原标题：Linear LTC2185双路16位125Msps模数转换方案

　　Linear 公司的LTC2185是双路16位125Msps低功耗模数转换器(ADC), 两路可同时取样, 76.8dB SNR, 90dB SFDR,单电源1.8V工作,每路功耗185mW/154mW/100mW, CMOS, DDR CMOS或DDR LVDS输出,输入范围1VP-P到 2VP-P,550MHz满功率带宽S/H,主要用在通信, 蜂窝基站,SDR,手提医疗图像,多路数据采集以及非破坏测试.本文介绍了LTC2185主要特性, 方框图,多种模拟输入和前端电路,以及典型应用电路和PCB布局图.

　　LTC2185 - 16-Bit, 125Msps Low Power Dual ADCs

　　The LTC.2185/LTC2184/LTC2183 are two-channel simultaneous sampling 16-bit A/D converters designed for digitizing high frequency, wide dynamic range signals.

　　They are perfect for demanding communications applications with AC performance that includes 76.8dB SNR and 90dB spurious free dynamic range (SFDR). Ultralow jitter of 0.07psRMS allows undersampling of IF frequencies with excellent noise performance. DC specs include ±2LSB INL (typ), ±0.5LSB DNL (typ) and no missing codes over temperature. The transition noise is 3.4LSBRMS.

　　The digital outputs can be either full rate CMOS, Double Data Rate CMOS, or Double Data Rate LVDS. A separate output power supply allows the CMOS output swing to range from 1.2V to 1.8V.

　　The ENC+ and ENC– inputs may be driven differentially or single-ended with a sine wave, PECL, LVDS, TTL, or CMOS inputs. An optional clock duty cycle stabilizer allows high performance at full speed for a wide range of clock duty cycles.

　　LTC2185主要特性:

　　Two-Channel Simultaneously Sampling ADC

　　76.8dB SNR

　　90dB SFDR

　　Low Power: 370mW/308mW/200mW Total

　　185mW/154mW/100mW per Channel

　　Single 1.8V Supply

　　CMOS, DDR CMOS, or DDR LVDS Outputs

　　Selectable Input Ranges: 1VP-P to 2VP-P

　　550MHz Full Power Bandwidth S/H

　　Optional Data Output Randomizer

　　Optional Clock Duty Cycle Stabilizer

　　Shutdown and Nap Modes

　　Serial SPI Port for Configuration

　　64-Pin (9mm × 9mm) QFN Package

　　LTC2185应用:

　　Communications

　　Cellular Base Stations

　　Software Defined Radios

　　Portable Medical Imaging

　　Multi-Channel Data Acquisition

　　Nondestructive Testing

　　图1.LTC2185方框图

　　图2.LTC2185采用变压器5MHz-700MHz模拟输入电路图

　　图3.LTC2185输入频率5MHz-150MHz的前端电路图

　　图4.LTC2185输入频率150MHz-250MHz的前端电路图

　　图5.LTC2185输入频率大于250MHz的前端电路图

　　图6.LTC2185采用高速差分放大器的前端电路图

　　图7.LTC2185基准电路图