ISL6334 INTERSIL [Intersil Corporation], ISL6334 Datasheet - Page 23

• Manufacturer Part Number: ISL6334
• Description: VR11.1, 4-Phase PWM Controller with Light Load Efficiency Enhancement and Load Current Monitoring
• Manufacturer: INTERSIL [Intersil Corporation]

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 18:
R
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 19
and 20:
With the NTC resistance value obtained from Equations 19
and 20, the temperature value T2 and T1 can be found from
the NTC datasheet.
Temperature Compensation
The ISL6334, ISL6334A supports inductor DCR sensing, or
resistive sensing techniques. The inductor DCR has a
positive temperature coefficient, which is about +0.385%/°C.
R
R
R
FIGURE 14. VR_HOT AND VR_FAN SIGNAL vs TM VOLTAGE
NTC(T3)
TM1
NTC T2
NTC T1
FIGURE 13. THE RATIO OF TM VOLTAGE TO NTC
VR_HOT
VR_FAN
0.451*Vcc
0.391*Vcc
0.333*Vcc
(
(
TM
=
100
90
80
70
60
50
40
30
20
2.75xR
)
)
is the NTC resistance at the VR_HOT threshold
0
=
=
1.267xR
1.644xR
TEMPERATURE WITH RECOMMENDED PARTS
NTC T3
20
(
NTC T3
NTC T3
40
)
TEMPERATURE (°C)
(
(
T1
)
)
60
23
T2
80
T3
100
TEMPERATURE
120
ISL6334, ISL6334A
140
(EQ. 18)
(EQ. 19)
(EQ. 20)
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. ISL6334, ISL6334A provides two
methods: integrated temperature compensation and external
temperature compensation.
Integrated Temperature Compensation
When the TCOMP voltage is equal or greater than VCC/15,
ISL6334, ISL6334A 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 15.
When the TM NTC is placed close to the current sense
component (inductor), the temperature of the NTC will track
the temperature of the current sense component. Therefore
the TM voltage can be utilized to obtain the temperature of
the current sense component.
Based on VCC voltage, ISL6334, ISL6334A converts the TM
pin voltage to a 6-bit TM digital signal for temperature
compensation. With the non-linear A/D converter of
ISL6334, ISL6334A, the TM digital signal is linearly
proportional to the NTC temperature. For accurate
temperature compensation, the ratio of the TM voltage to the
NTC temperature of the practical design should be similar to
that in Figure 13.
Depending on the location of the NTC and the airflow, the
NTC may be cooler or hotter than the current sense
component. The TCOMP pin voltage can be utilized to
correct the temperature difference between NTC and the
current sense component. When a different NTC type or
o
FIGURE 15. BLOCK DIAGRAM OF INTEGRATED
c
V
V
CC
CC
R
R
R
R
TCOMP
NTC
TC2
TM1
TC1
TM
TEMPERATURE COMPENSATION
NON-LINEAR
4-BIT
D/A
A/D
A/D
k
i
I
4
OVERCURRENT
PROTECTION
DROOP AND
CHANNEL
CURRENT
SENSE
I
3
I
2
February 26, 2008
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1
FN6482.0
I
I
I
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sen4
sen3
sen2
sen1