BACKGROUND

As is known, there are a variety of types of magnetic field sensing elements, including, but not limited to, Hall effect elements, magnetoresistance elements, and magnetotransistors. As is also known, there are different types of Hall effect elements, for example, a planar Hall element, a vertical Hall element, and a circular Hall element. As is also known, there are different types of magnetoresistance elements, for example, a giant magnetoresistance (GMR) element, an anisotropic magnetoresistance element (AMR), a tunneling magnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).

Hall effect elements generate an output voltage proportional to a magnetic field. In contrast, magnetoresistance elements change resistance in proportion to a magnetic field. In a circuit, an electrical current can be directed through the magnetoresistance element, thereby generating a voltage output signal proportional to the magnetic field.

Magnetic field sensors, i.e., circuits that use magnetic field sensing elements, are used in a variety of applications, including, but not limited to, a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor, a magnetic switch that senses the proximity of a ferromagnetic object, a rotation detector that senses passing ferromagnetic articles, for example magnetic domains of a ring magnet, and a magnetic field sensor that senses a magnetic field density of a magnetic field.

Magnetic field sensors may be trimmed, such at final test, to adjust the sensitivity, for example. It can be challenging to generate accurate magnetic fields to achieve desired levels of absolute sensitivity.

SUMMARY

In one aspect of the invention, a method comprises: trimming a magnetic field sensor having a first magnetic field sensing element within an IC package, the trimming comprising using a curve for normalized sensitivity of the first magnetic field sensing element derived from first and second curves, the first curve corresponding to current through a coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field having a first polarity, and the second curve corresponding to current through the coil in a second direction opposite to the first direction at a second time to produce a field affecting the first magnetic field sensing element versus the external field having a first polarity.

The method can further include one or more of the following features: the first polarity of the external field is negative, the curve for normalized sensitivity of the first magnetic field sensing element corresponds to an average of the first and second curves, the coil is integrated with the first magnetic field sensing element, trimming comprises determining an absolute sensitivity of the magnetic field sensor in LSB per mA, trimming comprises determining an absolute sensitivity of the magnetic field sensor in LSB per Gauss, the magnetic field sensor comprises a back-biased sensor, the coil is integrated in silicon in which the magnetic field sensing element is disposed, wherein the magnetic field sensing element comprises a Hall element, and/or determining a sensitivity of the coil while no external magnetic field is applied prior to packaging the first magnetic sensing element. In one embodiment, a magnetic field sensor is trimmed in accordance with any of the features set forth above.

In a further aspect of the invention, a device comprises: a magnetic field sensor having a first magnetic field sensing element within an IC package; and a memory configured to store trimming information for the magnetic field sensor, wherein the trimming comprises using a curve for normalized sensitivity of the first magnetic field sensing element derived from first and second curves, the first curve corresponding to current through a coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field having a first polarity, and the second curve corresponding to current through the coil in a second direction opposite to the first direction at a second time to produce a field affecting the first magnetic field sensing element versus the external field having a first polarity.

The device can further include one or more of the following features: the curve for normalized sensitivity of the first magnetic field sensing element corresponds to an average of the first and second curves, the coil is integrated with the first magnetic field sensing element, and/or the magnetic field sensor comprises a back-biased sensor.

In another aspect of the invention, a method comprises: trimming a magnetic field sensor having a first magnetic field sensing element within an IC package, the trimming comprising using a curve for normalized sensitivity of the first magnetic field sensing element derived from first and second curves, the first curve corresponding to current through a coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field having a first polarity, and the second curve corresponding to current through the coil in the first direction to produce a field affecting the first magnetic field sensing element versus an external field having a second polarity.

The method can further include one or more of the following features: the curve for normalized sensitivity of the first magnetic field sensing element corresponds to an average of the first and second curves, trimming comprises determining an absolute sensitivity of the magnetic field sensor in LSB per mA, the magnetic field sensor comprises a back-biased sensor, the magnetic field sensing element comprises a Hall element, and/or determining a sensitivity of the coil while no external magnetic field is applied prior to packaging the first magnetic sensing element.

In a further aspect of the invention, a device comprises: a magnetic field sensor having a first magnetic field sensing element within an IC package; and a memory configured to store trimming information for the magnetic field sensor, wherein the trimming comprises using a curve for normalized sensitivity of the first magnetic field sensing element derived from first and second curves, the first curve corresponding to current through a coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field having a first polarity, and the second curve corresponding to current through the coil in the first direction to produce a field affecting the first magnetic field sensing element versus an the external field having a second polarity.

The device can further include one or more of the following features: the curve for normalized sensitivity of the first magnetic field sensing element corresponds to an average of the first and second curves, the coil is integrated with the first magnetic field sensing element, and/or the magnetic field sensor comprises a back-biased sensor.

In another aspect of the invention, a method comprises: trimming a magnetic field sensor having differential first and second magnetic field sensing elements spaced a given distance within an IC package, the trimming comprising using a first combined curve for normalized sensitivity of the first magnetic field sensing element derived from first and second curves, the first curve corresponding to current through a first coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field having a first polarity, and the second curve corresponding to current through the first coil in a second direction opposite to the first direction at a second time to produce a field affecting the first magnetic field sensing element versus the external field having the first polarity. The method can further include using a second combined curve for normalized sensitivity of the second magnetic field sensing element derived from third and fourth curves, the third curve corresponding to current through a second coil in a third direction at a third time to produce a field affecting the second magnetic field sensing element versus an external field having the first polarity, and the fourth curve corresponding to current through the second coil in a fourth direction opposite to the third direction at a fourth time to produce a field affecting the first magnetic field sensing element versus the external field having the first polarity. The method can further include combining the first and second combined curves, and/or the first time overlaps with at least one of the third and fourth times.

In a further aspect of the invention, a device comprises: a magnetic field sensor having differential first and second magnetic field sensing elements within an IC package; and a memory configured to store trimming information for the magnetic field sensor, wherein the trimming comprises using a first combined curve for normalized sensitivity of the first magnetic field sensing element derived from first and second curves, the first curve corresponding to current through a first coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field having a first polarity, and the second curve corresponding to current through the first coil in a second direction opposite to the first direction at a second time to produce a field affecting the first magnetic field sensing element versus the external field having the first polarity. The device can further include the memory being further configure to use a second combined curve for normalized sensitivity of the second magnetic field sensing element derived from third and fourth curves, the third curve corresponding to current through a second coil in a third direction at a third time to produce a field affecting the second magnetic field sensing element versus an external field having the first polarity, and the fourth curve corresponding, to current through the second coil in a fourth direction opposite to the third direction at a fourth time to produce a field affecting the first magnetic field sensing element versus the external field having the first polarity. The device can further include the first and second combined curves being combined. The device can further include the first time overlapping with at least one of the third and fourth times.

