US90A / US91A
24V Hall IC Fan Driver
3 Glossary of Terms
Two-coil fan
MilliTesla (mT), Gauss
V
DD
I
DD
Peak output current
Continuous output current
Locked rotor
FG
RD
LFPM
A fan with two-coil windings where current alternates from 1 coil to the other
depending on the direction of the magnetic field.
Units of magnetic flux density :
1mT = 10 Gauss
Voltage on the coils common node.
Current supplying the chip which flows through the coil connected to the
switched off output driver.
The current flowing in the coil at start-up, only limited by the coil resistance
R
COIL
and the output driver resistance R
DSON.
The current flowing in the coil when the fan is spinning normally.
The state when the fan stopped spinning due to mechanical blockage.
Frequency generator or tachometer output
Rotation detection or alarm output
Linear Feet Per Minute – Unit of airflow velocity
4 Absolute Maximum Ratings
Parameter
Symbol
Fan Supply Voltage
V
DD
Peak Output Current
I
OUTp
Continuous Output Current
I
OUTc
FG / RD Output Current
I
FG (RD)
Operating Temperature Range
T
A
Junction Temperature
T
J
Storage Temperature Range
T
S
Magnetic Flux Density
B
Table 1: Absolute maximum ratings
Value
30
500
250
20
-40 to 85
125
-55 to 150
Unlimited
Units
V
mA
mA
mA
°C
°C
°C
mT
Exceeding the absolute maximum ratings may cause permanent damage. Exposure to absolute-maximum-
rated conditions for extended periods may affect device reliability.
5 Pin Definitions and Descriptions
Pin Name Pin number (VK) Pin number (DC) Pin number (VA)
FG (RD)
1
1
1
OUT1
2
2
2
OUT2
3
4
4
GND
4
3
3
-
-
5, 6, 7, 8
-
Table 2: Pin definitions and descriptions US90A (US91A)
Function
FG (RD) open drain output signal
Open Drain Coil Driver 1
Open Drain Coil Driver 2
Ground pin
Not Connected
390109026302
Rev 002
Page 3 of 12
Data Sheet
Apr/07
MELEXIS [ Melexis Microelectronic Systems ]
