AFE5808A_15 Datasheet, PDF (66/83 Pages) Texas Instruments – Ultrasound Analog Front-End

AFE5808A
SLOS729D – OCTOBER 2011 – REVISED NOVEMBER 2015
C_EXT
R_EXT
250Ω
250Ω
500Ω
1000Ω
R_INT
2000Ω
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CW_AMPINP
CW_AMPINM
I/V Sum
Amp
CW_OUTM
CW_OUTP
250Ω
250Ω
500Ω
1000Ω
R_INT
2000Ω
R_EXT
C_EXT
S0501-01
Figure 86. CW Summing Amplifier Block Diagram
Multiple AFE5808A devices are usually utilized in parallel to expand CW beamformer channel count. These
AFE5808A devices’ CW outputs can be summed and filtered externally further to achieve desired gain and filter
response. AC coupling capacitors C_AC are required to block the DC component of the CW carrier signal. C_AC can
vary from 1 μF to 10 μF depending on the desired low frequency Doppler signal from slow blood flow. Multiple
AFE5808A devices’ I/Q outputs can be summed together with a low noise external differential amplifiers before
16/18-bit differential audio ADCs. TI’s ultralow noise differential precision amplifier OPA1632 and THS4130 are
suitable devices.
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