I'm having some trouble with my PCF8574 IÂ²c port extender chip, possibly related to output current. I've successfully implemented 3 other of these chips, but this is the only one with relatively high output current. It started acting weird (micro controller, atmega168, hangs on it) when I decreased the loading resistor on the output from 47k to 10k.
Anyway, I'm confused about the maximum output current. The datasheet says under limiting values for I/O's:
- LOW level output current: min = 10 mA, typ = 25 mA.
- HIGH level output current: min = 30 ÂµA, max = 300 ÂµA.
These are my questions:
- Why is the max current for the low level so much higher? Should there be no current when the output is low?
- The features page says it has high current output capability for directly driving LEDs. A led needs about 20 mA, so how can that work with 300ÂµA?