ISL6266AIRZ Intersil, ISL6266AIRZ Datasheet - Page 24

• Manufacturer Part Number: ISL6266AIRZ
• Description: IC CORE CTRLR 2PHASE 48-QFN
• Manufacturer: Intersil

Specifications of ISL6266AIRZ

• Applications: Converter, Intel IMVP-6
• Voltage - Input: 5 ~ 25 V
• Number Of Outputs: 1
• Voltage - Output: 0.3 ~ 1.5 V
• Operating Temperature: -40°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 48-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

For 300kHz operation, R
discontinuous conduction mode (DCM), the ISL6266A runs
in period stretching mode. The switching frequency is
dependent on the load current level. In general, lighter loads
will produce lower switching frequencies. Therefore,
switching loss is greatly reduced for light load operation,
which conserves battery power in portable applications.
Voltage Regulator Thermal Throttling
lntel® IMVP-6+ technology supports thermal throttling of the
processor to prevent catastrophic thermal damage to the
voltage regulator. The ISL6266A features a thermal monitor
that senses the voltage change across an externally placed
negative temperature coefficient (NTC) thermistor.
Proper selection and placement of the NTC thermistor
allows for detection of a designated temperature rise by the
system.
Figure 38 shows the thermal throttling feature with
hysteresis. At low temperature, SW1 is on and SW2
connects to the 1.2V side. The total current going into NTC
pin is 60µA. The voltage on the NTC pin is higher than the
threshold voltage of 1.2V and the comparator output is low.
VR_TT# is pulled high by the external resistor.
When the temperature increases, the NTC resistor value
decreases, thus reducing the voltage on the NTC pin. When
the voltage decreases to a level lower than 1.2V, the
comparator output changes polarity and turns SW1 off and
connects SW2 to 1.24V. This pulls VR_TT# low and sends
the signal to start thermal throttle. There is a 6µA current
reduction on the NTC pin and 20mV voltage increase on the
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. Temperature will
decrease over time and the NTC thermistor voltage will go
up. When the NTC pin voltage achieves 1.24V, the
comparator output will resume its original state. This
temperature hysteresis feature of VR_TT# is illustrated in
V
FIGURE 38. CIRCUITRY ASSOCIATED WITH THE THERMAL
NTC
+
-
R
R
NTC
NTC
s
THROTTLING FEATURE IN ISL6266
1.24V
54µA
FSET
SW2
6µA
SW1
24
+
1.20V
is suggested to be 9.53kΩ. In
-
INTERNAL TO
ISL6266
ISL6266, ISL6266A
VR_TT#
Figure 39. T
which the VR_TT# goes from low to high due to the system
temperature rise. T
at which the VR_TT# goes high from low because the
system temperature decreases to acceptable levels.
Usually, the NTC thermistor's resistance can be
approximated by Equation 8.
T is the temperature of the NTC thermistor and b is a
parameter constant depending on the thermistor material.
T
is derived. The most common temperature for T
For example, there are commercial NTC thermistor products
with b = 2750kΩ, b = 2600kΩ, b = 4500kΩ or b = 4250kΩ.
From the operation principle of the VR_TT# circuit
explained, the NTC resistor satisfies Equations 9 through 13:
From Equation 9 and Equation 10, Equation 11 can be
derived:
Using Equation 8 into Equation 11, the required nominal
NTC resistor value can be obtained by Equation 12:
For those cases where the constant b is not accurate
enough to approximate the resistor value, the manufacturer
provides the resistor ratio information at different
temperatures. The nominal NTC resistor value may be
expressed in another way shown in Equation 13.
R
R
R
R
R
R
o
NTC
NTC
NTC
NTC
NTCTo
NTCTo
is the reference temperature in which the approximation
LOGIC_1
LOGIC_0
FIGURE 39. TEMPERATURE HYSTERESIS OF VR_TT#
VR_TT#
T ( )
(
(
(
T
T
T
1
2
2
)
)
) R
=
=
=
+
+
–
----------------------------------------------------------------------------- -
e
----------------------------------------------------------------------- -
R
R
R
Λ
R
1
b
NTC
NTCTo
S
S
2.96kΩ e
•
represents the higher temperature point at
NTC
⎛
⎝
=
=
---------------------- -
T
2
(
-------------- -
60μA
1.24V
--------------- -
54μA
1.2V
T
(
+
1
2
T
1
273
2.96kΩ
•
2
)
represents the lower temperature point
•
e
)
=
⎞
⎠
–
b
b
=
–
=
2.96kΩ
•
e
•
Λ
R
⎛
⎝
20kΩ
b
⎛
⎝
22.96kΩ
------------------- -
T
---------------------- -
T o
•
NTC
+
⎛
⎝
---------------------- -
T
+
1
1
273
1
273
T
(
+
T
2
1
273
1
⎞
⎠
–
)
-----------------------
To
⎞
⎠
T
+
1
1
273
⎞
⎠
o
T (°C)
is +25°C.
June 14, 2010
(EQ. 10)
(EQ. 12)
(EQ. 13)
(EQ. 11)
(EQ. 8)
(EQ. 9)
FN6398.3