Datasheet

TC650/TC651
DS21450D-page 8  2001-2012 Microchip Technology Inc.
4.6 Temperature Selection Guide
(Minimum Fan Speed/Full Speed)
There are two temperature thresholds that determine
the characteristics of the device. The minimum fan
speed temperature (T
L
) and the full fan speed temper-
ature (T
H
). Depending on the TC65X device selected,
when the temperature is below the T
L
trip point, the
PWM output will perform a different operation. For the
TC650, the PWM will be driven at the minimum PWM
frequency, while the TC651 will shut down the PWM
(PWM = L).
T
L
and T
H
can be selected in 5°C increments. T
L
can
range from 25°C to 35°C. T
H
can range from 35°C to
55°C and must be 10°C (or more) than the specified T
L
.
The five temperature regions defined by the six
thresholds are defined in the TC650/TC651 by means of
factory trimming. Once a T
L
and T
H
are set, the T
1
– T
4
thresholds are automatically equally spaced between T
L
and T
H
. Table 4-1 shows these 5 regions and what the
corresponding PWM duty cycle is.
TABLE 4-1: TEMPERATURE RANGE
DEFINITION
Table 4-2 shows the device codes that specify the T
H
and T
L
temperature thresholds. The following exam-
ples are given to assist in understanding the device-
ordering nomenclature.
Example 1: Suppose you wanted the fan to run at
40% speed at 25°C or less and go to full-
speed at 45°C. You would order the part
number TC650AEVUA.
Example 2: Suppose you wanted the fan to turn on at
30°C and go to full speed at 45°C. You
would order the part number
TC651BEVUA.
TABLE 4-2: DEVICE CODES FOR
TEMPERATURE
THRESHOLDS
Temperature
(T = T
J
)
(Note 1)
PWM Duty Cycle
TC650
(Minimum
Speed mode)
TC651
(Auto-shutdown
mode)
T < T
L
40% Off
T
L
< = T < T
1
50% 50%
T
1
< = T < T
2
60% 60%
T
2
< = T <T
3
70% 70%
T
3
< = T < T
4
80% 80%
T
4
< = T < T
H
90% 90%
T
H
< = T < T
OV
100% 100%
T
OV
< = T 100% with Overtemperature Alert
(T
OVER
= L)
Note 1: The temperature regions defined by the
six temperature thresholds are pre-
defined in the TC650/TC651 by means of
factory trimming. Once a T
L
and T
H
are
programmed, the T
1
– T
4
thresholds are
automatically equally spaced between T
L
and T
H
.
Temp.
Threshold
Difference
T
L
T
H
Threshold
Limits Code
10°C 25 35 AC
(1)
30 40 BD
(2)
35 45 CE
(2)
15°C 25 40 AD
(2)
30 45 BE
(1)
35 50 CF
(2)
20°C 25 45 AE
(1)
30 50 BF
(2)
35 55 CG
(1)
30°C 25 55 AG
(1)
Note 1: This temperature threshold option is
available for ordering.
2: This is a custom temperature threshold
option. Please contact the factory for
more information.