FSCT07A-UH5 STMicroelectronics, FSCT07A-UH5 Datasheet - Page 6

• Manufacturer Part Number: FSCT07A-UH5
• Description: IC CONTROLLER FAN SPEED IPPAK
• Manufacturer: STMicroelectronics
• Type: 18 Line 3-5 Volt Low Capacitance SCSI Active Terminatorr

Specifications of FSCT07A-UH5

• Applications: Fan Controller
• Number Of Outputs: 1
• Voltage - Supply: 9 V ~ 15 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: IPPAK-5
• Product: Fan / Motor Controllers / Drivers
• Operating Supply Voltage: 7 V
• Supply Current: 3 mA
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

FSCTxxA-UH5
2. Hysteresis control (mode OFF)
FSCT can be shut down by the ON signal. When, this signal is low, the OUT pin is at high level, i.e. the FAN
is turned off.
This mode enables to save the energy wasted by the FAN in case of operations at very low output power.
For a 12 V supply voltage, the shut-down of the FAN brings a 0.5 to 2.5 W power saving (for a 200 mA 12 V
DC motor).
During the mode OFF, the FSCT doesn't lose temperature control; indeed, in case of over-temperature,
the FAN is automatically switched on. This safety feature protects the power supply or the semiconductor
devices from unexpected over-temperature.
In order to keep the energy saving benefit, the FSCT turns back off the FAN when the temperature falls be-
low T
In practice, three cases can appear for a constant applied heating power (for instance, the output power of
the power supply where the FSCT is used) (cf. figure 8 ):
For example, with a 200 W computer power supply, working with a FSCT17 device put on the power semi-
conductors heatsink, Case 1 could be reached for a 25 W output power consumption (T
around 60 °C, i.e. below typical T
Case 2 could be reached for a 50 W power consumption. Then, thanks to the large Hysteresis value (30 °C
typ.), the ON/OFF period (refer to T
avoid too many FAN starts-up cycle per hour.
Case 3 could be reached for a 75W, or higher, power consumption. For 75W, the power supply ambient
temperature stabilizes itself around 42°C.
It should be noted that, for Case 3, such steady state points of operation, are allowed due to the fact that the
OUT voltage follows the same linear law as that in ON mode. Then, the Hysteresis control is smarter than a
simple ON/OFF control mode.
Fig. 7: OUT voltage versus junction temperature.
6/11
Case 1: the heating power is too low, and keeps T
Case 2: the heating power is high enough to raise T
down T
riodical cycle.
Case 3: the heating power is higher that in case 2, so that Tj remains above T
in that case, unless the heating power decreases.
OFF
threshold.
OFF
, and the temperature starts again to increase, up to T
V
V
OMS
V
1V
CC
OL
V
OUT
Mode ON
ON
T
).
P
MS
on figure 8 ) lasts approximately 15 minutes. This is long enough to
T
OFF
T
OL
j
below T
j
above T
T
ON
Mode OFF
ON
ON
. The FAN remains OFF.
. But, as this power is quite low, T
ON
. This results in a FAN ON/OFF pe-
OFF
. The FAN stays ON
T (°C)
j
j
will stabilize
j
falls