原标题：Linear LTC2508-32 32位过取样ADC解决方案

　　Linear公司的LTC2508-32是带可配置数字滤波器的 32位过取样ADC,具有低噪音低功耗和高性能等特性,工作电压2.5V,差分全输入范围±VREF,而VREF从2.5V到5.1V.器件具有±0.5ppm INL (典型),1Msps时的SNR为104dB,61sps时的动态范围148dB,保证32位不丢失码.主要用在地震学,能源勘探,自动测试(ATE)和高精度仪表.本文介绍了LTC2508-32主要特性,框图,应用电路图和演示板DC2222A主要特性,电路图,材料清单和PCB设计文件图.

　　The LTCR2500-32 is a low noise, low power, high performance32-bit ADC with an integrated configurable digitalfilter. Operating from a single 2.5V supply, the LTC2500-32 features a fully differential input range up to ±VREF,withVREF ranging from 2.5V to 5.1V. The LTC2500-32 supportsa wide common mode range from 0V to VREF simplifyinganalog signal conditioning requirements.

　　The LTC2500-32 simultaneously provides two outputcodes: (1) a 32-bit digitally filtered high precision lownoise code, and (2) a 32-bit no latency composite code.

　　The configurable digital filter reduces measurement noiseby lowpass filtering and down-sampling the stream of datafrom the SAR ADC core, giving the 32-bit filtered output code.The 32-bit composite code consists of an overrangedetection bit, a 24-bit code representing the differentialinput voltage and a 7-bit code representing the commonmode input voltage. The 32-bit composite code is availableeach conversion cycle, with no cycle of latency.

　　The digital filter is highly configurable through the SPIcompatibleinterface and features many distinct filter typesthat suit a variety of applications. The digital lowpass filterrelaxes the requirements for analog anti-aliasing. MultipleLTC2500-32 devices can be easily synchronized usingthe SYNC pin

　　优势和特点

　　±0.5ppm INL (典型值)

　　在 61sps 时的 145dB 动态范围 (典型值)

　　在 4ksps 时的 131dB 动态范围 (典型值)

　　保证 32 位，无漏失码

　　具同步功能的可配置数字滤波器

　　放宽的抗混迭滤波器要求

　　双输出 32 位 SAR ADC

　　32 位数字滤波低噪声输出

　　14 位差分 + 8 位共模 1Msps 无延迟输出

　　宽输入共模范围

　　保证工作至 85°C

　　1.8V 至 5V SPI 兼容型串行 I/O

　　低功率：24mW (在 1Msps)

　　24 引脚 7mm x 4mm DFN 封装

　　产品详情

　　LTC®2508-32 是一款低噪声、低功率、高性能 32 位 ADC，其具有一个集成的可配置数字滤波器。LTC2508-32 采用单个 2.5V 工作电源，具有一个高达 ±VREF 的全差分输入范围，且 VREF 的范围从 2.5V 至 5.1V。LTC2508-32 支持 0V 至 VREF 的宽共模范围，从而简化了模拟信号调理要求。

　　LTC2508-32 同时提供两个输出代码：(1) 一个 32 位数字滤波高精度低噪声代码;和 (2) 一个 22 位无延迟复合代码。可配置数字滤波器通过对来自 SAR ADC 内核的数据流实施低通滤波和降频采样以降低测量噪声，产生了 32 位滤波输出代码。22 位复合代码由一个代表差分电压的 14 位代码和一个代表共模电压的 8 位代码组成。22 位复合代码可在每个转换周期中提供，并没有延迟周期。

　　可通过引脚搭接方便地针对 4 种不同的降频转换因子配置数字滤波器。这些配置提供一个 131dB (在 3.9ksps) 和 145dB (在 61sps) 的动态范围。数字低通滤波器放宽了对于模拟抗混迭的要求。采用 SYNC 引脚可以很容易地实现多个 LTC2508-32 器件的同步。

　　应用

　　地震学

　　能源勘探

　　自动化测试设备 (ATE)

　　高准确度仪表

　　LTC2508-32主要特性:

　　±0.5ppm INL (Typ)

　　104dB SNR (Typ) at 1Msps

　　148dB Dynamic Range (Typ) at 61sps

　　Guaranteed 32-Bits No Missing Codes

　　Configurable Digital Filter with Synchronization

　　Relaxed Anti-Aliasing Filter Requirements

　　Dual Output 32-Bit SAR ADC

　　32-Bit Digitally Filtered Low Noise Output

　　24-Bit Differential + 7-Bit Common Mode 1MspsOutput with Overrange Detection

　　Wide Input Common-Mode Range

　　Guaranteed Operation to 85°C

　　1.8V to 5V SPI-Compatible Serial I/O

　　Low Power: 24mW at 1Msps

　　24-Lead 7mm × 4mm DFN Packages

　　LTC2508-32应用:

　　Seismology

　　Energy Exploration

　　Automatic Test Equipment

　　High Accuracy Instrumentation

　　演示板DC2222A

　　Demonstration circuit 2222A features the LTC®2500-32,LTC2508-32 and LTC2512-24 ADCs. The LTC2500-32,LTC2508-32 and LTC2512-24 are low power, low noise,high speed, 32-bit/24-bit SAR ADCs with an integrated configurabledigital averaging filter that operate from a single2.5V supply. The following text refers to the LTC2508-32but applies to all parts, the only difference being samplerate and number of bits. The DC2222A demonstrates theDC and AC performance of the LTC2508-32 in conjunctionwith the DC590 or DC2026 QuikEval™ and DC890 PScope™data collection boards. Use the DC590 or DC2026 todemonstrate DC performance such as peak-to-peak noiseand DC linearity. Use the DC890 if precise sampling ratesare required or to demonstrate AC performance such asSNR, THD, SINAD and SFDR. The DC2222A is intendedto show recommended grounding, component placementand selection, routing and bypassing for this ADC.

　　图3.演示板DC2222A连接图