I'm currently developing a sequencer based on midibox.org / ucapps.de hard/software solutions and button pads / RGB-LED's from sparkfun, I also wrote a Button/LED matrix driver for MIOS (MIDI-Box operationg system).
Now I'am occupied with the hardware side of the BLM. MIDI-Box uses 74HC595 shift registers to drive LED's, now there seems to be confusion about how much current a single output of a 74HC595 can source:
All the datasheets from different manufacturers specify 35mA max. source current and 20mA max. sink current per output. The number that is the reason for the confuction is "max. VCC or GND current 70mA": is this per logic unit / ouput or for the whole device/IC?
I contacted the technical support of ON semiconductors, they say it's for whole device. But fairchild semconductors, which I also contacted, tell me it's per unit (so the max. supply current would be 8x70mA).
I'am a bit confused, is it possible that different manufacturers of the same device type do not fit the same specifications? The numbers in the datasheets are excatly the same, only fairchild semiconductions adds "per pin" to the max. current through Vcc/GND:
DC VCC or GND Current,
per pin (ICC) ±70 mA
Thanks for your help