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CDB5522 Arkusz danych(PDF) 4 Page - Cirrus Logic |
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CDB5522 Arkusz danych(HTML) 4 Page - Cirrus Logic |
4 / 28 page CDB5521/22/23/24/28 4 DS317DB2 1. PART I: HARDWARE 1.1 Introduction The CDB5521/22/23/24/28 evaluation board pro- vides a means of testing the CS5521/22/23/24/28 Analog-to-Digital Converters (ADCs). The board interfaces the converters to an IBMTM compatible PC via an RS-232 interface while operating from a +5 V and -5 V power supply. To accomplish this, the board comes equipped with an 80C51 micro- controller and a 9-pin RS-232 cable, which physi- cally interfaces the evaluation board to the PC. Additionally, analysis software provides easy ac- cess to the internal registers of the converters and provides a means to capture data and display the converters’ time domain, frequency domain, and noise histogram performance. 1.2 Evaluation Board Overview The board is partitioned into two main sections: an- alog and digital. The analog section consists of the either the CS5521, CS5522, CS5523, CS5524 or CS5528, a precision voltage reference, and the cir- cuitry to generate a negative voltage. The digital section consists of the 80C51 microcontroller, the hardware test switches, the reset circuitry, and the RS-232 interface. The CS5521/22/23/24/28 is designed to digitize low level signals while operating from a 32.768 KHz crystal. As shown in Figures 1 and 2, a thermocouple can be connected to the converter’s inputs via J1’s AIN+ and AIN- inputs. Note, a sim- ple RC network filters the thermocouple’s output to reduce any interference picked up by the thermo- couple leads. The evaluation board provides two voltage refer- ence options, on-board and external. With HDR5’s jumpers in positions 1 and 4, the LT1019 provides 2.5 volts (the LT1019 was chosen for its low drift, typically 5ppm/°C). By setting HDR5’s jumpers to position 2 and 3, the user can supply an external voltage reference to J2’s REF+ and REF- inputs (Application Note 4 on the web details various voltage references). The A/D converters’ serial interfaces are SPITM and MICROWIRETM compatible. The interface control lines (CS, SDI, SDO, and SCLK) are con- nected to the 80C51 microcontroller via port one. To interface a different microcontroller to the ADC chip, the control lines to the ADC are available at HDR6 (Header 6). However, to connect an external microcontroller to the header, the evaluation board must be modified in one of three ways: 1) cut the interface control traces going to the on-board 80C51 microcontroller, 2) remove resistors R1-R6, or 3) remove the 80C51 microcontroller from its socket on the evaluation board. Figure 3 illustrates the schematic of the digital sec- tion. It contains the microcontroller, a Motorola MC145407 interface chip, and test switches. The test switches aid in debugging communication problems between the CDB5521/22/23/24/28 and the PC. The microcontroller derives its clock from an 11.0592 MHz crystal. From this, the controller is configured to communicate via RS-232 at 9600 baud, no parity, 8-bit data, and 1 stop bit. |
Podobny numer części - CDB5522 |
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Podobny opis - CDB5522 |
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