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CDB5521 参数 Datasheet PDF下载

CDB5521图片预览
型号: CDB5521
PDF下载: 下载PDF文件 查看货源
内容描述: 评估板和软件 [Evaluation Board and Software]
分类和应用:
文件页数/大小: 28 页 / 1051 K
品牌: CIRRUS [ CIRRUS LOGIC ]
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CDB5521/22/23/24/28  
reduce any interference picked up by the thermo-  
couple leads.  
1. PART I: HARDWARE  
1.1 Introduction  
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 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  
TM  
interfaces the converters to an IBM 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.  
TM  
The A/D converters’ serial interfaces are SPI  
and MICROWIRE  
TM  
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.  
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.  
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.  
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  
4
DS317DB2  
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