Cirrus CS5374双路高性能放大和调制评估方案

http://www.ic72.com 发布时间：2009/6/5 16:14:30

Cirrus Logic公司的CS5374是双路高性能放大器和Delta-Sigma调制器,包括有两路海洋地震模拟测量通路,每路包括有高输入阻抗可编增益差分放大器,把模拟信号传送给四阶Delta-Sigma调制器,而低噪音Delta-Sigma调制器把模拟信号转换成一比特串行流,以适合CS5376A数字迹滤波器的需求. CS5374的超低输入偏置小于1pA,最大信号幅度为5V, Delta-Sigma调制器的信号带宽从DC到2kHz.本文介绍了CS5374的主要特性,方框图, 系统方案图, 连接方框图, 和CS5376A的数字接口图以及CDB5374评估板主要特性和方框图,详细电路图和材料清单(BOM).

CS5374 :Dual High-performance Amplifier & ΔΣ Modulator

The CS5374 combines two marine seismic analog measurement channels into one 7 mm x 7 mm QFN package. Each measurement channel consists of a high input impedance programmable gain differential amplifier that buffers analog signals into a high performance, fourth-order Delta-Sigma modulator. The low-noise Delta-Sigma modulator converts the analog signal into a one-bit serial bit stream suitable for the CS5376A digital filter.

Each amplifier has two sets of external inputs, INA and INB, to simplify system design as inputs from a hydrophone sensor or the CS4373A test DAC. An internal 800ohm termination can also be selected for noise tests.

Gain settings are binary weighted (1x, 2x, 4x, 8x, 16x, 32x, 64x) and match the CS4373A test DAC output attenuation settings for full-scale testing at all gain ranges.

Both the input multiplexer and gain are set by registers accessed through a standard SPI port. Each fourth-order Delta-Sigma modulator has very high dynamic range combined with low total harmonic distortion and low power consumption. It converts differential analog signals from the amplifier to an oversampled Delta-Sigma serial bit stream which is decimated by the CS5376A digital filter to a 24-bit output at the final output word rate.

CS5374主要特性:

High Input Impedance Differential Amplifier

Ultra-low input bias: < 1 pA

Max signal amplitude: 5 Vpp differential

Fourth Order Delta-Sigma Modulator

Signal Bandwidth: DC to 2 kHz

Common mode rejection: 110 dB CMRR

Differential Analog Input, Digital Delta-Sigma Output

Multiplexed inputs: INA, INB, 800ohm termination

Selectable Gain: 1x, 2x, 4x, 8x, 16x, 32x, 64x

Excellent Amplifier Noise Performance

1.5uVpp between 0.1 Hz and 10 Hz

11 nV / √Hz from 200 Hz to 2 kHz

High Modulator Dynamic Range

126 dB SNR @ 215 Hz BW (2 ms sampling)

123 dB SNR @ 430 Hz BW (1 ms sampling)

Low Total Harmonic Distortion

–118 dB THD typical (0.000126%)

–108 dB THD maximum (0.0004%)

Low Power Consumption

Normal operation: 6.5 mA per channel

Power down: 20uA per channel max

Dual Power Supply Configuration

VA+ = +2.5 V; VA– = –2.5 V; VD = +3.3 V

图1.CS5374方框图

图2.CS5374系统方案图

图3.CS5374连接方框图

图4.CS5374和CS5376A数字接口图

图5.CS5374电源连接图

CDB5374评估板

The CDB5374 board is used to evaluate the functionality and performance of the Cirrus Logic multichannel marine seismic chip set. Data sheets for the CS5374, CS5376A, and CS4373A devices should be consulted when using the CDB5374 evaluation board.

Screw terminals connect external differential hydrophone sensors to the analog inputs of the measurement channels. An on-board test DAC creates precision differential analog signals for in-circuit performance testing without an external signal source.

The evaluation board includes an 8051-type microcontroller with hardware SPI and USB serial interfaces. The microcontroller communicates with the digital filter via SPI and with the PC evaluation software via USB.

The PC software controls register and coefficient initialization and performs time domain, histogram, and FFT frequency analysis on captured data.

The CDB5374 evaluation kit includes:

CDB5374 Evaluation Board

USB Cable (A to B)

Software Download Information Card

CDB5374评估板主要特性:

Four-channel Seismic Acquisition Node

– CS5374 dual amplifier & Delta-Sigma modulator (2x)

– CS5376A quad digital filter (1x)

– CS4373A test DAC (1x)

– Precision voltage reference

– Clock recovery PLL

On-board Microcontroller

– SPI interface to digital filter

– USB communication with PC

PC Evaluation Software

– Register setup & control

– FFT frequency analysis

– Time domain analysis

– Noise histogram analysis

图6.CDB5374评估板外形图

图7.CDB5374评估板方框图

Major blocks of the CDB5374 evaluation board include:

CS5374 Dual Amplifier & Delta-Sigma Modulator (2x)

CS5376A Quad Digital Filter

CS4373A Test DAC

Precision Voltage Reference

Interface CPLD

Microcontroller with USB

Phase Locked Loop

RS-485 Transceivers

Voltage Regulators