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External Frequency Reference

BCM4354 Data Sheet

BROADCOM CONFIDENTIAL

Broadcom®

October 15, 2014 • 4354-DS109-R

Page 28

External Frequency Reference

For operation in SDIO and HSIC modes only, an alternative to a crystal (an external precision frequency

reference) can be used. The recommended default frequency is 52 MHz ±10 ppm, and it must meet the phase

noise requirements listed in Table 3.

If used, the external clock should be connected to the WRF_XTAL_IN pin through an external 1000 pF coupling

capacitor, as shown in Figure 5. The internal clock buffer connected to this pin will be turned OFF when the

BCM4354 goes into sleep mode. When the clock buffer turns ON and OFF there will be a small impedance

variation. Power must be supplied to the WRF_XTAL_VDD1P5 pin.

Figure 5: Recommended Circuit to Use with an External Reference Clock

Table 3: Crystal Oscillator and External Clock —Requirements and Performance

Parameter

Conditions/Notes

Crystala

External Frequency

Referenceb,c

Min.

Typ.

Max.

Min.

Typ.

Max.

Units

Frequency

2.4G and 5G bands: IEEE

802.11ac operation, SDIO3.0,

HSIC and PCIe WLAN

interfaces

37.4

–

MHz

2.4G and 5G bands, IEEE

802.11ac operation, PCIe

interface alternative frequency

–40

––––MHz

5G band: IEEE 802.11n

operation only

–

MHz

2.4G band: IEEE 802.11n

operation, and both bands

legacy 802.11a/b/g operation

only

Ranges between 19 MHz and 52 MHzd,e

Frequency tolerance

over the lifetime of the

equipment, including

temperaturef

Without trimming

–20

–

–20

–

ppm

Crystal load

capacitance

–

––––pF

ESR

–

––

–––

Ω

Reference

Clock

1000 pF

WRF_XTAL_IN

WRF_XTAL_OUT

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