[jack55]

Hello All, Can someone explain what a Charge Pump is ? Also....what is a buffered input ? Thanks, Jack

[rustamd]

Charge pump is kind of safety system for electronics. It puts out 12.5Khz signal to break out board when system is in good condition. As windows boots up it can put out different signals to parallel port so your machine can be going "wild", which can move motors and turn on other stuff. Charge pump will not let it do that until mach3(or whatever else you use) will send out 12.5Khz signal to BOB

If i'm wrong someone can correct me

[jack55]

Thanks for the info rustamd....lots to learn ! Jack

[NC Cams]

You can also use a 555 chip and some external diodes and capacitors to make a "charge pump" voltage multiplier. You do this by taking 5 volts or whatever voltage that is powering the 555 and "pump it up" to double or tripple that of the supply voltage depending on the diode/capacitor configuration.

TI had a chip called a TL494 at one time that did the same thing abeit they used an inductor instead of caps and diodes. Either is real handy when you want to take 5-9vdc and ramp it up to 18 volts or so to drive a mosfet real hard and fast.

Although this charge pump will double or tripple the voltage, it doesn't profide a lot of current capability.

[Geof]

TI had a chip called a TL494 at one time that did the same thing abeit they used an inductor...

...Although this charge pump will double or tripple the voltage, it doesn't profide a lot of current capability.

The inductor based charge pumps are what were used to charge capacitors for small photoflash units. They were driven by a flyback oscillator and could pump up to 50 or 60 volts.

Many years ago I developed a chemical metering pump based on a flyback oscillator charging big caps which where then discharged through a solenoid to operate a diaphragm. This unit pumped 12 volts up to 65 volts.

[roundrocktom]

Many years ago I developed a chemical metering pump based on a flyback oscillator charging big caps which where then discharged through a solenoid to operate a diaphragm. This unit pumped 12 volts up to 65 volts.

Geof,

20 years back (??) Walther had an ELECTRONIC target pistol. 9V battery, that would run an oscillator to produce 90+ volts across a cap, enough to drive a solenoid (firing pin). A friend was having issues with it, and I started going though possible "fault problems". One was if the battery was disconnected when the circuit was charged. Uh, not a good result. Walther did recall all the target pistols, but it was one of the more interesting ones.

Jack -- Charge Pumps are common on Integrated Circuits. One of the first ones was a RS232 converter that was connected to a +5V supply. The capacitors attached were used to "charge up" to 5V, then put on top of the 5V... giving almost 10V. Another one then would "flip the leads" allowing for a -10V. Hence the +5V was able to drive the +-9V requirement for RS232. I think MAX232 are still around today, but that was great as you didn't have to have a +-12V power supply, only the 5V and still provide RS232 voltage levels.

Tom

[Al_The_Man]

To answer the second question, a buffer is a device to raise the current capability of a SS device or raise/change the voltage level that it works at, It often consists of an open collector output which allows flexibility in output device driving.
In the case of a buffered input, if generally does a similar function, that it conditions the signal you are inputing to conform to the type of technology that the circuit is operating at, i.e. TTL, CMOS etc.
Al.