CYW4343X
2.3 WLAN Power Management
The CYW4343X has been designed with the stringent power consumption requirements of mobile devices in mind. All areas of the
chip design are optimized to minimize power consumption. Silicon processes and cell libraries were chosen to reduce leakage cur-
rent and supply voltages. Additionally, the CYW4343X integrated RAM is a high volatile memory with dynamic clock control. The
dominant supply current consumed by the RAM is leakage current only. Additionally, the CYW4343X includes an advanced WLAN
power management unit (PMU) sequencer. The PMU sequencer provides significant power savings by putting the CYW4343X into
various power management states appropriate to the operating environment and the activities that are being performed. The power
management unit enables and disables internal regulators, switches, and other blocks based on a computation of the required
resources and a table that describes the relationship between resources and the time needed to enable and disable them. Power-up
sequences are fully programmable. Configurable, free-running counters (running at the 32.768 kHz LPO clock) in the PMU
sequencer are used to turn on/turn off individual regulators and power switches. Clock speeds are dynamically changed (or gated
altogether) for the current mode. Slower clock speeds are used wherever possible.
The CYW4343X WLAN power states are described as follows:
■
Active mode— All WLAN blocks in the CYW4343X are powered up and fully functional with active carrier sensing and
frame transmission and receiving. All required regulators are enabled and put in the most efficient mode based on the load
current. Clock speeds are dynamically adjusted by the PMU sequencer.
■
Doze mode—The radio, analog domains, and most of the linear regulators are powered down. The rest of the CYW4343X
remains powered up in an IDLE state. All main clocks (PLL, crystal oscillator) are shut down to reduce active power to the
minimum. The 32.768 kHz LPO clock is available only for the PMU sequencer. This condition is necessary to allow the
PMU sequencer to wake up the chip and transition to Active mode. In Doze mode, the primary power consumed is due to
leakage current.
■
■
Deep-sleep mode—Most of the chip, including analog and digital domains, and most of the regulators are powered off.
Logic states in the digital core are saved and preserved to retention memory in the always-on domain before the digital core
is powered off. To avoid lengthy hardware reinitialization, the logic states in the digital core are restored to their pre-deep-
sleep settings when a wake-up event is triggered by an external interrupt, a host resume through the SDIO bus, or by the
PMU timers.
Power-down mode—The CYW4343X is effectively powered off by shutting down all internal regulators. The chip is brought
out of this mode by external logic re-enabling the internal regulators.
2.4 PMU Sequencing
The PMU sequencer is used to minimize system power consumption. It enables and disables various system resources based on a
computation of required resources and a table that describes the relationship between resources and the time required to enable
and disable them.
Resource requests can derive 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 the following four states:
■
■
■
■
enabled
disabled
transition_on
transition_off
The timer value is 0 when the resource is enabled or disabled and nonzero during state transition. 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 dec-
rements 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 transition immediately from disabled to enabled. Similarly, a time_off value of 0
indicates that the resource can transition 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 nonzero. 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 depen-
dents.
Document No. 002-14797 Rev. *H
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