US4881LSO datasheet(7/11 Pages) MELEXIS

7 / 11 page

US4881

Bipolar Hall Switch

Low Voltage & Very High Sensitivity

3901004881

Page 7 of 11

Data Sheet

Rev 011

Feb/06

12 Application Information

13 Application Comments

For proper operation, a 100nF bypass capacitor should be placed as close as possible to the device between

the VDD and ground pin.

For reverse voltage protection, it is recommended to connect a resistor or a diode in series with the VDD pin.

When using a resistor, three points are important:

- the resistor has to limit the reverse current to 50mA maximum (VCC / R1 ≤ 50mA)

- the resulting device supply voltage VDD has to be higher than VDD min (VDD = VCC – R1.IDD)

- the resistor has to withstand the power dissipated in reverse voltage condition (PD = VCC

2 / 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 VDD. The diode D1 provides additional reverse voltage protection.

12.1 Typical Three-Wire Application Circuit

12.3 Automotive and Harsh, Noisy Environments

Three-Wire Circuit

12.2 Two-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.

BRP :

IOFF = IR + IDD = VDD/Rb + IDD

BOP :

ION = IOFF + IOUT = IOFF + VDD/RL

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