Integration Manual

ANNA-B4 series - System integration manual
UBX-21000517 - R03 Contents Page 15 of 76
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Figure 4 shows the low-power clock components used on the EVK-ANNA-B4 evaluation board.
Figure 4: Connecting ANNA-B412 to an external crystal oscillator
Table 6: Components used on the EVK-ANNA-B4 EVK evaluation board
External clock source, TCXO
An external clock can be supplied from various sources, including a temperature-compensated crystal
oscillator (TCXO) or host CPU. The clock signal can be either low-swing or full-swing.
The electrical parameters for a suitable low-swing clock are described in Table 7.
Pin name
Parameter
Min
Typ
Max
Unit
Remarks
XL1
Input characteristic:
Peak to Peak amplitude
200
1000
mV
Input signal must not swing outside
supply rails.
XL2
-
-
-
-
Connect to GND
Table 7: Electrical parameters for a low-swing clock
The electrical parameters for a suitable full-swing clock are described in Table 8.
Pin name
Parameter
Min
Typ
Max
Unit
Remarks
XL1
Input characteristic:
Low-level input
0
0.3*VCC
V
Input characteristic:
high-level input
0.7*VCC
VCC
V
XL2
-
-
-
-
-
Connect to GND or leave unconnected
Table 8: Electrical parameters for a full-swing clock
Selecting clock source
☞ With reference to the electrical parameters described in Table 8, note that the choice of clock
source is invariably a tradeoff between the current consumption and BOM count of the application
design. When using an internal oscillator, the expected increase in current consumption is
dependent on the software settings and the surrounding application environment.
Component
Value
Note
Crystal oscillator
32.768 kHz (20 ppm)
EPSON FC-12M used on ANNA-B4 EVK
Capacitors
22 pF