US5881
Unipolar Hall Switch – Low Sensitivity
12 Application Information
12.1 Typical Three-Wire Application Circuit
12.2 Two-Wire Circuit
12.3 Automotive and Harsh, Noisy Environments
Three-Wire Circuit
Note:
With this circuit, precise ON and OFF
currents can be detected using only
two connecting wires.
The resistors RL and Rb can be used
to bias the input current. Refer to the
part specifications for limiting values.
B
RP
:
B
OP
:
I
OFF
= I
R
+ I
DD
= V
DD
/R
b
+ I
DD
I
ON
= I
OFF
+ I
OUT
= I
OFF
+ V
DD
/R
L
13 Application Comments
For proper operation, a 100nF bypass capacitor should be placed as close as possible to the device between
the V
DD
and ground pin.
For reverse voltage protection, it is recommended to connect a resistor or a diode in series with the V
DD
pin.
When using a resistor, three points are important:
- the resistor has to limit the reverse current to 50mA maximum (V
CC
/ R1
≤
50mA)
- the resulting device supply voltage V
DD
has to be higher than V
DD
min (V
DD
= V
CC
– R1.I
DD
)
2
- the resistor has to withstand the power dissipated in reverse voltage condition (P
D
= V
CC
/ R1)
When using a diode, a reverse current cannot flow and the voltage drop is almost constant (≈0.7V).
Therefore, a 100Ω/0.25W resistor for 5V application and a diode for higher supply voltage are recommended.
Both solutions provide the required reverse voltage protection.
When a weak power supply is used or when the device is intended to be used in noisy environment, it is
recommended that figure 13.3 from the Application Information section is used.
The low-pass filter formed by R1 and C1 and the zener diode Z1 bypass the disturbances or voltage spikes
occurring on the device supply voltage V
DD
. The diode D1 provides additional reverse voltage protection.
3901005881
Rev 007
Page 7 of 11
Data Sheet
Feb/06
MELEXIS [ Melexis Microelectronic Systems ]
