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No. AN9505

Authors: David Jarman and John Kornblum

No. AN9505
March 1995
Application Note
Authors: David Jarman and John Kornblum
USING THE HI7190 EVALUATION KIT
Evaluation Kit Description
HI7190 Description
The HI7190 is a 24-bit sigma delta ADC intended for use in applications such as industrial weight scales, process controls, and process measurement systems. The block diagram shows that the device consists of a programmable gain instrumentation amplifier (PGIA), a second order sigma delta modulator, a digital filter, a clock generator, and digital control and interface circuitry. The input signal applied to the VINHI and VINLO pins comes into the PGIA where it is gained up by a factor of 1 to 8. The resulting signal is then passed into the oversampling second order sigma delta modulator for A / D conversion and noise shaping. The output of the modulator is a serial bit stream of "1"s and "0"s whose code density is a direct indication of the value of the input to the modulator. This bit stream is then input to the digital filter where it is band limited and decimated down to a lower frequency. The digital filter is also used (along with the PGIA) to implement gains up to 128. The clock generator and digital control circuits direct the internal conversion process while the serial interface unit provides access to the device from the outside world. For a detailed description of the operation of the converter, please refer to the HI7190 data sheet.
Hardware Description
The HI7190 evaluation board provides the user with a very simple way of interfacing to and evaluating the Intersil HI7190 sigma delta ADC. The board features a reference voltage generator, a crystal oscillator, and digital line drivers and receivers for interfacing to a PC running the evaluation software. The board consists of 4 layers with separate analog and digital ground planes for obtaining optimum noise performance.
Copyright
Application Note 9505 HI7190 Functional Block Diagram
VRHI AVDD TRANSDUCER BURN-OUT CURRENT (100nA) VRLO
REFERENCE INPUTS
MODULATOR
PGIA VINHI VINLO
DIGITAL FILTER 1
CONTROL AND SERIAL INTERFACE UNIT
SERIAL INTERFACE UNIT CLOCK GENERATOR CONTROL REGISTER
DRDY RESET SYNC
HI7190 Evaluation Board Block Diagram
CRYSTAL OSCILLATOR EXTERNAL CLOCK CRYSTAL
AIN+ AIN-
VINHI VINLO
OSC1 OSC2
ON BOARD REFERENCE VRHI EXTERNAL VREF VRLO DIGITAL I / O
LINE DRIVERS AND RECEIVERS
AGND HI7190
Application Note 9505
Software Description
The software provided with the HI7190 evaluation kit allows the user to operate the device in many of the various modes the part supports. The software is menu driven for ease of use. The simplified flow diagram shown in Figure 1 gives a good feel for the structure of the software. Every menu allows access to all other menus.
MAIN MENU
READ MENU RESET DUT
CHANGE MODE MENU EXIT PROGRAM
WRITE MENU
FIGURE 1. SIMPLIFIED SOFTWARE FLOW CHART
The Main Menu appears after invoking the HI7190 evaluation software. This menu is the gateway to other menus that allow the user to communicate with the HI7190. Main Menu: s c Reset DUT Change Mode Menu
w Write Menu r x Read Menu Exit
Application Note 9505
s c Entering s from the Main Menu sends an active low reset signal to the HI7190 which initializes the HI7190. Entering c from the Main Menu brings the Change Mode Menu up. The Change Mode Menu allows the user to custom configure the HI7190 without having to know the bit positions of the Control Register. 5 Entering 5 from the Change Mode Menu initiates a communication cycle with the HI7190 that invokes the System Negative Full Scale Calibration Mode with a notch frequency of 10Hz. Other operating parameters are offset binary coding, bipolar mode and a gain of one. Please note, the user should apply the negative full scale voltage to the HI7190 inputs before issuing this command. Executing this command returns the user to the Main Menu. Entering c from the Change Mode Menu allows the user to customize the operational parameters of the HI7190. The user will be asked a series of questions relating to HI7190 operation. After completing these questions, the software compiles the proper data and writes the Control Register to invoke the desired operating mode. Executing this command returns the user to the Main Menu. Entering r from the Change Mode Menu invokes the Read Menu.
w Entering w from the Main Menu brings the Write Menu up. The Write Menu allows the user write access to all writable registers without having knowledge of specific Instruction Register address details. r Entering r from the Main Menu brings the Read Menu up. The Read Menu allows the user to read all registers without having knowledge of specific Instruction Register address details. Entering x from the Main Menu exits the program.
Change Mode Menu: 1 2 3 4 5 c r Self Calibration - 10Hz Self Calibration - 2kHz System Offset Calibration - 10Hz System Positive Full Scale Calibration - 10Hz System Negative Full Scale Calibration - 10Hz Custom Menu Read Menu
w Entering w from the Change Mode Menu invokes the Write Menu. m Entering m from the Change Mode Menu invokes the Main Menu. x Entering x from the Change Mode Menu exits the program.
Write Menu: 1 2 3 4 r x 1 Command Register Offset Register Positive Full Scale Register Negative Full Scale Register Read Menu Exit Program Entering 1 from the Write Menu invokes a write communication cycle with the Control Register. The user will be prompted for the data to write. The software requires the data be entered in hex, most significant to least significant format. The Control Register is 3 bytes. All three bytes must be entered at the prompt. Entering 2 from the Write Menu invokes a write communication cycle with the Offset Calibration Register. The user will be prompted for the data to write. The software requires the data be entered in hex, most significant to least significant format. The Offset Calibration Register is 3 bytes. All three bytes must be entered at the prompt. Entering 3 from the Write Menu invokes a write communication cycle with the Positive Full Scale Calibration Register. The user will be prompted for the data to write. The software requires the data be entered in hex, most significant to least significant format. The Positive Full Scale Calibration Register is 3 bytes. All three bytes must be entered at the prompt. Entering 4 from the Write Menu invokes a write communication cycle with the Negative Full Scale Calibration Register. The user will be prompted for the data to write. The software requires the data be entered in hex, most
w Write Menu m Main Menu x 1 Exit Program Entering 1 from the Change Mode Menu initiates a communication cycle with the HI7190 that invokes the Self Calibration Mode with a notch frequency of 10Hz. Other operating parameters are offset binary coding, bipolar mode and a gain of one. Executing this command returns the user to the Main Menu. Entering 2 from the Change Mode Menu initiates a communication cycle with the HI7190 that invokes the Self Calibration Mode with a notch frequency of 2kHz. Other operating parameters are offset binary coding, bipolar mode and a gain of one. Executing this command returns the user to the Main Menu. Entering 3 from the Change Mode Menu initiates a communication cycle with the HI7190 that invokes the System Offset Calibration Mode with a notch frequency of 10Hz. Other operating parameters are offset binary coding, bipolar mode and a gain of one. Please note, the user should apply 0V to the HI7190 inputs before issuing this command. Executing this command returns the user to the Main Menu. Entering 4 from the Change Mode Menu initiates a communication cycle with the HI7190 that invokes the System Positive Full Scale Calibration Mode with a notch frequency of 10Hz. Other operating parameters are offset binary coding, bipolar mode and a gain of one. Please note, the user should apply the positive full scale voltage to the HI7190 inputs before issuing this command. Executing this command returns the user to the Main Menu.
m Main Menu
Application Note 9505
significant to least significant format. The Negative Full Scale Calibration Register is 3 bytes. All three bytes must be entered at the prompt. m Entering m from the Write Menu invokes the Main Menu. r x Entering r from the Write Menu invokes the Read Menu. Entering x from the Write Menu exits the program. key is touched to abort reads. It is generally not expected that this register will be read in continuous mode. 6 Entering 6 from the Read Menu invokes a read communication cycle with the Negative Full Scale Calibration Register. The user will be asked if a continuous read is required. If continuous read is not requested, executing this command will invoke a single read of the Negative Full Scale Calibration Register, display the data and return execution to the Main Menu. If continuous read is requested, the read executions will continue until any key is touched to abort reads. It is generally not expected that this register will be read in continuous mode.
Examples: 1. Write 8 (hex) to the Offset Calibration Register and then read it back. To accomplish this task, choose the Write Menu option from the Main Menu, choose the Offset Register option from the Write Menu. Enter 000008 at the prompt. The program returns to the Main Menu. Now select the Read Menu option from the Main Menu, choose the Offset Register option from the Read Menu. The user will be prompted to decide upon a single read or continuous read. Enter n for a single read. The data read will be displayed on the screen and the program will return to the Main Menu. 2. Configure the device for bipolar mode, offset binary coding, 10Hz filter notch frequency, gain of 1, and conversion mode operation. Select the Change Mode Menu option from the Main Menu and then the Custom Menu option from the Change Mode Menu. When prompted for data coding enter 0 for offset binary. The next prompt is to enter the notch frequency, enter 10 for 10Hz. Next, the operational mode table is displayed, choose 0 for conversion mode. The next prompt is for bipolar / unipolar operation, enter 1 for bipolar mode. The next screen displays the gain selection table, enter 1 for gain equal 1. The program determines the data required to configure the HI7190 as the user specified and invokes the proper communication cycle. Execution returns to the Main Menu.
m Main Menu w Write Menu x 1 Exit Program Entering 1 from the Read Menu invokes a read communication cycle with the Data Output Register. The Data Output Register will be read one time, the data will be displayed, and the program will return to the Main Menu. Entering 2 from the Read Menu invokes continuous read communication cycles with the Data Output Register. Refer to the Software Clarifications section of this document for details on the displayed data. Continuous data reads will be displayed until any key is pressed. When a key is pressed, the program returns to the Main Menu. Entering 3 from the Read Menu invokes a read communication cycle with the Control Register. The user will be asked if a continuous read is required. If continuous read is not requested, executing this command will invoke a single read of the Control Register, display the data and return execution to the Main Menu. If continuous read is requested, the read executions will continue until any key is touched to abort reads. It is generally not expected that this register will be read in continuous mode. Entering 4 from the Read Menu invokes a read communication cycle with the Offset Calibration Register. The user will be asked if a continuous read is required. If continuous read is not requested, executing this command will invoke a single read of the Offset Calibration Register, display the data and return execution to the Main Menu. If continuous read is requested, the read executions will continue until any key is touched to abort reads. It is generally not expected that this register will be read in continuous mode. Entering 5 from the Read Menu invokes a read communication cycle with the Positive Full Scale Calibration Register. The user will be asked if a continuous read is required. If continuous read is not requested, executing this command will invoke a single read of the Positive Full Scale Calibration Register, display the data and return execution to the Main Menu. If continuous read is requested, the read executions will continue until any
Software Execution
Application Note 9505
Executing the Program: Change directory (cd) into the directory containing the 7190BTA5.EXE file. At the DOS prompt type 7190BTA5 return. The software reminds the user to apply power to the board before continuing. At this point the software is menu driven and self explanatory. However, it is important that the user has read the previous section, Software Description, before starting the evaluation. Bypassing Calibration The HI7190 calibration algorithm can be effectively bypassed by writing all zeros into the Offset Calibration Register and 800000 (hex) into the Positive and Negative Full Scale Calibration Registers if operating in bipolar mode. If operation is in unipolar mode write all zeros into the Offset Calibration Register and 800000 (hex) into the Positive Full Scale Calibration Register. Display of Data Register in Continuous Mode Entering 2 from the Read Menu invokes a continuous read of the Data Register. The following data is displayed: 1) The binary output stream read from the HI7190, 2) The binary output stream converted to hex, 3) The binary output stream converted to volts, 4) The mean voltage of the last 10 conversion results, 5) The maximum voltage result, 6) the minimum voltage result, 7) The difference between the maximum voltage and minimum voltage, and 8) standard deviation, dynamic range and ENOB, which is updated in groups of 10 conversions.
NOTE: The CTRL input on the keyboard is used to "normalize" the statistical output. For example, the maximum voltage is set to 5.5V and the minimum is set to -5.5V. The maximum / minimum results displayed from then on will include only those conversions read since "normalization".
Software Clarifications
The Dynamic Range and ENOB Equations are as follows:
U3 SMA3 Y1 CLOCK SMA CRYSTAL 8 FOSC 7 DGND +5VD 14 VCC XTAL OSC SMA1
ANALOG IN+ SMA
TP1 CON1 1 CLOCK OUT
C1 0.01µF
Application Note 9505
JMP3 R10 50 C11 0.1µF R1 10K SMA
0.01µF
1N4000 D2
1N4000
-5V C5 4.7µF AT 10V R2 10 10 10
C3 0.01µF
1A 2A 3A 4A 5A 6A 7A -5V 8A 9A 10A 11A 12A 13A +5VD 14A 15A 16A 17A 18A 19A 20A 21A 22A
1B +5V 2B 3B 4B 5B 6B 7B -5V 8B 9B 10B 11B 12B 13B +5VD 14B 15B 16B 17B 18B 19B 20B 21B 22B CONNECTOR EDGE44AB
1N4000
MODE U4 2G 1G
Application Note 9505
3 5 7 9 12 14 16 18 2Y4 2Y3 2Y2 2Y1 1Y4 1Y3 1Y2 1Y1
2A4 2A3 2A2 2A1 1A4 1A3 1A2 1A1 74FCT244
10 8 U6C 74HC125 9
2.7k R5 JP4 U6D 74HC125 12 TP6 1 CON1 CON2 2.7k TP5 1 OPTION2 CON1 DRDY 2.7k R4 +5VD
CONNECTOR DB25
Application Note 9505 HI7090 Evaluation Board
COMPONENTS LAYOUT
COMPONENT SIDE
GROUND PLANES
Application Note 9505 HI7090 Evaluation Board (Continued)
POWER PLANE
SOLDER SIDE
Application Note 9505
All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification.
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and / or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
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