Texas Instruments DAC7554 User manual

DAC7554 Evaluation Module
User's Guide
Literature Number: SLAU154March 2005

2 SLAU154 – March 2005

Contents
1 EVM Overview ............................................................................................................ 51.1 Features .............................................................................................................. 51.2 Power Requirements ............................................................................................... 51.3 EVM Basic Functions............................................................................................... 62 PCB Design and Performance ...................................................................................... 72.1 PCB Layout ......................................................................................................... 73 Bill of Materials ......................................................................................................... 114 EVM Operation .......................................................................................................... 124.1 Factory Default Setting ........................................................................................... 124.2 Host Processor Interface ......................................................................................... 134.3 EVM Stacking ...................................................................................................... 134.4 The Output Operational Amplifier ............................................................................... 134.5 Jumper Setting ..................................................................................................... 154.6 Schematics ......................................................................................................... 165 Related Documentation From Texas Instruments .......................................................... 175.1 Questions About This or Other Data Converter EVMs? ..................................................... 17Trademarks .............................................................................................................. 17
Important Notices ............................................................................................................... 18
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List of Figures
1 EVM Block Diagram ......................................................................................................... 72 Top Silkscreen ............................................................................................................... 83 Top Layer (Signal and Split Ground Plane) .............................................................................. 84 Bottom Layer (Signal and Split Ground Plane) .......................................................................... 95 Bottom Silkscreen ........................................................................................................... 96 Drill Drawing ................................................................................................................ 107 Factory Default Jumper Setting .......................................................................................... 12
List of Tables
1 Parts List .................................................................................................................... 112 Factory Default Jumper Setting .......................................................................................... 123 DAC Output Channel Mapping ........................................................................................... 134 Unity Gain Output Jumper Settings ...................................................................................... 145 Gain of Two Output Jumper Settings .................................................................................... 146 Jumper Settings to Add an Offset to the Output Op-amp ............................................................. 147 Jumper Setting Function .................................................................................................. 15
List of Figures4 SLAU154 – March 2005

1 EVM Overview
1.1 Features
1.2 Power Requirements
User's GuideSLAU154 – March 2005
DAC7554EVM
This user’s guide describes the characteristics, operation, and the use of the DAC7554evaluation module. It covers all pertinent areas involved to properly use this EVM boardalong with the devices that it supports. The physical PCB layout, schematic diagramand circuit descriptions are included.
This section gives a general overview of the DAC7554 evaluation module (EVM), and describes some ofthe factors that must be considered in using this module.
This EVM features the DAC7554 digital-to-analog converter (DAC). The DAC7554 EVM is a simpleevaluation module designed for a quick and easy way to evaluate the functionality and performance of the12-bit resolution, quad-channel and serial input DAC. This EVM features an ultralow glitch voltage outputwith great linearity and monotonicity. The serial interface of this DAC can communicate with any hostmicroprocessor or TI DSP base system.
The following sections describe the power requirements of this EVM.
1.2.1 Supply Voltage
The dc power supply requirement for this DAC7554 EVM (VDD) is selectable between 3.3 V and 5 V viaW1 jumper header. The 3.3 V comes from J6-8 or J5-1 (if installed), and the 5 V comes from J6-3 or J5-3terminals (if installed), when plugged in via 5-6k interface card or the HPA449. These power supplyvoltages are referenced to ground through the J6-6 terminal. The V
CC
and V
SS
are only used by U2operational-amplifier, which ranges from 15 V to -15 V maximum and connects through J1-3 and J1-1respectively (if installed), or through J6-1 and J6-2 terminals. All the analog power supplies are referencedto analog ground through J1-2 and J6-6 terminals.
The negative rail of the output operational-amplifier, U2, can be selected between V
SS
and AGND via W5jumper. The external operational-amplifier is installed as an option to provide output signal conditioning orfor other output mode requirement desired.
CAUTIONTo avoid potential damage to the EVM board, make sure that the correctcables are connected to their respective terminals as labeled on the EVMboard.
Stresses above the maximum listed voltage ratings may cause permanentdamage to the device.
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1.3 EVM Basic Functions
EVM Overview
1.2.2 Reference Voltage
The 4.096-V precision voltage reference is provided to supply the external voltage reference and sets thevoltage output range of the DAC under test through REF3140, U3, via jumper W4 by shorting pins 1 and2. The test point TP4 as well as J4-20 are also provided to allow the user to connect to other externalreference source if the onboard reference circuit is not desired. The external voltage reference should notexceed the applied power supply, V
DD
, of the DAC under test.
The REF3140 precision reference is powered by +5VA through J6-4 or J5-3 (if installed) terminal.
CAUTIONWhen applying an external voltage reference through TP4 or J4-20, makesure that it does not exceed the DAC7554 power supply (V
DD
) maximum.Otherwise, this can permanently damage the DAC7574, U1, device undertest.
The DAC7554 EVM is designed primarily as a functional evaluation platform to test certain functionalcharacteristics of the DAC7554 DAC. Functional evaluation of the DAC device can be accomplished withthe use of any microprocessor, TI DSP or some sort of a waveform generator.
The headers J2 and P2 are the connectors provided to allow the control signals and data required tointerface a host processor or waveform generator to the DAC7554 EVM using a custom built cable.
An adapter interface card (5-6k adapter interface) is also available to fit and mate with TI’sTMS320C5000™ and TMS320C6000™ DSP Starter Kit (DSK). This alleviates the hassle involved inbuilding a custom cable. In addition, there is also an MSP430 based platform (HPA449) that uses theMSP430F449 microprocessor, with which this EVM can connect and interface. For more details orinformation regarding the 5-6k adapter interface card or the HPA449 platform, call Texas Instruments orsend email to [email protected].
The DAC outputs can be monitored through the selected pins of J4 header connector. All the outputs canbe switched through their respective jumpers W2, W11, W12 and W13, for the reason of stacking.Stacking allows a total of eight DAC channels to be used provided that the SYNC signal is unique for eachEVM board stacked. The SYNC signal must be decoded for the specific EVM, therefore, the decodershould be implemented but can only be done externally from the EVM board.
In addition, the option of selecting one DAC output that can be fed to the noninverting side of the outputoperational-amplifier, U2, is also possible by using a jumper across the selected pins of J4. If two EVMsare stacked together, the output operational-amplifier's noninverting input, are shorted together at the J4header. Alterations to the traces are necessary to use the U2 features. The traces for J4-1, J4-3, J4-5,and J4-7 are visible from the topside of the EVM. However, one issue still remains, the trace to thenoninverting pin of U2 cannot be seperated from J4-1. Therefore, only one of the stacked EVMs can beused with the U2 feature. Finally, the output operational-amplifier, U2, must first be configured correctly forthe desired waveform characteristic to be seen. See section 4 of this user’s guide.
A block diagram of the EVM is shown below in the Figure 1 .
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VCC
VDD
VOUT
REFIN
TP4
DAC Out
TP3
Output
Buffer
Module
TP2
R14
(J1)
(J5)
(J6)
(P6)
(J2)
(P2)
(J4)
(P4)
VSS
VSS
W1
W2
4 CH
8 CH#
W7
W3
W5
W2
W11
W12
W13
DIN
SCLK
SYNC
VCC
VSS
GND
GND
GND
DAC Module*
External
Reference
Module
*DAC module features the DAC7554.
# Up to 8 channels can be checked when 2 EVMs are stacked.
+5VA
+5VA +3.3VA
+3.3VA
2 PCB Design and Performance
2.1 PCB Layout
PCB Design and Performance
Figure 1. EVM Block Diagram
This section covers the layout design of the PCB; thereby, describing the physical and mechanicalcharacteristics of the EVM. The list of components used on the module is also included in this section.
The DAC7554 EVM is designed to preserve the performance quality of the DAC, device under test, asspecified in the data sheet. Carefully analyzing the EVM’s physical restrictions and the given or knownelements that contributes to the EVM’s performance degradation is the key to a successful designimplementation. These attributes that diminish the performance of the EVM can be addressed during theschematic design phase, by properly selecting the right components and building the circuit correctly. Thecircuit should include adequate bypassing, identifying and managing the analog and digital signals andknowing or understanding the components mechanical attributes.
The obscure part of the design is the layout process where lack of knowledge and inexperience can easilypresent a problem. The main concern here is primarily with the placement of components and the properrouting of signals. The bypass capacitors should be placed as close as possible to the pins and the analogand digital signals should be properly separated from each other. The power and ground plane is veryimportant and should be carefully considered in the layout process. A solid plane is ideally preferred butsometimes impractical, so when solid planes are not possible, a split plane does the job as well. Whenconsidering a split plane design, analyze the component placement and carefully split the board into itsanalog and digital sections starting from the device under test. The ground plane plays an important role incontrolling the noise and other effects that otherwise contributes to the error of the DAC output. To ensurethat the return currents are handled properly, route the appropriate signals only in their respectivesections, meaning the analog traces should only lay directly above or below the analog section and thedigital traces in the digital section. Minimize the length of the traces but use the biggest possible tracewidth allowable in the design. These design practice discussed can be seen in the following figurespresented below.
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PCB Design and Performance
The DAC7554 EVM board is constructed on a two-layer printed-circuit board using a copper-clad FR-4laminate material. The printed-circuit board has a dimension of 43,1800 mm (1.7000 inch) × 81,2800 mm(3.200 inch), and the board thickness is 1,5748 mm (0.0620 inch). Figures 2 through 6 show the individualartwork layers.
Figure 2. Top Silkscreen
Figure 3. Top Layer (Signal and Split Ground Plane)
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PCB Design and Performance
Figure 4. Bottom Layer (Signal and Split Ground Plane)
Figure 5. Bottom Silkscreen
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PCB Design and Performance
Figure 6. Drill Drawing
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