ISL6334ACRZ Intersil, ISL6334ACRZ Datasheet - Page 24

• Manufacturer Part Number: ISL6334ACRZ
• Description: IC CTRLR PWM 4PHASE BUCK 40-QFN
• Manufacturer: Intersil

Specifications of ISL6334ACRZ

• Applications: Controller, Intel VR11.1
• Voltage - Input: 3 ~ 12 V
• Number Of Outputs: 1
• Voltage - Output: 0.5 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 40-VFQFN, 40-VFQFPN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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
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 14 and that of the actual design. According to the
VCC voltage, ISL6334, ISL6334A 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.
ISL6334, ISL6334A 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
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 Equation 21 to calculate the resistance of the TM
5. Use Equation 22 to calculate the TCOMP factor N:
match the TM voltage vs temperature curve with the
recommended curve in Figure 13.
cooling condition.
the temperature (T
(inductor or MOSFET) and the voltage at TM and VCC
pins.
NTC, and find out the corresponding NTC temperature
T
R
N
NTC
NTC T NTC
=
209x T
------------------------------------------------------- -
(
from the NTC datasheet.
3xT
(
NTC
)
CSC
=
V
------------------------------- -
V
+
–
TM
CC
400
T
CSC
NTC
xR
–
V
TM1
)
) of the current sense component
TM
+
24
4
ISL6334, ISL6334A
(EQ. 21)
(EQ. 22)
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. In addition,
one external temperature compensation network, shown in
Figure 16, can be used to cancel the temperature impact on
the droop (i.e., load line).
The sensed current will flow out of the FB pin and develop a
droop voltage across the resistor equivalent (R
the FB and VDIFF pins. If R
temperature increases, the temperature impact on the droop
can be compensated. An NTC resistor can be placed close to
the power stage and used to form R
temperature characteristics of the NTC, a resistor network is
needed to make the equivalent resistance between the FB
and VDIFF pins reverse proportional to the temperature.
The external temperature compensation network can only
compensate the temperature impact on the droop, while it has
no impact to the sensed current inside ISL6334, ISL6334A.
Therefore, this network cannot compensate for the
temperature impact on the overcurrent protection function.
6. Choose an integral number close to the above result for
7. Choose the pull-up resistor R
8. If N = 15, one does not need the pull-down resistor R
9. Run the actual board under full load again with the proper
FIGURE 16. EXTERNAL TEMPERATURE COMPENSATION
the TCOMP factor. If this factor is higher than 15, use
N = 15. If it is less than 1, use N = 1.
If 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
TC2
=
NxR
---------------------- -
15 N
o
C
TC2
–
TC1
; if the output voltage decreases over 2mV
C O M P
V D IF F
TC2
F B
FB
using Equation 23:
resistance reduces as the
TC2
TC1
.
IN T E R N A L
FB
IS L 6 3 3 4 A
IS L 6 3 3 4 ,
C IR C U IT
(typical 10kΩ);
. Due to the non-linear
IS E N
FB
) between
May 28, 2009
(EQ. 23)
FN6482.1
TC2
.