Categorized | ICL7660, lesson, part review, tutorial

Part Review – Intersil ICL7660

Hello readers

Today we are going to quickly examine a very simple yet useful part – the Intersil ICL7660 CMOS voltage converter. Huh? 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 (as used in my defunct bbboost project).

But first of all, let’s say hello:

icl7660small

To do so with the ICl7660 is very simple, you only need two 10uF electrolytic capacitors! Honestly, I couldn’t believe my luck when I discovered this part, that is why I am writing about it today.

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.

7660circuit

And here it is in real life. The circuit on the breadboard to the left is my simple 12VAC > 5VDC converter. I am not that well off at the moment, so it will have to do.

7660circuitrealsmall

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; these parts purchased by myself without knowledge of manufacturers or retailers.

Once again,  thank you for reading. Please leave feedback and constructive criticism or comments at your leisure… and to keep track, subscribe using the services at the top right of this page!

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John Boxall

Founder, owner and managing editor of tronixstuff.com.

2 Responses to “Part Review – Intersil ICL7660”

  1. Kevin says:

    I just picked up four of these ic’s today at the local electronics shop. I have been needing to generate a negative charge for the contrast voltage for some LCD screens. This is just awesome. Thanks for the writeup as it took my only about four minutes to wire everything up and test. Voila, 2.53 volts in (2 dying AA batts) -2.53 volts out.

    Great post, thanks :)

    –kevin

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