HAL856 datasheet(29/42 Pages) MICRONAS

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DATA SHEET

HAL856

Micronas

March 23, 2010; DSH000142_002EN

4. Application Notes

Micronas recommends the following application cir-

cuits for HAL856.

It is recommended to connect a ceramic 4.7 nF capac-

itor between ground and the supply voltage. Further-

more it is recommended to place a 30

Ω resistor in the

supply voltage line.

Fig. 4–1: Application circuit HAL856

To use the HAL856 over the full temperature and sup-

ply voltage range and with all available high current

levels, Micronas recommends using a current mirror or

special interface devices. Fig. 4–2 shows an example

using a current mirror.

Fig. 4–2: Application circuit with current mirror

A special interface device could be, for example, the

MAXIM MAX9921 (Dual, 2-Wire Hall-Effect Sensor

Interface with Diagnostics) chip. With these interface

ICs, together with HAL 856, a single-wire interface is

possible.

Note: The third sensor pin should be floating or con-

nected to the GND line.

4.1. 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. 4–3).

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. 4–3: Definition of PWM signal

4.2. Measurement of a Biphase-M Output Signal

In order to read the Biphase-M signal Micronas sug-

gests to use a port interrupt which is configured to gen-

erate interrupts with both the falling and rising edge of

the incoming signal.

With each interrupt a timer shall be read out. The first

two edges (SYNC bit) define the bit time tp0. Compar-

ing subsequent timer readouts with tp0 successively

decodes the Biphase-M pattern.

CP = 4.7 nF

VDD

GND

Vbattery = 8 V...18 V

Rsense = 120 Ω

RP = 30 Ω

System side

Sensor side

VDD

HAL856

µC

VRef

4.7 nF

Update

Out

time

IDD,high

IDD,low

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