回到顶部

FREMONT (MAXREFDES6#):16位、高精度、0至100mV输入、隔离型模拟前端(AFE)

MAXREFDES6

参考设计免责声明 参照  重要声明和免责声明  涵盖参考设计和其他Maxim资源

描述

紧凑的Fremont (MAXREFDES6#)子系统参考设计(图1)利用高精度、16位模拟前端(AFE)准确测量0至100mV低压单端模拟信号,并配备隔离数据通路。设计充分利用以下器件的功能:超高精度、低噪声缓冲器(MAX9632);高精度ADC (MAX11100);超高精度4.096V电压基准(MAX6126);600VRMS单芯片数据隔离器(MAX14850);低压差(LDO)稳压器,提供稳压+6V、+5V和-5V电源(MAX1659MAX1735)。这种独一无二的AFE方案非常适用于要求低电压输入、高阻抗以及高精度模/数转换的众多应用。智能工厂、工业以及医疗应用使用的传感器越来越多,配置各异。尽管低压传感器提供关键数据,但它们也要求/产生高信噪比信号,致使许多分立式和集成式模/数转换器(ADC)不足以满足此类应用。

Fremont子系统设计方框图
图1. Fremont子系统设计方框图。

特征

  • 高精度模拟输入
  • 高阻抗
  • 0至100mV输入范围
  • 隔离数据通路
  • 小尺寸印刷电路板(PCB)
  • 器件驱动器
  • C语言源代码
  • Pmod™兼容规格

竞争优势

  • 独特的单端结构
  • 最优的电路板尺寸
  • 抗磁干扰数据通路隔离

  • MAXREFDES6

    This 16-bit high-accuracy industrial analog input design is optimized to accept 0 to 100mV analog voltage inputs and provides a digital SPI output. The data path and power is fully isolated. The design features an ultra-precision low-noise buffer and 16 bit ADC. MAXREFDES6

  • maxrefdes6fig00

    maxrefdes6fig00

This 16-bit high-accuracy industrial analog input design is optimized to accept 0 to 100mV analog voltage inputs and provides a digital SPI output. The data path and power is fully isolated. The design features an ultra-precision low-noise buffer and 16 bit ADC.

Icon

设计,建造,测试

图中的电路板已完全组装并经过测试。

 

细节部分

细节部分

Detailed Description of Hardware

Fremont interfaces with field-programmable gate array (FPGA) development boards using a Pmod connector. The Pmod specification allows for both 3.3V and 5V modules as well as various pin assignments. Fremont requires a 3.3V supply voltage and uses the SPI pin assignments as illustrated here.

Table 1 shows the power requirements. Table 2 shows the supported platforms and ports.

Table 1. Power Requirement for the Fremont Subsystem Reference Design

Power Type Input Input Voltage (V) Input Current (mA, typ)
External Power EXT_V+ 7 22
External Power EXT_V- -6 20

Table 2. Supported Platforms and Ports

Supported Platforms Ports
Nexys 3 platform (Spartan®-6) JB1
ZedBoard platform (Zynq®-7020) JA1

The MAX9632 (U1) op amp input circuit amplifies and buffers a 0 to100mV signal to match the input range of the ADC (MAX11100), which is 0 to 4.096V.

The MAX11100 (U2) is a 16-bit, successive-approximation register (SAR) ADC with AutoShutdown and fast 1.1µs wake-up features. The ADC’s reference input is driven by an ultra-high-precision 4.096V voltage reference, the MAX6126 (U3), with 0.02% initial accuracy and a 3ppm/°C maximum temperature coefficient (tempco).

The Fremont hardware design provides isolated data (MAX14850) for a high-accuracy, high-impedance, 0 to 100mV signal, analog-to-digital conversion application.

External power supplies power the Fremont board prior to voltage regulation. The MAX1659 LDO regulator provides +6V and +5V rails and the MAX1735 LDO regulator provides the -5V rail. The MAX14850 (U5) isolates the digital data up to 600V.

To power the Fremont board, connect the ground terminal of the external power supplies to the GND2 connector. Connect the +7V to +16.5V supply to the EXT_V+ connector, and the -6V supply to the EXT_V- connector.

Detailed Description of Firmware for Nexys 3 Platform

Table 2 shows currently supported platforms and ports. Support for additional platforms may be added periodically under Firmware Files in the All Design Files section below.

The Fremont firmware released for the Nexys 3 development kit targets a Microblaze soft-core microcontroller placed inside a Xilinx® Spartan-6 FPGA.

The firmware allows for immediate interfacing to the hardware, and for collection and saving of samples. Figure 2a shows the simple process flow. The firmware is in C, developed using the Xilinx software development kit (SDK) tool, based on the Eclipse open source standard. Custom Fremont-specific design functions (driver in the maximDeviceSpecificUtilities.c file) were created utilizing the standard Xilinx XSpi core version 3.03a. The SPI clock frequency is set to 3.125MHz.

Figure 2a. The Fremont firmware flowchart for Nexys 3 platform.
Figure 2a. The Fremont firmware flowchart for Nexys 3 platform.

The firmware accepts commands, writes status, and can download blocks of sampled data to a standard terminal program over a virtual COM port. The complete source code speeds customer development. Code documentation resides in the corresponding firmware platform files.

Detailed Description of Firmware for ZedBoard Platform

The Fremont firmware design also supports the ZedBoard kit and targets an ARM® Cortex® -A9 processor placed inside a Xilinx Zynq system-on-chip (SoC).

The firmware features an AXI MAX11100 custom IP core to optimize the sampling rate and SPI timing stability.

The firmware allows for immediate interfacing to the hardware, for collection and saving of samples. Figure 2b shows the simple process flow. The firmware is in C, developed using the Xilinx SDK tool, based on the Eclipse open source standard. Custom Fremont-specific design functions (driver in the maximDeviceSpecificUtilities.c file) were created utilizing the AXI MAX11100 custom IP core. The SPI clock frequency is 4.54MHz when the sample rate is 189.4ksps. The SPI clock frequency is set to 2.5MHz for all other sampling rate.

Figure 2b. The Fremont firmware flowchart ZedBoard platform.
Figure 2b. The Fremont firmware flowchart ZedBoard platform.

The firmware accepts commands, writes status, and can download blocks of sampled data to a standard terminal program over a virtual COM port. The complete source code speeds customer development. Code documentation resides in the corresponding firmware platform files.

Quick Start

Required equipment:

  • Windows® PC with two USB ports
  • Fremont (MAXREFDES6#) board
  • Fremont-supported platform (i.e., Nexys 3 development kit or ZedBoard kit)
  • Industrial sensor or signal source

Download, read, and carefully follow each step in the appropriate Fremont Quick Start Guide:
Fremont (MAXREFDES6#) Nexys 3 Quick Start Guide
Fremont (MAXREFDES6#) ZedBoard Quick Start Guide

Lab Measurements

Equipment:

  • HP 33120A waveform generator
  • Voltage calibrator DVC-8500
  • Windows PC with two USB ports
  • Fremont (MAXREFDES6#) board
  • Nexys 3 development kit
  • +7V power supply
  • -6V power supply

Take special care and use proper equipment when testing the Fremont design. Any high-accuracy design requires sources and measurement equipment of higher accuracy than the design under test. Duplication of the presented test data requires a low distortion signal source. A HP 33120A function generator produced the input signal, and the FFTs were created using the FFT control in SignalLab from Mitov Software.

Figure 3 and Figure 4 show AC and DC performance.

Figure 3. AC FFT using on-board isolated power, a 0 to 100mV, 1kHz sine-wave input signal, high-impedance input, a 20ksps sample rate, and a Blackman-Harris window.
Figure 3. AC FFT using on-board isolated power, a 0 to 100mV, 1kHz sine-wave input signal, high-impedance input, a 20ksps sample rate, and a Blackman-Harris window.


Figure 4. DC histogram using on-board isolated power; a 50mV input signal; a 20ksps sample rate; 65,536 samples; a code spread of 19 LSBs with 95.7% of the codes falling within the nine center LSBs; and a standard deviation of 2.236.

ARM is a registered trademark and registered service mark of ARM Limited.
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
Cortex is a registered trademark of ARM Limited.
Eclipse is a trademark of Eclipse Foundation, Inc.
MicroBlaze is a trademark of Xilinx, Inc.
Nexys is a trademark of Digilent Inc.
Pmod is a trademark of Digilent Inc.
Spartan is a registered trademark of Xilinx, Inc.
Windows is a registered trademark and registered service mark of Microsoft Corporation.
Xilinx is a registered trademark and registered service mark of Xilinx, Inc.
ZedBoard is a trademark of ZedBoard.org.
Zynq is a registered trademark of Xilinx, Inc.

参数化

输入类型 Vin(Min) Vin(Max) Iout(Max) 单路/多路输出 Vout(V) Pout(W) 隔离/非隔离 拓扑
DC - - - - - - Non-Isolated -

参数化

输入类型 DC
Vin(Min) -
Vin(Max) -
Iout(Max) -
单路/多路输出 -
Vout(V) -
Pout(W) -
隔离/非隔离 Non-Isolated
拓扑 -

Maxim设备 (5)

器件号 名称 产品线 购买 设计套件和评估模块
MAX1735 200mA、负输出、低压差线性稳压器,SOT23封装 线性稳压器 立即购买 设计套件
MAX1659 350mA、16.5V输入、低压差线性稳压器 线性稳压器 立即购买 设计套件
MAX11100 16位、+5V、200ksps ADC,具有10µA关断模式 模/数转换器(ADC) 立即购买 设计套件
MAX9632 36V、高精度、低噪声宽带放大器 放大器 立即购买 设计套件
MAX14850 六通道数字隔离器 隔离IC 立即购买 设计套件

Maxim设备 (5)

器件号 产品线
线性稳压器
200mA、负输出、低压差线性稳压器,SOT23封装
线性稳压器
350mA、16.5V输入、低压差线性稳压器
模/数转换器(ADC)
16位、+5V、200ksps ADC,具有10µA关断模式
放大器
36V、高精度、低噪声宽带放大器
隔离IC
六通道数字隔离器

设计资料 (11)

标题 类型 尺寸 日期
maxrefdes6-cad-ra ZIP 160KB 2017-11-01
maxrefdes6_cad_rb ZIP 159KB 2017-11-01
rd6v01_00 ZIP 42MB 2017-11-01
CAM output PDF 151KB 2017-11-01
MAXREFDES6BMA.xls PDF 11KB 2017-11-03
MAXREFDES6BMA.xls PDF 11KB 2019-07-09
CAM output PDF 151KB 2019-07-09
maxrefdes6-cad-rb ZIP 159KB 2019-07-09
rd6_nexys3_v01_00 ZIP 29MB 2019-07-09
rd6_zed_v01_00 ZIP 12MB 2019-07-09
rd6v02_00 ZIP 42MB 2019-07-09
日期 类型
2017-11-01

maxrefdes6-cad-ra

(ZIP, 160KB)

2017-11-01

maxrefdes6_cad_rb

(ZIP, 159KB)

2017-11-01

rd6v01_00

(ZIP, 42MB)

2017-11-01

CAM output

(PDF, 151KB)

2017-11-03

MAXREFDES6BMA.xls

(PDF, 11KB)

2019-07-09

MAXREFDES6BMA.xls

(PDF, 11KB)

2019-07-09

CAM output

(PDF, 151KB)

2019-07-09

maxrefdes6-cad-rb

(ZIP, 159KB)

2019-07-09

rd6_nexys3_v01_00

(ZIP, 29MB)

2019-07-09

rd6_zed_v01_00

(ZIP, 12MB)

2019-07-09

rd6v02_00

(ZIP, 42MB)

MAXREFDES6 相关视频

查看所有视频