Other Parts Discussed in Thread: LP2954, , TPS7A47
Hello
I need to drop my 24V input voltage to 24V - 0V5 - Vdo, i.e. ideally around 23V, to mitigate line voltage droops due to varying loads, and provide a necessarily stable output voltage. The load current is a constant 250mA. I want to minimize the voltage drop for both thermal and operational reasons, and this led me to search for an LDO regulator which meets these requirements. I was immediately surprised at how few suitable regs there are which meet the spec (although realizing that most LDO applications are low voltage): in the TI roster I could find only the LP2954, which I knew would be running right on the beam ends. On testing one on a representative area of bare 1oz PCB material, with only the GND pin connected to the copper area, at > 230mA current it rapidly went into thermal limiting. The LM2941 in TO263 looked more appealing, but the stated maximum output voltage is 20V, so no go. Micrel/Microchip offer the MIC2941A which does support >20V Vo. I have tested this and it appears to work very well. Now I know that TI does not publish absolute maximum ratings just for kicks and giggles!, but what is the exact reason for the the 20V limit and what would be the likely consequences of exceeding it by 3V?