| ??? 10/31/03 09:19 Read: times |
#57579 - Much too little headroom! Responding to: ???'s previous message |
In the meantime I could open a datasheet from National Semiconductors. There, a thermal resistance from junction to ambient (with 'standard' PCB mounting) of about 225°C/W is specified.
So, when using 9V, voltage drop across regulator is 4V. Times 80mA yields 320mW. Times 225°C/W gives 72K. Means, when ambient temperature is +40°C junction temperature is 112°C. At about 120°C junction temperature thermal 'fuse' begins to act. So, there's much too little headroom with your application!! I would recommend another solution, means the use of regulator with heat sink ability. Kai |
| Topic | Author | Date |
| Voltage regulator heat | 01/01/70 00:00 | |
| RE: Voltage regulator heat | 01/01/70 00:00 | |
| RE: Voltage regulator heat | 01/01/70 00:00 | |
| RE: Switchers - dirty ? | 01/01/70 00:00 | |
| RE: Switchers - dirty ? | 01/01/70 00:00 | |
| RE: Switchers - dirty ? | 01/01/70 00:00 | |
| RE: Switchers - flood | 01/01/70 00:00 | |
| RE: Switchers - dirty ?- Erik | 01/01/70 00:00 | |
| RE: Switchers - dirty ? Yes&No | 01/01/70 00:00 | |
RE: Switchers - dirty ? Yes&No | 01/01/70 00:00 | |
| Too Hot! | 01/01/70 00:00 | |
| RE: Too Hot! | 01/01/70 00:00 | |
| RE: Too Hot! | 01/01/70 00:00 | |
| RE: Too Hot! | 01/01/70 00:00 | |
| RE: Voltage regulator heat | 01/01/70 00:00 | |
| Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 | |
| RE: Much too little headroom! | 01/01/70 00:00 |