CC2533_11 Datasheet, PDF (25/34 Pages) Texas Instruments – An Optimized System-on-Chip Solution for 2.4-GHz IEEE 802.15.4 Remote Control Applications

CC2533
www.ti.com
SWRS087 – JUNE 2010
Table 5. Overview of External Components (Excluding Supply Decoupling
Capacitors) (continued)
Component
L261
R301
Description
Part of the RF matching network
Resistor used for internal biasing
Value
2 nH
56 kΩ
Input/Output Matching
When using an unbalanced antenna such as a monopole, a balun should be used to optimize performance. The
balun can be implemented using low-cost discrete inductors and capacitors. The recommended balun shown
consists of C262, L261, C252, and L252.
If a balanced antenna such as a folded dipole is used, the balun can be omitted.
Crystal
An external 32-MHz crystal, XTAL1, with two loading capacitors (C221 and C231) is used for the 32-MHz crystal
oscillator. See the 32-MHz Crystal Oscillator section for details. The load capacitance seen by the 32-MHz
crystal is given by:
C_L =
1
1
1
+ C_parasitic
C₂₂₁ ⁺ C₂₃₁
(1)
XTAL2 is an optional 32.768-kHz crystal, with two loading capacitors (C321 and C331) used for the 32.768-kHz
crystal oscillator. The 32.768-kHz crystal oscillator is used in applications where both very low sleep-current
consumption and accurate wake-up times are needed. The load capacitance seen by the 32.768-kHz crystal is
given by:
C_L = ₁ ¹ ₁ + C_parasitic
C₃₂₁ ⁺ C₃₃₁
(2)
A series resistor may be used to comply with the ESR requirement.
On-Chip 1.8-V Voltage-Regulator Decoupling
The 1.8-V on-chip voltage regulator supplies the 1.8-V digital logic. This regulator requires a decoupling capacitor
(C401) for stable operation.
Power-Supply Decoupling and Filtering
Proper power-supply decoupling must be used for optimum performance. The placement and size of the
decoupling capacitors and the power supply filtering are very important to achieve the best performance in an
application. TI provides a compact reference design that should be followed very closely.
REFERENCES
1. IEEE Std. 802.15.4-2006: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications
for Low-Rate Wireless Personal Area Networks (LR-WPANs)
http://standards.ieee.org/getieee802/download/802.15.4-2006.pdf
2. CC253x User's Guide – CC253x System-on-Chip Solution for 2.4 GHz IEEE 802.15.4 and ZigBee
Applications (SWRU191)
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