Weigh Scale / Body Composition Analog Front End - AFE4300

AFE4300 (ACTIVE)

Weigh Scale / Body Composition Analog Front End

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 its 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 TQFP-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)
    • 375-µArms, ±20% Excitation Source
    • Dynamic Range : 0 Ω to 2.8 kΩ
    • 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

View more

Parametrics Compare all products in Bio-Sensing

 
Resolution (Bits)
FIFO
# Input Channels
Interface
Analog Voltage AV/DD (Min) (V)
Analog Voltage AV/DD (Max) (V)
Architecture
Reference Mode
Rating
Operating Temperature Range (C)
Package Group
Estimated Package Size (WxL) (mm2)
Gain Error (Typ) (%)
Offset Error (Typ) (uV)
Offset error drift (Typ) (uV/C)
Sample Rate (max) (SPS)
AFE4300
16    
No    
2    
SPI    
2    
3.6    
Delta-Sigma    
Int
Ext    
Catalog    
0 to 70    
LQFP    
80LQFP: 144 mm2: 12 x 12    
5    
0.25    
80    
0.86KSPS