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Join us now! Forgot Your Password? Forgot your Username? Haven't received registration validation E-mail? User Control Panel Log out. Forums Posts Latest Posts. View More. Recent Blog Posts. Unread PMs. Forum Themes Elegant Mobile. Essentials Only Full Version. Starting Member. Different voltage levels Hi there, Just a question regarding different voltage levels. I have a PIC24 working off 3. I want to receive data from a PIC16 that works at 5V.
I read in the datasheet that all the PIC24 pins are 5V intolerant. Circuit breaker. Is a resistor usage legal in your country? I think so ; But how do you know what current you will draw, and therefore what resistor to choose? Super Member. Usually to ohms is OK. What PIC24 are you using? Many of them have pins which tolerate 5V. I think you should try reading the datasheet.
Voltage division with resistors can be found with Google. You could also use a 74LVC to convert levels. Also Google. Yeah; since OP is talking only about "receiving from 5V into 3. Ok thanks for these responses. I know about ohm's law and voltage dividers :P My question is how to get to that resistor value, since I don't know the input impedance Or should I just use the values jgmartinez suggested?
What is the lowest voltage it can detect as high? The PICs inputs are normally clamped the Vdd with a diode so the calculate the current from a 5V to 3. A Ohm series resistor will limit the input clamp current to about 4. The minimum voltage level for a logic 1 VIH is found in the 'Electrical Characteristics' section of the data sheet.
A typical value is about 2V but does depend on which pin on the PIC is used why you'll need to check the DS so it should detect a 3V signal as logic high. Ok thx. I see it's about 0. TTL buffer or Schmitt trigger buffer? Will 3. I just found Figure Anyone know which is really correct? If you're driving a 5Volt intolerant input use a divider and not a siingle resistor.
Thanks for this Just thought I'd quote Brian aka betwixt for anyone looking at this thread in the future. How to take 3.
Take the output from the collector. When the 3. Brian's idea is a good one. JackG Brian's idea is a good one. Yep, and that is how the SparkFun's level converter works that I posted a link to in an above post. Latest Posts. Where are they now? Active Posts. All FAQs. What's the alternative? Stay logged in. Thanks 1 15 Replies Related Threads. GODO 7.
74LVC244, 74LVC244A, 74LVC244ABD
Sign In Register. Quick Links Categories Recent Discussions. Categories The 10k resistors are the simplest solution, but will affect bandwidth somewhat. A resistor divider using 1k and 2k2 resistors will give good bandwidth, but will interfere with any signals that have pull-ups.
74LVC244 Philips Semiconductors, 74LVC244 Datasheet - Page 4
74LVC244 – Octal buffer/line driver with 5-volt tolerant inputs/outputs 3-Statetitle