Understanding a simple circuit

Hey,

I am trying to breakdown this circuit and understand every bit of it before i build it again. The picture is attached. Its an ultrasonic transmitter circuit. An explanation was given as well.

"The ultrasonic transmitter submodule drives a 40kHz piezo-electric open-air ultrasonic transmitter at 12 V [102]. Under software control, this submodule generates ultrasonic pulses of duration 125 μs. The voltage multiplier module generates 12 V from the 3 V supply voltage to drive the ultrasonic transmitter".

I guess the part i don't quite understand is the generation of 12v from 3v. Where does the 12v come from...I dont see another power source in the circuit. btw, US_OUT and US_OUT_EN goes into a Micro-controller, which generates pulses. Dont know exactly what does what yet, but i think US_OUT prolly generates pulses which compares it to the LM8261's SHDN/2...like a comparator. According to the datasheet for MAX864, SHDN = Vin Thats what im understanding. So wheres the 12v?

Also, I wanna build this transmitter, but the MAX864 does'nt come in PDIP. Is there any other similar charge pump with SHDN that comes in PDIP?

Thanks heaps.

What do you think the MAX864 does? Just Google it.

I did. "The charge pump first doubles the input voltage, then inverts the doubled voltage". From the configuration, I figured it provides the LM8261 with a +Vin and -Vin. And the 12v?

hobby_85 said:

I did. "The charge pump first doubles the input voltage, then inverts the doubled voltage". From the configuration, I figured it provides the LM8261 with a +Vin and -Vin. And the 12v?

Click to expand...

It's the output of the op amp driving the transducer. Apparently they are using peak-to-peak voltage in their description.