On the data sheet of SN74HC164 there are two statements that I apparently don't understand:
- Cover page says: ±4-mA Output Drive at 5V
- Page 3 says: Continuous output current Io at Vo between 0 and Vcc = ±25mA
So which one is what?
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
Page 3 in the Absolute Max Ratings chart, shows +-25mA.
This is the maximum ratings for that device, do not allow it to sink or source more than this, with all it's outputs on.
Cover page is referring to each output pin, being able to sink/source up to 4mA each. If you had all 8 outputs at maximum current sink, you would be exeeding the max ratings by (32-25 =) 7mA. The device will probably overheat and become damaged.
Page 3 is MAX specs; i.e. do not exceed!!! so in a short circuit situation you could see 25ma from the output. The recommended conditions is to use 4ma as the typical value. the table on page 4 shows the Ioh and Iol under varying load conditions but only up to 5.2ma.