| ??? 01/09/06 12:47 Read: times |
#106885 - Sourcing current to commong anode SSD. |
Dear Forum Members,
In one of my products I use 6 digit seven segment LED display. The Displays are common anode type. I have connected the cathodes of the segments to 74LS541. This 74LS541 sinks current from the segments and is connected to port 0 of micro. The common anodes are multiplexed the sourcing to common anodes is done using BC557B transisitors bases of which are connected to Port 2 of micro. The problem i am facing is the failure rate of transistors is very high. Most of the failures are born failures the transistors dont work right on day 1. very rarely they fail while working. I want to change the descrete transistors with some chip that can source 6 lines @ 500mA each line. What is the most commonly available source device. For sink there are plenty like ULN2003 ULN2803 etc but for source I need help. Thanks & Regards, Prahlad Purohit |
| Topic | Author | Date |
| Sourcing current to commong anode SSD. | 01/01/70 00:00 | |
| Not designed for switching purpose | 01/01/70 00:00 | |
| maybe even better | 01/01/70 00:00 | |
| Thanks for your reply erik. | 01/01/70 00:00 | |
| Oops I made serious design mistake. | 01/01/70 00:00 | |
| saturation required | 01/01/70 00:00 | |
| Try BC188 or BC640 | 01/01/70 00:00 | |
| Google fails | 01/01/70 00:00 | |
Indian creation | 01/01/70 00:00 | |
| Base resistors | 01/01/70 00:00 | |
| ULN2003 & ULN2803 | 01/01/70 00:00 | |
| Second sourced | 01/01/70 00:00 | |
| but thre aer newer "equivalents" | 01/01/70 00:00 | |
| try toyolite | 01/01/70 00:00 |