PRELIMINARY
CYW20710
3.6 Power Management Unit
The Power Management Unit (PMU) provides power management features that can be invoked through power management registers
or packet handling in the baseband core. This section contains descriptions of the PMU features.
3.6.1 RF Power Management
The BBC generates power-down control signals for the transmit path, receive path, PLL, and power amplifier to the 2.4 GHz trans-
ceiver. The transceiver then processes the power-down functions, accordingly.
3.6.2 Host Controller Power Management
The host can place the device in a sleep state, in which all nonessential blocks are powered off and all nonessential clocks are
disabled. Power to the digital core is maintained so that the state of the registers and RAM is not lost. In addition, the LPO clock is
applied to the internal sleep controller so that the chip can wake automatically at a specified time or based on signaling from the host.
The goal is to limit the current consumption to a minimum, while maintaining the ability to wake up and resume a connection with
minimal latency.
If a scan or sniff session is enabled while the device is in Sleep mode, the device automatically will wake up for the scan/sniff event,
then go back to sleep when the event is done. In this case, the device uses its internal LPO-based timers to trigger the periodic wake
up. While in Sleep mode, the transports are idle. However, the host can signal the device to wake up at any time. If signaled to wake
up while a scan or sniff session is in progress, the session continues but the device will not sleep between scan/sniff events. Once
Sleep mode is enabled, the wake signaling mechanism can also be thought of as a sleep signaling mechanism, since removing the
wake status will often cause the device to sleep.
In addition to a Bluetooth device wake signaling mechanism, there is a host wake signaling mechanism. This feature provides a way
for the Bluetooth device to wake up a host that is in a reduced power state.
There are two mechanisms for the device and the host to signal wake status to each other:
Bluetooth WAKE (BT_WAKE) and Host WAKE (and
HOST_WAKE) signaling
The BT_WAKE pin (GPIO_0) allows the host to wake the BT device, and
HOST_WAKE (GPIO_1) is an output that allows the BT device to wake the
host.
In-band UART signaling
The CTS and RTS signals of the UART interface are used for BT wake
(CTS) and Host wake (RTS) functions in addition to their normal function on
the UART interface. Note that this applies for both H4 and H5 protocols.
When running in SPI mode, the CYW20710 has a mode where it enters Sleep mode when there is no activity on the SPI interface for
a specified (programmable) amount of time. Idle mode is detected when the SPI_CSN is left deasserted. Whether to sleep on an idle
interface and the amount of time to wait before entering Sleep mode can be programed by the host. Once the CYW20710 enters
sleep, the host can wake it by asserting SPI_CSN. If the host decides to sleep, the CYW20710 will wake up the host by asserting
SPI_INT when it has data for it.
Note: Successful operation of the power management handshaking signals requires coordinated support between the device
firmware and the host software.
Document No. 002-14804 Rev. *H
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CYPRESS [ CYPRESS ]
