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AFE4300 Low-Cost, Integrated Analog Front-End
for Weight-Scale and Body Composition Measurement
AFE4300
SBAS506 – AUGUST 2019
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-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
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.
Device Information(1)
PART NUMBER PACKAGE
BODY SIZE (NOM)
AFE4300
LQFP (80)
12.00 mm × 12.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Functional Block Diagram
INPx
INMx
RG
VLDO
MUX
A1
+
offset
A2
OUTx_FILT
CLK
AVDD
y
Patient
&
ESD
Protection
VSENSEPx
VSENSEMx
MUX
A3
Full Wave
Rectifier
MUX
ADC
(16bit, 860SPS)
SPI
STE
SDIN
SDOUT
SCLK
RDY
IOUTPx
I/Q
Patient
Demodulator
&
Zs ESD
MUX
Protection
IOUTMx
0.9V
VDAC_FILT_IN
1.5k +/- 20%
VDACOUT
DAC
(6bit)
CLK
DDS
(10bits)
Reference
LDO
AUXx
VREF VLDO
AVSS
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
