How can I limit voltage to an IC???

[vortex]

I am having fun messing around with the Noise567 / Thing Modulator on the breadboard tonight. Thanks Tim Escobito and Hemmo P!

I have the data sheet for the LM567 and it specifies that the LM567s max voltage is 9V. (Typical 5V) At the moment I'm using an old 9V battery that's putting out around 7V just to be safe. Most of my new batteries are putting out 9.45 volts, so I am worried that if I box up the circuit once I am happy with it and absent mindedly pop in a new battery the chip might fry.

So, my question is how do I limit the voltage from the battery?

I tried adding a few different values of resistors in series with the positive battery lead and that doesn't seem to drop the voltage much. I tried adding various resistor values to ground from the positive lead and that didn't work either. I am stuck here, diode to ground ??

Here's the schematics




BTW The LM567 chip works in the Thing Modulator if you omit the 100K resistor connected to pin 4. I guess the LM567 chip needs more power than the LMC567 chip. I also noticed that the carrier signal bleedthrough is lessened in there is a buffer in front of the circuit.

Any help appreciated.

Thanks!

[Dragonfly]

TRY THIS !

[gez]

I have the data sheet for the LM567 and it specifies that the LM567s max voltage is 9V. (Typical 5V)

A better solution to the above (I use MOSFETs when using a series-pass arrangement like that as you can use large value trimpots and save current) is to use a 5V regulator.  They usually have three terminals which are self explanatory - Vin, Ground, Vout (5V).  Data sheet for the one you use (check your supplier's catalogue to see what they've got) will show you cap values to use (you need one on the output and one on the input).  Regulators such as the LP2950CZ-5.0 are micro-power and battery friendly, but most consume two or three milliamps.

An alternative is to stick a 3V3 zener in series with a Si diode to your V+ pin.  Works but voltage will vary as your battery flattens.  Plus you'll probably need some filtering after the zener as they can introduce noise.

[A.S.P.]

just a series-diode from +battery to circuit...
will drop 0.6 - 0.7V, regardless of current-draw
for <100mA use 1n4148 for more current use 1n4001;

more diodes in series drop multiples of 0.6V.

[Paul Perry (Frostwave)]

The trouble with dropping via a resistor or diodes from  a battery, is that it reduces the range over which the battery is operational. (try the maths!) Fortunately, there are a number of special "low dropout" 5v regulators that allow you to use a 9v battery till it is pretty well flat. Or if you are using a 9v wart, or a fresh battery, then a normal 5v reg is cool.

[gez]

Fortunately, there are a number of special "low dropout" 5v regulators that allow you to use a 9v battery till it is pretty well flat.

Indeed, the one I mentioned above is a beauty (low drop and miniscule tick-over current)!

[vortex]

Thanks for the help guys! I'll try all of the suggestions.