max2078ctk Maxim Integrated Products, Inc., max2078ctk Datasheet - Page 23

• Manufacturer Part Number: max2078ctk
• Description: Octal-channel Ultrasound Front-end With Cw Doppler Mixers
• Manufacturer: Maxim Integrated Products, Inc.

Octal-Channel Ultrasound Front-End
with CW Doppler Mixers
Ultrasound-Specific IMD3 Specification
Unlike typical communications applications, the two
input tones are not equal in magnitude for the ultra-
sound-specific IMD3 two-tone specification. In this
-25dB
measurement, f
represents reflections from tissue and
1
f
represents reflections from blood. The latter reflec-
2
tions are typically 25dB lower in magnitude, and hence
the measurement is defined with one input tone 25dB
lower than the other. The IMD3 product of interest
ULTRASOUND
IMD3
(f
- (f
- f
)) presents itself as an undesired Doppler
1
2
1
error signal in ultrasound applications (see Figure 6).
PCB Layout
The pin configuration of the MAX2078 is optimized to
facilitate a very compact physical layout of the device
and its associated discrete components. A typical
application for this device might incorporate several
devices in close proximity to handle multiple channels
of signal processing.
f
- (f
- f
)
f
f
f
+ (f
- f
)
1
2
1
1
2
2
2
1
The exposed pad (EP) of the MAX2078’s TQFN-EP
package provides a low thermal-resistance path to the
die. It is important that the PCB on which the MAX2078
Figure 6. Ultrasound IMD3 Measurement Technique
is mounted be designed to conduct heat from the EP.
In addition, provide the EP with a low-inductance path
to electrical ground. The EP MUST be soldered to a
ground plane on the PCB, either directly or through an
array of plated via holes.
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