Workings of a Power Sequencer
Ask any embedded engineer, how much attention does he pay to the powering up of a printed board circuit? Not much is the likely answer. But you have to pay attention because if you don’t, you are inviting problems. It is especially true for manufacturers of custom power supplies.
The problems will not be prominent until you begin volume production and put the tolerance of the designs and devices to test. But this is quite late in the process at which point it will become very expensive.
If you find errors at this late stage, you have no choice but to modify the PCB layout, make design alterations and other anomalies.
We have now come to a stage where we are able to incorporate multiple functional blocks into a single integrated circuit. As a result, you have to supply the blocks with multiple (equal or different) voltage supplies.
As we see more system-on-a-chip integrated ICs, the need for power management and supply sequencing will also go up.
FPGA vendors have also started to specify power sequencing needs now. If you follow the power sequence recommended by the manufacturer, you can actually avoid excessive current draw when you are starting up the device, preventing damage to the printed board. This is a good lesson for custom power supply makers.