Data Sheet

LC840PA
Datasheet
https://www.lairdconnect.com
37
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Table 24: Optional external 32.768 kHz crystal specification
Optional external 32.768kHz crystal
Min
Typ
Max
Crystal Frequency
-
32.768 kHz
-
Frequency tolerance requirement of Bluetooth LE stack
-
-
±500 ppm
Load Capacitance
-
-
12.5 pF
Shunt Capacitance
-
-
2 pF
Equivalent series resistance
-
-
100 kOhm
Drive level
-
-
1 uW
Input capacitance on XL1 and XL2 pads
-
4 pF
-
Run current for 32.768 kHz crystal based oscillator
-
0.23 uA
-
Start-up time for 32.768 kHz crystal based oscillator
-
0.25 seconds
-
Peak to peak amplitude for external low swing clock input signal
must not be outside supply rails
200 mV
-
1000 mV
Be sure to tune the load capacitors on the board design to optimize frequency accuracy (at room temperature) so it matches that
of the same crystal standalone, Drive Level (so crystal operated within safe limits) and oscillation margin (R
neg
is at least 3 to 5
times ESR) over the operating temperature range.
5.17 453-00087 On-board PCB Antenna Characteristics
The 453-00087 on-board PCB trace monopole antenna radiated performance depends on the host PCB layout.
The BL654PA development board was used for LC840PA development and the 453-00087 PCB antenna performance
evaluation. To obtain similar performance, follow guidelines in section PCB Layout on Host PCB for the 453-00087 to allow the
on-board PCB antenna to radiate and reduce proximity effects due to nearby host PCB GND copper or metal covers.
Unit in dBi @2440MHz
XY-plane
XZ-plane
YZ-plane
Peak
Avg
Peak
Avg
Peak
Avg
453-00087 PCB trace antenna
-1.05
-5.13
-1.51
-7.43
-2.49
-5.63
◆XY-plane ◆XZ-plane ◆YZ-plane