ISL6306IRZ Intersil, ISL6306IRZ Datasheet - Page 26

• Manufacturer Part Number: ISL6306IRZ
• Description: IC CTRLR PWM 4-PHASE 40-QFN
• Manufacturer: Intersil

Specifications of ISL6306IRZ

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 275kHz
• Duty Cycle: 66.7%
• Voltage - Supply: 4.75 V ~ 5.25 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-VFQFN, 40-VFQFPN
• Frequency-max: 275kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Depending on the location of the NTC and the airflow, the
NTC may be cooler or hotter than the current sense
component. 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, TCOMP voltage
can also be used to compensate for the difference between
the recommended TM voltage curve in Figure 16 and that of
the actual design. According to the VCC voltage, ISL6306
converts the TCOMP pin voltage to a 4-bit TCOMP digital
signal as TCOMP factor N.
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.
ISL6306 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 TM pin to match
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 20 to calculate the resistance of the TM
5. Use Equation 21 to calculate the TCOMP factor N:
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
the TM voltage V
recommended curve in Figure 15.
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
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
R
N
R
NTC
NTC T NTC
TC2
=
209x T
------------------------------------------------------- -
(
from the NTC datasheet.
=
3xT
NxR
---------------------- -
(
15 N
NTC
)
CSC
–
TC1
=
V
------------------------------- -
V
+
–
TM
S
CC
400
T
CSC
TC2
NTC
temperature curve with the
xR
–
V
TM1
)
) of the current sense component
TM
by Equation 22:
+
26
4
TC1
(typical 10kΩ).
TC2
(EQ. 20)
(EQ. 21)
(EQ. 22)
,
ISL6306
10. Record the output voltage as V1 immediately after the
11. If the output voltage increases over 2mV as the
The design spreadsheet is available for those calculations.
External Temperature Compensation
By setting the voltage of TCOMP pin to 0, the integrated
temperature compensation function is disabled. And one
external temperature compensation network, shown in
Figure 18, can be used to cancel the temperature impact on
the droop (i.e. load line).
The sensed current will flow out of IDROOP pin and develop
the droop voltage across the resistor equivalent (R
between FB and VDIFF pins. If R
the 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
non-linear temperature characteristics of the NTC, a resistor
network is needed to make the equivalent resistance
between FB and VDIFF pin is 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 ISL6306.
Therefore this network cannot compensate for the
temperature impact on the overcurrent protection function.
Current Sense Output
The current from IDROOP pin is the sensed average current
inside ISL6306. In typical application, IDROOP pin is
connected to FB pin for the application where load line is
9. Run the actual board under full load again with the proper
FIGURE 18. VOLTAGE AT IDROOP PIN WITH A RESISTOR
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
PLACED FROM IDROOP PIN TO GND WHEN
LOAD CURRENT CHANGES
TC2
IDROOP
; if the output voltage decreases over 2mV
COMP
VDIFF
FB
TC2
FB
.
resistance reduces as
o
c
FB
. Due to the
FB
May 5, 2008
)
FN9226.1