BCM4390DKWBGT Datasheet, PDF (16/78 Pages) Cypress Semiconductor – WICED™ Wi-Fi IEEE 802.11 b/g/n SoC with Embedded Application Processor

BCM4390 Advance Data Sheet
Power-Off Shutdown
Resource requests may come from several sources: clock requests from cores, the minimum resources defined
in the ResourceMin register, and the resources requested by any active resource request timers. The PMU
sequencer maps clock requests into a set of resources required to produce the requested clocks.
Each resource is in one of four states: enabled, disabled, transition_on, and transition_off and has a timer that
contains 0 when the resource is enabled or disabled and a non-zero value in the transition states. The timer is
loaded with the time_on or time_off value of the resource when the PMU determines that the resource must
be enabled or disabled. That timer decrements on each 32.768 kHz PMU clock. When it reaches 0, the state
changes from transition_off to disabled or transition_on to enabled. If the time_on value is 0, the resource can
go immediately from disabled to enabled. Similarly, a time_off value of 0 indicates that the resource can go
immediately from enabled to disabled. The terms enable sequence and disable sequence refer to either the
immediate transition or the timer load-decrement sequence.
During each clock cycle, the PMU sequencer performs the following actions:
• Computes the required resource set based on requests and the resource dependency table.
• Decrements all timers whose values are non zero. If a timer reaches 0, the PMU clears the
ResourcePending bit for the resource and inverts the ResourceState bit.
• Compares the request with the current resource status and determines which resources must be enabled
or disabled.
• Initiates a disable sequence for each resource that is enabled, no longer being requested, and has no
powered up dependents.
• Initiates an enable sequence for each resource that is disabled, is being requested, and has all of its
dependencies enabled.
Power-Off Shutdown
The BCM4390 provides a low-power shutdown feature that allows the device to be turned off. When the
BCM4390 is not needed in the system, VDDIO_RF and VDDC are shut down while VDDIO remains powered. This
allows the BCM4390 to be effectively off while keeping the I/O pins powered so that they do not draw extra
current from any other devices connected to the I/O.
During a low-power shut-down state, provided VDDIO remains applied to the BCM4390, all outputs are
tristated, and most inputs signals are disabled. Input voltages must remain within the limits defined for normal
operation. This is done to prevent current paths or create loading on any digital signals in the system, and
enables the BCM4390 to be fully integrated in an embedded device and take full advantage of the lowest
power-savings modes.
When the BCM4390 is powered on from this state, it is the same as a normal power-up and the device does
not retain any information about its state from before it was powered down.
BROADCOM ®
February 5, 2014 • 4390-DS103-R
WICED Wi-Fi IEEE 802.11 SoC w/Embedded App Processor
Page 15
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