Allegro Multimedia A1321 manual Characteristic Definitions

A1321, A1322, and A1323

Ratiometric Linear Hall Effect Sensor for High-Temperature Operation

Characteristic Definitions

Quiescent Voltage Output. In the quiescent state (no magnetic field), the output equals one half of the supply voltage over the operating voltage range and the operating temperature range. Due to internal component tolerances and thermal con- siderations, there is a tolerance on the quiescent voltage output both as a function of supply voltage and as a function of ambient temperature. For purposes of specification, the quiescent voltage output as a function of temperature is defined in terms of mag- netic flux density, B, as:

ΔVout(q)(ΔΤ) =	Vout(q)(ΤΑ) – Vout(q)(25ºC)	(1)
	Sens(25ºC)

This calculation yields the device’s equivalent accuracy, over the operating temperature range, in gauss (G).

Sensitivity. The presence of a south-pole magnetic field per- pendicular to the package face (the branded surface) increases the output voltage from its quiescent value toward the supply voltage rail by an amount proportional to the magnetic field applied. Conversely, the application of a north pole will decrease the output voltage from its quiescent value. This proportionality is specified as the sensitivity of the device and is defined as:

Sens =	Vout(–B) – Vout(+B)	(2)
	2B

The stability of sensitivity as a function of temperature is defined as:

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

Ratiometric. The A132X family features a ratiometric output. The quiescent voltage output and sensitivity are proportional to the supply voltage (ratiometric).

The percent ratiometric change in the quiescent voltage output is defined as:

ΔVout(q)(ΔV)	=	Vout(q)(VCC)	Vout(q)(5V)	⋅ 100%	(4)
		VCC	5 V

and the percent ratiometric change in sensitivity is defined as:

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

Linearity and Symmetry. The on-chip output stage

is designed to provide a linear output with a supply voltage of

5 V. Although application of very high magnetic fields will not damage these devices, it will force the output into a non-linear region. Linearity in percent is measured and defined as:

Lin+ =		Vout(+B) – Vout(q)		⋅ 100%	(6)
		2(Vout(+B / 2) – Vout(q) )
Lin– =		Vout(–B) – Vout(q)		⋅ 100%	(7)
		2(Vout(–B / 2) – Vout(q) )
and output symmetry as:
Sym =	Vout(+B) –Vout(q)		⋅ 100%		(8)

Vout(q) – Vout(–B)

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115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com