When the "Low side" (3.3 volt device) is high, mosfet off, "High side" (5 volt device) is at 5 votls via R2. When low, mosfet on, grounding high side. When 5 volt device drives "High side" to 5 volts, mosfet source pulled up to 3.3 volts for low side. When low, mosfet is activated via substrate diode, grounding low side.
NEW! RLC-2 RS232 Level Converter in a DB9 backshell
The Art of Electronics (Horowitz & Hill, Cambridge University Press, ISBN 0-521-37095-7) On page 574 is a nice little table that lists what you can drive with what.
| From To-> | TTL | HCT/ACT | HC/AC | 4000B/74C@5v |
| TTL | OK | OK | 1 | 1 |
| HCT/ACT | OK | OK | OK | OK |
| HC/AC | OK | OK | OK | OK |
| 4000B/74C@5v | OK* | OK | OK | OK |
1 pullup to +5V, or use HCT as interface.
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