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Texas Instruments ADS1224EVM User Manual Download Page 15

2-1

Circuit Description

 

   

This chapter describes the connectors, controls, and circuit design of the
ADS1224EVM in detail.

Topic

Page

2.1

I/O Connectors and Testpoints

2-2

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2.2

Jumpers

2-7

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2.3

Switches

2-9

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Chapter 2

Summary of Contents for ADS1224EVM

Page 1: ... April 2004 User s Guide SBAU095 Data Acquisition Products ...

Page 2: ...tute a license from TI to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or other intellectual property of the third party or a license from TI under the patents or other intellectual property of TI Reproduction of information in TI data books or data sheets is permissible only if reproduction is...

Page 3: ... handling or use of the goods Please be aware that the products received may not be regulatory compliant or agency certified FCC UL CE etc Due to the open construction of the product it is the user s responsibility to take any and all appropriate precautions with regard to electrostatic discharge EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR A...

Page 4: ...there is uncertainty as to the load specification please contact a TI field representative During normal operation some circuit components may have case temperatures greater than 60 C The EVM is designed to operate properly with certain components above 60 C as long as the input and output ranges are maintained These components include but are not limited to linear regulators switching transistors...

Page 5: ...f a caution statement A caution statement describes a situation that could potentially damage your software or equipment The information in a caution statement is provided for your protection Please read each caution carefully If You Have Questions If you have questions regarding either the use of this evaluation module or the information contained in the accompanying documentation please con tact...

Page 6: ...itle and litera ture number Data sheet Literature number ADS1224 Data Sheet SBAS286 REF1004 Data Sheet SBVS002 OPA350 Data Sheet SBOS099 FCC Warning This equipment is intended for use in a laboratory test environment only It generates uses and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to sub part J of part 15 of FCC rule...

Page 7: ...2 2 1 J4 Pins 1 4 ADS1224 Power Supply Measurement 2 7 2 2 2 J4 Pins 5 10 Digital Power Supply Select 2 8 2 2 3 J4 Pins 11 12 Analog Digital Ground Shorting Jumper 2 8 2 3 Switches 2 9 2 3 1 S1 4 Input Select Switches 2 9 2 3 2 S5 6 Reference Select 2 11 2 3 3 S5 System Clock Select 2 12 3 Usage 3 1 3 1 Input Filtering 3 2 3 2 Serial Interface 3 3 3 3 Serial EEPROM 3 3 3 4 Clock Circuitry 3 3 4 Sc...

Page 8: ...ut 3 2 4 1 Schematic 4 2 4 2 Top Side Layout 4 3 4 3 Bottom Side Layout 4 3 2 1 Analog Connector Pin Descriptions 2 4 2 2 Serial Connector Pin Descriptions 2 5 2 3 Power Connector Pin Descriptions 2 6 2 4 AIN0 1 Input Select Switch 2 9 2 5 Common Input Switch Settings 2 10 2 6 VRP Select Switch 2 11 2 7 VRN Select Switch 2 11 2 8 Common S5 6 Combination Settings 2 12 2 9 System Clock Select Switch...

Page 9: ... for the ADS1224 24 bit delta sigma Σ analog to digital converter ADC The ADS1224EVM is designed for prototyping and evaluation Topic Page 1 1 Introduction 1 2 1 2 Built In Accessories 1 3 1 3 Connectors 1 3 1 4 Controls 1 4 1 5 Setting Up 1 4 Chapter 1 ...

Page 10: ...You can even think of the ADS1224EVM as an alternate package for the ADS1224 one much larger than the device itself but also much easier to wire up by hand on your test bench The ADS1224EVM can be plugged directly into suitable motherboards such as the HPA449 MSP430 microcontroller development system from Soft Baugh Inc http www softbaugh com See TI s web site for example code using the ADS1224EVM...

Page 11: ... analog connector J1 carries analog I O The ADS1224 has a four input differential multiplexer connected through pins 1 8 An optional external differ ential reference can be connected to pins 18 and 20 The serial connector J2 carries the ADS1224 serial digital interface an optional external system clock signal and an I2C connection to the onboard serial EEPROM The power connector J3 carries the pow...

Page 12: ...together See Section 2 2 on page 2 7 for details 1 5 Setting Up The ADS1224EVM is configured according to its use Thus there is no single correct procedure to follow in order configure the test fixture Nevertheless it is useful to remember the following things when you are set ting up the board Make certain that the digital supply level is correct The jumper block has three positions that correspo...

Page 13: ...ock signal to the external clock input pin on J2 the ADS1224 will not operate The ADS1224 has several configuration input pins connected to pins on J2 If these configuration input pins are left floating the ADS1224 may not operate properly See the ADS1224 data sheet for further information about these pins ...

Page 14: ...Setting Up 1 6 ...

Page 15: ...Circuit Description This chapter describes the connectors controls and circuit design of the ADS1224EVM in detail Topic Page 2 1 I O Connectors and Testpoints 2 2 2 2 Jumpers 2 7 2 3 Switches 2 9 Chapter 2 ...

Page 16: ...e actually mounted as connector pairs in a pass through configuration Each pair has a surface mount header on the top component side of the board and a corre sponding surface mount socket on the bottom solder side of the board Vias in the pads connect each pin from top to bottom The headers mounted on top are suffixed A the sockets mounted on bottom are suffixed B In the schematic the connector pa...

Page 17: ... AN0 REF REF AGND AGND AN1 AN2 AN3 AN1 AN2 AN3 AGND AGND AGND OBREF Although certain pins are described as negative never apply voltages less than 0 3V to these pins The ADS1224 is not a bipolar input device and it cannot accept negative voltages below 0 3V without damaging the functional operation of the unit The negative input pins are so named because the voltage on such a pin is subtracted fro...

Page 18: ...egative input 2 Direct 6 AN2 AN2 Input Positive input 2 Direct 7 AN3 AN3 Input Negative input 3 Direct 8 AN3 AN3 Input Positive input 3 Direct 10 OBREF VCOM Output Reference output common mode reference Direct 18 SYSREFN REF Input Negative reference input Through S5 20 SYSREFP REF Input Positive reference input Through S6 9 11 13 17 19 GND AGND Power Signal ground n a Note Channels 0 and 1 are not...

Page 19: ...al Connector Pin Descriptions Pin Number Pin Name Standard Name Direction Function 1 TEMPSEN CNTL Input Temperature sensor enable 2 MUX0 GPIO0 Input Channel select bit 0 3 SCLK CLKX Input Serial clock input 6 MUX1 GPIO1 Input Channel select bit 1 7 CS FSX Input Chip select 13 DOUT DR Output Serial data output 15 DRDY INT Output Data ready signal 16 SCL SCL I O I2C clock line 17 EXTCLK TOUT Input E...

Page 20: ...ND Analog Ground Optional connection to DGND using J4 6 DGND Digital Ground Ground 7 1 8VD Positive Digital Supply 1 8V Digital supply selected using J4 8 VD1 Positive Digital Supply Not used 9 3 3VD Positive Digital Supply 3 3V Digital supply selected using J4 10 5VD Positive Digital Supply 5V Digital supply selected using J4 Note The ADS1224EVM has a single ground domain The ground is always con...

Page 21: ...5 Jumper Block 1 3 5 7 9 2 4 6 8 10 AVDD DVDD DGND 1 8VD 3 3VD ADCAVDD 5VD AGND 11 12 DVDD DVDD DVDD 2 2 1 J4 Pins 1 4 ADS1224 Power Supply Measurement These jumpers can be used to measure the current of the ADS1224 power supplies Pins 1 2 are inserted in the analog supply and pins 3 4 are inserted in the digital supply For normal operation pins 1 2 must be shorted and pins 3 4 must be shorted ...

Page 22: ...10 Shorting more than one of these jumpers can potentially damage your motherboard or even damage the ADS1224EVM itself The ADS1224 inputs are not 5V tolerant nor are they TTL compatible Although protection resistance is included in each digital line it may be neces sary to provide level translation if the ADS1224 digital supply must be powered from a different voltage than the external logic Note...

Page 23: ...Select Switches These switches control which lines are routed to the ADS1224 channel 0 AIN0 and channel 1 AIN1 inputs Each switch is configured in the same way and connects to a single input pin The positions of the switches are described in Table 2 4 Table 2 4 AIN0 1 Input Select Switch Board Marking Switch Position Input Source EXT Left External J1 pin 0V Right Ground VRP Middle Positive referen...

Page 24: ... 5V 0x000000 code 0x7FFFFF 3 EXT VRP Single ended midscale referenced 0 INP 5V 0xC00000 code 0x3FFFFF 4 0V 0V Inputs shorted to ground N A N A near zero 5 VRP VRP Inputs shorted to midscale N A N A near zero To measure external differential signals use Setting 1 To measure external 0V 5V signals use either Setting 2 or 3 Note that for single ended signals approximately one bit is lost from full sc...

Page 25: ...le 2 6 and Table 2 7 Some common combinations of S5 and S6 are shown in Table 2 8 Table 2 6 VRP Select Switch Board Marking Switch Position VRP Source EXT Left External J1 pin 20 2 5V Middle Onboard 2 5V reference voltage AVDD Right Analog supply voltage 5V typ Table 2 7 VRN Select Switch Board Marking Switch Position VRN Source EXT Left External J1 pin 20 0V Middle Ground 2 5V Right Onboard 2 5V ...

Page 26: ...t often used in ratiometric sensor connections A sensor excita tion voltage can be applied to the SYSREFP pin on J1 Note that the ADS1224 performance is greatly degraded over temperature for reference voltages above 2 5V The voltage selected from S5 is routed to the OBREF pin on J1 and also to the rightmost position of switches S1 4 This configuration allows any of the inputs to be connected to th...

Page 27: ...s chapter provides guidelines on using the ADS1224EVM and connecting other systems to it Topic Page 3 1 Input Filtering Capacitors 3 2 3 2 Serial Interface 3 3 3 3 Serial EEPROM 3 3 3 4 Clock Circuitry 3 3 Chapter 3 ...

Page 28: ...alues you like The pads are 0805 footprints so it is easy to solder resistors to them by hand If you do not have surface mount components it is possible to solder leaded components to these pads The physical layout of the components in each filter is the same and is shown in Figure 3 2 The pads of the differential capacitor are marked on the board with the pin they are connected to Figure 3 2 Chan...

Page 29: ...the serial interface of the ADS1224 3 3 Serial EEPROM The serial EEPROM is a Microchip 24LC256 32kB type You can use it for any thing you like the chip is not programmed during manufacturing Some possible uses include calibration data or board ID information Information on communicating with the EEPROM is available from Microchip Technology Inc 3 4 Clock Circuitry The ADS1224 does not have a built...

Page 30: ...Clock Circuitry 3 4 ...

Page 31: ...nted circuit board PCB layout for the ADS1224EVM Note Board layouts are not to scale They are intended to show how the board is laid out they are not intended to be used for manufacturing ADS1224EVM PCBs Topic Page 4 1 Schematic 4 2 4 2 Printed Circuit Board Layout 4 3 4 3 Bill of Materials 4 4 Chapter 4 ...

Page 32: ...11 INN3 12 INP2 13 INN2 14 INP1 15 INN1 16 GND 17 VRN 18 VRP 19 AVDD 20 U1 ADS1224PW C2 DNP C3 DNP C1 DNP R20 R10 C5 DNP C6 DNP C4 DNP R40 R30 C8 DNP C9 DNP C7 DNP R60 R50 C11 DNP C12 DNP C10 DNP R80 R70 AN0 2 AN1 4 AN2 6 AN3 8 AN4 10 AN5 12 AN6 14 AN7 16 REF 18 REF 20 AGND 17 AGND 19 AN0 1 AN1 3 AN2 5 AN3 7 AGND 9 AGND 11 AGND 13 VCOM 15 J1 ANALOGHDR S1 S2 S3 S4 S5 S6 2 3 6 7 4 U2 OPA350 AVDD TP1...

Page 33: ... to bottom is component top layer ground plane power plane and solder bottom layer Four layers were necessary to accommodate the many components on the board Four layers are not necessary for high performance with the ADS1224 the same level of performance can also be achieved on a two layer board Figure 4 2 Top Side Layout Figure 4 3 Bottom Side Layout ...

Page 34: ...1A105KA61D C17 22µF ceramic chip capacitor 10 X5R 6 3V Murata GRM31CR60J226KE19L U1 Analog to digital converter Texas Instruments ADS1224IPW U2 Operational amplifier Texas Instruments OPA350UA U3 Voltage reference 2 5V Texas Instruments REF1004I 2 5 U4 EEPROM 12C 256K bits Microchip 24LC256 I SN U5 Oscillator Epson SG 8002CA PWT J1A J2A SMT header 20 pin dual row Samtec TSM 110 01 L DV P J1B J2B S...

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