Datasheet

AFE5808A

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SLOS729B –OCTOBER 2011–REVISED APRIL 2012

Programmable Gain for CW Summing Amplifier

Different gain can be configured for the CW summing amplifier through the register 54[4:0]. By enabling and

disabling the feedback resistors between the summing amplifier inputs and outputs, the gain is adjustable

accordingly to maximize the dynamic range of CW path. Table 7 describes the relationship between the summing

amplifier gain and 54[4:0] settings.

Table 7. Register 54[4:0] Description

54[4:0]/0x36[4:0] FUNCTION

00000 No feedback resistor

00001 Enables 250 Ω feedback resistor

00010 Enables 250 Ω feedback resistor

00100 Enables 500 Ω feedback resistor

01000 Enables 1000 Ω feedback resistor

10000 Enables 2000 Ω feedback resistor

Table 8. Register 54[4:0] vs Summing Amplifier Gain

54[4:0]/0x36[4:0] 00000 00001 00010 00011 00100 00101 00110 00111

CW I/V Gain N/A 0.50 0.50 0.25 1.00 0.33 0.33 0.20

54[4:0]/0x36[4:0] 01000 01001 01010 01011 01100 01101 01110 01111

CW I/V Gain 2.00 0.40 0.40 0.22 0.67 0.29 0.29 0.18

54[4:0]/0x36[4:0] 10000 10001 10010 10011 10100 10101 10110 10111

CW I/V Gain 4.00 0.44 0.44 0.24 0.80 0.31 0.31 0.19

54[4:0]/0x36[4:0] 11000 11001 11010 11011 11100 11101 11110 11111

CW I/V Gain 1.33 0.36 0.36 0.21 0.57 0.27 0.27 0.17

Programmable Phase Delay for CW Mixer

Accurate CW beamforming is achieved through adjusting the phase delay of each channel. In the AFE5808A, 16

different phase delays can be applied to each LNA output; and it meets the standard requirement of typical

ultrasound beamformer, i.e. beamformer resolution. Table 7 describes the relationship between the phase

delays and the register 55 and 56 settings.

Table 9. CW Mixer Phase Delay vs Register Settings

CH1 - 55[3:0], CH2 - 55[7:4], CH3 - 55[11:8], CH4 - 55[15:12],

CH5- 56[3:0], CH6 - 56[7:4], CH7 - 56[11:8], CH8 - 56[15:12],

CHX_CW_MIXER_PHASE 0000 0001 0010 0011 0100 0101 0110 0111

PHASE SHIFT 0 22.5° 45° 67.5° 90° 112.5° 135° 157.5°

CHX_CW_MIXER_PHASE 1000 1001 1010 1011 1100 1101 1110 1111

PHASE SHIFT 180° 202.5° 225° 247.5° 270° 292.5° 315° 337.5°

Product Folder Links: AFE5808A