Today we are going to quickly examine a very simple yet useful part – the Intersil ICL7660 CMOS voltage converter.
This is the part you have been looking for when you needed -5V and you’re not running off a multi-tap transformer. For example, some old-school TTL electronics projects need +/-5VDC power rails. Or if you are using the ICL7107 analogue to digital/3.5-digit display driver IC .
But first of all, let’s say hello:
To do so with the ICl7660 is very simple, you only need two 10uF electrolytic capacitors!
Firstly, how does it work? A very simple definition would be: the 7660 charges one capacitor, then the other – an oscillator controls the charging cycles between C1 and C2 and inverts the polarity, allowing the capacitors to discharge at an inverted voltage (negative instead of positive).
For a more detailed explanation, have a loot at the data sheet. Furthermore, if the oscillation frequency interferes with other parts of your circuit, you can boost the oscillation rate with the use of a NAND gate, from an external logic IC (4011, etc.)
However due to the oscillations, there is a ripple in the supplied -5V. I only wish I had an oscilloscope to show you this, perhaps next month. In the meanwhile, there is an explanation of this in the data sheet.
At this stage, let’s have a quick look at an example circuit, from the data sheet – figure 13A.
And here it is in real life. The circuit on the breadboard to the right is a simple 12VAC > 5VDC converter, with the 7660 on the left breadboard.
So there you have it – a very easy and cheap way to get yourself -5 volts DC. Some information from this review obtained from Intersil website and the ICL7660 data sheet. You can order ICL7660 in both through-hole and surface-mount from PMD Way, with free delivery worldwide.
This post brought to you by pmdway.com – everything for makers and electronics enthusiasts, with free delivery worldwide.
To keep up to date with new posts at tronixstuff.com, please subscribe to the mailing list in the box on the right, or follow us on twitter @tronixstuff.