Allegro Multimedia A1302, A1301 manual Characteristic Definitions

A1301 and

A1302

Continuous-Time Ratiometric Linear Hall Effect Sensors

Characteristic Definitions

Quiescent Output Voltage. In the quiescent state (no sig- nificant magnetic field: B = 0), the output, VOUTQ, equals one half of the supply voltage, VCC, throughout the entire operating ranges of VCC and ambient temperature, TA. Due to internal component tolerances and thermal considerations, there is a tolerance on the quiescent output voltage, ΔVOUTQ, which is

a function of both ΔVCC and ΔTA. For purposes of specifica- tion, the quiescent output voltage as a function of temperature, ΔVOUTQ(ΔTA), is defined as:

ΔVOUTQ(ΔΤΑ) =	VOUTQ(ΤΑ) – VOUTQ(25ºC)	(1)
	Sens(25ºC)

where Sens is in mV/G, and the result is the device equivalent accuracy, in gauss (G), applicable over the entire operating tem- perature range.

Sensitivity. The presence of a south-polarity (+B) magnetic field, perpendicular to the branded face of the device package, increases the output voltage, VOUT, in proportion to the magnetic field applied, from VOUTQ toward the VCC rail. Conversely, the application of a north polarity (–B) magnetic field, in the same orientation, proportionally decreases the output voltage from its quiescent value. This proportionality is specified as the magnetic sensitivity of the device and is defined as:

Sens =	VOUT(–B) – VOUT(+B)	(2)
	2B

The stability of the device magnetic sensitivity as a function of ambient temperature, ΔSens (ΔTA) (%) is defined as:

ΔSens(ΔΤΑ)=	Sens(ΤΑ)	– Sens(25ºC)	⋅ 100%	(3)
	Sens(25ºC)

Ratiometric. The A1301 and A1302 feature a ratiometric output. This means that the quiescent voltage output, VOUTQ, and the magnetic sensitivity, Sens, are proportional to the supply voltage, VCC.

The ratiometric change (%) in the quiescent voltage output is defined as:

ΔVOUTQ(ΔV) =	VOUTQ(VCC)	VOUTQ(5V)	⋅ 100%	(4)
	VCC
		5 V

and the ratiometric change (%) in sensitivity is defined as:

ΔSens(ΔV) =	Sens(VCC)	Sens(5V)	⋅ 100%	(5)
	VCC	5 V

Linearity and Symmetry. The on-chip output stage is designed to provide linear output at a supply voltage of 5 V. Although the application of very high magnetic fields does not damage these devices, it does force their output into a nonlinear region. Linearity in percent is measured and defined as:

Lin+ =		VOUT(+B) – VOUTQ			⋅ 100%	(6)
		2 (VOUT(+B½) – VVOUTQ )
Lin– =		VOUT(–B) – VOUTQ		⋅ 100%		(7)
	2(VOUT(–B½) – VOUTQ)
and output symmetry as:
Sym =		VOUT(+B)	– VOUTQ	⋅ 100%		(8)

VOUTQ – VOUT(–B)

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