ISL6334CCRZ Intersil, ISL6334CCRZ Datasheet - Page 23

• Manufacturer Part Number: ISL6334CCRZ
• Description: IC CTRLR PWM SYNC BUCK 40-QFN
• Manufacturer: Intersil

Specifications of ISL6334CCRZ

• 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
• Rohs Compliant: YES
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

We recommend using those resistors for the accurate
temperature compensation.
There is an comparator with hysteresis to compare the TM
pin voltage to the fixed threshold for the VR_HOT signal.
The VR_HOT signal is set to high when the TM voltage goes
below 33.3% of VCC voltage, and is pulled to GND when the
TM voltage goes back to above 39.1% of VCC voltage.
Figure 14 shows the operation of those signals.
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 can be calculated as
shown in Equations 19:
With the NTC resistance value obtained from Equations 18
and 19, the temperature value T3 and T2 can be found from
the NTC datasheet.
R
R
NTC(T3)
TM1
NTC T2
FIGURE 13. THE RATIO OF TM VOLTAGE TO NTC
VR_HOT
0.391*Vcc
0.333*Vcc
(
TM
=
100
FIGURE 14. VR_HOT SIGNAL vs TM VOLTAGE
90
80
70
60
50
40
30
20
2.75xR
)
is the NTC resistance at the VR_HOT threshold
0
=
1.267xR
TEMPERATURE WITH RECOMMENDED PARTS
NTC T3
20
(
NTC T3
40
)
TEMPERATURE (°C)
(
)
60
23
T2
80
T3
100
TEMPERATURE
120
ISL6334B, ISL6334C
140
(EQ. 18)
(EQ. 19)
Temperature Compensation
The ISL6334B, ISL6334C supports inductor DCR sensing,
or resistive sensing techniques. The inductor DCR has a
positive temperature coefficient, which is about +0.385%/°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. ISL6334B, ISL6334C provides
two methods: integrated temperature compensation and
external temperature compensation.
Integrated Temperature Compensation
When the TCOMP voltage is equal or greater than VCC/15,
ISL6334B, ISL6334C 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, ISL6334B, ISL6334C converts the
TM pin voltage to a 6-bit TM digital signal for temperature
compensation. With the non-linear A/D converter of
ISL6334B, ISL6334C, 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.
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
August 31, 2010
I
1
FN6689.2
I
I
I
I
sen4
sen3
sen2
sen1