Analog Devices DC2873A User manual

User Guide | UG-2001
DC2873A
Evaluating the LTC2688 16-Channel, 16-Bit Voltage Output SoftSpan DAC
PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | 1 of 12
FEATURES
►Fully featured evaluation board for the LTC2688 multichannel
voltage output DAC
►Flexible output power supply configuration
►Easy connection to external loads
►Test points to monitor DAC status signals
►ACE evaluation software compatible
EVALUATION KIT CONTENTS
►DC2873A-B evaluation board
►Ribbon cable to connect to the Linduino DC2026C controller
board
EQUIPMENT NEEDED
►DC2026C controller board (must be purchased separately)
►PC running Windows® 7 or Windows 10
►Voltmeter
►Power supply
SOFTWARE NEEDED
►ACE evaluation software (available for download from the
DC2873A product page)
DOCUMENTS NEEDED
►LTC2688 data sheet
►DC2873A-B design files (see the DC2873A product page)
GENERAL DESCRIPTION
The DC2873A-B is a fully featured evaluation board that is used
to evaluate the LTC2688, a 16-channel, precision voltage output
digital-to-analog converter (DAC).
The DC2873A-B is controlled through a serial peripheral interface
(SPI) from the J1 connector. The SPI signals are sent from the
DC2026C controller board through the ribbon cable that is connect-
ed to the DC2873A-B.
The DC2873A-B uses Analysis, Control, Evaluation (ACE) software
to provide an intuitive graphical user interface (GUI) that configures
and controls the LTC2688 using the SPI interface.
The LTC2688 is used for various voltage mode biasing applications
such as optical modulators for data communications. The output
voltage range for each channel is software selectable, and any
channel can be routed to the DC2873A-B MUX pin, allowing either
the channel voltage or current to be externally monitored.
For full specifications on the LTC2688, see the LTC2688 data
sheet, which must be consulted in conjunction with this user guide
when using the DC2873A-B.
EVALUATION BOARD PHOTOGRAPH
001
Figure 1. DC2873A-B Evaluation Board

User Guide UG-2001
TABLE OF CONTENTS
analog.com Rev. 0 | 2 of 12
Features................................................................ 1
Evaluation Kit Contents......................................... 1
Equipment Needed................................................1
Software Needed...................................................1
Documents Needed...............................................1
General Description...............................................1
Evaluation Board Photograph................................1
Evaluation Board Hardware...................................3
Evaluation Board Overview................................3
Power Supplies.................................................. 3
Analog Outputs...................................................4
Digital Interface.................................................. 4
Reference...........................................................4
Multiplexer Output.............................................. 4
On-Board Connectors........................................ 4
Getting Started...................................................... 5
Software Installation Procedures........................5
Evaluation Hardware Setup................................5
Software Operation............................................ 5
Main Window......................................................6
Troubleshooting...................................................10
Hardware..........................................................10
Evaluation Board Schematic................................11
Ordering Information............................................12
Bill of Materials.................................................12
REVISION HISTORY
6/2021—Revision 0: Initial Version

User Guide UG-2001
EVALUATION BOARD HARDWARE
analog.com Rev. 0 | 3 of 12
EVALUATION BOARD OVERVIEW
The DC2873A-B requires the power connections and connection
to the DC2026C controller board shown in Figure 2. The ribbon
cable provided in the evaluation kit connects the DC2873A-B and
the DC2026C via the J1 connector. Turrets are provided to connect
the DC2873A-B to the power supplies.
The DC2873A-B has other optional features to allow the user to
select an external reference, provide separate supply voltages for
Channel 0 to Channel 7 and Channel 8 to Channel 15, and to
monitor various outputs through the on-board MUX pin. These
optional features do not need to be changed for normal operation.
POWER SUPPLIES
The DC2873A-B is powered using external supplies. The minimum
requirement to power the DC2873A-B is to provide 5.0 V to 21 V on
E1 (V1+) and connect E2 (GND) and E3 (V−) to ground (GND).
As an alternative, the supply connection to E3 (V−) can be in
the range between −21 V and ground (GND) to accommodate
applications that require a negative supply.
The default position for JP5 (V1+ = V2+) is in the CONNECT
position. This position connects the V1+ and V2+ power supplies so
that they are at the same voltage. By changing JP5 to the NC (not
connected) position, V1+ and V2+ are decoupled on the evaluation
board and can be driven with separate supplies. V1+ and V2+ have
the same requirement. They must be in the range of 5 V to 21 V but
do not need to be the same voltage when decoupled. However, V2+
must be less than or equal to V1+.
E31 (VCC) and E10 (IOVCC) are supplied from on-board regulators
by default. If desired, these voltages can be driven with an external
supply.
Figure 2. DC2873A-B Hardware Connections

User Guide UG-2001
EVALUATION BOARD HARDWARE
analog.com Rev. 0 | 4 of 12
ANALOG OUTPUTS
The analog outputs, VOUT0 to VOUT15, are available on the E6, E7,
E8, E9, E11, E12, E15, E16, E18, E19, E20, E21, E23, E25, E26,
and E27 turrets, respectively. Return paths for the ground currents
are available on the E4 and E30 (GND) turrets. These turrets must
be connected to load GND.
DIGITAL INTERFACE
DC2026C Connections
The DC2873A-B uses the DC2026C to communicate with the ACE
evaluation software through the USB port on the DC2026C. Use
the provided ribbon cable to connect J1 of the DC2873A-B to J1
of the DC2026C. When this connection is made, the DC2026C
powers the electrically erasable programmable read only memory
(EEPROM) on the DC2873A-B. The ACE evaluation software uses
the EEPROM to identify the DC2873A-B and load the proper plugin.
To ensure proper serial transfers and compatibility, the DC2026C
powers the IOVCC pin of the LTC2688, which is nominally 5 V.
DC2026C Connector Pin Descriptions
Figure 3 shows the pins for the DC2026C J1 connector. For de-
scriptions of each pin, see Table 1.
1 3 5 7 9 11 13
2 4 6 8 10 12 14
002
Figure 3. DC2026C J1 Connector Pins
Table 1. DC2026C Connector J1 Pin Descriptions
Pin No. Mnemonic Description
1 V+ Unregulated voltage from the DC2026C,
nominally 7 V
2 VCCIO I/O voltage set by JP3 on the DC2026C
3 GND Ground
4 SCL/SCK Serial clock from the DC2026C
5 MISO Serial data from the DC2873A-B
6 CS Chip select from the DC2026C
7 SDA/MOSI Serial data from the DC2026C
8 GND Ground
9 EEDA Serial data for EEPROM
10 EEVCC Power supply (VCC) for EEPROM
11 EESCL Serial clock for EEPROM
12 EEGND Ground for EEPROM
13 GND Ground
14 NC No connection
REFERENCE
By default, the DC2873A-B uses the internal reference of the
LTC2688. To use an external reference, place the DC2873A-B JP1
(REF SEL) jumper into the EXT position and apply an external
reference to E5 (REF).
MULTIPLEXER OUTPUT
The LTC2688 has an internal multiplexer that allows monitoring of
compliance voltages, output currents, and internal die temperature.
The output compliance voltages and representative voltages of
the output current and internal die temperature are available on
the LTC2688 MUX pin and can be routed to the DC2873A-B E28
connector (MUX) using the LTC2688-16 Memory Map view in the
ACE GUI (see Figure 8), and setting the appropriate bits in the
analog mux control register. Refer to the LTC2688 data sheet for
more details on the multiplexer functionality and register structure.
ON-BOARD CONNECTORS
Table 2 describes the on-board connectors on the DC2873A-B.
Table 2. On-Board Connectors
Connector Function
J1 SPI/I2C interface pin header connector
JP1 Internal or external reference select
JP2 Toggle Pin 0 (TGP0)
JP3 Toggle Pin 1 (TGP1)
JP4 Toggle Pin 2 (TGP2)
JP5 Connect or disconnect V1+ and V2+
E1 V1+
E2, E4, E13, E17, E30 GND connections
E3 V−
E5 REF
E6 Channel 0 voltage output (VOUT0)
E7 Channel 1 voltage output (VOUT1)
E8 Channel 2 voltage output (VOUT2)
E9 Channel 3 voltage output (VOUT3)
E10 IOVCC
E11 Channel 4 voltage output (VOUT4)
E12 Channel 5 voltage output (VOUT5)
E14 V2+
E15 Channel 6 voltage output (VOUT6)
E16 Channel 7 voltage output (VOUT7)
E18 Channel 8 voltage output (VOUT8)
E19 Channel 9 voltage output (VOUT9)
E20 Channel 10 voltage output (VOUT10)
E21 Channel 11 voltage output (VOUT11)
E22 CLR
E23 Channel 12 voltage output (VOUT12)
E24 LDAC
E25 Channel 13 voltage output (VOUT13)
E26 Channel 14 voltage output (VOUT14)
E27 Channel 15 voltage output (VOUT15)
E28 MUX
E29 FAULT
E31 VCC

User Guide UG-2001
GETTING STARTED
analog.com Rev. 0 | 5 of 12
The ACE evaluation software controls and configures the on-board
LTC2688 through the DC2026C.
SOFTWARE INSTALLATION PROCEDURES
Before connecting the DC2026C to the DC2873A-B, follow these
steps to set up the DC2873A-B for initial use in the ACE evaluation
software:
1. Download the ACE evaluation software package from the
DC2873A-B product page at www.analog.com/DC2873A to
start the ACE evaluation software installation.
2. Open the ACEInstall_1.21.xxxx.xxxx.exe file and follow the
instructions in the folder to complete the software installation
process.
EVALUATION HARDWARE SETUP
When the ACE evaluation software installation is complete, follow
these steps to set up the DC2026C and the DC2873A-B together:
1. Connect the DC2026C to the DC2873A-B via the J1 connectors
with the ribbon cable provided (see Figure 2).
2. Connect the desired power supplies to E1 (V1+), E2 (GND),
and E3 (V−) on the DC2873A-B.
3. Connect the desired load to the appropriate channel on the
DC2873A-B.
4. Connect the load ground to a ground (GND) turrets (either E4
or E30) on the DC2873A-B.
5. Connect the DC2026C to a PC or laptop using the USB cable.
6. Start the ACE evaluation software (see the Software Operation
section).
SOFTWARE OPERATION
To start the ACE evaluation software, from the Start menu, click
Analog Devices > ACE. The software window opens (see Figure
4) until the software recognizes the DC2873A-B. When the software
recognizes the DC2873A-B, the main software window in Figure 5
opens.
Figure 4. Interface Window

User Guide UG-2001
GETTING STARTED
analog.com Rev. 0 | 6 of 12
004
Figure 5. ACE Evaluation Software Main Window
MAIN WINDOW
In the main ACE evaluation software window (see Figure 5), each
channel can be controlled. Various settings for the LTC2688 are
available in this window, allowing the user to configure the output
range, output voltage, gain adjustment, offset adjustment, toggle
options, and dither options of each channel.
Refer to the LTC2688 data sheet for more information on the
device features associated with the different tab functions that are
described in the following sections.
Reference Configuration
The DC2873A-B uses the LTC2688 internal reference to set the
full-scale range. To apply an external reference, click the box
labeled Reference Select (see Figure 5).
Setting the Channel Output Range
To set the output range for a specific channel on the LTC2688,
1. Select the channel from the Channel Select dropdown box.
2. Select the desired range for the selected channel using the
Span selection dropdown box (see Figure 5).
Setting the Channel Voltage Value
To set the output voltage for a specific channel on the LTC2688,
1. Select the channel from the Channel Select dropdown box.
2. Type the desired value into the Register A text box (see
Figure 5).
Toggling Between A and B Output Registers
Each channel has two output registers that can be written inde-
pendently.
1. Click the Register A or Register B option to select the register
to write to.
2. Type the desired hexadecimal value into the Register A (or
Register B) text box (see Figure 5).
Settling Offset and Gain Values
Each channel can have an offset and gain value applied to the
output. The value is applied to each channel independently.
1. Select the channel from the Channel Select dropdown box.
2. Type the desired hexadecimal offset or gain adjust value into
the Offset Adjust or Gain Adjust text boxes (see Figure 5).

User Guide UG-2001
GETTING STARTED
analog.com Rev. 0 | 7 of 12
Enabling Toggle Mode
Toggle mode can be enabled by selecting the Enable Toggle/Dith-
er Functionality check box (see Figure 5). This check box enables
the toggle view shown in Figure 6. The toggle signal can then be
applied to the selected pin or supplied internally.
Enabling Dither Mode
After enabling the toggle view shown in Figure 6 as described in
the Enabling Toggle Mode section, select the dither mode from the
Mode dropdown box to bring up the dither options (see Figure 7).
The default values for the dither phase (ⱷ0) and period (N) are 0°
and N = 4. The phase and period of the dither can be modified
using the dropdown boxes to select from a fixed list of options.
005
Figure 6. Toggle View

User Guide UG-2001
GETTING STARTED
analog.com Rev. 0 | 8 of 12
Figure 7. Dither View

User Guide UG-2001
GETTING STARTED
analog.com Rev. 0 | 9 of 12
Memory Map View
To access the LTC2688-16 Memory Map view, click the Proceed
to Memory Map button from the software main window (see Figure
5).
Figure 8. LTC2688-16 Memory Map View

User Guide UG-2001
TROUBLESHOOTING
analog.com Rev. 0 | 10 of 12
HARDWARE
A comprehensive list of frequently asked questions (FAQ) is availa-
ble on the LTC2688 FAQs page in the EngineerZone™ site. For
other questions, submit them to the Precision DACs section of the
EngineerZone site.