# Ultrasound project - voltage/current, pulse width

I need help with my ultrasound project.

My plan is to generate -170 V powering voltage with MAX1847 DC/DC from 5 V. Excite the transducer (2,25 MHz, 50 ohms at resonant freq) with square wave (pulse excitation) with this pulser circuit:

The transducer is Olympus V305-SU-F, they don´t provide datasheet. I want to use one pulse per work cycle with repetition of few hertz.

I have following questions:

a) How to select pulse width?

My thoughts: Here is said, that "a square wave pulse must be tuned to the frequency of the transducer", so -> 2,25 MHz -> T = 1/f -> 440 ns pulse width?

What if it will be shorter/longer. I can think only about transfered power loss.

b) What is the relationship between voltage and current? When I apply -170 V at resonant frequency with 50 ohm from Ohms law I get 3.4 amps (like is said in my another question on this side here ) Correct?

How does this work with square wave excitation? Can I lower the current with input resistor without losing the possibility of sensing the returning echo? This seems tricky for me, because I can´t get so huge current from MAX1847 and through TC6320. Any thoughts how to solve this?

My confusion come from this: All ultrasound pulsers that I have found cant handle 3.4 A. Most of them generate pulses around +- 100V. With common transducer impedance of 50 ohms the current is still to high :/

P.S. For others interested in this topic, I have found great book: Piezoelectric_Transducers_and_Applications link on PDF file

• Seems like everybody has an ultrasound project these days Commented Mar 4, 2016 at 19:20
• @laptop2d Agreed, but at least this OP has an on-topic question to ask. Commented Mar 4, 2016 at 19:50
• @ToKra You may want to check the ratings on your ultrasonic pulse generators. Many devices will have a "maximum non-repetitive pulse" current rating up to a couple orders of magnitude higher than the "constant" or "steady-state" ratings. Also, with square-waves, a 5-10A@200V power MOSFET shouldn't be terribly hard to find. Commented Mar 4, 2016 at 19:52
• On topic but without answer :/ :D. I will check max short time ratings. Commented Mar 9, 2016 at 15:15
• Nothing?.....:/ Commented Mar 17, 2016 at 12:06

No body answered, so after some research I will try to anwer it by myself :)

Practically all anwers on my questions can be found here: http://www.ndt.net/article/0598/linas_eq/linas_eq.htm

and here: