ISL6262CRZ Intersil, ISL6262CRZ Datasheet - Page 21

• Manufacturer Part Number: ISL6262CRZ
• Description: IC CORE REG 2PHASE 48-QFN
• Manufacturer: Intersil

Specifications of ISL6262CRZ

• Applications: Converter, Intel IMVP-6
• Voltage - Input: 5 ~ 25 V
• Number Of Outputs: 1
• Voltage - Output: 0.3 ~ 1.5 V
• Operating Temperature: -10°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 48-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

When temperature increases, the NTC resistor value on
NTC pin decreases. Thus, the voltage on NTC pin
decreases to a level lower than 1.18V. The comparator
output changes polarity and turns SW1 off and connects
SW2 to 1.20V. This pulls VR_TT# low and sends the signal
to start thermal throttle. There is a 6µA current reduction on
NTC pin and 20mV voltage increase on threshold voltage of
the comparator in this state. The VR_TT# signal will be used
to change the CPU operation and decrease the power
consumption. When the temperature goes down, the NTC
thermistor voltage will eventually go up. The NTC pin voltage
increases to 1.20V, the comparator output will then be able
to flip back. Such a temperature hysteresis feature of
VR_TT# is illustrated in Figure 33. T
temperature point at which the VR_TT# goes from low to
high due to the system temperature rise. T
lower temperature point at which the VR_TT# goes high
from low because the system temperature decreases to the
normal level.
Usually, the NTC thermistor's resistance can be
approximated by the following formula:
T is the temperature of the NTC thermistor and b is a
parameter constant depending on the thermistor material.
T
is derived. Most common temperature for T
example, there are commercial NTC thermistor products
with b = 2750k, b = 2600k, b = 4500k or b = 4250k.
From the operation principle of the VR_TT# circuit
explained, the NTC resistor satisfies the following equation
group.
From Equation 6 and Equation 7, the following can be
derived,
R
R
R
R
o
NTC
NTC
NTC
NTC
is the reference temperature in which the approximation
FIGURE 33. TEMPERATURE HYSTERESIS OF VR_TT#
Logic_1
Logic_0
VR_TT#
T ( )
(
(
(
T
T
T
1
2
2
)
)
) R
=
+
+
–
R
R
R
NTC
NTCTo
S
S
=
=
(
1.18V
--------------- -
-------------- -
54μA
60μA
1.2V
T
1
•
)
e
=
b
=
=
2.55kΩ
•
⎛
⎝
22.22kΩ
19.67kΩ
------------------- -
T
+
21
1
273
T
2
–
-----------------------
To
1
represents the higher
T
+
1
1
273
2
o
⎞
⎠
represents the
is 25°C. For
T (°C)
(EQ. 5)
(EQ. 6)
(EQ. 7)
(EQ. 8)
ISL6262
Using Equation 5 into Equation 8, the required nominal NTC
resistor value can be obtained by:
For some cases, the constant b is not accurate enough to
approximate the NTC resistor value, the manufacturer
provides the resistor ratio information at different
temperature. The nominal NTC resistor value may be
expressed in another way as follows:
where
nominal value. Most datasheet of the NTC thermistor gives
the normalized resistor value based on its value at 25°C.
Once the NTC thermistor resistor is determined, the series
resistor can be derived by:
Once R
at T
One example of using Equations 9, 10 and 11 to design a
thermal throttling circuit with the temperature hysteresis
100°C to 105°C is illustrated as follows. Since T
and T
the Equation 9 gives the required NTC nominal resistance as
In fact, the datasheet gives the resistor ratio value at 100°C
to 105°C, which is 0.03956 and 0.03322 respectively. The b
value 4700K in Panasonic datasheet only covers to 85°C.
Therefore, using Equation 10 is more accurate for 100°C
design, the required NTC nominal resistance at 25°C is
402kΩ. The closest NTC resistor value from manufacturer is
470kΩ. So the series resistance is given by Equation 11 as
follows,
Furthermore, the NTC resistance at T
From the NTC datasheet, it can be concluded that the actual
temperature T
calculated to be 97.7°C. Check the NTC datasheet to decide
R
R
R
R
T
R
R
R
2_actual
NTCTo
NTCTo
S
NTC_T
NTC_To
S
NTC_T2
2
=
=
and the actual T
2
1.18V
--------------- - R
19.67kΩ R
60μA
R
Λ
NTCTo
= 100°C, if we use a Panasonic NTC with B = 4700,
2
NTC T
=
=
=
=
=
=
----------------------------------------------------------------------------- -
e
---------------------------------------------------------------------- -
---------------------------------------------------------------------------------- - 273
1
-- -
b
396kΩ
2.55kΩ
Λ
R
–
2.55kΩ
b
–
ln
NTC T
2.55kΩ e
•
2
and R
–
⎛
⎜
⎝
⎛
⎝
NTC
R
-------------------------
is about 97°C. If using the Equation 13, T
---------------------- -
T
is the normalized NTC resistance to its
R
2
NTC_T
NTC_105°C
NTCTo
–
+
1
(
+
+
2.55kΩ
273
T1
s
2
R
•
R
is designed, the actual NTC resistance
2
NTC_T
NTC_T1
–
)
⎞
⎠
2
b
temperature can be found in:
–
=
⎞
⎟
⎠
e
•
Λ
R
1
19.67kΩ R
+
b
⎛
⎝
NTC T
---------------------- -
T
•
1
o
=
1
⎛
⎝
⁄
---------------------- -
T
+
(
1
19.67kΩ 15.65kΩ
=
1
273
273
–
+
1
18.16kΩ
1
273
⎞
⎠
–
+
2
To
⎞
⎠
NTC_T 1
is given by Equation 12.
–
)
–
1
=
= 105°C
4.067kΩ
May 15, 2006
(EQ. 10)
(EQ. 12)
(EQ. 13)
(EQ. 11)
(EQ. 9)
FN9199.2
2
is