AFE4300PNR

The AFE4300 is a low-cost analog front-end with two independent signal chains: one for body weight scale (WS) measurements and the other for body composition measurement (BCM) analysis. A 16-bit, 860SPS ADC is multiplexed between the two signal chains. The weight measurement signal chain includes an INA with gain set by an external resistor, followed by a 6-bit DAC for offset correction, and a circuit that drives an external bridge/load cell (with a fixed 1.7V voltage for ratiometric measurements). The AFE4300 can also measure body composition by generating a sinusoidal current into the human body. This sinusoidal current is generated by an internal pattern generator and a 6-bit, 1MSPS DAC. A voltage-to-current converter applies this sinusoidal current to the human body across two terminals. The voltage developed across these two terminals is generated by the body's impedance, which is measured by a differential amplifier, then rectified, with its amplitude extracted and measured by the 16-bit ADC. The AFE4300 operates over a supply voltage range of 2V to 3.6V, is rated for 0℃ to +70℃, and is available in an LQFP-80 package.

Applications

• Body weight scale with body composition measurement capability

Key features

• Up to four load cell inputs supported
• On-chip load cell 1.7V excitation voltage for ratiometric measurement
• 68nVrms input-referred noise (0.1Hz to 2Hz)
• Best-fit linearity: 0.01% of full-scale
• Body weight measurement: 540μA
• Up to three tetrapolar bioimpedance measurements supported
• 6-bit 1MSPS sine wave generation DAC
• 247.5μArms, ±20% excitation source
• 0.1Ω measurement RMS noise in 2Hz bandwidth
• Body composition measurement: 970μA
• ADC: 16-bit, 860SPS
• Supply current: 110μA