Texas Instruments DAC7716EVM User Manual

User's Guide

SBAU159–October 2009

DAC7716EVM

This user's guide describes the characteristics, operation, and use of the DAC7716EVM. The evaluation module (EVM) is an evaluation board that allows for quick and easy evaluation of the DAC7716. The DAC7716 is a quad, high-accuracy, 12-bit R-2-R digital-to-analog converter (DAC). The device features low-power operation, good linearity, and the ability to use different reference voltages for the output channels. This EVM allows evaluation of all aspects of the DAC7716. Complete circuit descriptions, schematic diagrams, and bill of material are included in this document.

The following related documents are available through the Texas Instruments web site at

http://www.ti.com.

EVM-Compatible Device Data Sheets

Device Literature Number

DAC7716 SBAS463 REF5025 SBOS410 REF5050 SBOS410

OPA211 SBOS377

TL750L08 SLVS017

All trademarks are the property of their respective owners.

SBAU159–October 2009 DAC7716EVM

Submit Documentation Feedback

EVM Overview

1 EVM Overview ............................................................................................................... 2

2 Analog Interface ............................................................................................................. 3

3 Digital Interface .............................................................................................................. 3

4 Power Supplies .............................................................................................................. 5

5 Reference Voltage .......................................................................................................... 5

6 EVM Operation .............................................................................................................. 6

7 Schematics and Layout .................................................................................................... 8

1 Reference Test Points...................................................................................................... 6

2 DAC7716EVM Default Jumper Locations ............................................................................... 7

3 Default Settings for Switch S1 (LDAC Low) ............................................................................ 8

4 Default Settings for Switch S2 and S3 ................................................................................... 8

1 J1: Analog Interface Pinout................................................................................................ 3

2 J2: Serial Interface Pins ................................................................................................... 4

3 J3 Configuration: Power-Supply Input.................................................................................... 5

4 DAC7716EVM Bill of Materials ........................................................................................... 9

www.ti.com

Contents

List of Figures

List of Tables

1 EVM Overview

1.1 Features

DAC7716EVM:

• Contains all support circuitry needed for the DAC7716

• Voltage reference options: Either 5V or 2.5V onboard, or external

• Jumpers on output pins for gain adjustment

• Compatible with the TI Modular EVM System This manual covers the operation of the DAC7716EVM. Throughout this document, the abbreviation EVM

and the term evaluation module are synonymous with the DAC7716EVM.

1.2 Introduction

The DAC7716 uses a high-speed SPI interface (up to 50MHz) to communicate with a DSP or a microprocessor using a compatible serial interface. The DAC features four individual outputs whose gain is controlled by the addition of a feedback resistor. An additional V channels from the DAC or the signal from the AINpin.

The DAC7716EVM is designed to run in either bipolar (default mode) or unipolar modes of operation. This flexible design allows for a wide range of supply voltages. The operating mode can be controlled using an onboard switch or digitally, through the digital header.

The DAC7716EVM is an evaluation module built to the TI Modular EVM System specification. It can be connected to any modular EVM system interface card. The EVM ships in the TQFP-48 pin package option.

Note that the DAC7716EVM has no microprocessor and cannot run software. To connect it to a computer, some type of interface is required.

The device shown in the front-page figure is the DAC8734, the 16-bit version of the DAC7716. The DAC7716 is installed in place of the DAC8734 on the DAC7716 evaluation module.

pin can relay any of the four output

MON

DAC7716EVM SBAU159–October 2009

Submit Documentation Feedback

www.ti.com

2 Analog Interface

For maximum flexibility, the DAC7716EVM can interface to multiple analog sources. Samtec part numbers SSW-110-22-F-D-VS-K and TSM-110-01-T-DV-P provide a 10-pin, dual-row, header at J1. This header provides access to the analog input and output pins of the DAC. Consult Samtec at

http://www.samtec.com or call 1-800-SAMTEC-9 for a variety of mating connector options. Table 1 summarizes the pinouts for analog interface J1.

Pin Number Signal Description

J1.9-13 (odd) AGND Analog ground connections

J1.17-19 (odd) AGND Analog ground connections

Table 1. J1: Analog Interface Pinout

J1.1 SGND-0 Signal GND DAC output 0 J1.2 V J1.3 SGND-1 Signal GND DAC output 1 J1.4 V J1.5 SGND-2 Signal GND DAC output 2 J1.6 V J1.7 SGND-3 Signal GND DAC output 3 J1.8 V

J1.10 A J1.14 V J1.15 Unused —

J1.18 RefGND Reference ground pins on the

J1.20 EXTREF+ External reference source input (+

J1.12 Unused — J1.16 Unused —

-0 Analog output 0

OUT

-1 Analog output 1

OUT

-2 Analog output 2

OUT

-3 Analog output 3

OUT

MON_BUF

Auxiliary analog input

Monitor output after buffer

DAC7716 (see below)

side of reference input)

Analog Interface

The analog interface is populated on the top of the evaluation model. This configuration makes it possible to stack multiple EVMs to run them in daisy-chain mode. J4 can be installed with a 90-degree connector to allow access to the analog outputs if multiple EVMs are stacked. The J1B connector can be installed if the part is used as a standalone board.

The DAC7716 can be configured with an output gain of 2 or 4. By default, the analog outputs of the DAC7716EVM are configured with a gain of 4. If a gain of 2 is desired, the proper jumper must be installed (JP2-JP5, depending on the output channel), and the command register must be set accordingly.

The SGND pins of the DAC7716 are connected to the ground of the evaluation board. The Auxiliary Analog Input pin can be further protected from over-voltage and over-driving conditions. A

Schottky diode (D1) can be installed to protect the DAC7716 from an input over-voltage condition. An op amp buffer is placed on the V

The DAC7716EVM has an external reference voltage option. If an external reference voltage is used, switches S2 and S3 must be properly configured. Use the EXTREF+ (J1.20) to apply an external reference voltage.

The DAC7716 is designed to have the REFGND-A and REFGND-B pins within 0.3V of the AGND. Therefore, we recommend not using the RefGND pin when connecting an external reference. Connect the ground source of the reference voltage to the ground of the board (J1.19). See the Reference Voltage section for more information.

3 Digital Interface

The DAC7716EVM is a serial input data converter. The evaluation module is designed for interfacing to multiple control platforms.

output to limit the current that passes through the pin.

MON

SBAU159–October 2009 DAC7716EVM

Submit Documentation Feedback

Digital Interface

3.1 Serial Data Interface

Samtec part numbers SSW-110-22-F-D-VS-K and TSM-110-01-T-DV-P provide a 10-pin, dual-row, header/socket combination at J2. This header/socket provides access to the digital control and serial data pins from both J2A (top side) and J2B (bottom side) of the connector. Consult Samtec at

http://www.samtec.com or call 1-800-SAMTEC-9 for a variety of mating connector options. Table 2 describes the serial interface pins.

www.ti.com

OUT

(1)

clock; pins are shorted together

pins are shorted together

of Group A

in/out

of Group B

control LDAC for DAC output latch update

signal to control LDAC for DAC output latch update

-3.

Table 2. J2: Serial Interface Pins

Pin No. Signal Name I/O Type Pullup Function

J2.1 Unused — — J2.2 GPIO-0 In/Out High GPIO-0

J2.3 J2.5 SCLK In None DAC7716 SPI

J2.4 DGND In/Out None Digital ground J2.6 GPIO-1 In/Out High GPIO-1

J2.7 J2.9 CS In None SPI bus chip select;

J2.8 Uni/Bip A In High Output mode select

J2.10 DGND In/Out None Digital ground J2.11 SDO/SDI In/Out None DAC7716 SPI data

J2.12 Uni/Bip B In High Output mode select

J2.13 Unused — — J2.14 RST In High Input register reset J2.15 LDAC In High GPIO signal to

J2.16 Unused — — J2.17 LDAC In High Alternate GPIO

J2.18 DGND In/Out None Digital ground J2.19 Unused — — J2.20 Unused — —

(1)

Group A contains V

-0 and V

OUT

-1. Group B contains V

OUT

-2 and V

OUT

The SCLK signal and the CS signal can each be controlled by two different pins on J2. Pins J2.3 and J2.5 have been shorted together, as well as pins J2.7 and J2.9.

Pins J2.8, J2.12, J2.14, J2.15, and J2.17 have weak pull-up/pulldown resistors. These resistors provide default settings for many of the control pins. J2.3, J2.5, J2.7, J2.9, J2.11 correspond directly to DAC7716 pins. See the DAC7716 product data sheet for complete details on these pins.

Control signals to and from the DAC7716 can be accessed through the digital interface, or switches and jumpers found directly on the EVM. The /LDAC, Uni/Bip A, Uni/Bip B, and RST signals are initially pulled high through 10kΩ resistors and can be controlled by switch S1 or through J2.

The load DAC (LDAC) pin is connected via jumper JP1 to either the J2.15 or J2.17 pin. Updating the DAC registers can be completed in two different ways. LDAC can either be tied to ground, in which case the input registers are immediately updated, or LDAC can be pulled high. Therefore, the DAC registers update when LDAC is taken low. Switch S1.1 can be closed to hold the LDAC low. See the DAC7716 data sheet for more information on updating the DAC.

DAC7716EVM SBAU159–October 2009

Submit Documentation Feedback

+ 8 hidden pages