Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Fusible link or intentional destruct circuit
Reexamination Certificate
2000-06-26
2002-01-29
Tran, Toan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Fusible link or intentional destruct circuit
Reexamination Certificate
active
06342807
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to manufacturing techniques for electronic components and more particularly to techniques for calibrating and adjusting operating characteristics of electronic components by programming non-volatile memory within the electronic components.
BACKGROUND OF THE INVENTION
The process of manufacturing precision analog components results in completed analog components with variable operating characteristics. This is generally due to normal variations in processes and materials used during manufacture.
Recently, in order to compensate for variations in the manufacture of analog components, manufacturers have provided fuses on the analog components. The fuses are connected to adjustable elements associated with analog devices on the analog component. The fuses may be selectively blown after manufacturing in order to adjust or “trim” certain operating characteristics of the analog component. In this regard, aspects of a manufactured analog component's operation may be measured and this measurement data may be used to determine which fuses to blow in order to trim the component so that it operates closer to predetermined specifications. Trimming is advantageous in many ways. For example, trimming allows manufacturers to offer analog components with greater accuracy and built in flexibility to optimize analog components for particular applications.
Conventionally, fuses on integrated circuit analog components have been implemented as segments of poly-silicon, metal or other material. These fuses are conventionally blown selectively, causing the fuse to create an open circuit, using a laser or by introducing a destructive electrical charge across the fuse through probe pads on the integrated circuit. Each of these techniques has several disadvantages.
First, blowing a fuse by laser or by destructive electrical charge applied to probe pads requires the fuses to be blown prior to packaging the integrated circuit. This is disadvantageous because the operating characteristics of the analog component, such as its offset voltage, may change as a result of the packaging process as well as the electrical characteristics of the package itself. Thus, trimming prior to packaging does not allow the manufacturer or anyone else to compensate for the effects of packaging on the analog component. Moreover, because most analog components are packaged prior to delivery to customers, it is generally not possible for customers to perform trimming.
Second, because blowing fuses in the conventional manner is destructive, it is not possible to undo the trimming process if desired. Additionally, blowing fuses may result in damaging passivation and other layers and structures on an integrated circuit. This damage may result in corrosion or other failure either immediately or over time.
Third, blown fuses may have conductive remnants which may migrate over time and reconnect leading to failure during operation in the field.
For the foregoing reasons, there is a need for a new technique for trimming analog components, and particularly those implemented as integrated circuits. There is a need to be able to perform the trimming either before or after packaging by the manufacturer, customer or third party if desired. There is a further need for trimming by a non-destructive process to avoid reliability problems and, in some instances, the irreversibility of destructive processes. There is still a further need for a trimming process which may be performed using a small number of input pins to the analog component.
SUMMARY OF THE INVENTION
According to the present invention, trimming of analog components is performed electrically using non-volatile fuses. The non-volatile fuses may be programmed electrically without destroying any passivation layers or other devices on the electronic component. In the case of an integrated circuit analog component, the trimming may be performed either at the wafer level or at the packaging level. Trimming at the packaging level permits the trimming to be performed to compensate for packaging induced variations. It also allows trimming to be performed by customers or other third parties on the packaged parts. Moreover, when implemented as erasable non-volatile fuses, the fuses may be programmed more than once.
According to one embodiment of the present invention, an analog electronic component includes input and output pins, analog devices and non-volatile fuses. The analog devices are operative to perform analog signal processing on signals received via at least one input pin and to output processed signals on at least one output pin. The analog devices include adjustable elements. The non-volatile fuses are coupled to the adjustable elements and are electrically programmable via at least some of the input pins. Programming the non-volatile fuses adjusts the adjustable elements to alter characteristics of the analog signal processing.
The analog electronic component may be an integrated circuit. It may include registers for storing fuse configuration data received from the input pins. The registers may include serial registers for receiving the configuration data serially from a single input pin. It may further include a multiplexer coupled between outputs of the registers and outputs of the non-volatile fuses and inputs to the adjustable elements. The multiplexer is operable to provide configuration data from the registers to the adjustable elements during a calibration mode and from the non-volatile fuses to the adjustable elements after programming of the analog component.
According to another embodiment of the invention, a method provides electrically trimmable analog components. The method includes: providing non-volatile fuses on an analog component and coupling the non-volatile fuses to analog devices on the analog component, wherein the non-volatile fuses are electrically programmable through input pins on the analog component. The method may further include providing registers on the analog component coupled to at least one of the input pins. Such registers store fuse configuration data received from the input pins.
According to still another embodiment of the invention, a method of programming electrically trimmable analog components includes loading calibration data into the analog component; measuring output signals from the analog component when configured with the calibration data; repeating the loading and measuring with different values for the calibration data until desired calibration data is determined; and electrically programming non-volatile fuses on the analog component with the desired calibration data. The method may further include verifying the proper programming of the non-volatile fuses. The method may also include programming the non-volatile fuses with a fuse lock value at the end of the electrical programming. The fuse lock maybe a separate NVM cell from the analog trimming fuses. Once the lock fuse is programmed, control of the analog trim circuitry is fixed to the NVM trimming fuses. Prior to this, control of the trim circuitry is switched to the registers.
REFERENCES:
patent: 5473758 (1995-12-01), Allen et al.
patent: 5671183 (1997-09-01), Soenen et al.
patent: 6260104 (2001-07-01), Roohparvar
patent: 6262919 (2001-07-01), Chou
Bindra, Ashok, Precision Op Amps Adopt Digital Techniques, Analog Outlook, Jul. 26, 1999, Electronic Design, beginning at p. 49.
Baker Bonnie
Kranz Glen
Nolan James B.
Microchip Technology Incorporated
Swidler Berlin Shereff & Friedman, LLP
Tran Toan
LandOfFree
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