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temtronic
Joined: 01 Jul 2010
Posts: 9097
Location: Greensville,Ontario
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 Posted: Tue Mar 21, 2023 10:42 am |
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| hmm... ISA bus and PIC ! BTDT, one of the first real projects I did allowed PIC to interface to an ISA VGA 8 bit video card. Even Circuit Cellar Ink had articles about that 'joining'. |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Tue Mar 21, 2023 9:22 pm |
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MCUprogrammer wrote:
| Quote: | | " I'm assuming that I feed it with a 7805, which reduces 12volt to 5v as power in the circuit." |
I see that you have focused on getting a low power microcontroller for your project, assuming the use
of an inefficient voltage regulator in terms of power. In your project, current consumption seems to be
an important factor. Using a 7805 in this context, even at only 500 mA output (half its maximum
capability), it would dissipate 1.3 W at minimum.
That can be a lot of heat to get rid of in a small and sealed plastic package, you can't just plunk a surface
mount part on a board if it's going to dissipate that much power.
LM78xx/LM340 was presented in society early in the 80's in the Voltage Regulator Databook 1980
(National Semiconductor) an old style linear regulator architecture that have been used widely since there.
These days there are a new class of regulator called Low-Dropout Regulator, henceforth to be know as to LDO.
At 100 mA, the LDO only dissipates 50 mW, which even a SOT-23 package can handle it dissipation easily.
It not only guarantees that the voltage will be the regulated value despite some drop in the pre-regulated
voltage and produces a nice and clean supply since the local regulator will attenuate the ripple from the
pre-regulated supply.
According to its datasheets, the LT®1965 series are low noise, low dropout linear regulators, the devices supply
1.1A of output current with a 310mV typical dropout voltage.
Operating quiescent current is 500µA for the adjustable version, reducing to <1µA in shutdown.
These characteristics are more relevant to be considered than the PIC MCU own consumption.
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Humberto |
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MCUprogrammer
Joined: 08 Sep 2020
Posts: 220
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| Posted: Wed Mar 22, 2023 12:25 am |
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thank you very much answer.
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Best Regards...
MCUprogrammer
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