KR20240161089A - Packaged current sensor integrated circuit - Google Patents

Abstract

A packaged current sensor integrated circuit (300) has an input portion (332) and an output portion (334), and includes a primary conductor (330) configured to transmit a current to be measured by a magnetic sensing element (309a, 309b) supported by a semiconductor die (308) adjacent to the primary conductor (330). The primary current path includes a mechanical locking function (355a, 355b). The thickness of the molded body of the package is reduced to improve vibration resistance.

Description

Packaged current sensor integrated circuit

CROSS-REFERENCE TO RELATED APPLICATIONS: This application claims priority and the benefit of U.S. patent application Ser. No. 17/409,011, filed Aug. 23, 2021, entitled “Packaged Current Sensor Integrated Circuit,” which is incorporated herein by reference.

Some conventional current sensors are placed near a current-carrying conductor and detect the magnetic field generated by the current passing through the conductor. The current sensor produces an output signal whose magnitude is proportional to the magnetic field induced by the current passing through the conductor.

According to the present disclosure, a packaged current sensor integrated circuit comprises a primary conductor having an input lead, an output lead, a first die attach portion, a second die attach portion, and a current conductor portion between the first and second die attach portions, wherein the primary conductor is configured to conduct current from the input lead through the first die attach portion, the current conductor portion, and the second die attach portion to the output lead, wherein at least one of the first and second die attach portions has a die attach portion edge adjacent to each of the input or output leads. The packaged current sensor integrated circuit comprises a mechanical locking feature spaced from the die attach portion edge; at least one secondary lead; a semiconductor die supported by the first and second die attach portions; at least one magnetic field sensing element supported by the semiconductor die; Here, the at least one magnetic field sensing element is disposed adjacent to the current conducting portion, and may further include a package body surrounding the semiconductor die and at least a portion of the primary conductor, wherein the input lead and the output lead extend from a first side of the package body, and the at least one secondary lead extends from a second side of the package body opposite the first side of the package body.

The features may include one or more of the following, individually or in combination with other features: The packaged current sensor integrated circuit may further include at least three secondary leads. At least one of the secondary leads may provide an output connection, a voltage input connection, and a ground connection. The packaged current sensor integrated circuit may further include a front-end amplifier, wherein at least one magnetic field sensing element is connected to the front-end amplifier. The at least one magnetic field sensing element may be a Hall effect sensor. The packaged current sensor integrated circuit may further include a Hall effect current driving circuit connected to the Hall effect sensor. The Hall effect sensor may be disposed adjacent the current conducting portion of the primary conductor. The at least one magnetic field sensing element may include a first Hall effect sensor disposed adjacent a first side of the current conducting portion, and the packaged current sensor integrated circuit may further include a second Hall effect sensor disposed adjacent a second side of the current conducting portion opposite the first side. The front end amplifier may be coupled to the amplifier to provide an output of the current level of the first conductor. The packaged current sensor integrated circuit may further include a wafer backside coating material on a backside of the semiconductor die. The packaged current sensor integrated circuit may further include a second wafer backside coating material on the backside of the semiconductor die. A distance between the primary conductor lead frame and the at least one secondary lead frame may be at least 0.125 mm. The mechanical locking feature may be spaced from the die attach edge by at least 0.50 mm. The current conducting portion of the primary conductor may have shaped conductor regions. A thickness of the package body may be less than 1.0 mm. A thickness of the primary conductor lead frame may be between 0.140 mm and 0.162 mm.

Also, a method of sensing current in a current sensor integrated circuit package described herein comprises the steps of providing a primary conductor having an input lead, an output lead, a first die attach portion, a second die attach portion, and a primary conductor portion, wherein the primary conductor is configured to conduct current from the input lead through the first die attach portion, the primary conductor portion, the second die attach portion, and the output lead. The method further comprises the steps of providing a mechanical locking feature to the primary conductor spaced from an edge of the die attach portion; providing at least one secondary lead; providing a semiconductor die disposed adjacent to the primary conductor; providing at least one magnetic field sensing element supported by the semiconductor die; wherein the at least one magnetic field sensing element is disposed adjacent to the primary conductor portion, and providing an output signal indicative of the current in the primary conductor.

The features may include one or more of the following, individually or in combination with other features: The method may further comprise providing the at least one magnetic field sensing element as a first magnetic field sensing element disposed adjacent a first side of the current conducting portion, and the method may further comprise providing a second magnetic field sensing element disposed adjacent a second side of the current conducting portion opposite the first side. The method may also further comprise providing the magnetic field sensing element as one of a planar Hall effect element, a vertical Hall effect element, an anisotropic magnetoresistance (AMR) element, a giant magnetoresistance (GMR) element or a tunneling magnetoresistance (TMR) element.

The features of the present disclosure described above and the content of the present disclosure itself can be more fully understood from the description of the following drawings:
Figure 1 shows a plan view of a packaged current sensor integrated circuit.
Figure 1a shows a cross-sectional side view of the packaged current sensor integrated circuit package of Figure 1.
Figure 1b shows a bottom view of the packaged current sensor integrated circuit of Figure 1.
Figure 1c shows a side view of the packaged current sensor integrated circuit of Figure 1.
Figure 2 shows an exemplary circuit of a die in the packaged current sensor integrated circuit of Figure 1.
Figure 3 shows a plan view of a packaged integrated circuit having a small form factor.
Figure 3a shows a cross-sectional view along line A~A' of Figure 3.

The term "magnetic field sensing element" as used herein is used to describe a variety of electronic elements capable of sensing a magnetic field. The magnetic field sensing element may be, but is not limited to, a Hall effect element, a magnetoresistive element, or a magnetic transistor. As is known, there are various types of Hall effect elements, such as planar Hall elements, vertical Hall elements, and circular vertical Hall (CVH) elements. Also as is known, there are various types of 'magnetoresistive elements', such as semiconductor magnetoresistive elements, such as indium antimonide (InSb), giant magnetoresistive (GMR) elements, such as spin valves, anisotropic magnetoresistive (AMR) elements, tunneling magnetoresistive (TMR) elements, and magnetic tunnel junctions (MTJs). The magnetic field sensing element may be a single element, or may include two or more magnetic field sensing elements arranged in various configurations, such as a half-bridge or a full (Wheatstone) bridge. Depending on the device type and other application requirements, the magnetic field sensing element may be made of a type IV semiconductor material, such as silicon (Si) or germanium (Ge), or a type III-V semiconductor material, such as gallium-arsenide (GaAs) or an indium compound, such as indium-antimonide (InSb).

As is known, some of the magnetic field sensing elements described above tend to have their maximum sensitivity axes parallel to the substrate supporting the magnetic field sensing element, while other of the magnetic field sensing elements tend to have their maximum sensitivity axes perpendicular to the substrate supporting the magnetic field sensing element. In particular, planar Hall elements tend to have their sensitivity axes perpendicular to the substrate, while metal-based or metal magnetoresistive elements (e.g., GMR, TMR, AMR) and vertical Hall elements tend to have their sensitivity axes parallel to the substrate.

The term "magnetic field sensor" as used herein is generally used to describe a circuit that uses a magnetic field sensing element in combination with other circuitry. Magnetic field sensors include, but are not limited to, angle sensors that detect the angle of a magnetic field direction, current sensors that detect a magnetic field generated by a current carried by a current carrying conductor, magnetic switches that detect the proximity of a ferromagnetic object, rotation detectors that detect the magnetic field of a passing ferromagnetic object, e.g., a ring magnet or a ferromagnetic target (e.g., a gear tooth) when the magnetic field sensor is reverse biased or used in conjunction with another magnet, and magnetic field sensors that detect the magnetic field density of a magnetic field.

The term "processor" or "controller" as used herein is used to describe an electronic circuit that performs a function, operation, or sequence of operations. The function, operation, or sequence of operations may be hard-coded into the electronic circuit or soft-coded via instructions maintained in a memory device. The "processor" may perform the function, operation, or sequence of operations using digital values or analog signals. In some embodiments, the "processor" may be implemented as an application specific integrated circuit (ASIC), which may be an analog ASIC or a digital ASIC. In some embodiments, the "processor" may be implemented in a microprocessor having associated program memory. In some embodiments, the "processor" may be implemented as a discrete electronic circuit, which may be analog or digital. A processor may include an internal processor or internal module that performs portions of the function, operation, or sequence of operations of that processor. Likewise, a module may include an internal processor or internal module that performs portions of the function, operation, or sequence of operations of that module.

Although the electronic circuits depicted in this drawing may be depicted in the form of analog blocks or digital blocks, it will be understood that the analog blocks may be replaced with digital blocks performing the same or similar functions, and the digital blocks may be replaced with analog blocks performing the same or similar functions. Analog-to-digital conversion or digital-to-analog conversion may not be explicitly depicted in the drawing, but will be readily understood by those skilled in the art.

In particular, it should be understood that the so-called comparator may include an analog comparator having a two-state output signal indicating that an input signal is higher or lower than a threshold level (or that one input signal is higher or lower than another input signal). However, the comparator may also include a digital circuit having an output signal having at least two states indicating that an input signal is higher or lower than a threshold level (or that one input signal is higher or lower than the other input signal), or a digital value higher or lower than a digital threshold (or another digital value).

Fig. 1 shows a plan view of a packaged current sensor integrated circuit (100). The package body (102) may be a mold compound and is indicated by an outline for clarity.

The primary conductor (130) has input and output portions, each of which may include a die attach portion (132, 134) supporting a semiconductor die (108). The primary conductor (130) has input leads (136a, 136b) on a first side of the package, input leads (136c, 136d) on a second side of the package, output leads (138a, 138b) on a third side of the package, and output leads (138c, 138d) on the second side of the package. The input leads (136a, 136b, 136c, 136d) are connected to the die attach pad (132), and the output leads (138a, 138b, 138c, 138d) are connected to the die attach pad (134).

The current sensor integrated circuit (100) also has secondary leads (120a, 120b, 120c, 120d, 120e). Wire bonds (140a, 140B, 140c, 140d, 140e, 140f) connect the die (108) to the secondary leads, or signal leads (120a, 120b, 120c, 120d, 120e). The secondary lead (120c) is connected to the die (108) using two wire bonds (140c, 140e). This may be advantageous when a potential for higher current may exist, such as a power or ground connection to the die (108).

The current path portion (133) of the primary conductor can interconnect the die attach pads (132, 134) and can be a narrowed portion as illustrated. The primary conductor (130) has a partial current path forming a straight line across the package body from a first side of the package having leads (136a, 136b) to a third side of the package having leads (138a, 138b). The die (108) supports at least one magnetic field sensing element, and in FIG. 1, two magnetic field sensing elements (109a, 109b). The die (108) can also support circuitry for amplifying and processing a signal from the magnetic field sensing element and providing an output of the current sensor integrated circuit (100). When a current flows through the current conductor (133), a magnetic field is generated, which can be detected by the magnetic field sensing elements (109a, 109b). In FIG. 1, the magnetic field sensing elements (109a, 109b) are positioned away from the current conductor (133) or on one side of the current conductor (133) so that the magnetic field generated by the current flowing in the current conductor (133) has a component that is perpendicular to the die, so that a planar Hall effect sensor can be used for the magnetic field sensing elements (109a, 109b). In another embodiment, the magnetic field sensing elements or elements can be positioned over the primary current conductor to sense the magnetic field with a component parallel to the surface of the die (108). When the magnetic field component to be detected is parallel to the surface of the die, a vertical Hall element, a magnetoresistive element such as a GMR, TMR, or AMR element can be used.

Also referring to FIG. 1a, where like components are indicated with like reference numerals, a cross-sectional view of a packaged current sensor integrated circuit (100) is shown taken along line A-A of FIG. 1. A package body (102) may have a recessed portion (104) around a package bottom. A die (108) is supported by a primary conductive die attach portion (132) having a thinned portion (132a). The die (108) may be attached to the die attach portion (132) by a non-conductive coating, such as a wafer backside coating (WBC), shown in two layers (110, 112). In manufacturing, when two wafer backside coating layers (110, 112) are used, the first wafer backside coating layer (110) may be fully cured (or partially cured if only one layer of wafer backside coating is used) before the second wafer backside coating layer (112) is partially cured (also known as a B-stage cure) to be used for final attachment of the die (108) to the die attach portion (132) of the primary conductor (130) of FIG. 1.

In other embodiments, the die (108) may be attached to the die attach portion (132) by other materials including but not limited to a non-conductive die attach epoxy or tape. Multiple layers of wafer backside coatings, tapes, and non-conductive epoxies may be used for electrical insulation. A combination of wafer backside coatings, tapes, or non-conductive epoxies may be used to achieve electrical insulation and attachment to the die attach portion (132).

The die (108) can be electrically connected to the secondary lead (120b) using wire bonds (140). The secondary lead (120b) can have a recessed portion (122) and/or a thin portion (124) that provides locking features with the mold compound (102). The thin portion (124) can be the result of a half-etch lead frame process. An example of a half-etch process is where the lead frame is etched on both sides and one etched side is masked or patterned such that a portion of the thickness (or approximately half) of the lead frame remains on or in the lead frame. The package body (102) and the secondary lead (102b) can have cutouts or recesses (104), which in embodiments can be around all of the bottom edges of the packaged current sensor integrated circuit (100).

Also, referring to FIG. 1b, a bottom view of a packaged current sensor integrated circuit (100) is illustrated, wherein like components are indicated by like reference numerals. The secondary leads 120a, 120b, 120c, 120d, 120e have portions exposed on the bottom of the package (100). The primary current conductor (130) is illustrated with at least a portion of the die attach portion (132, 134), the current conducting portion (133), and the leads (136a, 136b, 136c, 136d, 138a, 138b, 138c, 138d) exposed on the bottom of the package (100). When used, the exposed portions of the die attach pads (132, 134) can be connected to a circuit board or other substrate, and due to the larger connection area that can be present between the substrate and the first conductor (130), the connection resistance can be lowered, which results in lower power loss due to the connection resistance of the current sensor package (100) to the circuit board. In another embodiment, the solder connection may be provided with a current conducting portion (133). If the solder connection or current path is below the area (133), the accuracy of the current sensor integrated circuit (IC) can be improved if the gain of the current sensor integrated circuit is programmed with the current path of the current conducting portion (133) that is parallel to the solder and PC board conductors.

Also referring to FIG. 1c, a side view of a packaged current sensor integrated circuit (100) is illustrated where like components are labeled with like reference numerals. The primary conductor input/output leads (138a, 138b) and the signal or secondary lead (120e) are exposed and substantially flush with the plastic of the package body (102). The distance between the secondary lead (120e) and the primary lead (138a) is selected to meet the electrical insulation requirements of the application. In an embodiment, the spacing from the primary lead to the secondary lead is at least 1.0 mm on the surface or exterior or on the package to allow for a voltage insulation rating of 100 V.

A recess (104) and leads (138a, 138b, 120e) of the package body (102) are depicted around the lower edge of the package. The recess (104) can be used to inspect or verify solder connections between the package (100) and a PC board or assembly when the packaged current sensor integrated circuit (100) is assembled to a printed circuit board or other assembly.

In one embodiment, the primary conductor (130) and the secondary leads (120a-e) can have a thickness of from about 0.2 mm to about 0.5 mm. In another embodiment, the primary and secondary leads have a thickness of from about 0.375 mm, and in some cases from about 0.35 to about 0.40 mm, which is thicker than standard integrated circuit packages where the standard thickness can be on the order of 0.2 mm-0.25 mm +/- 0.025 mm due to manufacturing tolerances. The thicker primary conductor serves to increase the cross-section perpendicular to the current flow. Increasing the thickness of the current conducting material in the primary conductor (130) and the current path (133) reduces power loss in a system utilizing the current sensor package (100) of FIG. 1.

As described above, the recessed portion (104) of the package body (102) can facilitate inspection of the packaged current sensor integrated circuit (100) once it has been put into use (e.g., soldered to a circuit board). Due to the configuration of the primary conductor leads (136a - 136d, 138a - 138d), such inspection can be performed on three sides of the package circuit (100). As illustrated in FIGS. 1 and 1B, the leads (136a, 136b and 136c, 136d) of the primary conductor (130) allow inspection of solder on adjacent sides of the package that are substantially orthogonal to one another. Likewise, leads (138a, 138b and 138c, 138d) allow for inspection of solder on adjacent sides of the package that are substantially orthogonal to one another. Leads (136c, 136d) and leads (138c, 138d) are on the same side of the package (100).

In another embodiment, the lead frame thickness may be a standard lead frame thickness. The primary current planned to be sensed by the current sensor package (100) or the absolute resistance required by the application may determine the required lead frame thickness.

Referring to FIG. 2, a schematic diagram of an exemplary circuit block diagram of an integrated circuit (200) that may be on the die (108) of FIG. 1 is illustrated. A primary current I _p (290) flows through the current conducting portion (233) (which may be identical to or similar to the primary conductor (130) of FIG. 1) and generates a magnetic field B (295). When the current conducting portion (233) is below the die (200) (according to the right-hand rule), the magnetic field (295) in FIG. 2 includes a component that rises into the die at the magnetic field sensing element (209b) and descends into the magnetic field sensing element (209a) for the current flowing from top to bottom. The magnetic field sensing elements (209a, 209b) may be, for example, planar Hall effect plates. The magnetic field (295) results in the Hall effect plates (209a, 209b) providing a signal to a front-end amplifier (250). The front-end amplifier (250) provides an output to an amplifier (254), which may be a linear amplifier, which is fed to an output circuit (256). The output circuit (256) may be a digital or analog circuit providing an output to at least one bond pad, or may be two bond pads (220d, 220e) as shown in FIG. 2. The output bond pad (220e) may be a linear output representing the magnetic field (295) measured and amplified by the amplifier (254). Any other number of output bond pads may be provided. In an alternative embodiment, the amplifier (254) may provide an output directly to the bond pad (220e). The output bond pad (220d) may be a fault output representing a fault condition of the current sensor integrated circuit package.

The bond pad (220a) provides voltage and current inputs (typically Vcc) to power the integrated circuit (200). A ground bond pad (220c) may be provided to the integrated circuit (200). In other embodiments, the voltage level provided to the bond pad (220c) may be a voltage other than ground, or a voltage higher or lower than ground as a reference voltage for the integrated circuit (200). The input bond pad (220a) is coupled to a master current supply circuit (260) that provides power to the circuitry within the integrated circuit (200). The master current supply circuit (260) is provided as a current supply, but it will be appreciated that voltages may also be provided to the circuitry on the integrated circuit (200). A Hall effect current drive circuit (262) takes current (or voltage) from the master current supply circuit (260) and provides a regulated current to the Hall effect sensing elements (209a, 209b). The master current supply circuit (260) also supplies power to a power on reset circuit (270). The power on reset circuit monitors power entering the circuit (200) and provides a signal to the EEPROM and control logic circuit (272). The power on reset circuit (270) and the EEPROM and control logic circuit (272) are used to configure and activate the integrated circuit including the output circuit (256).

The EEPROM and control circuit (272) provides a signal to the sensitivity control circuit (274), which provides a signal to the front end amplifier (250) to adjust the sensitivity of the front end amplifier. The adjustment may be a result of a change in the power level of the circuit (200) or a change in the temperature of the circuit (200). The temperature sensor circuit is not shown in FIG. 2. Examples of temperature sensor circuits may include, but are not limited to, the use of a diode temperature sensor or a known temperature compensation resistor.

The EEPROM and control circuit (272) provides a signal to the offset control circuit (276). The offset control circuit (276) provides a signal to the amplifier (254). The offset control circuit (276) allows the circuit (200) to adjust the offset of the amplifier (254) for changes in power or temperature (temperature compensation circuit not shown) or a combination of temperature and power changes. The offset control circuit (276) may also provide adjustment for other offset sources, such as stress on the integrated circuit die.

In other embodiments, the EEPROM and control circuitry (272) may be replaced with other types of memory, or used in combination with other types of non-volatile memory, including but not limited to metal or polysilicon fuses, flash memory, or MRAM.

An input lead (220b) may be provided to set a threshold for a fault indication circuit (280) (i.e., to provide a fault trip level). In one embodiment, the input lead (220b) provides a fault voltage level. The fault indication circuit (280) comprises a threshold circuit (282) and a fault comparator (284). The EEPROM and control circuit (272) provide an input to the threshold circuit (282). The threshold circuit (282) provides a signal to the fault comparator (284), which compares the output of the threshold circuit (282) with the output of the front end amplifier (250) to indicate when a fault is present in the output circuit block (256). The output circuit generates a fault output at the output bond pad (220d). The fault output may indicate an overcurrent condition in which the current detected in the current conductor path (233) exceeds a fault trip level, which may be provided in the form of a fault voltage level at the bond pad (220b). In one example, the fault allows a user of the current sensor package (100) of FIG. 1 to interrupt current in the primary current path to prevent a high current condition in an electrical circuit connected to the primary conductor (130) of FIG. 1.

In one embodiment, the function of the fault indication circuit (280) may be performed in a digital circuit or a digital processor. The comparison with the fault trip level may include an analog-to-digital circuit (ADC) prior to the digital logic circuit, which may include a processor or microprocessor circuit that compares the fault trip level voltage to a voltage provided by the front end amplifier and ADC circuitry and converts the analog voltage of the front end amplifier (250) to a digital voltage. In one embodiment, the amplifier (250) may be a buffer amplifier having a gain close to or equal to unity (or one (1)). In other embodiments, the amplifier (254) may introduce a non-unity gain.

In one embodiment, a multiplexer circuit may be used to allow the output of the front end amplifier circuit (250) and the fault trip level voltage to use the same ADC. It will be apparent to those skilled in the art that other circuits, such as timing circuits and sample and hold circuits, may be used to implement the multiplexer digital circuit.

FIG. 3 illustrates a perspective view of a packaged current sensor integrated circuit (300) that can be manufactured in a small package body, for example, a molded package body having cross-sectional dimensions of about 2.98 mm x 1.95 mm and a thickness of 1.00 mm. The package body (302) can be a mold compound and is outlined for clarity. The current sensor integrated circuit (300) of FIG. 3 can utilize thinner lead frame material than other integrated current sensors to reduce the package size. A smaller package can require less space when assembling or using the current sensor integrated circuit of FIG. 3 on a substrate, circuit assembly, or module. A thinner package can provide greater vibration immunity compared to a thicker molded package body. A standard SOIC-8 style package can measure on the order of 4.9 mm x 3.9 mm x 1.47 mm. An industry standard SOT23 package can measure on the order of 2.90 mm x 1.60 mm x 1.15 mm. Although the length and width of the described package are larger than the standard SOT23 package, reducing the package thickness from 1.15 mm for the standard SOT23 to less than 1.00 mm for the described package can increase vibration immunity or reduce the effects of mechanical vibration in current sensor applications.

The primary conductor (330) has an input portion and an output portion, and includes an input lead (336), an output lead (338), and a die attach portion (332, 334) that supports a semiconductor die (308). The primary conductor (330) has an input lead (336) and an output lead (338) on a first surface of the package. The input lead (336) is connected to the die attach pad (332), and the output lead (338) is connected to the die attach pad (334).

The current sensor integrated circuit (300) also has secondary leads (320a, 320b, 320c). Wire bonds (340a, 340b, 340c) connect the die (308) to the secondary leads or signal leads (320a, 320b, 320c). In one embodiment, a low loop height wire bond process may be used to allow for a reduction in package body thickness.

The current path (395) of the primary conductor lead frame includes an input lead (336), a die attach portion (332), a current conducting portion (333), a die attach portion (334), and an output lead (338) of the primary conductor (330). The current conducting portion (333) connects the die attach pads (332, 334) and may be a narrow portion as illustrated in FIG. 3. The die (308) supports two magnetic field sensing elements (309a, 309b). The die (308) may also support circuitry for amplifying and processing signals from the magnetic field sensing elements and providing an output of the current sensor integrated circuit (300). When current flows through the current conducting portion (333), a magnetic field is generated, which may be detected by the magnetic field sensing elements (309a, 309b). In FIG. 3, the magnetic field sensing elements (309a, 309b) are disposed on the die (308) and on the surface of the current conducting portion (333) such that a magnetic field generated by a current flowing in the current conducting portion (333) has a component in a direction perpendicular to the die (308) in the area where the magnetic field sensing elements (309a, 309b) are disposed, for example, a planar Hall effect sensor may be used for the magnetic field sensing elements (309a, 309b). In another embodiment, the magnetic field sensing elements, or elements, may be disposed over the primary current conducting portion to sense a magnetic field having a component parallel to the surface of the die (308). When the magnetic field component to be sensed is parallel to the surface of the die, a vertical Hall effect element or a magnetoresistive element such as a GMR, TMR or AMR element may be used.

Using two magnetic field sensing elements (309a, 309b) can improve stray field immunity and reduce the effects of external magnetic fields on the current sensor integrated circuit (300). For example, for current flowing from the left to right of the drawing from the input lead (336) to the output lead (338) as illustrated by arrow (395), the magnetic field outside the page is observed by the sensing element (309a), and the magnetic field inside the page is observed in the region of the sensing element (309b). A summing circuit can be used to calculate the magnetic field proportional to the current flowing in the current conducting portion (333). The sensing elements (309a, 309b) may be arranged or biased such that any stray or common external magnetic field affects one sensing element (309a) positively and the other sensing element (309b) negatively, such that when combined, the external magnetic fields cancel each other out, but the expected magnetic field generated by the current in the primary conductor may be arranged or biased such that it has, for example, twice the value from either magnetic sensing element.

Other magnetic field sensing elements, such as vertical Hall elements, GMR, or TMR magnetic field sensing elements, may be positioned on the current conducting portion (333) of FIG. 3. The TMR, GMR, or vertical Hall elements may be used to measure the magnetic flux in a direction generally parallel to the surface of the die (308), which is the direction of the magnetic flux generated by the current in the primary conductor on the current conducting portion (333). A second vertical Hall element, GMR, or TMR magnetic field sensing element may also be positioned on the current conducting portion (333). Other combinations of magnetic field sensing elements, including but not limited to planar Hall elements, vertical Hall elements, GMR, TMR, or AMR, may be positioned on the surface-facing regions of the current conducting portion (333) or on the region above the current conducting portion (333). The placement of the magnetic sensing elements will be determined in part by the maximum sensitivity axis of the selected magnetic sensing element type, for example, a planar Hall element will have its maximum sensitivity axis perpendicular to the plane of the die (308), whereas vertical Hall elements, GMR, TMR and AMR elements will have their maximum sensitivity axes parallel to the surface of the die (308).

In another embodiment, only one magnetic field sensing element may be positioned on the die (308) at the location of the element (309a or 309b) or positioned over the current conducting portion (333). In another embodiment, there may be additional magnetic field sensing elements. For example, the elements (309a, 309b) may include multiple Hall elements, including but not limited to multiple dual Hall effect elements or multiple quad Hall effect elements. The multiple magnetic field sensing elements may be on top of the current conducting portion (333) or on only one side. In an embodiment, one magnetic field sensing element (309a or 309b) may be present only on the current conducting portion (333), and multiple magnetic field sensing elements may be present at different locations or on the current conducting portion (333).

FIG. 3A illustrates a side view of the current sensor integrated circuit (300) of FIG. 3 taken along line A-A' of FIG. 3. As the lead frame thickness is reduced, the molded package thickness (350) can be further reduced or made thinner. As the mold body package thickness (350) is reduced, the mechanical vibration performance of the current sensor integrated circuit package (300) can be improved, for example, when assembled on a circuit board. In one embodiment, the package thickness (350) is less than 1.0 mm. In another embodiment, the package thickness ranges from 0.95 to 0.98 mm. In one embodiment, the lead frame thickness (331) is typically 150 microns or 6 mils thick.

In an embodiment, the current sensor integrated circuit (300) of FIGS. 3 and 3A can use a lead frame material thickness (331) of about 150 microns, or 6 mils, or a thin lead frame material. The lead frame thickness (331) can vary between 5 and 7 mils, or between about 125 and 175 microns (about 0.125 mm to 0.175 mm), depending on manufacturing tolerances. In other embodiments, the lead frame thickness can be between 0.140 mm and 0.162 mm. For example, a standard lead frame thickness for a SOIC-8 style current sensor package can be nominally 8 mils, or in the range of 200 microns or 190 to 210 microns.

To achieve 300 V dielectric insulation, the distance between the primary conductor (330) and the signal leads (320a, 320b, 320c) should be nominally 0.160 mm or about 6.4 mils, with a minimum distance of at least 0.125 mm or about 5 mils taking into account manufacturing tolerances. In an embodiment, the secondary leads (320a, 320b, 320c) are provided on a second opposite side of the package body from the primary input lead (336) and the primary output lead (338).

The die (308) is supported by a first conductor die attach portion (332, 334). The die (308) may be attached to the die attach portion (332, 334) by a non-conductive coating, such as a wafer backside coating (WBC), which may be two-layered as illustrated in FIG. 1A. In manufacturing, when a two-layer wafer backside coating is used, after the first wafer backside coating layer is fully cured (or partially cured if only one layer of the wafer backside coating is used), the second wafer backside coating layer is partially cured (also called a B-stage cure) and can be used to finally attach the die (308) to the die attach portion (332, 334) of the primary conductor (330) of FIG. 3.

In other embodiments, the die (308) may be attached to the die attach portion (332, 334) by other materials including but not limited to a non-conductive die attach epoxy or tape. Multiple layers of wafer backside coatings, tapes, and non-conductive epoxies may be used for electrical insulation. A combination of wafer backside coatings, tapes, or non-conductive epoxies may be used to achieve electrical insulation and attachment to the die attach portion (332, 334).

In an embodiment, the primary conductor (330) can include filleted, contoured, or shaped conductor regions (358a, 358b, 358c, 358d) between the die attach portions (332, 334) and the current conducting portion (333). In one embodiment, the fillet can have a radius of greater than or equal to about 0.20 mm. In one embodiment, the fillet dimension can be between 0.18 mm and 0.30 mm. The shaped conductor regions (358a, 358b, 358c, 358d) change the current flow within the first conductor (330) such that the magnetic field generated by the current flow in the first conductor (330) becomes more uniform near the magnetic field sensing elements (309a, 309b) or over the current conducting portion (333) of the first conductor (330). The more elongated conductor regions (358a, 358b, 358c, 358d) reduce the error of the current measured at the primary conductor portion (333), thereby enabling the current sensor having the shaped conductor regions to achieve more accurate current measurements. In an embodiment, the distance from the die attach portion (332) to the die attach portion (334), which is indicated by the dimension (352) including the shaped conductor regions (358a, 358b, 358c, 358d) and the current conductor portion (333), is about 0.60 mm, and in one embodiment between 0.50 mm and 0.70 mm.

The first conductor (330) may include mechanical locking features (355a, 355b) that serve to improve the moisture sensitivity level (MSL) performance of the package, which is critical to reliability. The mechanical locking features (355a, 355b) may be positioned as follows: that is, the mechanical locking features (355a, 355b) may be positioned such that the proximate edges (357a, 357b) of the mechanical locking features (355a, 355b) are positioned such that there is space between the die attach edges (351a, 351b) adjacent the primary input and output leads (336, 338) and the proximate edges (357a, 357b) of the mechanical locking features (355a, 355b). Any material removed from the primary conductor (330) can increase resistance. Placing the mechanical locking feature (355a, 355b) outside of the primary current path (395) increases the resistance of the primary conductor (330) less. Creating one or more holes in the primary conductor near the input lead (336) and/or the output lead (338) increases the electrical resistance of the primary conductor (330) because there is less lead frame material for the current to pass through. The gap (353a, 353b) allows more of the lead frame material to remain intact in the primary current path (395), thereby maintaining a lower resistance of the primary conductor as measured at the input and output leads (336, 338) created by the removal of lead frame material to form the mechanical locking feature (355a, 355b). In one embodiment, the mechanical locking features (355a, 355b) are semicircular with a radius of 0.15 mm to 0.25 mm. In one embodiment, the mechanical locking features (355a, 355b) have a radius of nominally 0.20 mm. The die attach edges (351a, 351b) are 0.2 mm inside the package body (302), and the gap (353a, 353b) is at least 0.4 mm. In one embodiment, the gap (353a, 353b) is between 0.4 mm and 0.6 mm. In one embodiment, the gap (353a, 353b) is nominally 0.50 mm. In another embodiment, the mechanical locking features (355a, 355b) can have a gap (353a, 353b) of 0.0 mm. The shape of the mechanical locking features may be other than semicircular, including but not limited to a hole in the primary conductor, a rectangular cut-out, or a triangular cut-out.

The current sensor integrated circuit (300) may have a circuit similar to that illustrated in FIG. 2. The three signal leads (320a, 320b, 320c) of the current sensor integrated circuit (300) may be a Vcc or input voltage or power pin or lead, an output pin or lead, and a ground or reference pin or lead. The current sensor integrated circuit (300) may have an output protocol circuit to provide an output protocol on the output lead or pins so that more data can be transmitted from a single pin or output lead. In another embodiment, a two-wire output may be used where data is transmitted by changes in current provided on the Vcc or ground leads.

It is understood that any of the processing described above may be implemented in hardware, firmware, software, or a combination thereof. The processing may be implemented in a computer program running on programmable computers or machines, each of which may include a processor, a storage medium or other article readable by the processor (including volatile and/or nonvolatile memory and/or storage elements), at least one input device, and one or more output devices. The program code may be applied to data input using the input device to perform processing and generate output information.

Having described the exemplary embodiments of the present disclosure, it will now be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. The embodiments included herein should not be limited to the disclosed embodiments, but rather should be limited only by the spirit and scope of the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

Components of the different embodiments described herein may be combined to form other embodiments not specifically set forth above. Various elements described in the context of a single embodiment may also be provided separately or in any suitable subcombination. Other embodiments not specifically set forth herein are also within the scope of the following claims.

Claims (19)

A primary conductor having an input lead and an output lead, a first die attach portion, a second die attach portion, and a current conducting portion between the first and second die attach portions; wherein the primary conductor is configured to conduct current from the input lead through the first die attach portion, the current conducting portion, and the second die attach portion to the output lead, and at least one of the first and second die attach portions has a die attach portion edge adjacent to a respective one of the input or output leads;
A mechanical locking feature spaced from the die attachment edge;
At least one secondary lead;
A semiconductor die supported by the above and second die attach portions;
At least one magnetic field sensing element supported by said semiconductor die; wherein said at least one magnetic field sensing element is disposed adjacent to said current conducting portion, and
A packaged current sensor integrated circuit comprising a package body surrounding the semiconductor die and at least a portion of the primary conductor, wherein the input lead and the output lead extend from a first side of the package body, and wherein the at least one secondary lead extends from a second side of the package body opposite the first side of the package body. A packaged current sensor integrated circuit characterized in that in claim 1, it further comprises at least three secondary leads. A packaged current sensor integrated circuit, characterized in that in claim 2, at least one secondary lead provides an output connection, at least one secondary lead provides a voltage input connection, and at least one secondary lead provides a ground connection. A packaged current sensor integrated circuit, characterized in that in the first aspect, further comprising a front-end amplifier, wherein the at least one magnetic field sensing element is connected to the front-end amplifier. A packaged current sensor integrated circuit, characterized in that in claim 1, at least one magnetic field sensing element is a Hall effect sensor. A packaged current sensor integrated circuit, characterized in that in claim 5, further comprises a Hall effect current driving circuit connected to the Hall effect sensor. A packaged current sensor integrated circuit, characterized in that in claim 5, the Hall effect sensor is disposed adjacent to the current conducting portion of the primary conductor. A packaged current sensor integrated circuit, characterized in that in claim 7, the at least one magnetic field sensing element comprises a first Hall effect sensor disposed adjacent to a first side of the current conducting portion, and the packaged current sensor integrated circuit further comprises a second Hall effect sensor disposed adjacent to a second side of the current conducting portion opposite to the first side. A packaged current sensor integrated circuit, characterized in that in the first aspect, the front-end amplifier is connected to the amplifier to provide an output of the current level of the primary conductor. A packaged current sensor integrated circuit, characterized in that in claim 1, further comprises a wafer backside coating material on the backside of the semiconductor die. A packaged current sensor integrated circuit, characterized in that in claim 10, a second wafer backside coating material is further provided on the backside of the semiconductor die. A packaged current sensor integrated circuit, characterized in that in the first aspect, the distance between the primary conductor lead frame and the at least one secondary lead frame is at least 0.125 mm. A packaged current sensor integrated circuit, characterized in that in the first aspect, the mechanical locking function portion is spaced apart from the die attach edge portion by at least 0.50 mm. A packaged current sensor integrated circuit, characterized in that in the first aspect, the current conducting portion of the primary conductor has shaped conductor regions. A packaged current sensor integrated circuit, characterized in that in claim 1, the thickness of the package body is less than 1.0 mm. A packaged current sensor integrated circuit, characterized in that in the first paragraph, the thickness of the primary conductor lead frame is between 0.140 mm and 0.162 mm. A step of providing a primary conductor having an input lead and an output lead, a first die attach portion, a second die attach portion, and a primary conductor portion; wherein the primary conductor is configured to conduct current from the input lead through the first die attach portion, the primary conductor portion, the second die attach portion, and the output lead;
A step of providing a mechanical locking feature to the primary conductor spaced from the die attach edge;
A step of providing at least one secondary lead;
A step of providing a semiconductor die positioned adjacent to the primary conductor;
providing at least one magnetic field sensing element supported by said semiconductor die; wherein said at least one magnetic field sensing element is disposed adjacent to said primary conducting portion, and
A method for detecting current in a current sensor integrated circuit package, characterized by comprising the step of providing an output signal representing the current of the primary conductor. A method for sensing current in a current sensor integrated circuit package, wherein in claim 17, the at least one magnetic field sensing element comprises a first magnetic field sensing element disposed adjacent to a first surface of the current conducting portion, and the method further comprises a step of providing a second magnetic field sensing element disposed adjacent to a second surface of the current conducting portion opposite to the first surface. A method for sensing current in a current sensor integrated circuit package, characterized in that in claim 17, the magnetic field sensing element is one of a planar Hall effect element, a vertical Hall effect element, an anisotropic magnetoresistance (AMR) element, a giant magnetoresistance (GMR) element, or a tunneling magnetoresistance (TMR) element.