Texas Instruments ADS1244EVM User manual



 
June 2003
User’s Guide
SBAU087

IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third−party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Mailing Address:
Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright 2003, Texas Instruments Incorporated

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 2003, Texas Instruments Incorporated

EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the specified input and output ranges described in
the EVM User’s Guide.
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
60°C. The EVM is designed to operate properly with certain components above 60°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 2003, Texas Instruments Incorporated

Contents
iii
Contents
Preface

About This Manual
This manual describes the ADS1224EVM and ADS1245EVM evaluation fix-
tures and how to use them.
Notational Conventions
The ADS1244EVM and ADS1245EVM boards are identical except for the
evaluation device installed on them. This manual covers both boards, and
refers to them in the singular, when necessary, as “ADS1244/45EVM.”
When a statement applies to both the ADS1244 and ADS1245 devices,
they may be referred to in the singular, when necessary, as “ADS1244/45.”
Information About Cautions
This book contains cautions.
This is an example of a caution statement.
A caution statement describes a situation that could potentially
damage your software or equipment.
The information in a caution statement is provided for your protection. Please
read each caution carefully.

Contents
iv
Related Documentation From Texas Instruments
To obtain a copy of any of the following TI documents, visit our web site at
http://www.ti.com/ or call the Texas Instruments Literature Response Center
at (800) 477−8924 or the Product Information Center at (972) 644−5580.
When ordering, identify the booklet(s) by both title and literature number.
Data sheets Literature number
ADS1244 SBAS273
ADS1245 See http://www.ti.com/
REF1004 SBVS002
SN74LVC1G80 SCES221
FCC Warning
This equipment is intended for use in a laboratory test environment only. It
generates, uses, and can radiate radio frequency energy and has not been
tested for compliance with the limits of computing devices pursuant to sub-
part J of part 15 of FCC rules, which are designed to provide reasonable
protection against radio frequency interference. Operation of this equip-
ment in other environments may cause interference with radio communica-
tions, in which case the user at his own expense will be required to take
whatever measures may be required to correct this interference.
Trademarks
I2C is a registered trademark of Royal Philips Electronics B.V., The Nether-
lands.
All other trademarks are the property of their respective owners.

Contents
v

1 Introduction 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Introduction 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Built-in Accessories 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Connectors 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Controls 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Setting Up 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Circuit Description 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 I/O Connectors and Testpoints 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 J1: Analog Connector 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.2 J5: Serial Connector 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.3 J6: Power Connector 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.4 Testpoints 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Jumpers 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 J2: Analog−Digital Ground Shorting Jumper 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 J3: ADS1244/45 Analog Supply Current Measurement Jumper 2-7. . . . . . . . . . .
2.3 Switches 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 S1: System Clock Select 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 S2: Input Select 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.3 S3: Reference Input Select 2-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.4 S5: Digital Power Supply Level 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Usage 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 The Input Filtering Capacitors 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 The Serial Interface 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 The Serial EEPROM 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Schematic and Layout 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Schematic 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Component Layout 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Bill of Materials 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents
vi

2−1. Connectors and Jumpers 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−2. Analog Connector Pinout 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−3. Serial Connector Pinout 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−4. Power Connector Pinout 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−5. Jumpers 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−6. Switches 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4−1. Schematic Diagram 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4−2. Top Side Layout 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4−3. Bottom Side Layout 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2−1. Analog Connector Pin Descriptions 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−2. Serial Connector Pin Descriptions 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−3. Power Connector Pin Descriptions 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−4. Testpoints 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−5. System Clock Select Switch 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−6. Input Select Switch 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−7. Reference Input Select Switch 2-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2−8. Digital Power Supply Level Select Switch 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4−1. Bill of Materials 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
Introduction

The ADS1244EVM and ADS1245EVM are evaluation fixtures for the
ADS1244 and ADS1245 24−bit delta−sigma analog−to−digital converters.
Designed for prototyping and evaluation, they include a reference circuit and
an oscillator circuit with two selectable frequencies.
Topic Page
1.1 Introduction 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Built−in Accessories 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Connectors 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Controls 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Setting Up 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1

Introduction
1-2
1.1 Introduction
Many data converter evaluation fixtures contain a computer interface or a mi-
crocontroller, but the ADS1244/45EVM contains only the ADS1244 or
ADS1245 device and a few support components. All ADS1244/45 pins are ac-
cessible through various pins on the ADS1244/45EVM’s analog and digital
connectors.
The ADS1244/45EVM is designed using a simple card format developed by
TI. This simple, consistent design makes it very easy to connect the
ADS1244/45EVM to your own prototype system. You can even think of the
ADS1244/45EVM as an alternate package for the ADS1244/45 – one much
larger than the device itself, but also much easier to wire up by hand on your
test bench.
The ADS1244/45EVM can be plugged directly into suitable motherboards
such as the HPA449 MSP430 microcontroller development system from Soft-
Baugh, Inc. (http://www.softbaugh.com/). See TI’s web site for sample code
using the ADS1244/45EVM with the HPA449.
The ADS1244/45EVM, together with the HPA449 and the appropriate soft-
ware, also forms a complete evaluation system for verifying the performance
of the ADS1244/45. See TI’s web site for more information and software.
1.2 Built−in Accessories
The ADS1244/45EVM includes a system clock generator and a low−noise
voltage reference. Both features are optional; you can select an external sys-
tem clock and an external reference using the slide switches.
The +2.5V reference circuit is based on a REF1004−2.5. Its noise perfor-
mance is sufficient to allow the ADS1244/45 to perform at its lowest noise lev-
el.
The system clock is based on a 4.9152MHz CMOS crystal clock generator
module. A flip−flop divides the clock generator by two in order to provide an
additional 2.4576MHz clock source. The two clocks can be selected using the
clock source select switch.
1.3 Connectors
The ADS1244/45 device on the ADS1244/45EVM is connected through three
headers: the analog connector, the serial connector, and the power connector.
Pinouts and locations for the connectors are given in the following chapter.
The analog connector(J1) carries analog I/O. The ADS1244/45 has a single
differential input channel connected to pins 1 and 2. An optional external differ-
ential reference can be connected to pins 18 and 20.
The serial connector (J5) carries the ADS1244/45 serial digital interface, an
optional external system clock signal, and an I2C connection to the on−board
serial EEPROM.

Introduction
1-3
Introduction
Thepower connector (J6) carries the power supplies. The ADS1244/45EVM
requires a +5V analog supply and either a +5V or +3.3V digital supply. The
board is designed using a single ground net connected to DGND. An AGND
pin is also provided, and it can be connected to DGND using jumper J2.
The ADS1244/45 uses separate supplies for its analog and digital sections.
A jumper is inserted in each supply line. These jumpers allow the current of
each supply to be measured independently.
Four loop−style testpoints provide easy access to the ADS1244/45 clock and
the power supplies on the board. Other signals can be probed using the I/O
connector pins.
1.4 Controls
The ADS1244/45EVM is configured using four slide switches and a jumper.
Switch S1 selects the system clock source for the ADS1244. You can select
from the 4.9152MHz clock source, the 2.4576MHz clock source, or an exter-
nally provided clock. When the external clock is selected, the onboard oscilla-
tor is disabled to save power and prevent interference.
Switch S2 selects the input signal provided to the ADS1244/45. Normally you
will use the external input, but you can also use the switch to short the inputs
together and to connect the reference voltage to the inputs. The latter two posi-
tions are useful for conducting noise tests.
Switch S3 selects the reference input. One position selects the external refer-
ence input pins on the analog connector (J1). The other two positions connect
the onboard +2.5V reference in one of two ways: between ground and the ref-
erence, or between the reference and the analog supply.
Switch S5 is used to select one of two digital power supply pins provided on
the power connector. One pin is used for +3.3V, and the other is used for +5V;
some motherboards, such as the HPA449, provide both voltages. This switch
determines the logic levels that the ADS1244/45 will use to communicate, so
it is important to set it correctly.

Introduction
1-4
1.5 Setting Up
The way you configure the ADS1244/45EVM depends on how you will use it.
There is therefore no single correct procedure to follow to configure the
ADS1244/45EVM.
Nevertheless, it is useful to remember the following things when you are set-
ting up the board:
-Make certain that S5, the digital power supply select switch, is in the
right position for your system, and that you have a power supply con-
nected to the proper pins on the power connector.
-If you are not measuring the ADS1244/45’s supply current, remember
to place shorting blocks on jumpers J3 and J4. Without these blocks,
the ADS1244/45 will not be powered on, and will not work properly, if at
all.
-Unless you are using two entirely separate power supplies for analog
and digital, place a shorting block on jumper J2. This connects the
analog and digital grounds together, which is the usual way to operate
the ADS1244/45.
-Check the system clock switch. If it is set to “EXT,” and you have not
connected a clock signal to the external clock input pin on J5, the
ADS1244/45 will not operate.

1-5
Introduction

2-1
Circuit Description
 
This chapter describes the ADS1244/45EVM connectors, controls, and circuit
design in detail.
Topic Page
2.1 I/O Connectors and Testpoints 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Jumpers 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Switches 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2

2-2
2.1 I/O Connectors and Testpoints
The positions and functions of the connectors and testpoints are shown in
Figure 2−1.
Figure 2−1.Connectors and Jumpers
Many of the pins on the connectors are not used. On the pinout diagrams, un-
used pins are not marked. In the pin description tables, unused pins are not
listed, and ground pins are listed together, with the exception of the power con-
nector.
J1, J5, and J6, though treated as a single connector, are actually mounted as
connector pairs in a pass−through configuration. Each pair has a male sur-
face−mount header on the top (component) side of the board, and a corre-
sponding female surface−mount socket on the bottom (solder) side of the
board. The headers, mounted on top, are suffixed A, and the sockets, mounted
on bottom, are suffixed B.
In the schematic, the connector pairs are shown as one symbol. For J1, J5,
and J6, all bottom−side pins are connected to their corresponding top−side
pins; for example, J1B pin 1 connects to J1A pin 1, J1B pin 2 connects to J1A
pin 2, etc. This scheme is used with every pin on connectors J1, J5, and J6.
In the following descriptions, we will treat the connector pairs as a single con-
nector.

2-3
Circuit Description
2.1.1 J1: Analog Connector
The analog connector pinout is shown in Figure 2−2. and described in
Table 2−1.
Figure 2−2.Analog Connector Pinout
Caution: Although certain pins are described as “negative,” never
apply voltages less than −0.3V to these pins. The ADS1244 is not
a bipolar−input device, and it cannot accept negative voltages
below −0.3V without damage.
The negative input pins are so named because the voltage on such
a pin is subtracted from a positive pin during a reading.
Table 2−1.Analog Connector Pin Descriptions
Pin No. Pin Name Standard Name Direction Function
1 SYSINN AN0− Input Negative analog in-
put
2 SYSINP AN0+ Input Positive analog input
18 SYSREFN REF− Input Negative external
reference input
20 SYSREFP REF+ Input Positive external
reference input
17, 19 GND AGND Power Signal ground
Note that the input pins are not used unless the input select switches are
set to the appropriate positions. See Table 2−3 for details.

2-4
2.1.2 J5: Serial Connector
The serial connector’s pinout is shown in Figure 2−3 and described in
Table 2−2.
Figure 2−3.Serial Connector Pinout
Table 2−2.Serial Connector Pin Descriptions
Pin No. Pin Name Standard Name Direction Function
3 SCLK CLKX Input Serial clock input
13 DOUT DR Output Serial data output / data ready
15 DOUT INT Output Serial data output / data ready
16 SCL SCL I/O I2C clock line
17 SYSCLK TOUT Input External system clock input
19 OBCLKEN GPIO5 Output Clock mode indicator
20 SDA SDA I/O I2C data line
6, 12, 18 GND DGND Power Signal ground
The ADS1244/45 serial interface is connected through pins 3, 13, and 15.
SCL and SDA are used to communicate with the I2C serial EEPROM.
OBCLKEN is logic high when either of the onboard clock sources are se-
lected, and low when the external clock source is selected. It can be used
by external systems to determine whether to generate a clock signal for the
ADS1244/45EVM.

2-5
Circuit Description
2.1.3 J6: Power Connector
The power connector pinout pattern is shown in Figure 2−4 and described
in Table 2−3.
Figure 2−4.Power Connector Pinout
Table 2−3.Power Connector Pin Descriptions
Pin No. Pin Name Function Usage on
ADS1244/45EVM
1 +VA Positive analog supply, +5V to +18V Not used
2 −VA Negative analog supply, −5V to −18V Not used
3 +5VA Positive analog supply, +5VA Analog supply
4 −5VA Negative analog supply, −5VA Not used
5 AGND Analog ground Optionally connected to
DGND through J2
6 DGND Digital ground Ground
7 +1.8VD Positive digital supply, +1.8V Possible digital supply,
selected using S5
8 VD1 Positive digital supply Not used
9 +3.3VD Positive digital supply, +3.3V Possible digital supply,
selected using S5
10 +5VD Positive digital supply, +5V Not used
The ADS1244/45EVM always uses DGND for its single ground domain.
The AGND pin may optionally be connected to DGND through jumper J2.
The ADS1244/45 uses an analog supply of +5V and a digital supply of
+1.8V to +3.3V. Both +1.8V and +3.3V are available as standard supply
voltages over the power connector, so the ADS1244/45EVM allows you to
switch between them using S5.

2-6
2.1.4 Testpoints
The testpoints are marked on the board with the net to which they are at-
tached, instead of with their schematic reference designators. Table 2−4
lists the testpoints.
Table 2−4.Testpoints
Board Marking Reference Designator Signal
CLK TP4 System clock
AVDD TP3 Analog supply
DVDD TP1 Digital supply
GND TP2 Ground
The CLK testpoint is attached to the CLK pin on the ADS1244/45. It reflects
the actual CLK signal controlling the ADS1244/45. When the onboard oscil-
lator is in use, its waveform can be observed from the CLK testpoint.
The supply testpoints are provided for convenience. The GND testpoint is
slightly larger than the others to accommodate multiple probe clips.

Jumpers
2-7
Circuit Description
2.2 Jumpers
The jumpers are shown in Figure 2−5. Jumper positions and functions are
shown in Figure 2−1.
Figure 2−5.Jumpers
2.2.1 J2: Analog−Digital Ground Shorting Jumper
This jumper is used to connect the analog and digital grounds together.
If you are using a single power supply, you should usually place a shorting
block across this jumper. If you are using two different supplies, each with
its own ground, you should usually leave this jumper unconnected.
2.2.2 J3: ADS1244/45 Analog Supply Current Measurement Jumper
This jumper can be used to measure the current drawn by the ADS1244/45
analog supply line.
For normal operation, when not measuring current, place a shorting block
across this jumper.