CC256X Datasheet, PDF (16/51 Pages) Texas Instruments – Bluetooth® Smart Ready Controller

CC256x
SWRS121C – JULY 2012 – REVISED OCTOBER 2013
V_IN [V]
1V
www.ti.com
VPP = 0.4 – 1.6 Vp-p
0.8
0.2
0
t
–0.2
–0.8
SWRS097-022
Figure 3-8. External Fast Clock (Sine Wave, AC-Coupled)
In cases where the input amplitude is greater than 1.6 Vp-p, the amplitude can be reduced to within limits.
Using a small series capacitor forms a voltage divider with the internal input capacitance of approximately
2 pF to provide the required amplitude at the device input.
3.4.2.3 Fast Clock Using External Crystal
The CC256x device incorporates an internal crystal oscillator buffer to support a crystal-based fast-clock
scheme. The supported crystal frequency is 26 MHz.
The frequency accuracy of the fast clock source must not exceed ±20 ppm (including the accuracy of the
capacitors, as specified in the Bluetooth specification).
Figure 3-9 shows the recommended fast-clock circuitry.
CC256x
XTALM
C1
Oscillator
buffer
XTALP
XTAL
C2
SWRS098-003
Figure 3-9. Fast-Clock Crystal Circuit
Table 3-3 lists component values for the fast-clock crystal circuit.
Table 3-3. Fast-Clock Crystal Circuit Component
Values
FREQ (MHz)
26
C1 (pF)⁽¹⁾
12
C2 (pF)⁽¹⁾
12
(1) To achieve the required accuracy, values for C1 and C2 must be
taken from the crystal manufacturer's data sheet and layout
considerations.
16
Detailed Description
Submit Documentation Feedback
Copyright © 2012–2013, Texas Instruments Incorporated