US90A / US91A
24V Hall IC Fan Driver
11.7 VOL vs TJ
0.5
11.8 Power Dissipation vs. TA
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
VK - RTH = 200°C/W - PDMAX = 500mW
VA - RTH = 170°C/W - PDMAX = 588mW
DC - RTH = 150°C/W - PDMAX = 666mW
TA = 25°C
0.4
0.3
0.2
0.1
0
VDD=5V ; Iol=10mA
VDD=24V ; Iol=10mA
TA max = 85°C
TJ max = 125°C
-40
-20
0
20
40
60
80
100
120
-40
-20
0
20
40
60
80
100
120
140
Tj (°C)
Ta (°C)
12 Application Information
12.1 Typical application with pull-up
resistor
12.2 Configuration for reverse voltage /
ground hot-switch protection and
enhanced ESD module protection
13 Application Comments
Figure 12.2 shows the application including several external protections.
The diode DREVPROT best protects the chip and fan coils for reverse voltage condition.
The capacitor CBYPASS is recommended if the supply ground may be disconnected while running even though
the positive supply point is still connected. This capacitor provides a path to ground for the remaining energy
in the coil which has to be evacuated. Without it, the energy can flow from OUT1/OUT2 to the FG/RD driver,
without any limitation and may cause EOS damage.
Its value has to be tuned depending on the coils characteristics. Bigger inductance requires bigger capacitor.
The no-VDD design enables ESD protection at fan module level to be easily improved. The fan coils prevent
and filter fast current stress on OUT1 and OUT2, resulting in better ESD protection. Adding the optional
capacitor COUT enhances the ESD protection of the logic output. Hence, the fan module is able to withstand
ESD stress at relatively high value without damage.
390109026302
Rev 002
Page 7 of 12
Data Sheet
Apr/07
MELEXIS [ Melexis Microelectronic Systems ]
