Article Details

ID: 5769
Case Type: faq
Category: Architecture
Related To: Power
Family: iCE40 UltraPlus

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Can an iCE40 UltraPlus device be put into a sleep or standby mode to save power and then be woken to return to normal operation mode?

iCE40 UltraPlus devices do not have a Power Management Unit like the ones in Crosslink devices. But technically, a form of "Sleep State" can be created by powering down some of the hard blocks through the RTL such as the internal oscillators and SPRAM. Another approach is to utilize Warm boot primitive and switch between 2 configuration patterns: 1 for the normal pattern which is the original design and the other one is a blank pattern that is described below: 

1.) It does not use any EBR's (In the erased state the iCE device has EBR's active). A design that does not use EBR's puts the EBR's in off state (Lower leakage).

2.) Standby, sleep or power off state upon instatiation can be chosen when using SPRAM.

3.) Tri-state all IO's so nothing toggles except for the required IOs for the warm boot primitive.

4.) Instantiate the Oscillators and power them down.

5.) Instantiate the warm boot primitive to change back to the functional pattern.

6.) It should not have any other logic.

Also, follow these general guidelines in the overall design to minimize consumption:

1.) Apply correct Power-up sequencing per the documentation (this limits leakage during boot)

2.) Use standby features of internal blocks (HSOSC, LFOSC, PLL, SPRAM) to minimize static consumption.

3.) Gate IOs via \u2018Latch' to decouple internal logic from external switching \u2013 minimizes dynamic consumption.

4.) Switch to LFOSC for any internal watchdog circuit (i.e. to wake on event or timer).

5.) Where possible ensure pin connections to the device don't conflict with default IO state (to minimize leakage in the blank and un-configured state).

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