FSCT07A-UH5 STMicroelectronics, FSCT07A-UH5 Datasheet - Page 9

• 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

P
These interfaces offer very low thermal resistance. For example, the Sil-Pad
BERGQUIST, which is designed for low cost applications and low mounting pressures, present a typical
thermal impedance of 0.45 °C.in²/W. This impedance can increase up to 0.92 °C.in²/W for a 10 psi pres-
sure, which is below the normal atmospheric one (1 atm = 1013 hPa = 1013 x 100 x 14.5 x 10-3 = 14.7 psi).
Furthermore, a mounting clip will apply a force between 15 to 50 N. This leads to a 25 to 200 psi pressure.
In this case, the thermal impedance varies from 0.6 to 0.29 °C.in²/W for the Sil-Pad
For the example, we take the worst case hypothesis of a 1°C.in²/W interface between the FSCT case and
the heat sink.
We take into account only the tab surface for the heat exchange. This surface equals typically:
S = 4.7 x 5.1 mm
This yields to a supplementary resistance of: R
Then, the maximum power dissipated in the FSCT, for the maximum output power, is given by the following
equation:
The following numerical application gives (for a 150 mA FAN DC current, a 80 gain for the PNP and a 12 V
power supply):
I
Then, the temperature error is: T
The temperature sensing error can then be neglected whan one considers the operation range (from 0 to
100 °C), even with low cost interface material and without any mounting clip. For example, with a higher
pressure, thanks to a clip, this error could be divided by three.
4. TEMPERATURE/VOLTAGE SLOPE CHANGE
The OUT voltage versus temperature characteristic of the FSCT has been designed to fit majority cases of
application, in the field of PC power supplies.
The advantage for the user is to have a minimum count of components while achieving a smart
temperature regulation.
Nevertheless, some applications require dedicated temperature regulation characteristic. Figure 13
provides an example of a solution which allows to change the ratio between PNP base voltage and the
temperature. This schematic only requires a dual
single-voltage amplifier (in DIL8 package for
example) and less than ten supplementary
resistors.
This schematic keeps the advantage of applying a
constant minimum voltage (V
perature. Indeed, the U1A operational amplifier
subtracts 5.1 V (thanks to the D1 Zener diode, re-
fer to V
change is only taken into account when V
lower than 5.1 V. For higher voltages (V
ON or V
age (V
So, if one wants to increase accurately the
voltage-temperature ratio, i.e. that V
decrease more quickly when T
13 schematics should be implemented. Indeed,
the voltage at the operational amplifier U1B (which
acts as a follower) output is:
OUT
max
= 150 / 80 = 1.87mA
NEW
3 12 10
REF
CC
) remains the same (cf. figure 12 ).
in mode OFF), the new base to GND volt-
) from V
2
= 0.037 in
3
OUT
187 5 5 10
. This means that the ratio
.
2
OMS
.
V
V
j
NEW
NEW
) below T
increases, figure
0 046
3
OMS
.
P
V
V
max
OUT
OUT
46
OUT
MS
in mode
mW
OUT
if V
I
tem-
RN
RD
CC
3
thc-h
will
OUT
is
V
27
= 1/0.037 = 27°C/W
CC
V
V
REF
REF
Fig. 12: Modified characteristics.
V
V
NEW
OMS
I
OUT
138
V
.
OUT
V
OUT
V
Mode ON
C
OMS
Step-down
otherw
ise
T
OFF
T
®
ON
800 family.
®
Mode OFF
800 family, from
FSCTxxA-UH5
9/11
T (°C)
j