DAC7741EVM
User’s Guide
October 2002
DAP EVMs
SLAU093
EVM IMPORTANT NOTICE
Texas Instruments (TI) provides the enclosed product(s) under the following conditions:
This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION
PURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being provided
may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective
considerations, including product safety measures typically found in the end product incorporating the goods.
As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic
compatibility and therefore may not meet the technical requirements of the directive.
Should this evaluation kit not meet the specifications indicated in the EVM User’s Guide, the kit may be returned
within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE
WARRANTY MADE BY SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED,
IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY
PARTICULAR PURPOSE.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user
indemnifies TI from all claims arising from the 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 ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
TI currently deals with a variety of customers for products, and therefore our arrangement with the user is not
exclusive.
TI assumes no liability for applications assistance, customer product design, software performance, or
infringement of patents or services described herein.
Please read the EVM User’s Guide and, specifically, the EVM Warnings and Restrictions notice in the EVM
User’s Guide prior to handling the product. This notice contains important safety information about temperatures
and voltages. For further safety concerns, please contact the TI application engineer.
Persons handling the product must have electronics training and observe good laboratory practice standards.
No license is granted under any patent right or other intellectual property right of TI covering or relating to any
machine, process, or combination in which such TI products or services might be or are used.
Mailing Address:
Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright 2002, Texas Instruments Incorporated
EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the input voltage range of 15 V and the output
voltage range of 10 V.
Exceeding the specified input range may cause unexpected operation and/or irreversible
damage to the EVM. If there are questions concerning the input range, please contact a TI
field representative prior to connecting the input power.
Applying loads outside of the specified output range may result in unintended operation and/or
possible permanent damage to the EVM. Please consult the EVM User’s Guide prior to
connecting any load to the EVM output. If 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
xxx°C. The EVM is designed to operate properly with certain components above xxx°C as
long as the input and output ranges are maintained. These components include but are not
limited to linear regulators, switching transistors, pass transistors, and current sense
resistors. These types of devices can be identified using the EVM schematic located in the
EVM User’s Guide. When placing measurement probes near these devices during operation,
please be aware that these devices may be very warm to the touch.
Mailing Address:
Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright 2002, Texas Instruments Incorporated
Preface
Read This First
About This Manual
This user’s guide describes the characteristics, operation, and the use of the
DA7741 evaluation module. It covers all pertinent areas involved to properly
use this EVM board along with the devices that it supports. The physical PCB
layout, schematic diagram and circuit descriptions are included.
How to Use This Manual
This document contains the following chapters:
- Chapter 1—EVM Overview
- Chapter 2—Physical Description
- Chapter 3—EVM Operation
Information About Cautions and Warnings
This book may contain cautions and warnings.
This is an example of a caution statement.
A caution statement describes a situation that could potentially
damage your software or equipment.
This is an example of a warning statement.
A warning statement describes a situation that could potentially
cause harm to you.
The information in a caution or a warning is provided for your protection.
Please read each caution and warning carefully.
iii
Trademarks
Related Documentation From Texas Instruments
To obtain a copy of any of the following TI documents, call the Texas Instru-
ments Literature Response Center at (800) 477 – 8924 or the Product Informa-
tion Center (PIC) at (972) 644 – 5580. When ordering, identify this manual by
its title and literature number. Updated documents can also be obtained
through our website at www.ti.com.
Data Sheets:
DAC7741
REF102
Literature Number:
SBAS248
PDS-900E
OPA627
PDS-998H
Questions about this or other Data Converter EVM’s?
If you have questions about this or other Texas Instruments Data Converter
evaluation modules, please feel free to e-mail the Data Converter Application
product you have questions or concerns with.
FCC Warning
This equipment is intended for use in a laboratory test environment only. It gen-
erates, uses, and can radiate radio frequency energy and has not been tested
for compliance with the limits of computing devices pursuant to subpart J of
part 15 of FCC rules, which are designed to provide reasonable protection
against radio frequency interference. Operation of this equipment in other en-
vironments may cause interference with radio communications, in which case
the user at his own expense will be required to take whatever measures may
be required to correct this interference.
Trademarks
TI Logo is a trademark of Texas Instruments Incorporated. SPI and QSPI are
trademarks of Motorola, Inc.
iv
Contents
1
EVM Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1
1.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2.1 Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2.2 Reference Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
EVM Basic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.3
2
3
Physical Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1
2.2
PCB Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
EVM Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1
3.2
Factory Default Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Host Processor Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.2.1 Unity Gain Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.2.2 Output Gain of Two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.2.3 Capacitive Load Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Jumper Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
3.3
3.4
Figures
1-1
2-1
2-2
2-3
2-4
2-5
EVM Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Layer One (Top Silkscreen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Layer Two (Ground Plane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Layer 3 (Power Plane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Layer 4 (Bottom Plane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Drill Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
v
Tables
2-1
3-1
3-2
3-3
3-4
3-5
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Factory Default Jumper Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Unity Gain Output Jumper Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Gain of Two Output Jumper Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Capacitive Load Drive Output Jumper Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Jumper Setting Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
vi
Chapter 1
EVM Overview
This chapter gives a general overview of the DAC7741 evaluation module
(EVM), and describes some of the factors that must be considered in using this
module.
Topic
Page
1.1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2 Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.3 EVM Basic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1-1
Features
1.1 Features
This EVM features the DAC7741 digital-to-analog converter. The DAC7741
EVM is a simple evaluation module designed for a quick and easy way to
evaluate the functionality of the high resolution, single-channel, and parallel
input DAC. This EVM features a parallel interface to communicate to any host
processor base system.
1.2 Power Requirements
The following sections describe the power requirements of this EVM.
1.2.1 Supply Voltage
The dc power supply requirement for the digital section of this EVM is typically
5 V connected to the J11-2 or via J6-2 terminal (when plugged in with another
EVM board or interface card) and is referenced to ground through the J11-1
and J6-1 terminal. The dc power supply requirement for the analog section
(V and V ) of this EVM range from 15.75 V to -15.75 V maximum and
CC
SS
connects through J10-4 and J12-1 or through J7-6 and J7-8 terminals and
is referenced to analog ground through J10-2, J12-2 and J7-1 terminals.
A dc source of 15 V supply is required to provide the rails for the external
output op-amp provided for output signal conditioning or boost capacitive load
drive and for other output modes of application. The 15 V supply connects
through J10-1 or J7-2 terminal, and the –15 V supply connects through J10-3
or J7-4 terminals. The 15 V supply is referenced to ground through J10-2
or J7-3 terminals. The supply source for V and V can also be used as the
CC
SS
supply source for 15 V and -15 V respectively.
To avoid potential damage to the EVM board, make sure that the
correct cables are connected to their respective terminals as
labeled on the EVM board.
Stresses above the maximum listed voltage ratings may cause
permanent damage to the device.
1.2.2 Reference Voltage
Although the DAC7741 has a built-in 10-V voltage reference, an external
reference circuit is provided in the EVM board. The external reference circuit
can be isolated if the internal reference voltage is selected.
The 10-V precision voltage reference is provided to supply the external voltage
reference for the DAC through REF102, U3, via jumper W4 by shorting pins
1 and 2. An adjustable 100-kΩ potentiometer, R11, is installed in series with
20 kΩ, R10, to allow the user to adjust the reference voltage to its desired
settings. TP1 and TP2 are also provided, as well as J4-20, to allow the user
to connect other external reference source if the onboard reference circuit is
not desired. The external voltage reference should not exceed 10-V dc.
1-2
EVM Basic Functions
The REF102 precision reference derives its power of 15-V supply through
J10 or J7 terminal. The (plus) 15 V connects through J10-1 or J7-2 terminals,
while the (minus) -15 V connects through J10-3 or J7-4 terminals. They are
both referenced to analog ground through J10-2 and J7-1.
The DAC7741 has a REFEN pin to enable the internal reference circuit or
disable it and select an external reference source. The REFEN pin can be
hardware driven through W2 jumper. Likewise, it can also be software driven
through J2-11 terminal via W2 jumper by shorting pins 1 and 2. The REF
OUT
pin of the DAC7741 must be connected to the REF pin to use the internal
IN
voltage reference. This can be done through W3 jumper by shorting pins 1 and
2. Shorting pins 2 and 3 of W3 selects the external voltage reference source.
The on-chip reference buffer output is channeled out through V
REF
pin which
is used to set up the DAC7741 output amplifier into one of three voltage output
modes. V can also be used to drive other system components that require
REF
external voltage reference.
When applying an external voltage reference through TP1 or J4-20,
make sure that it does not exceed 10 V maximum. Otherwise, this
can permanently damage the DAC7741, U11, device under test.
1.3 EVM Basic Functions
The DAC7741 EVM is a functional evaluation platform to test certain functional
characteristics of the DAC7741 digital-to-analog converter. Functional
evaluation of the DAC device can be accomplished with the use of any
microprocessor, TMS320VC33 DSP, or some sort of a waveform generator.
The headers, J1, J2 and J3 are provided to channel in the necessary control
signals and data needed to interface a microprocessor/microcontroller, TI’s
DSP starter kit or waveform generator to the DAC7741 EVM, through a custom
cable.
A specific adapter interface card is also available for most of TI’s DSP starter
kit (DSK) and the card model depend on the type of the DSP starter kit to be
used. The user must specify the DSP used as an interface to acquire the right
adapter interface card. Call or email TI for more information regarding the
adapter interface card.
The output of the DAC can be monitored through two different access points
which are as follows; a BNC connector (J5, if installed), and also a header
through pin 2 of J4. The 6-pin header, W13, provides different options of the
DAC output, but requires the output op-amp, U2, to be configured correctly first
for the desired waveform characteristic. Shorting pins 1 and 2 of W13 allows
the user to monitor the raw output of the DAC7741.
EVM Overview
1-3
EVM Basic Functions
A block diagram of the EVM is shown below in the Figure 1-1.
Figure 1-1. EVM Block Diagram
+15 V
-15 V
+15 V
GND
-15 V
GND
VCC
VDD
VSS
(J6)
(J7)
VCC
VDD
VSS
External
Reference
Module
W14
Output
Buffer
Module
TP1
W4
REFEN
LDAC
RST
W3
+REF
DAC Out
IN
Ext Ref
Input
RSTSEL
(J2)
(J3)
W13
(J4)
REF
REF
IN
out
(J5)
DAC Module
CS
R/W
TP2
DB15 (MSB)
DB1 (LSB)
(J1)
1-4
Chapter 2
Physical Description
This chapter describes the physical characteristics and PCB layout of the EVM
and lists the components used on the module.
Topic
Page
2.1 PCB Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.2 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2-1
PCB Layout
2.1 PCB Layout
The EVM is constructed on a four-layer printed-circuit board using a
copper-clad FR-4 laminate material. The printed-circuit board has a dimension
of 99,06 mm (3.90 inch) × 104,14 mm (4.10 inch), and the board thickness is
1,57 mm (0.062 inch). Figures 2-1 through 2-6 show the individual artwork
layers.
Figure 2-1. Layer One (Top Silkscreen)
2-2
PCB Layout
Figure 2-2. Layer Two (Ground Plane)
Physical Description
2-3
PCB Layout
Figure 2-3. Layer 3 (Power Plane)
2-4
PCB Layout
Figure 2-4. Layer 4 (Bottom Plane)
Physical Description
2-5
PCB Layout
Figure 2-5. Drill Drawing
2-6
Bill of Materials
2.2 Bill of Materials
Table 2-1.Parts List
Item # Qty Designator
Manufacturer
Part Number
Description
1
2
3
4
5
1
2
5
1
5
C8
Panasonic
ECJ3VB1C105K
1 µF, 1206 multilayer ceramic
capacitor
C9 C10
Panasonic
Panasonic
Panasonic
ECUV1H103KBM
ECJ3VB1C104K
ECUV1H102JCH
C1210C106K8PAC
0.01 µF, 1206 multilayer ceramic
capacitor
C1 C2 C3 C7
C13
0.1 µF, 1206 multilayer ceramic
capacitor
C12
1 nF, 1206 multilayer ceramic
capacitor
C4 C5 C6 C11 Kemet
C14
10 µF, 1210 multilayer ceramic X5R
capacitor
6
7
8
1
2
6
R8
Panasonic
Panasonic
ERJ-8GEY0R00V
ERJ-8ENF2002V
ERJ-8ENF1002V
0 Ω, 1/4W 1206 chip resistor
20 kΩ, 1/4W 1206 chip resistor
10 kΩ, 1/4W 1206 chip resistor
R7 R10
R4 R5 R6 R12 Panasonic
R13 R14
9
2
1
R1 R2
Bourns
3214W-103E
3214W-104E
10 kΩ, BOURNS_32X4W Series 5T
pot
10
R11
Bourns
100 kΩ, BOURNS_32X4W Series 5T
pot
11
12
1
2
R3
Panasonic
Samtec
ERJ-8ENF1003V
100 kΩ, 1/4W 1206 chip resistor
5X2X0.1
J6 J7
IPT1-105-01-S-D-VS
10-pin 3A isolated power socket
13
14
15
16
3
1
2
1
J2 J3 J4
J1
Samtec
TSM-110-01-S-DV-M
TSM-116-01-S-DV-M
KRMZ2
10X2X.1, 20-pin 0.025” sq SMT socket
16X2X.1, 32-pin 0.025” sq SMT socket
2-pin Terminal screw connector
Samtec
J11 J12
Lumberg
AMP (TYCO)
J5 (Not
227699-2
PCB Mounted BNC - Amphenol
Installed)
17
18
19
20
1
1
1
1
J10
U1
U2
U3
Lumberg
KRMZ4
4-pin Terminal screw connector
16-bit, 48-LQFP DAC
Texas Instruments
Texas Instruments
Texas Instruments
DAC7741
OPA627AU
REF102AU
8-SOP(D) Precision op amp
10 V, 8-SOP(D) Precision voltage
reference
21
22
23
2
1
3
TP1 TP2
W13
Cambion
Samtec
Samtec
180-7337-02-05
Turret terminal test point
TSW-103-07-L-D
3X2X 0.1 6-Pin IDC header
20-pin 0.025” sq SMT terminal strips
P2 P3 P4
SSW-110-22-S-D-VS-P
(see Note)
24
25
1
2
P1 (see Note) Samtec
SSW-116-22-S-D-VS-P
IPS1-105-01-S-D-VS
32-pin 0.025” sq SMT Terminal Strips
P6 P7
Samtec
3A Isolated power header
(see Note)
26
10 W6 W7 W8
W9 W10 W11
W14 W15
Samtec
TSW-102-07-L-S
2 Position jumper_ 0.1” spacing
W16 W17
27
28
6
1
W1 W2 W3
W4 W5 W12
Samtec
Bourns
TSW-103-07-L-S
3214W-203E
3 Position Jumper_ 0.1” spacing
R9
20 kΩ, BOURNS_32X4W Series 5T
pot
Note: P1, P2, P3, P4, P8, & P9 parts are not shown in the schematic diagram. All the P designated parts are installed in the
bottom side of the PC Board opposite the J designated counterpart. Example, J1 is installed on the topside while P1 is
installed in the bottom side opposite of J1.
Physical Description
2-7
Bill of Materials
(This page has been left blank intentionally.)
2-8
Chapter 3
EVM Operation
This chapter covers in detail the operation of the EVM to provide guidance to
the user in evaluating the onboard DAC and how to interface the EVM to a
specific host processor.
Refer to the DAC7741 data sheet, SBAS248, for information about its parallel
interface and other related topics.
The EVM board is factory tested and configured to operate in the bipolar output
mode.
Topic
Page
3.1 Factory Default Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.2 Host Processor Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.3 Jumper Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.4 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
3-1
Factory Default Setting
3.1 Factory Default Setting
The EVM board is set to its default configuration from factory as described on
the table below to operate in bipolar 10V mode of operation using the internal
reference.
Table 3-1.Factory Default Jumper Setting
Jumper
Position
Reference
W1
Function
V output pin is floated and not used for offset adjustment.
OPEN
2-3
REF
REFEN pin is tied to AGND to enable 10 V internal reference.
REF pin is strapped to REF to provide 10 V internal voltage reference.
W2
W3
1-2
OUT
IN
W4
OPEN
1-2
Onboard external reference through U3 is disconnected.
Negative supply rail of U2 op-amp is supplied with -15 V.
REFADJ pin is floated.
W5
W6
OPEN
W7
CLOSE RFB2 pin is strapped to V
pin for DAC output feedback.
OUT
CLOSE TEST pin is tied to DGND.
W8
W9
OPEN
OPEN
SJ pin is floated.
RFB1 is floated.
W10
W11
W12
W13
W14
CLOSE AGND and DGND are tied together to a common point.
1-2
3-4
Positive supply rail of U2 op-amp is supplied with 15 V.
Buffered output of DAC is channeled through to J5 and J4-2.
OPEN
External reference is disconnected from the negative input of U2 to configure U2 for
unity gain.
W15
W16
W17
OPEN
OPEN
OPEN
Configure U2 op-amp for unity gain.
RSTSEL pin is tied high to set DAC reset value to midscale.
RST pin is tied high by default.
3-2
Host Processor Operation
3.2 Host Processor Operation
The host processor basically drives the DAC, so the DACs proper operation
depends on the successful configuration between the host processor and the
EVM board. In addition, a properly written code is also required to operate the
DAC.
A custom cable can be made specific to the host interface platform. The EVM
allows interface to the host processor through J2 and J3 header connectors
for the control signals, and J1 header connector for the data input. The output
can be monitored through the J5 BNC connector (if installed) or J4 header
connector. An interface adapter card is also available for specific DSP starter
kits as mentioned in Chapter 1 of this manual.
The EVM includes an optional signal conditioning circuit for the DAC output
through an external operational amplifier, U2. This is set to a unity gain
configuration by default. Regardless, the raw output of the DAC can be probed
through W13 pin 2 so that it can be compared with the output of U2 if
necessary. The output terminals J5 and J4 are provided to monitor the desired
output of the DAC by shorting the respective pins of W13.
The following sections describe the different configurations of the output
amplifier, U2.
3.2.1 Unity Gain Output
The buffered output configuration is used to prevent loading the DAC7741 and
should closely match the raw output of the DAC with maybe some slight
distortion because of the feedback resistor and capacitor. The user can tailor
the feedback circuit to closely match their desired wave shape by simply
desoldering R7 and C11 and replacing them with the desired values. You can
also simply get rid of R7 and C11 altogether and just solder a zero-Ω resistor
in replacement of R7, if desired.
Table 3-2 shows the jumper setting for the unity gain configuration of the DAC
external output buffer in unipolar or bipolar mode.
Table 3-2.Unity Gain Output Jumper Settings
Jumper Setting
Reference
Function
Unipolar
Bipolar
W5
2-3
2-3
1-2
1-2
Supplies the voltage for the negative rail of op-amp.
Supplies the voltage for the positive rail of op-amp.
DAC output is channeled to the output terminals.
exREFin is disconnected from the negative input of op-amp.
Disconnect negative input of op-amp from GND
W12
W13
W14
W15
3-4
3-4
Open
Open
Open
Open
EVM Operation
3-3
Host Processor Operation
3.2.2 Output Gain of Two
This configuration allows the DAC output with a gain of two, but is limited to
the effective rails of the operational amplifier. When the DAC7741 is
configured to operate in bipolar mode, the DAC output must be within the
range of 12 V
or less. Anywhere above the range of 12 V
would clip the
P- P
P- P
output of the op-amp. Likewise, when operating the DAC in unipolar mode, the
DAC output must not exceed 6 V
.
P- P
Table 3-3 shows the proper jumper settings of the EVM for the 2× gain output
of the DAC.
Table 3-3.Gain of Two Output Jumper Settings
Reference
Jumper Setting
Function
W5
1-2 (Bipolar)
2-3 (Unipolar)
Negative rail of the op-amp tied to -15 V for bipolar operation or AGND
for unipolar operation.
W12
W13
W14
W15
1-2
Positive rail supply of the op-amp tied to 15 V
Amplified output of DAC is channeled to the output terminals
Disconnect exREFin from negative input of op-amp
Configures op-amp for a 2× gain output
3-4
Open
Close
3.2.3 Capacitive Load Drive
Another output configuration option is to drive a wide range of capacitive load
requirement. However, all op-amps under certain conditions may become
unstable depending on the op-amp configuration, gain, and load value. These
are just few factors that can affect op-amps stability performance and should
be considered when implementing.
In unity gain, the OPA627 op-amp, U2, performs very well with very large
capacitive loads. Increasing the gain enhances the amplifier’s ability to drive
even more capacitance, and by adding a load resistor would even improve the
capacitive load drive capability.
Table 3-4 shows the jumper setting configuration for a capacitive load drive.
Table 3-4.Capacitive Load Drive Output Jumper Settings
Reference
Jumper Setting Function
W5
1-2 (Bipolar)
2-3 (Unipolar)
Negative rail of the op-amp tied to -15 V for bipolar operation or AGND
for unipolar operation.
W12
W13
W14
W15
1-2
Positive rail supply of the op-amp tied to 15 V
Capacitive load drive output of DAC is channeled to the output terminals
Disconnect exREFin from negative input of op-amp
Disconnect R12 (see note)
5-6
Open
Open
Note:
If there is a need to incrementally adjust the capacitive load output, replace R12 with a capacitor with the desired capaci-
tance value and CLOSE W15.
3-4
Jumper Setting
3.3 Jumper Setting
The figures in Table 3-5 will show the function of each jumper on the
EVM.
Table 3-5.Jumper Setting Function
Jumper
Setting
Reference
Function
is strapped to V
1
1
1
1
1
1
1
1
1
3
3
3
3
3
3
3
3
3
R
to set V (summing junction) to V
/2. Refer to the data
OFFSET
REF
SJ
REF
sheet for offset adjustment.
is not connected to set V (summing junction) to V /3. Refer to the data
REF
R
OFFSET
SJ
W1
sheet for offset adjustment.
is strapped to AGND to set V (summing junction) to V /6. Refer to the
REF
R
OFFSET
SJ
data sheet for osset adjustment.
Disables the internal reference voltage.
W2
W3
W4
Enables the internal reference voltage of +10V.
REF is strapped to REF
to allow the internal 10 V to supply the DAC reference
IN
OUT
voltage.
REF is strapped to exREFin to allow either the onboard adjustable reference or user
supplied reference to supply the DAC reference voltage.
IN
Routes the onboard 10 V reference through the adjustable pot to W3 and W14.
Routes the user supplied reference from TP1 or J4-20 through the adjustable pot to
W3 and W14.
1
3
Negative supply rail of op-amp is powered by -15 V.
Negative supply rail of op-amp is tied to AGND.
REFADJ pin is not connected.
W5
W6
1
3
REFADJ pin is connected to R1 pot for gain adjustment input when internal reference
is used.
RFB2 pin is not connected to the V
pin.
OUT
W7
W8
RFB2 pin is strapped to the V
pin for feedback.
OUT
TEST pin not connected to DGND.
TEST pin connected to DGND (default mode).
SJ (summing junction) pin of the DAC output amplifier is not connected.
W9
SJ (summing junction) pin of the DAC output amplifier is connected to R2 pot to allow
small amount of current for offset adjustment.
RFB1 pin is not connected.
W10
RFB1 pin is strapped to RFB2 pin for DAC V
feedback.
OUT
EVM Operation
3-5
Jumper Setting
Table 3-5. Jumper Setting Function (Continued)
Jumper
Setting
Reference
Function
Disconnects AGND from DGND.
W11
Connects AGND and DGND together.
Positive supply rail of op-amp is powered by +15V.
1
1
3
3
W12
Positive supply rail of op-amp is powered by V
.
CC
2 4 6
Routes the raw output of the DAC7741 to J4-2 and J5 output terminals.
1 3 5
2 4 6
Routes the output of U2 to J4-2 and J5 output terminals. Used for unipolar and bipolar
modes of operation.
W13
1 3 5
2 4 6
Routes the output of U2 to J4-2 and J5 output terminals. Used for capacitive load
driving.
1 3 5
Disconnects exREFin from the negative input terminal of U2.
W14
W15
Allows exREFin to be routed to the negative input terminal of U2 used for
experimentation purposes only.
Disconnect the negative terminal of U2 to AGND and disable 2x gain.
Configures U2 for a 2× gain output.
RSTSEL pin is pulled high and configures the DAC to midscale when POR or reset is
initiated.
W16
RSTSEL pin is pulled low and configures the DAC to minscale when POR or reset is
initiated.
RST pin is pulled high and configures the DAC not to reset (default state).
W17
RST pin is pulled low and holds the DAC to reset state.
Legend:
Indicates the corresponding pins that are shorted or closed.
3-6
Schematic
3.4 Schematic
A schematic of the DAC7741 is found on the following page.
EVM Operation
3-7
1
2
3
4
5
6
Revision History
REV
ECN Number
Approved
VCC
J1
32 31
VSS
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
C7
C5
30 29
28 27
26 25
24 23
22 21
20 19
18 17
16 15
14 13
12 11
U1
DB15
0.1µF 10µF
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
35
34
33
32
31
30
29
28
27
22
21
20
19
18
17
16
41
42
40
CS
R/W
LDAC
CS
R/W
LDAC
C1
C4
10µF
DB14
DB13
DB12
DB11
DB10
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
D
C
B
A
D
C
B
A
VDD
0.1µF
39
43
3
RST
RSTSEL
RST
RSTSEL
VCC
J3
J2
R13
10k
CS
R/W
R14
10k
1
2
4
6
8
1
2
4
6
8
10
D4
D3
D2
D1
2
3
5
7
9
10
8
6
4
2
9
7
5
3
1
VSS
REFadj
Vref
3
5
7
9
R1
10K
LDAC
RST
RSTSEL
REF_en
W6
46
4
D4
D3
D2
D1
10
D0
11 12
13 14
15 16
17 18
19 20
11 12
13 14
15 16
17 18
19 20
W1
W16
W17
D0
5
Roffset
REFout
REFin
Vout
VDD
38
R7
0/5K/20K
VDD
R3
45
47
11
44
100K
W9
10
9
Sum_Junc
SJ
C8
1µF
W3
C14
C13
RFB1
R2
W10
C6
10µF
C2
0.1µF
0.1µF
10µF
DAC_VOUT
Sum_Junc
8
W7
W8
RFB2
TEST
10K
DAC_VOUT
26
REFEN
exREFin
6
7
AGND
AGND
R4
37
REF_en
DGND
VDD
10K
W2
+15V
VCC
DAC7741
J5
W12
C9
0.01µF
R8
3
2
U2
DAC_VOUT
W13
2
4
6
A1
B3
C5
J4
0
6
2
4
6
8
1
3
5
7
9
+15V
W14
R5
R9
20K
Op Amp
exREFin
2
10K
10
U3
12 11
14 13
16 15
18 17
20 19
5
2
8
7
6
3
1
TRIM OUT
V+ TEMP
NC
NC
-15V
W4
+REFin
1
3
NC
C11
10µF
Tantalum
R11
2
REF102AU(8)
W5
C10
TP1
TP2
C3
0.1µF
+REFin
EXTERNAL
REFERENCE
(exREFin)
100K
0.01µF
R6
10K
C12
R10
20K
VDD
+15V -15V VCC VSS
1nF
W15
J6
J7
1
2
4
6
8
1
2
4
6
8
10
3
5
7
9
3
5
7
9
J10
J12
J11
10
R12
10K
+15V
-15V VCC
VSS
VDD
CLD_OUT
W11
ti
6443168
12500 TI Boulevard. Dallas, Texas 75243
Title:
DAC7741
Engineer:
J. PARGUIAN
DOCUMENTCONTROL #
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