Guru
Joined: 21/06/2018
Location: AustraliaPosts: 1190
| Posted: 05:24am 09 Jun 2024 |
I found an interesting part in my stock last night it is a weird 7805 family member going under the part number KA78R05 I only have about 480 left. The part is marked as obsolete not too distant from how I feel lately....
KA78R12CTU-D.pdf
After a bit of a search on Digikey I found KA278R05 which is not obsolete and is a pin equivalent drop in, likewise at LCSC you can drive away with a KIA78R05 for 38c one off pricing.
The TO220 plastic pack part has 4 Legs, in, out, ground and output enable. Max 35Vin Iout 1A. I tested one on the bench last night, it appears to have a 400uA source to the enable pin, if left open, the device defaults to a 5V output. However if you place a 10V zener in series with the 12V supply connected to the enable pin along with a 4K7 pulldown to ground it appears to work really well, as the 12V decays to under 10V the device truncates the 5V output. There is no soft stop or slow decay, maybe a good part for Rev8.
Does not hurt to have rail supervisors fitted and a crystal clean well behaved 5V. I think I will send out some of these with the circuit boards for everyone so they have the option to use them instead of the 12V - 5V sawtooth generators that seem to abound.