ISL6326 Intersil Corporation, ISL6326 Datasheet - Page 23

• Manufacturer Part Number: ISL6326
• Description: 4-Phase PWM Controller
• Manufacturer: Intersil Corporation

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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, ISL6326 converts the TM pin voltage
to a 6-bit TM digital signal for temperature compensation.
With the non-linear A/D converter of ISL6326, 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 12.
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
different voltage divider is used for the TM function, the
TCOMP voltage can also be used to compensate for the
difference between the recommended TM voltage curve in
Figure 13 and that of the actual design. According to the
VCC voltage, ISL6326 converts the TCOMP pin voltage to a
4-bit TCOMP digital signal as TCOMP factor N.
The TCOMP factor N is an integer between 0 and 15. The
integrated temperature compensation function is disabled for
N = 0. For N = 4, the NTC temperature is equal to the
temperature of the current sense component. For N < 4, the
NTC is hotter than the current sense component. The NTC is
cooler than the current sense component for N > 4. When
N > 4, the larger TCOMP factor N, the larger the difference
between the NTC temperature and the temperature of the
current sense component.
V
V
FIGURE 14. BLOCK DIAGRAM OF INTEGRATED
CC
CC
R
R
R
R
TCOMP
NTC
TC2
TM1
TC1
TM
TEMPERATURE COMPENSATION
Non-linear
A/D
D/A
4-bit
A/D
k
23
i
Over current protection
I
Channel current
4
Droop &
sense
I
3
I
2
I
1
I
I
I
I
sen4
sen3
sen2
sen1
ISL6326
ISL6326 multiplexes the TCOMP factor N with the TM digital
signal to obtain the adjustment gain to compensate the
temperature impact on the sensed channel current. The
compensated channel current signal is used for droop and
overcurrent protection functions.
Design Procedure
10. Record the output voltage as V1 immediately after the
11. If the output voltage increases over 2mV as the
External Temperature Compensation
By pulling the TCOMP pin to GND, the integrated
temperature compensation function is disabled. And one
external temperature compensation network, shown in
Figure 15, can be used to cancel the temperature impact on
the droop (i.e. load line).
1. Properly choose the voltage divider for the TM pin to
2. Run the actual board under the full load and the desired
3. After the board reaches the thermal steady state, record
4. Use the following equation to calculate the resistance of
5. Use the following equation to calculate the TCOMP
6. Choose an integral number close to the above result for
7. Choose the pull-up resistor R
8. If N = 15, do not need the pull-down resistor R
9. Run the actual board under full load again with the proper
match the TM voltage vs temperature curve with the
recommended curve in Figure 12.
cooling condition.
the temperature (T
(inductor or MOSFET) and the voltage at TM and VCC
pins.
the TM NTC, and find out the corresponding NTC
temperature T
R
factor N:
N
the TCOMP factor. If this factor is higher than 15, use
N = 15. If it is less than 1, use N = 1.
otherwise obtain R
resistors connected to the TCOMP pin.
output voltage is stable with the full load. Record the
output voltage as V2 after the VR reaches the thermal
steady state.
temperature increases, i.e. V2-V1 > 2mV, reduce N and
redesign R
as the temperature increases, i.e. V1-V2 > 2mV, increase
N and redesign R
R
NTC T
TC2
=
209x T
------------------------------------------------------- -
(
=
NTC
3xT
NxR
---------------------- -
(
15 N
TC2
NTC
)
CSC
–
TC1
=
NTC
; if the output voltage decreases over 2mV
V
------------------------------- -
V
+
–
TM
CC
400
T
TC2
CSC
TC2
NTC
from the NTC datasheet.
xR
–
.
V
TM1
) of the current sense component
)
TM
by the following equation:
+
4
TC1
(typical 10kΩ).
TC2
April 21, 2006
(EQ. 20)
(EQ. 21)
(EQ. 22)
FN9262.0
,