No. AN9505 Application Note March 1995 USING THE HI7190 EVALUATION KIT Authors: David Jarman and John Kornblum Evaluation Kit Description Layout and Power Supplies The HI7190 evaluation kit (evaluation board and evaluation software) can be used to evaluate the performance of the HI7190 24-bit sigma delta analog-to-digital converter (ADC). The evaluation board includes a reference circuit, a crystal, an oscillator, and digital circuitry used to interface to a personal computer running the evaluation software. The board also provides a means for the user to supply an external reference and an external clock. The HI7190 evaluation board consists of 4 layers laid out to optimize performance of the ADC. The figures at the end of this document include the various layers of the board and their layout, a list of the board components, and schematics. Users should feel free to copy this layout for use in their applications. The power supplies are provided to the board via the edge connector located at the top of the board. It is recommended that twisted pair wires be used to connect the power supplies to the connector and that analog and digital grounds be tied together back at the power supplies. The separate supplies are necessary to keep the digital noise from coupling into the analog portions of the circuit. One of the internal layers of the board is the ground plane layer. This layer is roughly divided in half with one half of the layer being digital ground and the other half being analog ground. The other internal layer is the power plane. It is divided into three sections; AVDD, AVSS, and DVDD. Nominal values for the supplies are AVDD = +5V, AVSS = -5V, and DVDD = +5V. In some cases (for instance if there is a substantial offset between AGND and DGND) it may be necessary to tie the two grounds together on the board. Resistors R2, R8, and R9 provide a means of connecting the two ground planes together through a low impedance. 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. A prototype area is provided on the left side of the board. This area has a small section of analog ground plane in the center and may be useful for input signal conditioning before the HI7190. Reference Circuit The reference inputs of the HI7190, VRHI and VRLO, provide a differential reference input capability. The reference inputs provide a high impedance dynamic load similar to the analog inputs. For proper circuit operation these pins must be driven by low impedance circuitry. Reference noise outside of the band of interest will be removed by the on chip digital filter but excessive reference noise inside the band of interest will degrade performance of the HI7190. 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 The actual reference voltage is given by VREF = VRHI - VRLO. The VRLO pin is hard wired to analog ground on the evaluation board which means that VREF = VRHI. The nominal reference voltage for the HI7190 is 2.5V. Larger values of VREF © Intersil Corporation 1995 1 Application Note 9505 HI7190 Functional Block Diagram VRHI AVDD VRLO REFERENCE INPUTS TRANSDUCER BURN-OUT CURRENT (100nA) ∑−∆ MODULATOR PGIA VINHI ∑ VINLO ∫ ∫ ∑ DIGITAL FILTER 1 1-BIT D/A VCM CONTROL AND SERIAL INTERFACE UNIT SERIAL INTERFACE UNIT CONTROL REGISTER CLOCK GENERATOR OSC1 OSC2 DRDY RESET SYNC CS MODE SCLK SDIO HI7190 Evaluation Board Block Diagram CRYSTAL OSCILLATOR EXTERNAL CLOCK AIN+ CRYSTAL AIN- VINHI OSC1 VINLO OSC2 ON BOARD REFERENCE DIGITAL I/O VRHI EXTERNAL VREF VRLO VCM AGND DGND HI7190 2 LINE DRIVERS AND RECEIVERS TO PC SDO Application Note 9505 J1 must be removed from the board when using an external clocking source and the external clocking source must be disconnected from the board when using either of the on board clocking methods. When J1 is in the right most position the 10MHz crystal oscillator is selected and when J1 is in the left most position the combination 10MHz crystal and on chip oscillator clocking method is selected. The external clock can be used from a minimum frequency of 1MHz up to a maximum frequency of 10MHz. can be used without degradation in performance. Smaller values of VREF can also be used but performance will be degraded since the system noise becomes larger relative to the LSB size. The jumper JP2 controls whether the VRHI pin of the HI7190 is connected to an external reference, which connects to the VREF SMA pad, or to the on board reference which is preset to 2.5V. If JP2 is in the far right position VRHI is connected to the on board low noise reference and when JP2 is in the far left position VRHI is connected to the external reference. If an external reference is used it is recommended that a twisted pair wire be used and soldered directly to the SMA pad on the evaluation board. The potentiometer R1 can be used to vary the on board reference voltage. Please note that the specifications for the HI7190 are tested with VRHI set to 2.5V. VRHI must always be greater than VRLO for proper operation of the device. For the best noise performance the crystal should be removed from the board when using the crystal oscillator and vice versa. Both the crystal and crystal oscillator should be removed when using an external clock. Digital Inputs/Outputs The digital input and output pins of the HI7190 are interfaced through line drivers and receivers to the 25 pin D connector at the right edge of the board. These pins are activated and deactivated by the evaluation software which controls the functionality of the HI7190. Please refer the HI7190 data sheet for a detailed description of the functionality of these pins. Analog Inputs The analog input on the HI7190 is a fully differential input with programmable gain capabilities. The input accepts both unipolar and bipolar input signals and gains range from 1 to 128. The user must pay careful attention to the input driver and/or input filter circuitry as the input sampling rate (or modulator clock rate) varies with the selected PGIA gain, and the input impedance is dependent upon the modulator clock rate. Please refer to the data sheet for more information. U5 on the evaluation board is an “open socket” which is used in conjunction with the test modes of the HI7190 for Intersil internal testing and evaluation. 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. The analog inputs come onto the board via the SMA pads labeled AIN+ and AIN-. Once again it is recommended that twisted pair wire be used to drive the positive and negative analog inputs. Common Mode Input The jumper JP1 is provided to allow the VCM pin to be tied to either analog ground (upper position), or VRHI (lower position). The input voltage for VCM should always be set at the midpoint between AVDD and AVSS. So if AVDD = +5V and AVSS = -5V, VCM should be at analog ground. Please note the HI7190 is specified for AVDD = +5V and AVSS = -5V operation only. MAIN MENU READ MENU CHANGE MODE MENU RESET DUT Clock Input The master clock into the HI7190 can be supplied by either a crystal connected between the OSC1 and OSC2 pins or a CMOS compatible clock signal connected to the OSC1 pin. The input sampling frequency, modulator clock frequency, filter -3dB frequency, output update rate, and calibration times are all directly related to the master clock frequency, fOSC. For example, if a 1MHz clock is used instead of a 10MHz clock, what is normally a 10Hz conversion rate becomes a 1Hz conversion rate. Lowering the clock frequency will also lower the power supply currents. Please note that the HI7190 specifications are written for a 10MHz clock only. WRITE MENU EXIT PROGRAM 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 Reset DUT c Change Mode Menu w Write Menu The HI7190 evaluation board allows for the HI7190 master clock to be supplied externally, generated by the on board crystal oscillator, or generated by an on board crystal used in conjunction with the on chip oscillator circuitry. The jumper 3 r Read Menu x Exit Application Note 9505 s Entering s from the Main Menu sends an active low reset signal to the HI7190 which initializes the HI7190. c 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. 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. x Entering x from the Main Menu exits the program. Change Mode Menu: 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. c 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. r Entering r from the Change Mode Menu invokes the Read Menu. 1 Self Calibration - 10Hz 2 Self Calibration - 2kHz 3 System Offset Calibration - 10Hz 4 System Positive Full Scale Calibration - 10Hz m Entering m from the Change Mode Menu invokes the Main Menu. 5 System Negative Full Scale Calibration - 10Hz x c Custom Menu r Read Menu w Entering w from the Change Mode Menu invokes the Write Menu. Write Menu: w Write Menu m Main Menu x Exit Program 1 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. 2 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. 3 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. 4 Entering x from the Change Mode Menu exits the program. 1 Command Register 2 Offset Register 3 Positive Full Scale Register 4 Negative Full Scale Register m 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. 4 r Read Menu x Exit Program 1 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. 2 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. 3 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. 4 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 Application Note 9505 key is touched to abort reads. It is generally not expected that this register will be read in continuous mode. significant to least significant format. The Negative Full Scale Calibration Register is 3 bytes. All three bytes must be entered at the prompt. 6 m Entering m from the Write Menu invokes the Main Menu. r Entering r from the Write Menu invokes the Read Menu. x Entering x from the Write Menu exits the program. Read Menu: 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. 1 Data Output Register, ‘Read Once’ 2 Data Output Register, ‘Read Continuous’ 3 Command Register 4 Offset Calibration Register Examples: 5 Positive Full Scale Register 6 Negative Full Scale Register 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. m Main Menu w Write Menu x Exit Program 1 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. 2 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. 3 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. 4 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. 5 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. Software Execution The PORT_ID.DAT file contains the port identification for the parallel printer port interfacing the HI7190 Evaluation board to the PC. This file needs to be edited (as discussed in the HI7190RDME.TXT file) before running the software. The DOS MSD command can be used to find the printer port identification. Loading Software: Copy the four files (7190BTA5.CPP, 7190BTA5.EXE, PORT_ID.DAT, and 7190RDME.TXT) from the diskette onto your PC hard drive into the directory of your choice. The file 7190BTA5.CPP is the evaluation software source code. The file 7190BTA5.EXE is the executable program and 7190RDME.TXT is a README file containing valuable information. Please read the 7190RDME.TXT file before continuing. 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 5 Application Note 9505 Bypassing Calibration 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. 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. Software Clarifications Display of Data Register in Continuous Mode Resetting the DUT 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. Entering s from the Main Menu resets the HI7190 to its initial state. The initial state of the HI7190 is as follows: offset binary data coding, notch frequency of 30Hz, Self Calibration mode, gain = 1, bipolar mode. The burn-out current and sleep mode bits are inactive. The Serial Interface configuration is MSB first bit positioning, descending byte order, bidirectional I/O pin. Writing the Control Register Caution should be taken when writing the Control Register via the Write Menu. The least significant byte contains information regarding the Serial Interface configuration that must be maintained when running the software provided. To insure proper functionality of the evaluation software, the Serial Interface must be configured in MSB first mode, descending byte order and bidirectional I/O pin operation. This configuration is maintained by writing logic zeros into the 3 least significant bits of the Control Register. 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”. The Dynamic Range and ENOB Equations are as follows: 2 ( 2.5 ) ⁄ 2 Dynamic Range = 10log10 -------------------------------------------------------2 2 V RMS – V REFNOISE Invalid Inputs Dynamic Range – 1.76 ENOB = -----------------------------------------------------------6.02 Entering invalid inputs at some menu prompts will lock up the software. Generally a CTL-C will return the user to the DOS prompt. V MAX – V MIN V RMS = ------------------------------------6.6 Notch Frequency Input V REFNOISE = When executing from the Custom Menu (of Change Mode Menu) the notch frequency value must be entered in decimal. That is, 2kHz is entered as 2000. – 14 4.452 × 10 (0.275 F N) F N = Notch Frequency 6 -5V +5V C2 C1 0.01µF 7 C3 0.01µF 0.01µF V- 4 TRIM VOUT 2 V+ REF 5 6 U2 SMA SMA2 SMA + SMA SMA4 50 3 2 1 JP2 JMP3 C5 4.7µF AT 10V VREF R1 10K JMP3 R10 JP1 J1 3 2 J2 1 + C4 4.7µF AT 10V ANALOG IN- ANALOG IN+ C11 0.1µF 7 17 18 19 5 4 2 1 3 20 R8 10 10 6 RESET_ DGND DRDY_ SYNC_ CS_ SD O SCLK< SD I/O MODE 15 HI7190 U1 DVDD 16 3 2 1 J1 JMP3 + TP1 CON1 1 CLOCK OUT 10 R9 TP2 TP3 TP4 CON1 CON1 CON1 1 1 1 RESET' SYNC' DRDY' CS' SDO SCLK SDIO MODE +5VD C7 0.01µF CRYSTAL Y1 C6 4.7µF AT 10V CLOCK SMA SMA3 R2 14 AGND AVSS 9 V 8 RHI VRLO 10 V CM 12 V INHI 11 V INLO 13 AV DD XTAL OSC VCC 8 FOSC 7 DGND OSC1 U3 OSC2 SMA1 +5VD 14 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 1A 2A 3A 4A 5A 6A 7A -5V 8A 9A 10A 11A 12A 13A +5VD 14A 15A 16A 17A 18A 19A 20A 21A 22A +5V J3 1N4000 D3 1N4000 D2 1N4000 D1 Application Note 9505 8 RESET' SYNC' DRDY' CS' SDO SDIO SCLK MODE 8 1 5 2 12 U6C 74HC125 10 4 9 13 11 U6D 74HC125 6 U6B 74HC125 U6A 74HC125 3 CON1 1 TP6 3 5 7 9 12 14 16 18 2A4 2A3 2A2 2A1 1A4 1A3 1A2 1A1 2G 1G 74FCT244 2Y4 2Y3 2Y2 2Y1 1Y4 1Y3 1Y2 1Y1 U4 12 JP4 CON2 17 15 13 11 8 6 4 2 19 1 J2 CON2 12 DRDY 10k R3 +5VD 11 10 9 6 7 8 SOCKET_16 16 15 14 13 12 U5 1 2 3 4 5 13 25 12 24 11 23 10 22 9 21 8 20 7 19 6 18 5 17 4 16 3 15 2 14 1 +5VD CONNECTOR DB25 OPTION2 CON1 1 TP5 2.7k R4 2.7k R5 2.7k R6 P1 Application Note 9505 Application Note 9505 HI7090 Evaluation Board COMPONENTS LAYOUT COMPONENT SIDE GROUND PLANES 9 Application Note 9505 HI7090 Evaluation Board (Continued) POWER PLANE SOLDER SIDE 10 Application Note 9505 HI7190 EVALUATION BOARD COMPONENT LIST ITEM QUANTITY REFERENCE PART 1 7 C1, C2, C3, C7, C8, C9, C10 0.01µF 2 3 C4, C5, C6 10µF at 16V Tantalum 3 1 C11 0.1µF 4 3 D1, D2, D3 1N4000 5 3 JP1, J1, JP2 JMP3 - Strip 1 x 3 6 2 JP4, J2 CON2 Wire Strap 7 1 J3 Connector Edge 44AB 8 1 P1 Connector DB25 9 1 R1 10K 5%, 1/4Ω 10 3 R2, R8, R9 10 5%, 1/4Ω 11 3 R4, R5, R6 2.7K 5%, 1/4Ω 12 1 R10 49.9 1%, 1/4Ω 13 1 U1 HI7190 14 1 U2 REF (LT1019CN8-2.5) 15 1 U3 XTAL OSC 10MHz 16 1 U4 74HC244 (INTERSIL) 17 1 U6 74HC125 (INTERSIL) 18 1 Y1 Crystal 10MHz 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. For information regarding Intersil Corporation and its products, see web site http://www.intersil.com 11