BCM89071A1CUBXGT Datasheet, PDF (37/69 Pages) Cypress Semiconductor – Single-Chip Automotive Grade Bluetooth Transceiver and Baseband Processor

BCM89071 Data Sheet
External Frequency Reference
External Frequency Reference
An external frequency reference generated by a TCXO signal may be directly connected to the crystal input pin
on the BCM89071, as shown in Figure 7. The external frequency reference input is designed to not change
loading on the TCXO when the BCM89071 is powered up or powered down.
When using the BCM89071 with the TXCO OR gate option, GPIO 6 must be driven active high or active low.
Excessive leakage current results if GPIO6 is allowed to float.
Figure 7: Recommended TCXO Connection
TCXO
10–1000 pF*
No Connection
* Recommended value is 100 pF.
Higher values produce a longer startup time.
Lower values have greater isolation.
Larger values help small signal swings.
XIN
XOUT
TCXO Clock Request Support
If the application utilizes an external TCXO as a clock reference, the BCM89071 provides a clock request output
to allow the system to power off the TCXO when not in use. The BCM89071 supports a TCXO OR function that
allows a clock request in the system to be combined with the BCM89071 clock request output, without requiring
an extra component on the board.
Clock Request Output
The CLK_REQ signal on the GPIO_5 lead is asserted whenever the BCM89071 is in the Awake state. It is
deasserted when in Sleep state. When the BCM89071 is sleeping, it uses an LPO clock (external or internal) as
the timing reference. In the BCM89071, the clock request output (CLK_REQ) is configured as active high. If the
clock request feature is not desired, GPIO_5 can be configured for other functions.
Broadcom^®
April 16, 2015 • 89071-DS106-R
Baseband Transceiver and Baseband Processor
Page 36