| ??? 06/19/06 19:26 Read: times |
#118545 - As long as we must guess... Responding to: ???'s previous message |
Farshid said:
Really ? The ST or Toshiba or TI manufactured 74HC595s datasheet's doesn't say more than +/-6mA capability. I was blaming myself since I have designed a pcb where 4 of this chips where used to work at +/-20mA , So are you saying that we can easily push this chip near to it's absolute maximum rating ? Farshid, I wrote This chip could also directly drive your traffic LEDs. We don't know much about Munazas application. Munaza could possibly drive the red, yellow and green traffic lights by the same chip. Then, as "green" and "red" never occurs at the same time he could have a higher current flowing through the LEDs. Total maximum current of chip is 50mA, maximum current per output is 25mA. So, there's some reserve and with the "red", "yellow" and "green" arrangement more than 8mA per output could be sinked by the 74HCMOS chips at the same time, which is twice the maximum current of 82C55. Also, there are super high efficiency LEDs arround, which need only a few mA to shine as bright as others at 20mA. The issue was not to tell the OP that he can drive whatever he wants with these shift registers, but that the 74HCMOS chips have stronger output drivers than the 82C55. Kai |
