What Is Power-Down Sequencing and why it is as Important as Power-Up?

Semiconductor Integrated Circuits (ICs)
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For many FPGA designs, power-down sequencing is just as important as power-up sequencing.

During shutdown, large bulk electrolytic capacitors on high-power rails can remain charged and store significant amounts of energy to harm components that aren’t properly protected.

With this, FPGA vendors like Altera provide their recommended power-down sequencing to mitigate the risk.6 In general, the recommended power-down sequencing is the reverse order of the power-up sequence.

Power-down sequencing requires careful control of stored energy to ensure predictable shutdown timing and to prevent damage to devices.

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Figure 5. Altera Arria 10 power-down sequencing group order.6

In applications like the Altera Arria 10, power rails must fall below 10% of their nominal voltage before the next rail group powers down. To support this requirement, the ADM6840 provides factory-trimmed power-down threshold options (VSEQOFF_TH) of 0.333 V, 0.167 V, and 0.050 , enabling accurate and controlled power-down sequencing.

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Figure 6. Power-down threshold architecture of the ADM6840

In comparison to other sequencers, the power-down threshold can be set through external component programming, such as with resistors or capacitors, which can introduce variation in the actual power-down threshold due to resistor tolerance and PCB leakage.

Related Topics:
Reliable Power Up and Power Down Sequence
Why Do FPGAs Need Multirail Power Sequencing?
What Is the Difference Between a Power Sequencer and a Voltage Supervisor?
Why an 8-Channel Power Sequencer is Better Than Multiple 4-Channel Devices?
How does the ADM6840 help ensure consistent power-up timing in FPGA?

Applicable Part Numbers

|DigiKey Part Number|Manufacturer Part Number|

|—|—|

|MAX16050ETI+TTR-ND,MAX16050ETI+TCT-ND,MAX16050ETI+TDKR-ND|MAX16050ETI+T|

|MAX16050ETI±ND|MAX16050ETI+|

|175-MAX16165ATPH+TTR-ND,175-MAX16165ATPH+TCT-ND,175-MAX16165ATPH+TDKR-ND|MAX16165ATPH+T|

|505-MAX16165ATPH±ND|MAX16165ATPH+|

|MAX16025TE±ND|MAX16025TE+|

|MAX16025TE+TTR-ND,MAX16025TE+TCT-ND,MAX16025TE+TDKR-ND|MAX16025TE+T|

|175-ADM6840EAWABFH+TTR-ND, 175-ADM6840EAWABFH+TCT-ND, 175-ADM6840EAWABFH+TDKR-ND|ADM6840EAWABFH+T|