MAXREFDES5# datasheet, PDF - EEWORLD Datasheet

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MAXREFDES5#: DescriptionREFERENCE DESIGN SANTA FE; CategoryDevelopment board/suite/development tools; File Size666KB，12 Pages; ManufacturerMaxim; Websitehttps://www.maximintegrated.com/en.html; Environmental Compliance

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MAXREFDES5# Overview

REFERENCE DESIGN SANTA FE

MAXREFDES5# Parametric

Parameter Name	Attribute value
type	interface
Function	Analog Front End (AFE)
Embedded	-
IC/parts used	MAX1301
Main attributes	4 channels (quad)
What's included	plate
Auxiliary properties	-

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> APP 5561

Keywords:

Santa Fe, MAXREFDES5#, subsystem reference design, analog front end, AFE, industrial sensors,

isolated power and data, industrial automation, PLC, medical, MAXREFDESS#, MAXREFDE55#,

MAXREFDESS, MAXREFDE55, isolation

SUBSYSTEM BOARD 5561

Santa Fe (MAXREFDES5#): 16-Bit High Accuracy

Multi-Input Isolated Analog Front End (AFE)

Jan 11, 2013

Abstract: This document explains how the Santa Fe (MAXREFDES5#) subsystem reference design meets the

higher resolution, higher voltage, and isolation needs of industrial control and industrial automation applications.

Hardware and firmware design files as well as FFTs and histograms from lab measurements are provided.

On February 28, 2014, the name of MAXREFDES5# was changed from Cupertino to Santa Fe. Maxim made this

change in an effort to distinctly identify MAXREFDES5# as a design focused on industrial applications. Other

than the name change, the design remains the same, with similar high performance analog functionality.

Introduction

Today's field programmable gate

arrays (FPGAs) and microcontrollers

with internal analog-to-digital

converters (ADCs) are capable of low-

resolution and low-voltage analog

More detailed image

(JPG)

inputs. However, they fall short on

being able to meet the needs of

industrial control and industrial automation applications, where isolation, higher resolutions, and higher voltage

system solutions are often needed. The Santa Fe (MAXREFDES5#) subsystem reference design is a 16-bit high-

accuracy industrial analog front end (AFE) that accepts -10V to +10V, 0 to 10V, and 4–20mA current loop signals

with isolated power and data integrated into a small form factor. The Santa Fe design integrates low-noise high-

impedance analog buffers (MAX9632); a highly accurate ADC with innovative on-chip attenuation (MAX1301); an

ultra-high precision 4.096V voltage reference (MAX6126); 600V

RMS

data isolation (MAX14850); and

isolated/regulated +12V, -12V, and 5V power rails (MAX256/MAX1659). This AFE solution can be used in any

application that needs high-accuracy analog-to-digital conversion, but it is mainly targeted for industrial sensors,

industrial automation, process control, programmable logic controllers (PLCs), and medical applications.

Page 1 of 12

Table 1. Power Options for the Santa Fe Subsystem Reference Design

Power Type

On-board isolated power

Jumper Shunt

JU3: 1-2

JU4: 2-3

JU5: 1-2

JU3: 2-3

JU4: 1-2

JU5: 2-3

Input Voltage (V)

3.3

+12

-12

Input Current (mA, typ)

221

6.3

30.4

7.3

External power

Table 2. Supported Platforms and Ports

Supported Platforms

Nexys

™

3 platform (Spartan

-6)

ZedBoard

™

platform (Zynq

-7020)

Ports

JB1

JA1

The Santa Fe hardware design is specifically optimized for applications that use -10V to +10V, 0 to 10V, and 4–

20mA signals. Depending on the application requirements, certain portions of the circuit may be omitted. A

complete discussion of what portions are needed or may be omitted follows. See the file for the schematic under

the

All Design Files

section.

The MAX1301 (U3) is a 16-bit, successive-approximation register (SAR) ADC with unique multirange inputs

capable of accepting input voltage signals up to +12.288V to -12.288V. The ADC also has integrated analog

input buffers with a 17k½ input resistance.

The first MAX9632 amplifier (U1) is optimized for low-noise, -10V to +10V input voltages. The second MAX9632

amplifier (U2) is optimized for low-noise, 4–20mA input currents. Both U1 and U2 provide high input impedance

for input signals that have a large source resistance, or in the case of the 4–20mA loop, a 250½ load resistance.

Large source resistances often attenuate signals by an undesirable factor. Add an optional 500½ series resistor

in front of both MAX9632 amplifiers if input protection is desired while the Santa Fe design is not powered. The

500½ series resistor prevents the input current from exceeding the maximum input current specification when

10V is applied at the input and the Santa Fe board has no power.

If the signal source has a significantly low source resistance compared to 17k½, or in the case of the 4–20mA

loop, if the parallel combination of 250½ and 17k½ provides acceptable accuracy in the application, then U1 and

U2 can be eliminated. ADC channels AIN1 and AIN3 are examples of using only the internal 17k½ analog input

buffers.

Although the MAX1301 ADC has an internal 4.096V voltage reference, for highest accuracy use the external

MAX6126 (U4) voltage reference with 0.02% initial accuracy and a 3ppm/°C maximum temperature coefficient

(tempco).

The MAX256 (U5) provides an isolated, functional insulation class power solution that accepts 3.3V and converts

it to ±12V using an off-the-shelf TGM-H281NF Halo

transformer with a 1:2.6 primary to secondary turns ratio

plus an external on-board voltage-doubler circuit. Post-regulation is accomplished using the MAX1659 low

dropout (LDO) regulators. The ±12V isolated power solution is optional and is only needed for applications that

Page 3 of 12

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