US90A / US91A
24V Hall IC Fan Driver
3 Glossary of Terms
Two-coil fan
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 :
MilliTesla (mT), Gauss
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.
VDD
IDD
Peak output current
The current flowing in the coil at start-up, only limited by the coil resistance
RCOIL and the output driver resistance RDSON.
Continuous output current The current flowing in the coil when the fan is spinning normally.
Locked rotor
FG
RD
The state when the fan stopped spinning due to mechanical blockage.
Frequency generator or tachometer output
Rotation detection or alarm output
LFPM
Linear Feet Per Minute – Unit of airflow velocity
4 Absolute Maximum Ratings
Parameter
Symbol
VDD
Value
30
Units
V
Fan Supply Voltage
Peak Output Current
IOUTp
IOUTc
IFG (RD)
TA
TJ
TS
500
250
20
-40 to 85
125
mA
mA
mA
Continuous Output Current
FG / RD Output Current
Operating Temperature Range
Junction Temperature
Storage Temperature Range
Magnetic Flux Density
Table 1: Absolute maximum ratings
°C
°C
°C
mT
-55 to 150
Unlimited
B
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)
Function
FG (RD)
OUT1
OUT2
GND
-
1
2
3
4
-
1
2
4
3
1
2
4
3
-
FG (RD) open drain output signal
Open Drain Coil Driver 1
Open Drain Coil Driver 2
Ground pin
5, 6, 7, 8
Not Connected
Table 2: Pin definitions and descriptions US90A (US91A)
390109026302
Rev 002
Page 3 of 12
Data Sheet
Apr/07
MELEXIS [ Melexis Microelectronic Systems ]
