BCM4354 datasheet(13/165 Pages) CYPRESS

13 / 165 page

Document Number: 002-14809 Rev. *J

Page 13 of 165

CYW4354

2.5 Power-Off Shutdown

The CYW4354 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 CYW4354 is not needed in the system, VDDIO_RF and VDDC are shut down while

VDDIO remains powered. This allows the CYW4354 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 CYW4354, 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 CYW4354 to be fully integrated in an embedded device and

take full advantage of the lowest power-savings modes.

When the CYW4354 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 CYW4354 has two signals (see Table 3) 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 153.

Table 3. 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 CYW4354 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 kΩ 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 CYW4354

regulators. If BT_REG_ON and WL_REG_ON are low, the regulators will be disabled. This pin has an internal

200 kΩ pull-down resistor that is enabled by default. It can be disabled through programming.

BCM4354 Datasheet(PDF) 13 Page - Cypress Semiconductor