AFE4300 Weight-scale and body-composition measurement analog front end (AFE) | TI.com

AFE4300
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Weight-scale and body-composition measurement analog front end (AFE)

 

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Description

The AFE4300 is a low-cost analog front-end incorporating two separate signal chains: one chain for weight-scale (WS) measurement and the other for body composition measurement (BCM) analysis. A 16-bit, 860-SPS analog-to-digital converter (ADC) is multiplexed between both chains. The weight measurement chain includes an instrumentation amplifier (INA) with the gain set by an external resistor, followed by a 6-bit digital-to-analog converter (DAC) for offset correction, and a circuit to drive the external bridge/load cell with a fixed 1.7 V for ratiometric measurements.

The AFE4300 can also measure body composition by applying a sinusoidal current into the body. The sinusoidal current is generated with an internal pattern generator and a 6-bit, 1-MSPS DAC. A voltage-to-current converter applies this sinusoidal current into the body, between two terminals. The voltage created across these two terminals as a result of the impedance of the body is measured back with a differential amplifier, rectified, and the amplitude is extracted and measured by the 16-bit ADC.

The AFE4300 operates from 2 V to 3.6 V, is specified from 0°C to +70°C, and is available in a LQFP-80 package.

Features

  • Weight-scale front-end:
    • Supports up to four load cell inputs
    • On-chip load cell 1.7-V excitation voltage for ratiometric measurement
    • 68-nVrms Input-Referred noise
      (0.1 Hz to 2 Hz)
    • Best-fit linearity: 0.01% of full-scale
    • Weight-scale measurement : 540 µA
  • Body composition front-end:
    • Supports up to three tetra-polar complex impedance measurements
    • 6-Bit, 1-MSPS sine-wave generation digital-to-analog converter (DAC)
    • 247.5-µArms, ±20% Excitation source
    • 0.1-Ω Measurement RMS noise in 2-Hz BW
    • Body composition measurement : 970 µA
  • Analog-to-digital converter (ADC):
    • 16 Bits, 860 SPS
    • Supply current: 110 µA

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Parametrics

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Part number Order Number of input channels Resolution (Bits) Interface Number of LEDs Features Operating temperature range (C) Package Group Package size: mm2:W x L (PKG) Approx. price (US$)
AFE4300 Order now 2     16     SPI     0     Biosensing     0 to 70     LQFP | 80     80LQFP: 196 mm2: 14 x 14 (LQFP | 80)     1.70 | 1ku