ISL6326CRZ-T Intersil, ISL6326CRZ-T Datasheet - Page 22

• Manufacturer Part Number: ISL6326CRZ-T
• Description: IC CTRLR PWM 4PHASE BUCK 40-QFN
• Manufacturer: Intersil

Specifications of ISL6326CRZ-T

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 275kHz
• Duty Cycle: 25%
• 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: 0°C ~ 70°C
• Package / Case: 40-VFQFN, 40-VFQFPN
• Frequency-max: 275kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Based on the NTC temperature characteristics and the
desired threshold of the VR_HOT signal, the pull-up resistor
R
R
temperature T3.
The NTC resistance at the set point T2 and release point T1
of VR_FAN signal can be calculated in Equations 18 and 19:
With the NTC resistance value obtained from Equations 17
and 18, the temperature value T2 and T1 can be found from
the NTC datasheet.
Temperature Compensation
ISL6326 supports inductor DCR sensing, or resistive
sensing techniques. The inductor DCR has a positive
R
R
R
FIGURE 13. VR_HOT AND VR_FAN SIGNAL vs TM VOLTAGE
TM1
NTC(T3)
TM1
NTC T2
NTC T1
FIGURE 12. THE RATIO OF TM VOLTAGE TO NTC
0.39*V
0.33*V
0.28*V
VR_HOT
VR_FAN
(
(
of TM pin is given by Equation 17:
=
100
TM
90
80
70
60
50
40
30
20
CC
CC
CC
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
V
TM
40
)
TEMPERATURE (°C)
(
(
/V
CC
)
)
T1
22
60
vs TEMPERATURE
T2
80
T3
100
TEMPERATURE
120
(EQ. 17)
(EQ. 18)
(EQ. 19)
140
ISL6326
°C
temperature coefficient, which is about +0.38%/°C. 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. ISL6326 provides two methods:
Integrated Temperature Compensation
When the TCOMP voltage is equal or greater than VCC/15,
ISL6326 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 14.
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
1. Integrated temperature compensation
2. External temperature compensation
V
V
FIGURE 14. BLOCK DIAGRAM OF INTEGRATED
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
OVERCURRENT PROTECTION
CHANNEL CURRENT
I 4
DROOP AND
SENSE
I 3
I 2
I 1
May 5, 2008
FN9262.1
I SEN4
I SEN3
I SEN2
I SEN1