of VCC
voltage. The VR_FAN signal is set to high when the TM voltage
goes below 33.3% of VCC voltage, and is pulled to GND when the
TM voltage goes back to above 39.1% of VCC voltage. Figure 19
shows the operation of those signals.
VCC
VR_FAN
R _TM1
TM
°_C
R _NTC
0.391VCC
0.333VCC
VR_HOT
FIGURE 17. BLOCK DIAGRAM OF THERMAL MONITORING
FUNCTION
100
90
80
70
60
50
40
30
20
0
20
40 60
80 100 120 140
TEMPERATURE (°C)
FIGURE 18. THE RATIO OF TM VOLTAGE TO NTC TEMPERATURE
WITH RECOMMENDED PARTS
TM
0.451*Vcc
0.391*Vcc
0.333*Vcc
VR_FAN
VR_HOT
TEMPERATURE
T1 T2 T3
FIGURE 19. VR_HOT AND VR_FAN SIGNAL vs TM VOLTAGE
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 Equation 17:
R_TM1 = 2.75xR_{NTCT3}
(EQ. 17)
R_NTC(T3) is the NTC resistance at the VR_HOT threshold
temperature T3.
The NTC resistance at the set point T2 and release point T1 of
VR_FAN signal can be calculated as shown in Equations 18 and 19:
R_{NTCT2} = 1.267xR_{NTCT3}
(EQ. 18)
R_{NTCT1} = 1.644xR_{NTCT3}
(EQ. 19)
With the NTC resistance value obtained from Equations 18 and
19, the temperature value T2 and T1 can be found from the NTC
datasheet.
Temperature Compensation
The ISL6336D supports inductor DCR sensing, or resistive
sensing techniques. The inductor DCR has a positive temperature
coefficient, which is about +0.385%/°C. Since the voltage across
the 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. The ISL6336D provides two methods: integrated
temperature compensation and external temperature
compensation.
Integrated Temperature Compensation
When the TCOMP voltage is equal or greater than VCC/15,
ISL6336D 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 20.
V_CC
R _TM1
TM
o_c
R _NTC
V_CC
R _TC1
TCOMP
R _TC2
NON-LINEAR
A/D
CHANNEL
CURRENT
SENSE
I₄
I₃
I₂
I_SEN4
I_SEN3
I_SEN2
I_SEN1
I₁
D/A
k_i
4-BIT
A/D
OVERCURRENT
PROTECTION
FIGURE 20. BLOCK DIAGRAM OF INTEGRATED TEMPERATURE
COMPENSATION
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FN8320.0
October 6, 2014