AFE-ADS1248-MVK MAVRK Module

Board Status: Level 7

= Purpose of this Wiki Page = This page explains the Analog Front End (AFE) ADS1248 Modular and Versatile Reference Kit (MAVRK) module in detail. For more information on the MAVRK system, referring to the MAVRK Introduction page is good start. After reading this guide, a developer should understand the features of the AFE-ADS1248 MAVRK module.

= EVM Overview= The AFE-ADS1248-MVK module highlights the ADS1248 24 bit data converter, a device which is commonly used in Electrocardiography applications. Coupled with the SCI-ADS1248FE-MVK MAVRK module, it can be interfaced to patient ECG simulators.

EVM Description
The AFE-ADS1248-MVK is an 8 channel, 24 bit data acquisition system that can be used in either a differential or single ended configuration. The EVM is designed to use the ADS1248's on chip clock and reference as well as providing a 2.5 V external reference. An SMA connector will allow an external clock to be driven into the device from external sources or a AFE clock module such as the AFE-CDCE913-MVK MAVRK module. A dual pin header can also be used to drive an external reference into the circuit. This module uses an Analog Front End (AFE) slot in the MAVRK motherboard to provide a Serial Peripheral Interface (SPI), control of the digital I/O lines, and the analog and digital power. The analog channels are routed to the Signal Conditioning (SCI) slot. The companion module for the AFE-ADS1248-MVK is the SCI-ADS1248FE-MVK which provides the differential power supply and a 16 pin interface to the analog channels.

Figure 1: AFE-ADS1248-MVK MAVRK Module

ADS1248 Features

 * Eight low-noise PGAs and eight high-resolution ADCs (ADS1248, ADS1248R)
 * Low power: 0.75 mW/channel
 * Input-referred noise: 4 µVpp (peak-to-peak) (150Hz BW, G = 6)
 * Input bias current: 200 pA
 * Data rate: 250 SPS to 32 kSPS
 * CMRR: –115 dB
 * Programmable pain: 1, 2, 3, 4, 6, 8, or 12
 * Unipolar or bipolar supplies: AVDD = 2.7 V to 5.25 V, DVDD = 1.65 V to 3.6 V
 * Built-in right leg drive amplifier, lead-off detection, WCT, PACE detection, test signals
 * Integrated Respiration Impedance Measurement (ADS1294R/6R/8R only)
 * Digital PACE detection capability
 * Built-in oscillator and reference
 * Flexible power-down, standby modes
 * SPI™-compatible serial interface
 * Operating temperature range: –40 °C to +85 °C

AFE-ADS1248-MVK Features

 * Single ended or deferentially configurable through Signal Conditioning (SCI) companion module (the SCI-ADS1248FE-MVK)
 * On board 2.5 V reference
 * Configurable for AC- or DC-coupled inputs
 * Configurable for up to twelve (12) standard ECG leads
 * Wilson Central Terminal (WCT) circuit incorporated (can be disabled by removing a series of zero ohm resistors)
 * Access to the following:
 * External clock and reference capable
 * External right leg drive (JPS1)
 * External shield drive amplifier
 * External Wilson Central voltage (JPS2)

Featured Applications
The AFE-ADS1248-MVK MAVRK module can be used to demonstrate the following applications:
 * Electrocardiography (ECG) medical instrumentation
 * Electromyography (EMG) medical instrumentation
 * Electroencephalography (EEG) medical instrumentation
 * Patient monitoring; Holter, event, stress, and vital signs including ECG, AED, and telemedicine
 * High-precision, simultaneous, multi-channel signal acquisition applications

Highlighted Products
The AFE-ADS1248-MVK MAVRK module highlights the following devices:
 * ADS1248 - 8-Channel, 24-Bit Analog-To-Digital Converter With Integrated ECG Front End
 * REF5025 - Low Noise, Very Low Drift, Precision Voltage Reference
 * OPA320 - Precision, 20MHz, 0.9pA Ib, RRIO, CMOS Operational Amplifier
 * OPA333 - 1.8V, 17µA, microPower, Precision, Zero Drift CMOS Op Amp
 * TS5A3159A - 1 Ohm SPDT Analog Switch 5-V/3.3-V Single Channel 2:1 Multiplexer/Demultiplexer
 * TS5A2066 - Dual-Channel 10-Ohm SPST Analog Switch
 * SN74LVC573A - Octal Transparent D-Type Latches With 3-State Outputs

Block Diagram


Figure 2: A block diagram of the AFE-ADS1248-MVK

EVM Wiki
The most up-to-date information on this module can be found at the AFE-ADS1248-MVK MAVRK module wiki page.

EVM Landing Page
Ordering information and availability of this module can be found at the AFE-ADS1248-MVK MAVRK module tool folder.

= Hardware Description =

Power Requirements
The AFE-ADS1248-MVK module uses the 3.3 V digital supply and should not take more than 30 mA. Table 1 below shows the power budget for the 3.3 V digital supply.

* The SN74LVC573A has an absolute maximum drive current of 24 mA. The only application that would match this amount of current is one that would drive multiple LEDs. Most GPIO lines used by the AFE to drive the target devices are pulled up or pulled down at its desired power up (default) state with 100k resistors. Driving these resistors will pull 33 uA per GPIO.

** AFE-ADS1248-MVK operating current assumes all 100k pull ups are driven and the LEDs are off.

*** AFE-ADS1248-MVK maximum current assumes all 100k pull ups are driven and the LEDs are on.

**** ADS1248 operating current numbers are with RLD, PACE, and WCT disabled. Max current not given (typical used). Power down typical number is 10 uW (Power Down)/3.3 V. Power down maximum number is 2 mW (Standby)/3.3 V. The AFE-ADS1248-MVK module uses the 5.5 V analog supply and should not take more than 10 mA. Table 2 below shows the power budget for the 5.5 V analog supply.

The Signal Conditioning (SCI) slot provides power for both the ADS1248 analog supply and the reference supply. This is done to provide either differential or single ended power which is determined by the requirements of the SCI module and the signals that will be interfacing with it.

The AFE_AVDD/AFE_AVSS Analog Supply should either be +/-2.5 V (differential) or 5 V (single ended) and should not take more than 10 mA. It should be noted that these supplies should have a low ripple voltage (< 5 mV is ideal). Table 3 below shows the power budget for the AFE_AVDD/AFE_AVSS Analog Supply.

* REF5025 has a maximum drive current of 30 mA and a typical drive current of 25 mA. In this application, the REF5025 is buffered, so the drive current is not required. REF5025 has no sleep mode, so typical and maximum operating numbers are used.

** The version of OPA320 used does not have a shutdown pin, so typical and maximum operating numbers are used.

*** The TS5A3159 and OPA333 does not have a shutdown capability, so typical and maximum operating numbers are used.

**** ADS1248 operating current numbers are with RLD, PACE, and WCT disabled. Max current not given (typical used). Power down typical number is 10 uW (power down)/5 V. Power down maximum number is 2 mW (Standby)/5 V.

The AFE_REF_VDD/AFE_REF_VSS Reference Supply should either be +/-2.75 V (differential) or 5.5 V (single ended). The AFE-ADS1248-MVK module does not use this supply.

AFE-ADS1248-MVK Performance Test Data
The MAVRK team tests the performance of the AFE module using both the internal and external resources available on the module. The AFE-ADS1248-MVK can use either the internal 2.4 V reference or an external 2.5 V reference.

Below is the test setup of the AFE-ADS1248-MVK MAVRK module. The test incorporates shorting the analog inputs at the ADS1248 to ground of the AFE-ADS1248-MVK.

of the AFE-ADS1248-MVK Test Setup.

 AFE-ADS1248-MVK Test 



Getting Started: Configuring the EVM
The AFE-ADS1248-MVK module is supported by the MAVRK AppMonitor and AppSelect tools. For more information on these tools and how to install them, refer to the How to get the MAVRK Software link below.



The preferred method of working with this EVM is through the use of the MAVRK Pro motherboard, the motherboard will provide the needed power and digital control for this EVM. The software demo uses MAVRK_AFE3 as the image in Figure 4 shows, however (with a small change in software) it is also possible to insert the AFE-ADS1248-MVK into any of the other 3 AFE slots are retain full functionally. Also in the picture is the SCI-ADS1248FE-MVK in MAVRK_SCI3 which provides access to the analog channels and differential power to the AFE-ADS1248-MVK.

The power source in this demo shown in Figure 4 is the USB cable. It should be noted that when any board on the MAVRK board is installed or removed, all power sources should be moved first by pressing the Standby button.

Typical installation of the module is as follows:

1. Plug in the USB. a. The Standby button should be blue, which effectively removes all power from the modules on the mother board. 2. Run the MAVRK AppSelect tool 3. Install all modules required for the demo a. An MCU module to initialize the motherboard and the AFE-ADS1248-MVK b. At least one AFE-ADS1248-MVK. It should be noted multiple AFE's can be installed. c. At least one SCI module in the slot below the AFE module. The SCI-ADS1248-MVK is an example d. The AFE-BREAKOUT-MVK module is not required, but can be installed to watch signals GPIO and SPI signals of the adjacent module. 3. Install the JTAG debugger if a C Compiler is used to download code into the MCU. Otherwise the QT tool will use the USB connection to download the code. 4. Press the Standby button to provide power to the modules.

Figure 4: ADS1248 Demo Setup in Standby Mode

EVM Connectors, Fuses, and Switches
The Figure 4 shows the front of the AFE-ADS1248-MVK module. Highlighted in the image is the external connections that can be used on the module.

The SMA connector in the upper left corner can be used to bring in an external clock signal. To use the external clock, the user will need to set the AFE GPIO that controls the AFE_CLK_SEL.

Below the SMA connector on the lower left side is a two pin header that can be used to bring in an external reference voltage. To bring the voltage into the ADS1248, the two pin header labeled "External Reference Enable" in Figure 5 will need to be jumpered with a shunt. Otherwise the on-board 2.5 V reference is used by the ADS1248. To use either of the external references, the user will need disable the Reference Buffer in the AFE-ADS1248-MVK demo software.

The four pin header in the lower right corner allows the user access to the GPIO on the ADS1248. It should be noted that these GPIO's are tied to LEDs. For more information on the use of these LEDs, see the EVM LEDs section below.

Below the ADC GPIO four pin header is the Right Leg Drive Inverted Input select. If the jumper is in the far right position as seen in Figure 5, the Right Leg Drive input is used. If the jumper is in the far left position, the Right Leg Drive Inverted input is used.

Below the Right Leg Drive Inverted Input select header is the Wilson Central Terminal (WCT) Enable. Jumpering the two pin header with a shunt as shown in Figure 5 will route the WCT signal into the companion SCI and enable the WCT signal. Removing the jumper will disconnect the WCT from the SCI.

Figure 5: AFE-ADS1248-MVK Front View

Figure 6 shows the back of the AFE-ADS1248-MVK. The connectors shown in Figure 6 are the AFE connectors that allow the board to interface with a MAVRK motherboard such as the MB-PRO-MVK.



Figure 6: AFE-ADS1248-MVK Back View

EVM Test Points
The AFE-ADS1248-MVK module has two test points, both allow the user access to the ground plane. Figure 7 shows the location of these test points.



Figure 7: AFE-ADS1248-MVK Test Points

EVM LEDs


Figure 8 shows the LEDs on the AFE-ADS1248-MVK module. ADC_GPIO_1 through ADC_GPIO_4 are tied to the ADS1248 GPIO and can be controlled via software. AFE_GPIO_6 and AFE_GPIO_7 are tied to the bits 6 and 7 on the AFE Latch. The are commonly used for User Alert (Yellow LED) and Error Alert (Red LED). There are also two power LEDs. AVDD_5_5V shows the 5.5 V analog power is available from the motherboard. DVDD_3_3V shows the 3.3 V digital power is available from the motherboard.

Figure 8: AFE-ADS1248-MVK LED Diagram

= Software Installation =


 * Specific related projects for this part are: \mavrk_embedded\Modular_EVM_Projects\Component_Demo_Projects\ADS1248-MSP430F5438_Demo_Project

MAVRK ADS1248 Demo Application?
Demonstrating the ADS1248 MAVRK Module

Features not Supported
Please note that these features are not supported by the current version of the firmware, however they may be added at a later time.


 * 1) Real-time data processing
 * 2) AC lead-off detection filters
 * 3) QRS detection algorithms
 * 4) Software PACE detection algorithms
 * 5) High-pass filtering
 * 6) 50Hz/60Hz notch filtering at rates other than 500SPS

= Board Files =

Bill of Materials (BOM)
of the bill of materials.

 AFE-ADS1248-MVK Bill of Materials 

Layout (PDF)
of additional board layers.

 AFE-ADS1248-MVK Board Top Silkscreen 

Schematics (PDF)
of all schematics.

 AFE-ADS1248-MVK Schematics 

Fabrication Drawings (PDF)
of the fabrication drawing.

 AFE-ADS1248-MVK Fabrication Drawing 

Gerber Files
of the Gerber files.

 AFE-ADS1248-MVK Gerber Files 

Cadence Schematic and Board Files
of the Cadence schematic and board files.

 AFE-ADS1248-MVK Cadence Schematic and Board Files 

= Precautions and Certifications =

Certifications
FCC and ICES standard EMC test report for the AFE-ADS1248-MVK, aboard the MAVRK Pro Motherboard

Eco-Info &amp; Lead-Free Home

RoHS Compliant Solutions

Statement on Registration, Evaluation, Authorization of Chemicals (REACh)

= Important Notices =