Datasheet

MAX2078
Octal-Channel Ultrasound Front-End
with CW Doppler Mixers
16 ______________________________________________________________________________________
Detailed Description
The MAX2078 is a high-density, octal-channel ultra-
sound receiver optimized for low cost, high-channel
count, high-performance portable and cart-based ultra-
sound applications. The integrated octal LNA, VGA,
AAF, and programmable CWD beamformer offer a
complete multi-specialty, ultrasound receiver solution.
Imaging path dynamic range has been optimized for
exceptional second-harmonic performance. The com-
plete imaging receive channel exhibits an exceptional
68dBFS** SNR at 5MHz. The bipolar front-end has also
been optimized for exceptionally low near-carrier mod-
ulation noise for exceptional low-velocity pulsed and
color-flow Doppler sensitivity under high-clutter condi-
tions, achieving an impressive near-carrier SNR of
140dBc/Hz at 1kHz offset from a V
OUT
= 1V
P-P
, 5MHz
clutter signal.
The MAX2078 also integrates an octal quadrature
mixer array and programmable LO phase generators
for a complete continuous-wave Doppler (CWD) beam-
forming solution. Separate mixers for each channel are
available for optimal CWD sensitivity, yielding an
impressive SNR of 154dBc/Hz at 1kHz offset from a
200mV
P-P
, 1.25MHz input signal. The LO phase selec-
tion for each channel is programmed using a digital
serial interface and a single high-frequency clock. The
serial interface is designed to allow multiple devices to
be easily daisy-chained to minimize program interface
wiring. The outputs of the mixers are summed into sin-
gle I and Q differential current outputs.
Modes of Operation
The MAX2078 requires programming before it can be
used. The operating modes are controlled by 47 pro-
gramming bits. Tables 1 and 2 show the functions of
these programming bits.
BIT NAME DESCRIPTION
D40, D41, D42 Input impedance programming
D43 LNA gain (D43 = 0 is low gain)
D44, D45 Anti-alias filter f
C
programming
D46 Don’t care
D0–D39 Beamformer programming, from channel 1 to 8
Table 1. Summary of Programming Bits
D46 D45 D44 D43 D42 D41 D40 MODE
XXX1000 R
IN
= 50Ω, LNA gain = 18.5dB
XXX1001 R
IN
= 100Ω
XXX1010 R
IN
= 200Ω
XXX1011 R
IN
= 1000Ω
XXX0000 R
IN
= 100Ω, LNA gain = 12.5dB
XXX0001 R
IN
= 200Ω
XXX0010 R
IN
= 400Ω
XXX0011 R
IN
= 2000Ω
X X X 1 1 X X Open feedback
X00XXXX f
C
= 9MHz
X01XXXX f
C
= 10MHz
X10XXXX f
C
= 15MHz
X11XXXX f
C
= 18MHz
Table 2. Logic Functions of Programming Bits
X = Don’t care.
** When coupled with the MAX1437B ADC.