BCM4339XKWBGT Datasheet, PDF (35/183 Pages) Cypress Semiconductor – Single-Chip 5G WiFi IEEE 802.11ac MAC/Baseband/Radio with Integrated Bluetooth 4.1 and FM Receiver

BCM4339 Preliminary Data Sheet
External 32.768 kHz Low-Power Oscillator
External 32.768 kHz Low-Power Oscillator
The BCM4339 uses a secondary low-frequency clock for low-power-mode timing. Either the internal low-
precision LPO or an external 32.768 kHz precision oscillator is required. The internal LPO frequency range is
approximately 33 kHz ± 30% over process, voltage, and temperature, which is adequate for some applications.
However, one trade-off caused by this wide LPO tolerance is a small current consumption increase during power
save mode that is incurred by the need to wake up earlier to avoid missing beacons.
Whenever possible, the preferred approach is to use a precision external 32.768 kHz clock that meets the
requirements listed in Table 3.
Table 3: External 32.768 kHz Sleep Clock Specifications
Parameter
Nominal input frequency
Frequency accuracy
Duty cycle
Input signal amplitude
Signal type
Input impedance^a
Clock jitter (during initial start-up)
a. When power is applied or switched off.
LPO Clock
32.768
±200
30–70
200–1800
Square-wave or sine-wave
>100k
<5
<10,000
Units
kHz
ppm
%
mV, p-p
–
Ω
pF
ppm
Broadcom^®
November 17, 2014 • 4339-DS106-R
Page 34