HAL710 datasheet(11/12 Pages) ETC

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ADVANCE INFORMATION

HAL710

Micronas

4. Application Notes

4.1. Ambient Temperature

Due to the internal power dissipation, the temperature

on the silicon chip (junction temperature TJ) is higher

than the temperature outside the package (ambient

temperature TA).

TJ = TA + ∆T

At static conditions, the following equation is valid:

∆T = I

DD * VDD * Rth

For typical values, use the typical parameters. For

worst case calculation, use the max. parameters for

IDD and Rth, and the max. value for VDD from the appli-

cation.

For all sensors, the junction temperature range TJ is

specified. The maximum ambient temperature TAmax

can be calculated as:

TAmax = TJmax − ∆T

4.2. Extended Operating Conditions

All sensors fulfil the electrical and magnetic character-

istics when operated within the Recommended Oper-

ating Conditions (see page 8)

Supply Voltage Below 3.8 V

Typically, the sensors operate with supply voltages

above 3 V, however, below 3.8 V some characteristics

may be outside the specification.

Note: The functionality of the sensor below 3.8 V is not

tested. For special test conditions, please contact Mic-

ronas.

4.3. Signal Delay

The extra circuitry required for the direction detection

increases the latency of the ‘Count and Direction Sig-

nal’ compared to a simple switch (e.g. HAL 525). This

extra delay corresponds to 0.5 and 1 clock period for

the ‘Direction Signal’ and ‘Count Signal’ respectively.

4.4. Test Mode Activation

In order to obtain the normal operation as described

above, two external pull-up resistors with appropriate

values are required to connect each output to an exter-

nal supply, such that the potential at the open-drain

output rises to at least 3 V in less than 10

µs after hav-

ing turned off the corresponding pull-down transistor or

after having applied VDD.

If the ‘Direction Output’ is pulled low externally (the

potential does not rise after the internal pull-down tran-

sistor has been turned off), the device enters Manufac-

turer Test Mode.

Direction Detection is not functional in Manufacturer

Test Mode. The device returns to ‘Normal Operation’

as soon as the ‘Count Output’ goes high.

Please note, that the presence of a Manufacturer Test

Mode requires appropriate measures to prevent acci-

dental activation (e.g. in response to EMC events).

4.5. Start-up Behavior

Due to the active offset compensation, the sensors

have an initialization time (enable time ten(O)) after

applying the supply voltage. The parameter ten(O) is

specified in the Electrical Characteristics (see page 9)

During the initialization time, the output states are not

defined and the outputs can toggle. After ten(O) both

outputs will be either high or low for a stable magnetic

field (no toggling) and the ‘Count Output’ will be low if

the applied magnetic field B exceeds BON. The ‘Count

Output’ will be high if B drops below BOFF. The ‘Direc-

tion Output’ will have the correct state after the second

edge (rising or falling) in the same direction.

The device contains a Power-On Reset circuit (POR)

generating a reset when VDD rises. This signal is used

to initialize both outputs in the ‘Off-state’ (i.e. Output

High) and to disable Test Mode. The generation of this

Reset Signal is guaranteed when VDD at the chip rises

to minimum 3.8 V in less than 4

µs monotonically. If

this condition is violated, the internal reset signal might

be missing. Under these circumstances the chip will

still operate according to the specification, but the risk

of toggling outputs during ten(O) increases and for mag-

netic fields between BOFF and BON, the output states

of the Hall sensor after applying VDD will be either low

or high. In order to achieve a well defined output state,

the applied magnetic field then must exceed BONmax,

respectively drop below BOFFmin.

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