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Interfacing 3.3V microcontroller to a 5V devices

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Jan 26, 2004
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3.3 to 5v buffer

Hello and marry xmas :)))
Can someone give me an idea how to interface a 3.3V microcontroller (ADuC702x) to a 5V MAX7219? The 7219 needs a minimum of 3.5V for the SPI clock, so i need something to convert the level (3.3 -> 5) in one direction at 1.6MHz minimum.

buffer 3.3 to 5v

If you look only of the one way convertor you can use NPN transistor, signal will be inverted, or any CMOS element with the open drain output.

p.s. in the future you can use this, if you don't know:
h**p:// , very good forum in Bulgarian language ;)

Have a look at pictures below ..
On coverts level from 5V to 3V logic, the other converts the opposite way around ..
I prefer the nFET, because you can have a true 0V at logic L, but any 2n2222 or other general purpose NPN will do ..
As pullups use resistors of 500Ω to 2KΩ for fast rise times ..

5 volt to 3.3 volt buffer

the schem is OK but you can have a problem with a frequency, the MOSFET have a high capacitance between gate and source. On 2 Mhz this capacitance can be a problem for the output circuit on the controller, the result will be slide edge. If you use JFET the result will be better, because JFET have a lowest capacitance. And, something other, the more of the MOSFET is need around 5 V to saturation, if will use MOSFET first look for the saturation voltage.

interfacing 3.3 v 5v


IanP circuit is a very good one, but the draw back is that it works only one way.
In the attaced picture, this circuit works both ways, and it is from the I2C specification page #43. **broken link removed**
I know it works as i have used it before...

Good luck.

bufor 3.3-5v

You cand use two resistors to div volt :
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interfacing 3.3v microcontroler to 5v lcd

from 3.3v interface to 5v interface you can use a buffer...for example the buffer with 5v and connect your 3.3v interface to buffer directly....

from 5v interface to 3.3v interface a basic resistor divider will work fine enough....

74hct244 examples

The cheapest translator is probably the one used by Ian. My approach though is different. I use digital switch like 3244 and can convert to ANY level by using appropriate VCC and series diodes. And no penalty in speed. The other direction I found working good is to use HCT or AHCT or ACT series that has TTL levels. You do have somewhat increased consumption but most of the time it can be sacrificied.


BTW, in the past I often did the inverter - but single stage and had my data inverted in the MCU by software routine. Works great too and avoid one more delay etc....
Today there are lots of TrenchFET's on the market with very decent performance.

interfacing 3.3 volt logic with 5v

MAX3002 can also be a good option for bidirectional bus level translation...

hope this helps,

bidirectional buffer 3.3 to 5v

MAx series translators are rip off all the way.
Been looking 20 times and find them prohibitively overpriced. Many other good alternatives exist.

buffers 3.3 5v

You can use 74LSxx buffer in any direction.
for example 74LS09.

74hc541 5v tolerant

also look at this application note

3.3V DSP for Digital Motor Control:

**broken link removed**

5v npn transistor ttl

maybe a voltage comparator will also be nice option
(eg. LM393 from National Semiconductor)


how to connect a 3.3v microcontroller to a 5v spi

A lot depends on whether your 3.3V logic is 5V tolerant or not.

For unidirectional, I'd take a look at 74HCT logic. very cheap and widely available. there are buffers, transceivers, NAND gates, etc. For example, the 74HCT244 is an octal buffer and costs around $.30 for 8 drivers in an SOIC or TSSOP. less than 4 cents a driver.

I also like the Fairchild Tinylogic series. They have several single gate packages with TTL (2V) like input levels in SOT packages. very small but still hand solderable. No TTL buffers, unfortunately.

buffer de 3.3 a 5v

If the line is bidirectional, as a data bus is, keep in mind that you'll need to control the sense of the signal. For instance if you want control an 5V LCD whith a 3.3V microcontroler.

gidimiz give an interesting solution.


74hct244 circuit +3.3

You can using 74LCX4245 for your project .

i need to convert 5 volt data signal to 3.3 volt

what is about 74HC573?

Re: max3002 invertiert

Thank You friends, Now I am having more number of options shortly I will post which ever I used.

Thanking You,
Ravi Kumar

use level translators from TI, good choice available. or use low priced ooptocouplers. or simple NPN transistors. Logic may change depending on your design, however level translation may be implemented in many different ways.

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