Integrated circuit with authomatic pin-strapping configuration

The present invention relates generally to the field of integrated circuits in general and configuration of internal parameters in particular.

An integrated circuit or “chip” is generally installed on a system board which is ultimately installed in an end product. Commonly, an integrated circuit may be purchased for use in several (or many) different end products, often by different manufacturers. Consequently, a single chip design may have to be “fine tuned” or configured for optimal performance in a particular product. Moreover, due to tolerances and other inaccuracies in other components, it may even be important to be able to configure each chip when it is installed on the system board.

It will be appreciated that it may be impractical to use a separate chip design for similar applications. However, in the past, it has also been impractical to fine tune chips with external components. One known technique requires that specified pins of the chip be tied to external fixed components having values chosen to provide the necessary adjustment to a particular chip parameter. Another technique requires the use of external variable components which can be adjusted iteratively until the chip achieves the desired level of performance. In still another technique, internal fuses or the like in parallel with circuit trimming components are “blown” to attain target values.

Pin strapping techniques have been used, for example, to test chips. An otherwise unused pin is tied to an external ground or voltage to place a chip in either a test mode or a normal operating mode.

However, there remains a need for an integrated circuit having an inexpensive and efficient method for configuring internal parameters.

The present invention provides an integrated circuit in which one or more internal parameters may be automatically configured for a particular application. The integrated circuit includes a plurality of program select pins, each being in a predetermined fixed state, and at least one configuration pin associated with a parameter to be adjusted. Jumpers on the system board to which the integrated circuit is mounted connect the mounting pad of each configuration pin with the mounting pad of a selected program select pin. Consequently, when the integrated circuit is mounted on the system board, each configuration pin receives a selected value which internal configuration circuitry detects and adjusts the corresponding parameter accordingly.

Any of the program select pins may have functions in addition to the configuration function and the present invention respects and, in fact, makes use of such other functions thereby reducing or even eliminating the need for special pins which are not used once the chip has been configured.

Preferably, each configuration pin is a digital input port (or digital input/output port). When the system board is powered on or undergoes a reset, a processor internal to the chip scans each the configuration pin to determine its value. The processor then sets internal registers accordingly, completing the configuration process, and the chip begins normal operation.

FIG. 1 is a high level functional diagram illustrating the data flow of an exemplary integrated circuit in which the present invention may be incorporated;

FIG. 2 is a block diagram of the integrated circuit of FIG. 1 illustrating program select and calibration pins; and

FIG. 3 is a block diagram of the integrated circuit of FIG. 1 in the context of circuitry on a system board.

Functional Overview of Exemplary Integrated Circuit

FIG. 1 is a high level function diagram illustrating the data flow of an exemplary integrated circuit 100 in which the present invention may be incorporated.

The particular chip 100 illustrated is a low cost power/energy integrated circuit with a pulse output, part number CS5462 designed by Cirrus Logic, Inc. The chip 100 accurately measures and calculates energy for single-phase two or three wire power metering applications and can drive a mechanical counter. Although the CS5462 100 will be used as the exemplary chip throughout this application to illustrate the present invention, such illustration should not be construed as a limitation; rather, the present invention may be incorporated with various other types of chips.

The CS5462 100 includes two delta-sigma analog-to-digital converters (ADCs) 102 and 104 , one for receiving a current input and the other for receiving a voltage input, and associated digital filters 106 and 108 . After being filtered, the instantaneous voltage and current digital codes are subject to value adjustments by calibration, gain and frequency select circuitry 200 . Finally, the resulting signals are processes by an energy-to-pulse rate converter 110 having one output EOUT, each pulse of which represents a predetermined magnitude of energy, and a second output EDIR, each pulse of which represents the sign of the corresponding EOUT pulse. These pulsed outputs may be used to drive a mechanical counter, such as in a power meter.

Various stages of circuitry, such as calibration, gain select and frequency select, within the chip 100 may be adjusted for optimal performance. In a conventional integrated circuit, such adjustments might be made by connecting pins to external potentiometers or fixed-value components. However, a chip of the present invention avoids such methods by employing automatic internal configuration circuitry. It will be appreciated that use of external configuration components is not precluded by the present invention. In one embodiment, such components may supplement the configuration circuitry. Alternatively, a system board designer may forego or bypass the configuration circuitry entirely. However, the presence of such circuitry embedded in the integrated circuit provides the system board designer with several options.

Program Select and Configuration Pin Description

FIG. 2 is a block diagram of the integrated circuit 100 of FIG. 1 illustrating the configuration circuitry 200 and program select and configuration pins. As is evident, the chip 100 includes single-use pins for conventional functions, such as current and voltage inputs 202 and 204 , analog voltage supply and ground pins 206 and 208 , reset 210 , and a pulse output 212 . Multiple-use program select pins are also associated with additional conventional functions, including digital voltage supply and ground pins P 1 214 and P 5 216 and the second pulse output P 4 218 . Single-use program select pins P 2 220 and P 3 222 are not associated with any conventional function. The chip 100 also includes four configuration pins: a GAIN select pin 224 , a FREQUENCY select pin 226 , and two calibration pins CAL 0 228 and CAL 1 230 .

Each configuration pin 224 - 230 is connected by jumpers on the system board to one of the program select pins P 1 -P 5 214 - 222 . When the power is supplied to the chip 100 , or when the chip 100 is reset, the configuration circuitry 200 enters a configuration mode and is directed by code (burned into ROM, for example, and executed by an internal processor) to scan the GAIN, FREQUENCY, CAL 1 and CAL 2 pins and to determine the digital value on each pin. Based on such values, the configuration circuitry then sets:

the gain of a programmable gain amplifier 114 associated with the current ADC 102 ;

the frequency of the energy-to-pulse rate converter 110 ; and

the calibration adjustment for the voltage and current digital codes being sent to the converter 110 .

With five program select pins and four configuration pins, a total of 5 4 =625 combinations are possible.

After the configuration has been completed, the chip 100 is accurately set to meet the desired specifications and enters a normal operation mode.

Configuration Process

Gain Configuration

The gain amplifier 116 at the voltage input 204 of the chip 100 has a fixed gain of 10×. However, the programmable gain amplifier (PGA 114 ) at the current input provides one of five full scale input level options. Thus, with a single +5V supply across the analog input VA+ 206 and analog ground AGND 208 , both of the input channels 202 and 204 will accommodate common mode signal levels between −0.25V and +5V (VA+). The gain range is chosen by the user to be one of: 10×, 12.5×, 25×, 50× or 100×, which correspond to ranges of ±250 mV, ±200 mV, ±100 mV, ±50 mV and ±25 mV, respectively, allowing the user different input ranges on the current channel 202 . As indicated in Table 1, tying the GAIN figuration pin 224 to one of the five program select pins 214 - 222 results in the PGA 114 being set to the desired gain.

Frequency Configuration

The pulse rate frequency of the EOUT and EDIR output pins 212 and 218 are similarly set by an adjustment made to the energy-to-pulse converter 110 by the configuration circuitry 200 . Again referring to Table 1, tying the FREQ configuration pin 224 to one of the five program select pins 214 - 222 results the converter 110 being set to one of five pulse rates (1 Hz, 2 Hz, 4 Hz, 8 Hz or 10 Hz).

Internal Calibration

The CS5462 100 is designed to permit the user to calibrate the chip 100 with a user friendly digital option (although, as previously noted, the chip 100 may still be calibrated with external components). Columns 1 and 2 of Table 1 indicate the different calibration options. Both of the calibration pins CAL 0 and CAL 1 228 and 230 may be tied to any of the five program select pins 214 - 222 , resulting in a calibration range of ±6% total in 5 2 =25 possible steps. To determine which combination of program select pins to tie to the CAL 0 and CAL 1 pins 228 and 230 , the user applies a known current and known voltage to the inputs 202 and 206 of the uncalibrated chip 100 . The output is measured and will be within some percentage of the expected energy value. The CAL 0 and CAL 1 pins 228 and 230 are then tied to the appropriate program select pins 214 - 222 in order to bring the output to a desired value.

If it is desired that the pulse-frequency on the EOUT pin 212 be 8 Hz and the gain on the current channel PGA 114 be 10× (250 mV), the chip 100 is mounted on the system board and the configuration pins FREQ 226 and GAIN 224 tied on the system board to program select pins P 4 218 and P 5 216 , respectively. A known signal (for example, a 60 Hz, ±225 mV peak-to-peak sine wave) is supplied to the current and voltage inputs 202 and 204 . The RMS value will be approximately 159.1 mV (˜90% of full scale on each channel). If it is expected that the energy output V*I be 81% of full scale, and if the output on EOUT 212 is measured to be 85% of full scale, it will be necessary to adjust the output down by about 5% (0.85/0.81=˜104.94%). Consequently, configuration pin CAL 0 228 should be tied to program select pin P 3 and configuration pin CAL 1 230 should be tied to program select pin P 5 216 , thereby shifting the output down to be within the accuracy level of the original input signal. Other combinations of CAL 0 and CAL 1 may be made to achieve other desired results.

FIG. 3 illustrates an integrated circuit (the exemplary CS5462) 100 of the present invention mounted on a system board 300 . The board 300 is connected to a single-phase, two-wire service mains 302 and various board components are connected to the chip 100 to measure the power used. The power is tracked by and read from a mechanical counter 304 . The configuration pins 224 - 228 are tied to the program select pins P 1 -P 5 214 - 218 through jumpers or the like 306 on the system board 300 .

The objects of the invention have been fully realized through the embodiments disclosed herein. Those skilled in the art will appreciate that the various aspects of the invention may be achieved through different embodiments without departing from the essential function of the invention. The particular embodiments are illustrative and not meant to limit the scope of the invention as set forth in the following claims.