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Hi,
I got sick of blowing up 7660 charge pumps by sticking too much voltage across them, and I didn’t want to keep paying the extra for the 7662. So I used a garden variety 555 timer as a one shot. It works very well using the coil drive of my PI detectors as a clock source, and being synchronised to the system removes glitches during sampling. My units run at 7 to 8kHz so if your unit is going to be running at less than 10kHz you’ll need to source the clock from a master that you then divide down for pulse rate etc.,
http://www.geocities.com/kejamnz/misc/CHARGEPUMP.JPG
Watch the 555, many have differing output current ratings. The old bipolar varieties will give 100mA, but are self hungry, while some CMOS types still give 100mA but require very little to run on.
I used to wonder why I kept blowing the 7660 on my Stuart Mk2 until I realised the variety I was using could only handle 10Volts and I was using 12 as a source, one to watch out for.
Cheers
Kev.
I got sick of blowing up 7660 charge pumps by sticking too much voltage across them, and I didn’t want to keep paying the extra for the 7662. So I used a garden variety 555 timer as a one shot. It works very well using the coil drive of my PI detectors as a clock source, and being synchronised to the system removes glitches during sampling. My units run at 7 to 8kHz so if your unit is going to be running at less than 10kHz you’ll need to source the clock from a master that you then divide down for pulse rate etc.,
http://www.geocities.com/kejamnz/misc/CHARGEPUMP.JPG
Watch the 555, many have differing output current ratings. The old bipolar varieties will give 100mA, but are self hungry, while some CMOS types still give 100mA but require very little to run on.
I used to wonder why I kept blowing the 7660 on my Stuart Mk2 until I realised the variety I was using could only handle 10Volts and I was using 12 as a source, one to watch out for.
Cheers
Kev.
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