HAL855UT-K datasheet(27/42 Pages) MICRONAS

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DATA SHEET

HAL855

Micronas

Nov. 26, 2008; DSH000149_003EN

4. Application Notes

Micronas recommends the following application cir-

cuits for HAL855. The first is recommended for appli-

cations with connection to a regualted 5 V supply; the

second schould be used for applications connected

dicrectly to the car battery and a pull-up to a 5 V line.

For both circuits, it is recommended to connect a

ceramic 4.7 nF capacitor between ground and the sup-

ply voltage, respectively, the output pin.

Fig. 4–1: Application circuit HAL855

Fig. 4–2: Application circuit HAL855 for connection

with car battery

4.1. Use of Two HAL855 in Parallel Operation

Two different HAL855 sensors which are operated in

parallel to the same supply and ground line can be

programmed individually. In order to select the IC

which should be programmed, both Hall ICs are deac-

tivated by the “Deactivate” command on the common

supply line. Then, the appropriate IC is activated by an

“Activate” pulse on its output. Only the activated sen-

sor will react to all following read, write, and program

commands. If the second IC has to be programmed,

the “Deactivate” command is sent again, and the sec-

ond IC can be selected.

Detailed information can be found in the application

note for the programmer board.

Fig. 4–3: Parallel operation of two HAL855

4.2. Measurement of a PWM Output Signal

In case that the PWM output mode is activated, the

magnetic field information is coded in the duty cycle of

the PWM signal. The duty cycle is defined as the ratio

between the high time “s” and the period “d” of the

PWM signal (see Fig. 4–4).

Note: The PWM signal is updated with the falling

edge. Hence, for signal evaluation, the trigger-

level must be the falling edge of the PWM sig-

nal.

Fig. 4–4: Definition of PWM signal

CP = 4.7 nF

VDD

GND

Vsupply = 5 V ±0.5 V

Rpull-up

System side

Sensor side

CL = 4.7 nF

OUT

CP = 4.7 nF

VDD

GND

Rpull-up

System side

Sensor side

CL = 4.7 nF

OUT

Vsupply = 8 V...18 V

Vpull-up = 5 V ±0.5 V

RP = 120 Ω

HAL 855

GND

10 nF

HAL855

4.7 nF

Sensor A

Sensor B

VDD

OUT B & Select B

OUT A & Select A

Update

Out

time

Vhigh

Vlow

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