AFE5805 Datasheet, PDF (32/53 Pages) Texas Instruments – 8-CHANNEL ANALOG FRONT-END FOR ULTRASOUND

AFE5805
SBOS421D – MARCH 2008 – REVISED MARCH 2010
www.ti.com
PROGRAMMABLE GAIN
ADDRESS
IN HEX
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
X
X
X
X
X
X
X
X
2A
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
2B
X
X
X
X
X
X
X
X
NAME
GAIN_CH4<3:0>
GAIN_CH3<3:0>
GAIN_CH2<3:0>
GAIN_CH1<3:0>
GAIN_CH5<3:0>
GAIN_CH6<3:0>
GAIN_CH7<3:0>
GAIN_CH8<3:0>
The AFE5805, through its registers, allows for a digital gain to be programmed for each channel. This
programmable gain can be set to achieve the full-scale output code even with a lower analog input swing. The
programmable gain not only fills the output code range of the ADC, but also enhances the SNR of the device by
using quantization information from some extra internal bits. The programmable gain for each channel can be
individually set using a set of four bits, indicated as GAIN_CHN<3:0> for Channel N. The gain setting is coded in
binary from 0dB to 12dB, as shown in Table 15.
GAIN_CH1<3>
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
GAIN_CH1<2>
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Table 15. Gain Setting for Channel 1
GAIN_CH1<1>
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
GAIN_CH1<0>
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
CHANNEL 1 GAIN SETTING
0dB
1dB
2dB
3dB
4dB
5dB
6dB
7dB
8dB
9dB
10dB
11dB
12dB
Do not use
Do not use
Do not use
32
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