Texas Instruments ADS528 Series User manual

ADS528x EVM User's Guide
User's Guide
January 2008
SLAU205

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Contents
1 Overview .................................................................................................................... 51.1 Purpose............................................................................................................ 51.2 EVM Basic Functions ............................................................................................ 61.3 ADS528x EVM Quick Start Procedure ........................................................................ 72 Circuit Description ...................................................................................................... 82.1 Schematic Diagram .............................................................................................. 82.2 Circuit Function ................................................................................................... 83 TI ADC SPI Control Interface ....................................................................................... 103.1 Installing the ADC SPI Control Software .................................................................... 103.2 Using the TI ADC SPI Interface Software ................................................................... 104 ADC Evaluation ......................................................................................................... 134.1 Hardware Selection ............................................................................................ 134.2 Coherent Input Frequency Selection ......................................................................... 145 Errata ....................................................................................................................... 155.1 Silkscreen Errata ............................................................................................... 156 Physical Description .................................................................................................. 166.1 PCB Layout ...................................................................................................... 166.2 Bill of Materials .................................................................................................. 206.3 PCB Schematics ................................................................................................ 23
Important Notices ............................................................................................................... 28
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List of Figures
1 ADS5281 EVM ............................................................................................................... 62 TI ADC SPC Interface Screen ........................................................................................... 103 Top Silkscreen .............................................................................................................. 164 Ground Plane ............................................................................................................... 175 Power Plane ................................................................................................................ 186 Bottom Silkscreen .......................................................................................................... 197 EVM Schematics (Sheet 1 of 5) .......................................................................................... 238 EVM Schematics (Sheet 2 of 5) .......................................................................................... 249 EVM Schematics (Sheet 3 of 5) .......................................................................................... 2510 EVM Schematics (Sheet 4 of 5) .......................................................................................... 2611 EVM Schematics (Sheet 5 of 5) .......................................................................................... 27
List of Tables
1 Three-Pin Jumper List ....................................................................................................... 72 EVM Power-Supply Options ................................................................................................ 83 ADS528X Frequently Used Registers ................................................................................... 124 Bill of Materials ............................................................................................................. 20
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1 Overview
1.1 Purpose
User's GuideSLAU205 – January 2008
This preliminary user's guide gives a general overview of the ADS5281/82/87 (ADS528X) QFN evaluationmodule (EVM) and provides a general description of the features and functions to be considered whileusing this module. The EVM is pictured in Figure 1 .
The EVM provides a platform for evaluating the eight-channel ADS528X analog-to-digital converter (ADC)under various signal, reference, and supply conditions. This document should be used in combination withthe EVM schematic diagram supplied. The ADS5281 and ADS5282 are 12-bit ADCs, whereas theADS5287 is a 10-bit ADC.
Windows is a trademark of Microsoft Corporation.On Semiconductor is a trademark of Semiconductor Components Industries, L.L.C.Xilinx is a trademark of Xilinx, Inc.
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1.2 EVM Basic Functions
Overview
Figure 1. ADS5281 EVM
Eight analog inputs to the ADC are provided via external SMA connectors.
The EVM provides an external SMA connector for input of the ADC clock. The ADC can be clocked usingeither a single-ended or differential clock. Provisions are made on the EVM to allow users to evaluate theADC using a single-ended PECL clock and a differential transformer-coupled clock.
Digital output from the EVM is via a high-speed, high-density Samtec output header. The digital outputconnector mates directly to the TSW1200 Rev B or through an adapter to the TI ADSDeSer-50EVM, bothof which deserialize the serial data stream into parallel CMOS data.
Power connections to the EVM are via banana jack sockets. Separate sockets are provided for the ADCanalog and ADC digital supplies and for the auxiliary circuits.
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1.3 ADS528x EVM Quick Start Procedure
Overview
The ADS528x EVM provides a flexible means of evaluating the ADS528x in a number of modes ofoperation. A basic setup procedure that can be used as a board confidence check is as follows:1. Verify all jumper settings against the schematic jumper list in Table 1 .
Table 1. Three-Pin Jumper List
JUMPER FUNCTION LOCATION: PINS 1–2 LOCATION: PINS 2–3 DEFAULT
JP2 ADC internal or external reference ADC internal reference ADC external reference 1–2selectionJP3 (SMT) EVM clock input selection Transformer coupled Single-ended PECL 1–2JP4 (SMT) ADC CLKP Transformer Single-ended PECL 1–2JP5 (SMT) ADC CLKM Transformer GND 1–2JP8 Selects power management ADC powered by LDO (3.3 V) ADC powered by J4 (3.3 V) 1–2configurationJP9 Selects power management ADC powered by LDO (1.8 V) ADC powered by J5 (1.8 V) 1–2configuration
2. Connect a 5-V supply to J1 and its return to J2.3. Switch power supplies on.4. Using a function generator with 50- Ωoutput, generate a 0-V offset, 1.5-Vpp sine-wave clock into J26.The frequency of the clock must be within the specification for the device speed grade.5. Use a frequency generator with a 50- Ωoutput to provide a 5-MHz, 0-V offset, –1-dBFS-amplitudesine-wave signal into J9. This provides a transformer-coupled differential input signal to the ADC.6. Connect the USB cable, open the PC software and provide a reset command. For first-time use, seeSection 3.1 for installation instructions.7. Connect J8 to the ADS5281DeSerAdapter+ADSDeser-50EVM or TSW1200 deserializer card toevaluate the ADC digital data using a logic analyzer.
Note: Software Operation: Users must use the accompanying software to issue a reset commandbefore taking measurements. In addition to providing the ADS528X with the initializationregister writes detailed in the data sheet, the accompanying software also sets the state ofADC pins ADCRESET and PD. Failure to do so can cause improper operation.
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2 Circuit Description
2.1 Schematic Diagram
2.2 Circuit Function
2.2.1 Power
2.2.2 Clock Input
2.2.3 External References
Circuit Description
The schematic diagram for the EVM is in Section 6.3 .
The following sections describe the function of individual circuits. Refer to the relevant data sheet fordevice operating characteristics.
Power is supplied to the EVM via banana jack sockets. By default, the EVM is configured to use a powermanagement solution to supply the ADC and analog and digital power supplies, allowing users to powerthe board with a single 5-V power supply. The ADC power management solution is based on TI'sTPS77533 and TPS73218, which supply 3.3 V and 1.8 V, respectively. In addition, the EVM offers thecapability to supply to the ADC independent 3.3-V analog and 1.8-V digital supplies. The circuit boarduses only one ground plane, and the heat slug is tied to ground with multiple vias to provide for thermaldissipation. Table 2 offers a snapshot of the power-supply options.
Table 2. EVM Power-Supply Options
EVM Banana Jack DESCRIPTION
J1 Auxiliary circuit 5-V digital supply: PECL driver and USB circuitryJ2 Single ground planeJ4 ADS528x 3.3-V analog supply (only active when JP8 = 2–3)J5 ADS528x 1.8-V digital supply (only active when JP9 = 2–3)
A single-ended square or sinusoidal clock input should be applied to J26. The clock frequency should notexceed the maximum speed rating found in the data sheet. Several different clocking options exist to allowflexible evaluation of the ADC.
In the default case, a single-ended clock is converted to a differential clock using a Mini-Circuits TC1-1Ttransformer. When using this option, the ADC should be configured in differential clock mode by writing0x8001 to ADC register address 0x42. By default, after a software reset this option is asserted to coincidewith the EVM default.
A second EVM option allows the ADC to be configured in single-ended mode. This is provided to the ADCusing an On Semiconductor™ MC100EPT21 amplifier, which provides for sine-wave to square-waveconversion. This configuration can be used for both ADS528X and ADS527X devices. To use this mode,use the surface-mount jumpers JP3, JP4, and JP5, and configure each one of them to have positions 2–3shorted.
The EVM offers the ability to force external references to the ADC. By default, the ADC is configured touse the references generated internal to the ADC. To force the ADC to use external references, usersmust short JP2 pads 2–3, which in turn grounds the INT/EXT pin of the ADC. Users can then use J6 pin 1to force a REFB and pin 3 to force a REFT voltage. GND should be connected to J6 pin 2.
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2.2.4 Analog Inputs
2.2.5 Digital Outputs
Circuit Description
The EVM provides eight analog inputs, using an SMA connector for each of the eight channels of theADC. SMA channel inputs are J9, J10, J13, J14, J17, J18, J21, and J22. By default, the ADC accepts asingle-ended input and translates it to a differential signal using a Mini Circuits TC1-1T transformer. TheADC inputs are dc-biased by feeding the ADC VCM voltage to the transformer center tap on thesecondary windings. Provisions have also been made on the EVM to allow for differential inputs using twoSMAs per input channel.
The serial LVDS digital outputs can be accessed through the J8 output connector. The EVM is designedto be interfaced to the TI TSW1200 Rev B deserializer card, which plugs into J8. In addition, the EVM canbe interfaced to the ADSDeSer-50EVM using a translation card, the ADS5281DeSerAdapter. Both theTSW1200 Rev B and the ADSDeSer-50EVM contain the required parallel 100- Ωtermination resistor thatmust be placed at the receiver to terminate each LVDS data pair properly.
Note: TSW1200 Rev B: Users wishing to use the TSW1200 for deserialization should note that theminimium ADC sampling frequency this can be operated at is 32 MHz. The TSW1200 uses adigital clock manager (DCM) with a minimium operational frequency of 32 MHz.
Full documentation on the TI ADSDeSer-50EVM deserializer is found in the ADSDeSer-50EVM EvaluationModule User's Guide (SBAU091 ) and Connecting Xilinx FPGAs to Texas Instruments ADS527x SeriesADCs, Xilinx™ application report XAPP774 . The VHDL deserializer source code can be found on theXilinx Web site.
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3 TI ADC SPI Control Interface
3.1 Installing the ADC SPI Control Software
3.2 Using the TI ADC SPI Interface Software
TI ADC SPI Control Interface
This section describes the software designed to communicate with the ADC three-wire SPI interface. Theinformation is to be used in conjunction with the device data sheet, which explains the valid registers ofthe device.
The ADC SPI control software can be installed on a personal computer by running the setup.exe filelocated on the CD. This file installs the graphical user interface (GUI) along with the USB drivers neededto communicate to the USB port that resides on the EVM. After the software is installed and the USBcable has been plugged in for the first time, the user is prompted to complete the installation of the USBdrivers. When prompted, users should allow the Windows™ operating system to search for device drivers,and it should automatically find the TI ADC SPI interface drivers. See Figure 2 .
Note: First-time operation: For proper installation of the necessary USB drivers, users shouldinstall the accompanying software before connecting the USB cable to the EVM for the firsttime. Not doing so could cause problems in communicating to the EVM.
Figure 2. TI ADC SPC Interface Screen
Once the software is installed and the USB cable is connected, three primary modes of operating thesoftware are available: SPI register write, SPI register write using a script file, and ADS528X frequentlyused registers.
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