CYW20702
3.6.4 Backdrive Protection
The CYW20702 provides a backdrive protection feature that allows the device to be turned off while the host and other devices in the
system remain operational. When the device is not needed in the system, VDD_RF and VDDC are shut down and VDDO remains
powered. This allows the device to be effectively off, while keeping the I/O pins powered so that they do not draw extra current from
other devices connected to the I/O.
Note: VDD_RF collectively refers to the VDDTF, VDDIF, VDDLNA, VDDPX, and VDDRF RF power supplies.
Note: Never apply voltage to I/O pins if VDDO is not applied.
During the low power shutdown state and as long as VDDO remains applied to the device, all outputs are tristated and all digital and
analog clocks are disabled. Input voltages must remain within the limits defined for normal operation. This is done to either prevent
current draw and back loading on digital signals in the system. It also enables the device to be fully integrated in an embedded device
and take full advantage of the lowest power savings modes. If VDDC is powered up externally (not connected to VREG), VDDC
requires 750K ohms to ground during low-power shutdown. If VDDC is powered up by VREG, VDDC does not require 750K ohms to
ground because the internal main LDO has about 750 K ohms to ground when turned off.
Several signals, including the frequency reference input (XTAL_IN) and external LPO input (LPO_IN), are designed to be high-
impedance inputs that will not load down the driving signal, even if VDDO power is not applied to the chip. The other signals with back
drive prevention are RST_N, COEX_IN, PCM_SYNC, PCM_CLK, PCM_OUT, PCM_IN, UART_RTS_N, UART_CTS_N, UART_RXD,
UART_TXD, GPIO_0, GPIO_1, GPIO_4, GPIO_7, HUSB_DP, HUSB_DN, CFG_SEL, and OTP_DIS.
All other I/O signals must remain at VSS until VDDO is applied. Failing to do this can result in unreliable startup behavior.
When powered on, using REG_EN is the same as applying power to the CYW20702. The device does not have information about its
state before being powered-down.
3.7 Adaptive Frequency Hopping
The CYW20702 supports host channel classification and dynamic channel classification Adaptive Frequency Hopping (AFH)
schemes, as defined in the Bluetooth specification.
Host channel classification enables the host to set a predefined hopping map for the device to follow.
If dynamic channel classification is enabled, the device gathers link quality statistics on a channel-by-channel basis to facilitate channel
assessment and channel map selection. To provide a more accurate frequency hop map, link quality is determined using both RF and
baseband signal processing.
3.8 Collaborative Coexistence
The CYW20702 provides extensions and collaborative coexistence to the standard Bluetooth AFH for direct communication with
WLAN devices. Collaborative coexistence enables WLAN and Bluetooth to operate simultaneously in a single device. The device
supports industry-standard coexistence signaling, including 802.15.2, and supports Broadcom and third-party WLAN solutions.
Using a multitiered prioritization approach, relative priorities between data types and applications can be set. This approach maximizes
the performance-WLAN data throughput vs. voice quality vs. link performance.
A PA shutdown pin is available to allow full external control of the RF output for other types of coexistence, such as WIMAX.
Document Number: 002-14773 Rev. *L
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