Question about LM4871 application for VFD fiament.

Chaos Hydra

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Jul 12, 2016, 11:23:19 PM7/12/16

to neonixie-l

Hi guys! As the forum has discussed, LM4871 is almost the same as the obsolete LM9022 VFD filament driver and I am trying to fit it to my design to eliminate the brightness gradient problem. So I took a sop-8 LM4871, put it on a SMD break out and threw it to a bread board. For convenience, i hooked pin 1, 2, 3, 7 to GND and used my Arduino to generate a 4Hz squarewave signal (5V to 0V). But, the voltage between Vo1 and Vo2 is constantly - 4.5V. What should I do to make it work?
Thanks in advance for help!

LM9022_datasheet.pdf

lm4871.pdf

petehand

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Jul 13, 2016, 5:12:40 AM7/13/16

to neonixie-l

The LM4871 wouldn't be my choice for a filament driver. I use the Si9986, which is an H bridge, with my VFD projects.

http://www.alliedelec.com/siliconix-vishay-si9986cy-e3/70026303/

Chaos Hydra

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Jul 13, 2016, 5:23:23 AM7/13/16

to neonixie-l

Ok, H-bridge is a nice idea too. It just happens that I do got several LM4871 looted from school's lab and I was trying to testify that LM4871 == LM9022 statement. Still, Si9986 seems a little like a overkill for a filament, considering the price, lol.

threeneurons

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Jul 13, 2016, 3:42:53 PM7/13/16

to neonixie-l

How about an old LM1877 stereo audio amp:

Comes in a 14-pin DIP. Can deliver several 100's mA of current. And don't take the supply voltage as "Gospel". In can vary a bit, both up and down.

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