BCM4356 datasheet(13/155 Pages) CYPRESS

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Document Number: 002-15053 Rev. *D

Page 13 of 155

ADVANCE

CYW4356

2.5 Power-Off Shutdown

The CYW4356 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 CYW4356 is not needed in the system, VDDIO_RF and VDDC are shut down while VBAT

and VDDIO remain powered. This allows the CYW4356 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 CYW4356, 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 CYW4356 to be fully integrated in an embedded device and

take full advantage of the lowest power-savings modes.

When the CYW4356 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 CYW4356 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

Section 21. Power-Up Sequence and Timing.

2.7 Wireless Charging

The CYW4356 combo IC is designed for paired operation with the BCM59350 wireless power transfer front-end chip. Working

together, the two chips form a power receiver unit (PRU) that is compliant with the Alliance for Wireless Power specification (A4WP).

High-level functional block diagram for wireless charging is provided in Figure 4. The power transmit unit (PTU) resides in the charging

pad while the power receive unit is integrated into the mobile device. The charging process begins as the mobile device is placed onto

the charging pad. The power is transferred from PTU to PRU through the TX and RX coils by means of magnetic induction. The

Bluetooth control link handles communications, i.e., handshaking, between them. PTU is a BLE client, which gets performance data

from the BLE server (PRU) in order to adapt its power to the mobile's need.

Figure 4. High-Level Functional Block Diagram for Wireless Charging

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 CYW4356 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

CYW4356 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.

Power Receiver Unit (PRU)

BCM59350

WPT

Front End

CYW4356

Bluetooth

Low‐Energy (BLE)

WPT

Rx Coil

Resonator

System control i/f

WPT Control

Power Transmit Unit (PTU)

WPT

Transmit

BLE

WPT

Tx Coil

Resonator

Wireless Power

Transfer

USB

Power

Switch

VBUS Detect

Application

Processor

Bluetooth Control

Link

PMU

WPT 1.8/3.3

VBUCK

Charger

Battery

GPIO

System power

BT Antenna

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