SPI Programmable-Gain Amplifier with Input VOS Trim and Output OPAMP

  • Rajkumar Sharma
  • 57 Views
  • easy
  • Tested
  • SKU: EL120691
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The project presented here is an SPI programable Gain Amplifier using MAX9939. The MAX9939 is a general-purpose, differential-input programmable-gain amplifier (PGA) that is ideal for conditioning a variety of wide dynamic range signals such as those found in motor current-sense, medical instrumentation, and sonar data acquisition applications. It features SPI-programmable differential gains from 0.2V/V to 157V/V, input offset-voltage compensation, and an output amplifier that can be configured either as a high-order active filter or to provide a differential output.

The PGA is optimized for high-signal bandwidth and its gain can be programmed to be 0.2V/V, 1V/V, 10V/V, 20V/V, 30V/V, 40V/V, 60V/V, 80V/V, 119V/V, and 157V/V. Precision resistor matching provides extremely low gain tempco and high CMRR. Although the MAX9939 operates from a single supply VCC between 2.9V to 5.5V, it can process signals both above and below ground due to the use of an input level-shifting amplifier stage. Furthermore, its inputs are protected to ±16V, allowing it to withstand fault conditions and signal overranges. The output amplifier is designed for high bandwidth and low-bias currents, making it ideal for use in multiple-feedback active filter topologies that offer much higher Qs and stopband attenuation than Sallen-Key architectures. The MAX9939 draws 3.4mA of quiescent supply current at 5V, and includes a software-programmable shutdown mode that reduces its supply current to only 13µA.

Note: This is a general-purpose SPI programable gain amplifier, all components are user-defined, capacitors and resistors value as per application. Refer to the datasheet of the chip for more information.

Key Features

  • Operating Power Supply 3V to 5V DC
  • SPI-Programmable Gains: 0.2V/V to 157V/V
  • Extremely Low Gain Tempco
  • Integrated Amplifier for R/C Programmable Active Filter
  • Input Offset-Voltage Compensation
  • Input Protection to ±16V
  • 13µA Software Shutdown Mode
  • -40°C to +125°C Operating Temperature Range
  • 10-Pin µMAX Package
  • Amplification
  • Differential to Single-Ended Conversion
  • Differential-Input, Differential-Output Signal
  • Medical Signal Conditioning
  • Sensor Interface and Signal Processing
  • Sensorless Motor Control
  • Sonar and General-Purpose Data Acquisition
  • PCB Dimensions 37.94 x 15.72mm

Schematic

Example Application



Parts List

NOQNTY.DESC.REF.MANUFACTURERSUPPLIERPART NO
11CN15 PIN MALE HEADER PITCH 2.54MMWURTHDIGIKEY732-5318-ND
21CN25 PIN MALE HEADER PITCH 2.54MMWURTHDIGIKEY732-5318-ND
31CN35 PIN MALE HEADER PITCH 2.54MMWURTHDIGIKEY732-5318-ND
48C1,R2,R3,C4,R5,C5,C7,C8DNPUSER DEFINED
51C210uF/25V SMD SIZE 1206MURATA/YAGEODIGIKEY
62C3,C100.1uF/50V SMD SIZE 0805MURATA/YAGEODIGIKEY
71C64K7PF/50V SMD SIZE 0805MURATA/YAGEODIGIKEY
81C9220PF/50V SMD SIZE 0805MURATA/YAGEODIGIKEY
91D1LED SMD SIZE 0805LITE ON INCDIGIKEY160-1427-1-ND
103R1,R7,R100E SMD SIZE 0805MURATA/YAGEODIGIKEY
112R4,R866.5K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
121R6121K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
131R91.21K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
141R111K 1% SMD SIZE 0805MURATA/YAGEODIGIKEY
151U1MAX9939AUBANALOG DEVICEDIGIKEYMAX9939AUB+CT-ND
C1, C2 AND C8 = SIZE 1206ALL OTHER RESISTORS AND CAPACITORS = SIZE 0805

Connections

Gerber View

Photos

MAX9939 Datasheet

MAX9939

PCB

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Emiliano

what’s the input impedance?

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