ADI AD8295信号处理和精密仪表放大方案

ADI 公司的AD8295是带有信号处理放大器的精密仪表放大器,包括了精密仪表放大器前端所需要的全部元件,封装尺寸为4x4mm. AD8295包含了高精密的仪表放大器,两个通用放大器和两个精密匹配(0.03%,温度系数1ppm/度C)的10k欧姆电阻.工作电压从±2.3 V 到±18 V,增益为1时的CMRR大于90dB,转换速率2V/us,输入电压噪音小于8 nV/√Hz @ 1 kHz. AD8295广泛应用在工业控制控制, 惠施登电桥,精密数据采集系统,医疗仪器以及应力表等.本文介绍了AD8295的主要特性,功能方框图, 电源去耦电路, 对RFI抑制电路图, 带缓冲基准电压源的单电源连接图以及驱动差分ADC电路图.

Precision Instrumentation Amplifier with Signal Processing Amplifiers AD8295
The AD8295 contains all the components necessary for a precision instrumentation amplifier front end in one small 4 mm × 4 mm package. It contains a high performance instrumentation amplifier, two general-purpose operational amplifiers, and two precisely matched 10 kΩ resistors.
The AD8295 is designed to make PCB routing easy and efficient. The AD8295 components are arranged in a logical way so that typical application circuits have short routes and few vias. Unlike most chip scale packages, the AD8295 does not have an exposed metal pad on the back of the part, which frees additional space for routing and vias. The AD8295 comes in a 4 mm × 4 mm LFCSP that requires half the board space of an 8-pin SOIC package.

The AD8295 includes a high performance, programmable gain instrumentation amplifier. Gain is set from 1 to 1000 with a single resistor. The low noise and excellent common-mode rejection of the AD8295 enable the part to easily detect small signals even in the presence of large common-mode interference. For a similar instrumentation amplifier without the associated signal conditioning circuitry, see the AD8221 or AD8222 data sheet.

The AD8295 operates on both single and dual supplies and is well suited for applications where ±10 V input voltages are encountered. Performance is specified over the entire industrial temperature range of −40°C to +85°C for all grades. The AD8295 is operational from −40°C to +125°C; see the Typical Performance Characteristics section for expected operation up to 125°C.

AD8295主要特性:
Saves board space
Includes precision in-amp, 2 op amps, and 2 matched resistors
4 mm × 4 mm LFCSP
No heat slug for more routing room
Differential output fully specified
In-amp specifications
Gain set with 1 external resistor (gain range: 1 to 1000)
8 nV/√Hz @ 1 kHz, maximum input voltage noise
90 dB minimum CMRR (G = 1)
0.8 nA maximum input bias current
1.2 MHz, −3 dB bandwidth (G = 1)
2 V/μs slew rate
Wide power supply range: ±2.3 V to ±18 V
1 ppm/°C, 0.03% resistor matching

AD8295应用:
Industrial process controls
Wheatstone bridges
Precision data acquisition systems
Medical instrumentation
Strain gages
Transducer interfaces
Differential output



图1.AD8295功能方框图



图2.AD8295电源去耦电路及REF与输出对地连接图



图3.AD8295对RFI抑制电路图



图4.AD8295差分输出最少元件连接图



图5.AD8295带缓冲基准的单电源连接图



图6.采用AD8295的2极点Sallen-Key滤波器电路



图7.AD8295  AC耦合连接图



图8.AD8295驱动差分ADC电路图