AD5940
Data Sheet
BODY IMPEDANCE ANALYSIS (BIA)
MEASUREMENT USING A HIGH BANDWIDTH
LOOP
The AD5940 uses its high bandwidth impedance loop to perform
an absolute, 4-wire impedance measurement on the body. The
high performance, 16-bit ADC, along with on-chip DFT hard-
ware accelerator, target 100 dB of SNR at 50 kHz with impedance
measurements up to 200 kHz. For details, see AN-1557.
WAVEFORM
GENERATOR
HSDAC
GAIN
D5
C
ISO1
R
CE0
LIMIT
EXCITATION
BUFFER
N
P
P5
F+
S+
V
V
BIAS
C
LPDAC0
ISO3
AIN2
ZERO
R
+
FILTER
SEQUENCER
LPTIA
–
10MΩ
16MHz
OSC
AIN4/
LPF0
C
LPF
VCM
BODY
10MΩ
ADC/
800kHz
DFT
FIFO
C
C
ISO4
AIN3
AIN1
S–
F–
N2
1.11V
+
HSTIA_P
ISO2
HSTIA
–
T2
T9
R
TIA
C
TIA
AD5940
Figure 51. High Frequency, 4-Wire, Bioimpedance Loop (Maximum Bandwidth = 200 kHz)
Rev. 0 | Page 126 of 130
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