1 Features

1• 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-toanalog

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

2 Applications

Weight scales with body composition

measurements

3 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.