Maxim > Design Support > Technical Documents > Application Notes > Amplifier and Comparator Circuits > APP 5131
Maxim > Design Support > Technical Documents > Application Notes > Analog Switches and Multiplexers > APP 5131
Keywords: industrial, ultrasound, NDT, flow meter, sonar, probe, system channels, high voltage, AFE, pulser, switch,
unipolar, bipolar, low frequency, high frequency probe, HV
APPLICATION NOTE 5131
Maxim Addresses High-Voltage Needs in Industrial
Ultrasound Applications
By: Luigi Franchini
Aug 26, 2011
Abstract:
Most ICs
for ultrasound transmission available today are aimed to cover medical applications and do not
necessarily fit the needs for industrial applications. Industrial applications such as nondestructive tests (NDTs), flow
meters, and sonar often have different requirements for voltage capability, current capability, and frequency. Thanks to
their great flexibility, Maxim's high-voltage (HV) products can be used in a broad range of applications. This article
presents a variety of applications for the MAX4940 quad HV digital pulser and the MAX4968 HV multiplexer (mux).
Table of Contents
Overview
The MAX4940 HV Digital Pulser
The MAX4968 HV Analog Switch
Supported Applications
Bipolar
Unipolar Positive
Unipolar Negative
Doubling the Voltage Capability with BTL Configurations
Increasing the Current Capability with Parallelization
Low- and High-Frequency Operations
Low-Frequency Operation (< 1MHz)
High-Frequency Operation (> 20MHz)
Overview
The MAX4940 HV Digital Pulser
Figure 1 shows the essential functional diagram of the MAX4940, a device that features 4 channels for high-voltage
(HV) digital pulsing. (Only 1 out of the 4 channels is displayed in the diagram.)
S1 and S2 switches (connected to V
PP
_ and V
NN
_, respectively) feature 200V voltage capability and 2A current
capability.
S3 switch (called "clamp" in the data sheet) features 200V voltage and 1A current capability.
The digital pulser can operate in both bipolar and unipolar applications. In other words, all of the
following cases are supported:
[V
PP
, V
NN
] = [+100V, -100V] bipolar
[V
PP
, V
NN
] = [0, -200V] unipolar negative
[V
PP
, V
NN
] = [+200V, 0] unipolar positive
INP_ and INN_ control S1 and S2, respectively.
INC_ controls S3 (clamp), but it is conditioned by S1 and S2. In most applications, INC_ does not need to be
driven. You can always keep it high and drive INP_ and INC_ only. In doing so, S3 is activated every time both
S1 and S2 are off.
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