FSCT07A-UH5 STMicroelectronics, FSCT07A-UH5 Datasheet - Page 5

• 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

DETAILED DESCRIPTION & APPLICATION INFORMATION
1. OUTPUT CHARACTERISTIC VERSUS TEMPERATURE
1.1 FAN speed control
As it's well known, BRUSHLESS DC motors present the advantage of a quasi-linear speed-voltage char-
acteristic. Hence, the fan speed is varying linearly versus the voltage which is applied across its terminals.
The FSCT Integrated Circuit provides at its OUT terminal, a voltage which changes versus the temperature
sensed through its tab. This OUT voltage decreases as temperature increases, following two modes of op-
eration. By connecting this OUT terminal to the Base of a PNP transistor, as shown in figure 1 , the FAN
voltage will increase with the sensed temperature.
The FAN voltage is given by the following equation: V
Typically, for a 12 V V
It can be noticed that the PNP operates as a linear amplifier. This avoids EMI and acoustic noise compared
to Pulse Width Modulation control circuits.
1.2 ON/OFF Mode Selection
The figure 6 gives the algorithm flowchart of the FSCT behavior. First, two modes of operation are distin-
guished by the ON pin signal.
During Mode ON, the OUT voltage follows a three-parts characteristic, according to its junction tempera-
ture (T
During Mode OFF, an Hysteresis control allows
the system to switch to mode ON only if the tem-
perature exceeds the T
back off, if the system is cooled enough to lower
the temperature below T
The figure 7 sums up the FSCT Output character-
istic versus the temperature, for the two operation
modes.
1.3 Minimum speed (mode ON)
Mode ON allows users to ensure that the FAN will
be always ON, whatever the ambient temperature
is.
The OUT voltage is clamped to V
perature (below T
The V
minimum voltage applied across the FAN is 5.5 V
(according to Equation 2 ). This voltage is above
stalling value of most fans and will then ensure that
the controlled FAN will always run, in mode ON,
avoiding spurious turn-off due to too low voltage at
low temperature. Annoying noises due to FAN
repetitive starts up are also suppressed.
Mode ON: activated when ON pin is at High Level or Not Connected (thanks to an internal Pull-up
curren source "I
Mode OFF: activated when ON pin is at Low Level.
T
T
T
j
MS
j
< T
> T
OMS
< T
j
):
MS
OL
j
: in this case, V
: in this case, V
< T
has been set to 5.5 V max , thus the
OL
: V
MS
S
")
OUT
= 37 °C typically).
FAN+
ON
is linearly regulated versus the junction temperature
OFF
OUT
OUT
value. The Fan is turned
and a 1 V V
.
is clamped to its minimum value (V
is limited to V
OMS
for low tem-
EB
voltage, this gives: V
OMS
to avoid stalling the fan rotor
FAN
Fig. 6: FSCT behavior flow-chart.
V
V
V
OUT
OUT
V
V
FAN
V
V
OUT
OUT
OUT
OUT
FAN V
= V
= V
= V
= V
= V
= V
OL
OMS
OMS
( )
FAN ON
FAN ON
BEGIN
BEGIN
ON is
ON is
LOW
LOW
OMS
OMS
OL
OL
V
).
OR
OR
OR
OR
?
?
– k
– k
IF T
IF T
EB
no
no
IF T
IF T
SL
SL
11
.(T
.(T
j
j
j
j
> T
> T
< T
< T
j
j
V
– T
– T
OL
OL
MS
MS
OUT
yes
yes
V
MS
MS
OUT V
)
)
(1)
( )
V
V
(2)
OUT
OUT
FAN OFF (V
FAN OFF (V
V
V
OUT
OUT
= V
= V
= V
= V
V
V
OMS
OMS
T
T
FAN OFF
FAN OFF
T
T
FAN ON
FAN ON
OUT
OUT
FSCTxxA-UH5
j
j
j
j
< T
< T
OL
OL
> T
> T
OR
OR
– k
– k
?
?
?
?
= V
= V
IF T
IF T
OUT
OUT
OFF
OFF
ON
ON
SL
SL
yes
yes
yes
yes
CC
CC
.(T
.(T
j
j
= V
= V
> T
> T
j
j
– T
– T
CC
CC
OL
OL
)
)
MS
MS
no
no
no
no
)
)
5/11