Texas Instruments ADS8688EVM-PDK User manual

User’s Guide
ADS8688EVM-PDK Evaluation Module
Data Acquisition Products
ABSTRACT
ADS8688EVM-PDK
This user's guide describes the operation and use of the ADS8688 evaluation module (EVM). The ADS8688 is a
16-bit, 500ksps, 8 channel multiplexed, single-supply, SAR ADC with bipolar input ranges. Operating on a single
5V the integrated analog front end can support ±10.24V input ranges with a ±20V over-voltage protection. The
performance demonstration kit (PDK) eases EVM evaluation with additional hardware and software for computer
connectivity through a universal serial bus (USB). The ADS8688EVM-PDK includes the ADS8688EVM as a
daughter card, Precision Host Adaptor (PHI) digital controller, and a A-to-B USB cable. This user's guide covers
circuit description, schematic diagram, and bill of materials for the ADS8688EVM daughter card.
Table 1-1. Related Documentation
Device Literature Number
ADS8688 SBAS582
OPA320 SBOS513
TPS7A4700 SBVS204
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Table of Contents
2 ADS8688EVM-PDK Overview.................................................................................................................................................3
3 EVM Analog Interface.............................................................................................................................................................4
3.1 ADC Analog Input Connections and Filter......................................................................................................................... 4
3.2 Voltage Reference, Aux Input, and Supply Decoupling..................................................................................................... 5
4 Digital Interface.......................................................................................................................................................................6
4.1 Serial Interface (SPI)..........................................................................................................................................................6
4.2 I2C Bus for Onboard EEPROM..........................................................................................................................................6
5 Power Supplies....................................................................................................................................................................... 7
6 ADS8688 Initial Setup.............................................................................................................................................................8
6.1 Software Installation...........................................................................................................................................................8
7 EVM Operation...................................................................................................................................................................... 11
7.1 Connecting the Hardware.................................................................................................................................................11
7.2 Modifying Hardware and Using Software to Evaluate Other Devices in the Family.........................................................12
7.3 EVM GUI Global Settings for ADC Control...................................................................................................................... 13
7.4 Time Domain Display....................................................................................................................................................... 14
7.5 Frequency Domain Display.............................................................................................................................................. 15
7.6 Histogram Display............................................................................................................................................................ 16
8 Bill of Materials, Schematics, and Layout.......................................................................................................................... 17
8.1 Bill of Materials.................................................................................................................................................................17
8.2 Board Layout....................................................................................................................................................................19
8.3 Schematic........................................................................................................................................................................ 20
10 Revision History................................................................................................................................................................. 23
List of Figures
Figure 2-1. System Connection for Evaluation............................................................................................................................ 3
Figure 3-1. ADC Analog Input Connections and Filter.................................................................................................................4
Figure 3-2. Voltage Reference, Aux Input, and Supply Decoupling.............................................................................................5
Figure 4-1. EEPROM for EVM ID................................................................................................................................................ 6
Figure 5-1. Power Supplies, Regulators, and Indicators............................................................................................................. 7
Figure 6-1. ADS8688 Software Installation Prompts................................................................................................................... 8
Figure 6-2. Device Driver Installation Wizard Prompts................................................................................................................ 9
Figure 6-3. LabVIEW Run-Time Engine Installation.................................................................................................................... 9
Figure 6-4. ADS8688EVM GUI Folder Post-Installation............................................................................................................ 10
Figure 7-1. ADS8688EVM Hardware Setup and LED Indicators...............................................................................................11
Figure 7-2. Launch the EVM GUI Software................................................................................................................................11
Figure 7-3. Enable EEPROM for Writing................................................................................................................................... 12
Figure 7-4. Configure EEPROM and Software for the New Device...........................................................................................12
Figure 7-5. EVM GUI Global Input Controls.............................................................................................................................. 13
Figure 7-6. Time Domain Display Tool Options......................................................................................................................... 14
Figure 7-7. Spectral Analysis Tool............................................................................................................................................. 15
Figure 7-8. Histogram Analysis Tool.......................................................................................................................................... 16
Figure 8-1. ADS8688EVM PCB.................................................................................................................................................19
Figure 8-2. Input Filter............................................................................................................................................................... 20
Figure 8-3. ADC and Digital Interface........................................................................................................................................21
Figure 8-4. Power and EEPROM...............................................................................................................................................22
List of Tables
Table 1-1. Related Documentation.............................................................................................................................................. 1
Table 7-1. Compatible Devices in the Family.............................................................................................................................12
Table 8-1. ADS8688EVM Bill of Materials................................................................................................................................. 17
1 Trademarks
All trademarks are the property of their respective owners.
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2 ADS8688EVM-PDK Overview
Table 1-1 lists the related documents that are available for download from Texas Instruments at
ADS8688EVM Features
• Hardware and software required for diagnostic testing as well as accurate performance evaluation of the
ADS8688 ADC
• USB powered—no external power supply is required
• The PHI controller that provides a convenient communication interface to the ADS8688 ADC over USB 2.0
(or higher) for power delivery as well as digital input and output
• Easy-to-use evaluation software for 64-bit Microsoft Windows™7, Windows 8, and Windows 10 operating
systems
• The software suite includes graphical tools for data capture, histogram analysis, and spectral analysis. This
suite also has a provision for exporting data to a text file for post-processing. Fig
• Integrated 4.096-V voltage reference.
• Bipolar (±10.24 V, ±5,12 V, ±2.56 V ) or unipolar (0 V to 10.24 V, 0 V to 5.12 V) input ranges for each channel.
• Onboard, second-order, Butterworth, low-pass filters for four channels.
• Onboard regulator for generating a ±15-V bipolar supply for second-order, Butterworth, low-pass filters.
• Capable of accepting a ±100-mV signal on the negative analog inputs (AIN_xGND).
Signal
Source #1
Included in kit
ADS8688EVM
PHI Board
xx
xx
x
x
x
x
x
xx
xx
xx
xx
xx
ADS8688
GUI
Signal
Source #1
8 Channels total
Figure 2-1. System Connection for Evaluation
ADS8688EVM Features:
• Eight input channels connected to external single ended signals source applied to SMA connectors or header
• Serial interface connects to the PHI controller via 60 pin connector (J3).
• Serial interface connects to the PHI controller via 60 pin connector (J2).
• All power for device from USB via PHI controller.
• Onboard ultra-low noise low-dropout (LDO) regulator generates 5.0V AVDD supply. Input to LDO from PHI
controller.
• DVDD (3.3V) powered by PHI controller.
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3 EVM Analog Interface
The ADS8688EVM is an evaluation module built to the TI Modular EVM system specifications. The EVM by itself
has no microprocessor and cannot run software. Thus, the EVM is available as part of the ADS8688EVM-PDK
kit that combines the ADS8688EVM as a daughter board with PHI controller using software as a graphical user
interface (GUI).
3.1 ADC Analog Input Connections and Filter
The circuit shown in Figure 3-1 shows a typical analog input connection for the ADS8688 ADC. This circuit is
reapeated eight times for all eight input channels. The resistor R01 can be used for input float detection but
is not populated in the default configuration. The TVS diode D01, can be used for input protection, but is not
populated. Refer to Video Series on Electrical Overstress. C01, R03, and R04 form the 79.5kHz low pass input
the input filter for the ADC. R05 connects the negative input to ground. R05 can be removed and the negative
input can be accessed in the header J6.
1 2
3 4
5 6
7 8
J6
TSW-104-07-G-D
Ain0+
Ain0-
Ain1+
Ain1-
GND
0
R02
1.00k
R03
GND
1.00k
R04
GND GND
14V
D01
SMBJ14CA
DNP
GND
A0+
A0-
0
R05
Ain0+
Ain0-
50V
1000pF
C01
1
2
3 4 5
J00
5-1814832-1 49.9k
R01
DNP
Figure 3-1. ADC Analog Input Connections and Filter
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3.2 Voltage Reference, Aux Input, and Supply Decoupling
The circuit shown in Figure 3-2 illustrates the decoupling on AVDD, DVDD, and the reference IO. It is possible
on the ADS8688 to use an external voltage reference, but typically the integrated internal reference is sufficient.
In cases where you need to use an enthral voltage reference it can be connected via the REF test point. The
capacitors for decoupling match the recomendations in the ADS8688 data sheet. The layout (see Figure 8-1)
uses the shortest possible connections to the decouplign capacitors and connections the ground end to the GND
plane using vias. The AUX input is a standard SAR input and does not have an analog front end. Thus, this input
cannot accept high voltage input signals (Vin Full Scale = VREF = 4.096V). Furthermore, this input requires an
external buffer amplifier U4 to achieve good settling.
SDI 1
RST/PD 2
DAISY 3
REFSEL 4
REFIO 5
REFGND 6
REFCAP 7
AGND 8
AVDD
9
AUX_IN
10
AUX_GND
11
AIN_6P
12
AIN_6GND
13
AIN_7P
14
AIN_7GND
15
AIN_0P
16
AIN_0GND
17
AIN_1P
18
AIN_1GND
19
AIN_2GND
20 AIN_2P
21
AIN_3GND
22 AIN_3P
23
AIN_4GND
24 AIN_4P
25
AIN_5GND
26 AIN_5P
27
AGND 28
AGND 29
AVDD
30
AGND 31
AGND 32
DGND 33
DVDD
34
DNC 35
SDO 36
SCLK 37
CS 38
ADS8688IDBT
U1
A0+
A0-
A1+
A1-
A2+
A3+
A4+
A5+
A6+
A7+
A2-
A3-
A4-
A5-
A6-
A7-
49.9
R10
GND
CS
SCLK_R
SCLK
SDI
SDO
49.9
R6
49.9
R7
49.9
R8
49.9
R9
1µF
25V
C8
25V
10uF
C7
25V
22uF
C9
GND
AVDD
DVDD
DVDD
1µF
25V
C6
GND
25V
10uF
C5
GND
47.0k
R16
47.0k
R17
47.0k
R19
1µF
25V
C4
GND
1
2
3
4
5
OPA320AIDBVR
U4
1
2
3 4 5
J09
5-1814832-1
GND
AVDD
100nF
50V
C13
GND
50V
1000pF
C12
GND
GND
49.9
R26
49.9
R27
RefSel
REF
RST
GND
Alt
100
R29
GND
1.00k
R30
GND
47.0k
R36
DNP DVDD
AUX
Figure 3-2. Voltage Reference, Aux Input, and Supply Decoupling
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4 Digital Interface
As noted in Section 2, the EVM interfaces with the PHI and communicates with the computer over the USB.
There are two devices on the EVM with which the PHI communicates: the ADS8688 ADC (over SPI) and the
EEPROM (over I2C). The EEPROM comes pre-programmed with the information required to configure and
initialize the ADS8688 platform. When the hardware is initialized, the EEPROM is no longer used.
4.1 Serial Interface (SPI)
As noted in Section 2, the EVM interfaces with the PHI and communicates with the computer over the USB.
There are two devices on the EVM with which the PHI communicates: the ADS8688 ADC (over SPI) and the
EEPROM (over I2C). The EEPROM comes pre-programmed with the information required to configure and
initialize the ADS8688 platform. When the hardware is initialized, the EEPROM is no longer used.
4.2 I2C Bus for Onboard EEPROM
The circuit shown in Figure 4-1 is used with our EVM controller (PHI), for EVM identification. This circuit is not
required by the ADS8688 for operation. The switch (S2) is a write protect and does not need to be changed for
EVM operation.
A0
1
A1
2
A2
3
VSS
4SDA 5
SCL 6
WP 7
VCC 8
U2
BR24G32FVT-3AGE2
10.0k
R20
GND
GND
SCL
SDA
ID_PWR
ID_PWR
100nF
50V
C10
GND
WP 2
1
3
S1
Figure 4-1. EEPROM for EVM ID
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5 Power Supplies
The PHI provides multiple power-supply options for the EVM, derived from the USB supply of the computer. The
EEPROM on the ADS8688EVM uses a 3.3-V power supply generated directly by the PHI. The EVM_REG_5V5
is a 5.5V supply from the PHI and is applied to the input of a low dropout regulator (LDO) to generate AVDD
on the EVM. The analog supply of the ADC (AVDD = 5.0V) is powered by the TPS7A4700RGWR (U3). The
ADC Digital supply (DVDD = 3.3V), is generated by the PHI. Two LEDs are connected to the AVDD, and DVDD
supplies. These LEDs will illuminate after the software GUI loads and the PHI turns on its output power supplies.
Green
12
D1
APT2012LZGCK
AVDD DVDD
Green
12
D2
APT2012LZGCK
GND GND
6.65k
R2
6.65k
R3
OUT 1
NC 2
SENSE 3
6P4V2
4
6P4V1
5
3P2V
6
GND 7
1P6V
8
0P8V
9
0P4V
10
0P2V
11
0P1V
12
EN
13
NR 14
IN
15
IN
16
NC 17
NC 18
NC 19
OUT 20
PAD 21
TPS7A4700RGWR
U3
0
R5
0
R4
GND
AVDD5.5V
AVDD DVDD
25V
22uF
C1
GND
100k
R1
1µF
25V
C3
GND
GND
GND
25V
10uF
C2
GND
Figure 5-1. Power Supplies, Regulators, and Indicators
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6 ADS8688 Initial Setup
This section explains the initial hardware and software setup procedure that must be completed for properly
operating the ADS8688EVM.
6.1 Software Installation
Download the latest version of the EVM GUI installer from the Tools and Software folder of the ADS8688EVM
and run the GUI installer to install the EVM GUI software on your computer.
CAUTION
Manually disable any antivirus software running on the computer before downloading the EVM GUI
installer onto the local hard disk. Depending on the antivirus settings, an error message may appear
or the installer. The exe file can be deleted.
Accept the license agreements and follow the on-screen instructions shown in Figure 6-1 to complete the
installation.
Figure 6-1. ADS8688 Software Installation Prompts
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As a part of the ADS8688EVM GUI installation, a prompt with a Device Driver Installation (as shown in Figure
6-2) appears on the screen. Click Next to proceed.
Figure 6-2. Device Driver Installation Wizard Prompts
The ADS8688EVM requires the LabVIEW™ run-time engine and may prompt for the installation of this software,
as shown in Figure 6-3, if not already installed.
Figure 6-3. LabVIEW Run-Time Engine Installation
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Verify that C:\Program Files (x86)\Texas Instruments\ADS8688EVM is as shown in Figure 6-4 after these
installations.
Figure 6-4. ADS8688EVM GUI Folder Post-Installation
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7 EVM Operation
The following instructions are a step-by-step guide to connecting the ADS8688EVM to the computer and
evaluating the performance of the ADS8688:
7.1 Connecting the Hardware
After installing the software connect the EVM as shown in Figure 7-1
1. Physically connect P2 of the PHI to J2 of the ADS8688EVM. Install the screws to assure a robust connection
2. Connect USB on PHI to the computer first
• LED D5 on the PHI lights up, indicating that the PHI is powered up
• LEDs D1 and D2 on the PHI start blinking to indicate that the PHI is booted up and communicating with
the PC; Figure 7-1 shows the resulting LED indicators
3. Start the software GUI as shown in Figure 7-2. You will notice that the LEDs blink slowly as the FPGA
firmware is loaded on the PHI. This will take a few seconds then the AVDD and DVDD power supplies will
turn on.
4. Connect the signal generators to SMA inputs or headers (8 channels available). The input range is ±10.25V.
2. Connect USB power before
applying signal source.
3. Start the software GUI.
1. Connect PHI to ADS8860EVM
and install screws.
4. Headers or SMA connectors can be
used for signal connection. Single
ended input range = ±10.24V.
D5
D1
D2
Signal
Generator #1
Signal
Generator #2
Figure 7-1. ADS8688EVM Hardware Setup and LED Indicators
Select EVM GUI
from start menu, or
associated shortcut
Figure 7-2. Launch the EVM GUI Software
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7.2 Modifying Hardware and Using Software to Evaluate Other Devices in the Family
The ADS8688 is part of a family of related devices. This EVM hardware and software support the entire family
because all the devices are pin-for-pin compatable. Table 7-1 lists other compatible devices in the family. The
following procedure shows how to modify the hardware and software to evaluate the other devices in this family.
1. Desolder the ADS8688 and replace this device with the device you want to evaluate.
2. Enable the EEPROM for writing. This process is done by changing switch S2 to the top position using
tweezers.Figure 7-3 details this process.
3. Connect the EVM and start the GUI as described in Section 7.1.
4. Use the Tools menu to Load EEPROM according to the device that is currently installed. When this
procedure is successfully completed, you will see the status bar at the top of the software update according
to the device installed on the hardware. For details, see Figure 7-4.
Table 7-1. Compatible Devices in the Family
Number of Channels Resolution
12-Bit 14-Bit 16-Bit 18-Bit
4 ADS8664 ADS8674 ADS8684 ADS8684A ADS8694
8 ADS8668 ADS8678 ADS8688 ADS8688A ADS8698
Use tweezers to change position of
switch S1 up as shown to allow the
EEPROM write operation.
Figure 7-3. Enable EEPROM for Writing
1. KvšZ^š}}o•_uvµ•oš
^>}WZKD_
2. hvŒ^^µ‰‰}ŒšÀ]•_•oš
šZ•]ŒÀ]•v‰Œ••^>}
WZKD_.
3. (šŒ‰Œ••]vP^o}WZKD_]šÁ]oo
take a few minutes to load the
EEPROM.
4. The top of the status bar on the software
will indicate what the EVM connected has
been updated to.
Figure 7-4. Configure EEPROM and Software for the New Device
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7.3 EVM GUI Global Settings for ADC Control
Figure 7-5 shows that the EVM Global controls are located on the right hand side of the GUI. These controls
choose the page display, SPI Mode, SCLK frequency, and sampling frequency.
Pages selects the
analysis display.
EVM GUI Global Settings for ADC
Control are on the left hand side
of the GUI.
The SCLK frequency is set here. It is
limited by the ^Sampling Rate_
below.
The maximum sampling rate is
500kHz for this device.
The ^Channel Range_sets the
input voltage range.
Auto mode will scan the selected
channels below. Manual allows
selection of one channel.
Figure 7-5. EVM GUI Global Input Controls
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7.4 Time Domain Display
The time domain display tool allows visualization of the ADC response to a given input signal. This tool is
useful for both studying the behavior and debugging any gross problems with the ADC or drive circuits. The
user can trigger a capture of the data of the selected number of samples from the ADS8688EVM, as per the
current interface mode settings indicated in Figure 7-6 by using the Capture button. The sample indices are on
the x-axis and there are two y-axes showing the corresponding output codes as well as the equivalent analog
voltages based on the specified reference voltage. Switching pages to any of the Analysis tools described in the
subsequent sections causes calculations to be performed on the same set of data.
Selects the channel for the
statistical summary.
Select the channels to display.
Time domain selected here.
Figure 7-6. Time Domain Display Tool Options
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7.5 Frequency Domain Display
The spectral analysis tool, shown in Figure 7-7, is intended to evaluate the dynamic performance (SNR, THD,
SFDR, SINAD, and ENOB) of the ADS8688 ADC through single-tone sinusoidal signal FFT analysis using the 7-
term Blackman-Harris window setting. The FFT tool includes windowing options that are required to mitigate the
effects of non-coherent sampling (this discussion is beyond the scope of this document). The 7-Term Blackman
Harris window is the default option and has sufficient dynamic range to resolve the frequency components of up
to a 24-bit ADC. The None option corresponds to not using a window (or using a rectangular window) and is not
recommended.
Figure 7-7. Spectral Analysis Tool
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7.6 Histogram Display
Noise degrades ADC resolution and the histogram tool can be used to estimate effective resolution, which
is an indicator of the number of bits of ADC resolution losses resulting from noise generated by the various
sources connected to the ADC when measuring a DC signal. The cumulative effect of noise coupling to the
ADC output from sources such as the input drive circuits, the reference drive circuit, the ADC power supply,
and the ADC itself is reflected in the standard deviation of the ADC output code histogram that is obtained by
performing multiple conversions of a DC input applied to a given channel. As shown in Figure 7-8, the histogram
corresponding to a DC input is displayed on clicking the Capture button.
Figure 7-8. Histogram Analysis Tool
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8 Bill of Materials, Schematics, and Layout
Schematics for the ADS8688EVM are appended to this user's guide. The bill of materials is provided in Table 8-1. Section 8.2 shows the PCB layouts for
the ADS8688EVM.
8.1 Bill of Materials
Note
All components are compliant with the European Union Restriction on Use of Hazardous Substances (RoHS) Directive. Some part numbers
may be either leaded or RoHS. Verify that purchased components are RoHS-compliant. (For more information about TI's position on RoHS
compliance, see www.ti.com.)
Table 8-1. ADS8688EVM Bill of Materials
Item # Designator Quantity Value Part Number Manufacturer Description Package Reference
1 !PCB1 1 ADS8688EVM Any Printed Circuit Board
2 C1, C9 2 22uF GRM32ER71E226KE15L MuRata CAP, CERM, 22 uF, 25 V, +/-
10%, X7R, 1210
1210
3 C01, C11, C12, C21, C31,
C41, C51, C61, C71
9 1000pF GRM1885C1H102FA01J MuRata CAP, CERM, 1000 pF, 50 V, +/-
1%, C0G/NP0, 0603
0603
4 C2, C5, C7 3 10uF CL21A106KAFN3NE Samsung Electro-
Mechanics
CAP, CERM, 10 uF, 25 V, +/-
10%, X5R, 0805
0805
5 C3, C4, C6, C8 4 1uF C0603C105K3RACTU Kemet CAP, CERM, 1 uF, 25 V, +/- 10%,
X7R, 0603
0603
6 C10, C13 2 0.1uF GRM188R71H104KA93D MuRata CAP, CERM, 0.1 uF, 50 V, +/-
10%, X7R, 0603
0603
7 D1, D2 2 Green APT2012LZGCK Kingbright LED, Green, SMD LED_0805
8 H1, H2 2 RM3X4MM 2701 APM HEXSEAL Machine Screw Pan PHILLIPS
M3
9 H3, H4, H5, H6 4 SJ-5303 (CLEAR) 3M Bumpon, Hemisphere, 0.44 X
0.20, Clear
Transparent Bumpon
10 H7, H8 2 9774050360R Wurth Elektronik ROUND STANDOFF M3 STEEL
5MM
ROUND STANDOFF M3
STEEL 5MM
11 J00, J01, J02, J03, J04,
J05, J06, J07, J09
9 5-1814832-1 TE Connectivity SMA Straight PCB Socket Die
Cast, 50 Ohm, TH
SMA Straight PCB Socket
Die Cast, TH
12 J2, J5, J6, J7 4 TSW-104-07-G-D Samtec Header, 100mil, 4x2, Gold, TH 4x2 Header
13 J3 1 QTH-030-01-L-D-A-K-TR Samtec Header(Shrouded), 19.7mil,
30x2, Gold, SMT
Header (Shrouded),
19.7mil, 30x2, SMT
14 J4 1 TSW-108-07-G-D Samtec Header, 100mil, 8x2, Gold, TH 8x2 Header
15 R1 1 100k CRCW0603100KFKEA Vishay-Dale RES, 100 k, 1%, 0.1 W, AEC-
Q200 Grade 0, 0603
0603
16 R2, R3 2 6.65k CRCW04026K65FKED Vishay-Dale RES, 6.65 k, 1%, 0.063 W, AEC-
Q200 Grade 0, 0402
0402
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Table 8-1. ADS8688EVM Bill of Materials (continued)
Item # Designator Quantity Value Part Number Manufacturer Description Package Reference
17 R02, R12, R22, R32, R42,
R52, R62, R72
8 0 ERJ-8GEY0R00V Panasonic RES, 0, 5%, 0.25 W, AEC-Q200
Grade 0, 1206
1206
18 R03, R04, R13, R14, R23,
R24, R33, R34, R43, R44,
R53, R54, R63, R64, R73,
R74
16 1.00k RG1608P-102-B-T5 Susumu Co Ltd RES, 1.00 k, 0.1%, 0.1 W, 0603 0603
19 R4, R5 2 0 RC0402JR-070RL Yageo America RES, 0, 5%, 0.063 W, 0402 0402
20 R05, R15, R18, R25, R35,
R45, R55, R65, R75
9 0 CRCW06030000Z0EA Vishay-Dale RES, 0, 5%, 0.1 W, AEC-Q200
Grade 0, 0603
0603
21 R6, R7, R8, R9, R10 5 49.9 CRCW040249R9FKED Vishay-Dale RES, 49.9, 1%, 0.063 W, AEC-
Q200 Grade 0, 0402
0402
22 R16, R17, R19 3 47.0k RC0402FR-0747KL Yageo America RES, 47.0 k, 1%, 0.0625 W,
0402
0402
23 R20 1 10.0k RC0603FR-0710KL Yageo RES, 10.0 k, 1%, 0.1 W, 0603 0603
24 R26, R27 2 49.9 RC0603FR-0749R9L Yageo RES, 49.9, 1%, 0.1 W, 0603 0603
25 S1 1 CAS-120TA Copal Electronics Switch, Slide, SPDT 100mA,
SMT
Switch, 5.4x2.5x2.5mm
26 TP1, TP2, TP3, TP4 4 5001 Keystone Test Point, Miniature, Black, TH Black Miniature Testpoint
27 U1 1 ADS8688IDBT Texas Instruments 16-Bit, 500-kSPS, 8-Channel,
Single-Supply, SAR ADCs with
Bipolar Input Ranges, DBT0038A
(TSSOP-38)
DBT0038A
28 U2 1 BR24G32FVT-3AGE2 Rohm I2C BUS EEPROM (2-Wire),
TSSOP-B8
TSSOP-8
29 U3 1 TPS7A4700RGWR Texas Instruments 36V, 1A, 4.17μVRMS,
RF Low-Dropout (LDO)
Voltage Regulator, RGW0020A
(VQFN-20)
RGW0020A
30 U4 1 OPA320AIDBVR Texas Instruments Precision, 20 MHz, 0.9 pA
Ib, RRIO, CMOS Operational
Amplifier, 1.8 to 5.5 V, -40 to
125 degC, 5-pin SOT23 (DBV5),
Green (RoHS & no Sb/Br)
DBV0005A
31 D01, D11, D21, D31, D41,
D51, D61, D71
0 14V SMBJ14CA Littelfuse Diode, TVS, Bi, 14 V, SMB SMB
32 FID1, FID2, FID3 0 N/A N/A Fiducial mark. There is nothing to
buy or mount.
N/A
33 R01, R11, R21, R31, R41,
R51, R61, R71
0 49.9k CRCW060349K9FKEA Vishay-Dale RES, 49.9 k, 1%, 0.1 W, AEC-
Q200 Grade 0, 0603
0603
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8.2 Board Layout
Figure 8-1 shows the PCB layout for the ADS8688EVM.
Note
The board layouts is not to scale. This figure is intended to show how the board is laid out and is not
intended to be used for manufacturing ADS8688EVM PCBs.
Top
Botom
Figure 8-1. ADS8688EVM PCB
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8.3 Schematic
Figure 8-2 shows the input filter, terminal block, and SMA connections.
0
R42
1.00k
R43
GND
1.00k
R44
GND GND
14V
D41
SMBJ14CA
DNP
GND
A4+
A4-
0
R45
Ain4+
Ain4-
0
R52
1.00k
R53
GND
1.00k
R54
GND GND
14V
D51
SMBJ14CA
DNP
GND
A5+
A5-
0
R55
Ain5+
Ain5-
0
R62
1.00k
R63
GND
1.00k
R64
GND GND
14V
D61
SMBJ14CA
DNP
GND
A6+
A6-
0
R65
Ain6+
Ain6-
0
R72
1.00k
R73
GND
1.00k
R74
GND GND
14V
D71
SMBJ14CA
DNP
GND
A7+
A7-
0
R75
Ain7+
Ain7-
0
R02
1.00k
R03
GND
1.00k
R04
GND GND
14V
D01
SMBJ14CA
DNP
GND
A0+
A0-
0
R05
Ain0+
Ain0-
0
R12
1.00k
R13
GND
1.00k
R14
GND GND
14V
D11
SMBJ14CA
DNP
GND
A1+
A1-
0
R15
Ain1+
Ain1-
0
R22
1.00k
R23
GND
1.00k
R24
GND GND
14V
D21
SMBJ14CA
DNP
GND
A2+
A2-
0
R25
Ain2+
Ain2-
0
R32
1.00k
R33
GND
1.00k
R34
GND GND
14V
D31
SMBJ14CA
DNP
GND
A3+
A3-
0
R35
Ain3+
Ain3-
50V
1000pF
C41
50V
1000pF
C51
50V
1000pF
C61
50V
1000pF
C21
50V
1000pF
C71
50V
1000pF
C31
50V
1000pF
C01
50V
1000pF
C11
1
2
3 4 5
J04
5-1814832-1
1
2
3 4 5
J05
5-1814832-1
1
2
3 4 5
J06
5-1814832-1
1
2
3 4 5
J07
5-1814832-1
1
2
3 4 5
J00
5-1814832-1
1
2
3 4 5
J01
5-1814832-1
1
2
3 4 5
J02
5-1814832-1
1
2
3 4 5
J03
5-1814832-1
GND
1 2
3 4
5 6
7 8
J6
TSW-104-07-G-D
Ain0+
Ain0-
Ain1+
Ain1-
1 2
3 4
5 6
7 8
J2
TSW-104-07-G-D
Ain6+
Ain7+
Ain6-
Ain7-
GND
GND 1 2
3 4
5 6
7 8
J7
TSW-104-07-G-D
1 2
3 4
5 6
7 8
J5
TSW-104-07-G-D
Ain3+
Ain3-
Ain2+
Ain2-
Ain4+
Ain4-
Ain5+
Ain5-
49.9k
R31
DNP
49.9k
R21
DNP
49.9k
R71
DNP
49.9k
R61
DNP
49.9k
R51
DNP 49.9k
R11
DNP
49.9k
R41
DNP 49.9k
R01
DNP
Figure 8-2. Input Filter
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