PRELIMINARY
CYW4339
■ 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.
2.5 Power-Off Shutdown
The CYW4339 provides a low-power shutdown feature that allows the device to be turned off while the host, and any other devices
in the system, remain operational. When the CYW4339 is not needed in the system, VDDIO_RF and VDDC are shut down while
VDDIO remains powered. This allows the CYW4339 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, the provided VDDIO remains applied to the CYW4339, all outputs are tristated, and most input
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 CYW4339 to be fully integrated in an embedded device and
take full advantage of the lowest power-savings modes.
When the CYW4339 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.
2.6 Power-Up/Power-Down/Reset Circuits
The CYW4339 has two signals (see Table 1) that enable or disable the Bluetooth and WLAN circuits and the internal regulator blocks,
allowing the host to control power consumption. For timing diagrams of these signals and the required power-up sequences, see
Power-Up Sequence and Timing on page 119.
Table 1. Power-Up/Power-Down/Reset Control Signals
Signal
Description
WL_REG_ON
This signal is used by the PMU (with BT_REG_ON) to power up the WLAN section. It is also OR-gated with the BT_REG_ON
input to control the internal CYW4339 regulators. When this pin is high, the regulators are enabled and the WLAN section is
out of reset. When this pin is low, the WLAN section is in reset. If BT_REG_ON and WL_REG_ON are both low, the regulators
are disabled. This pin has an internal 200 k pull-down resistor that is enabled by default. It can be disabled through
programming.
BT_REG_ON
This signal is used by the PMU (with WL_REG_ON) to decide whether or not to power down the internal CYW4339 regulators.
If BT_REG_ON and WL_REG_ON are low, the regulators will be disabled. This pin has an internal 200 k pull-down resistor
that is enabled by default. It can be disabled through programming.
Document No. 002-14784 Rev. *H
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