SWRS096D December   2012  – April 2015 CC2538


  1. 1Device Overview
    1. 1.1 Features
    2. 1.2 Applications
    3. 1.3 Description
    4. 1.4 Functional Block Diagram
  2. 2Revision History
  3. 3Device Comparison
  4. 4Terminal Configuration and Functions
    1. 4.1 Signal Descriptions
  5. 5Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Electrical Characteristics
    5. 5.5  General Characteristics
    6. 5.6  RF Receive Section
    7. 5.7  RF Transmit Section
    8. 5.8  32-MHz Crystal Oscillator
    9. 5.9  32.768-kHz Crystal Oscillator
    10. 5.10 32-kHz RC Oscillator
    11. 5.11 16-MHz RC Oscillator
    12. 5.12 RSSI/CCA Characteristics
    13. 5.13 FREQEST Characteristics
    14. 5.14 Frequency Synthesizer Characteristics
    15. 5.15 Analog Temperature Sensor
    16. 5.16 ADC Characteristics
    17. 5.17 Control Input AC Characteristics
    18. 5.18 DC Characteristics
    19. 5.19 USB Interface DC Characteristics
    20. 5.20 Thermal Resistance Characteristics for RTQ Package
  6. 6Applications, Implementation, and Layout
    1. 6.1 Input, Output Matching
    2. 6.2 Crystal
    3. 6.3 On-Chip 1.8-V Voltage-Regulator Decoupling
    4. 6.4 Power-Supply Decoupling and Filtering
    5. 6.5 References
  7. 7Device and Documentation Support
    1. 7.1 Device Support
      1. 7.1.1 Development Support
      2. 7.1.2 Device Nomenclature
    2. 7.2 Documentation Support
      1. 7.2.1 Community Resources
    3. 7.3 Additional Information
      1. 7.3.1 Texas Instruments Low-Power RF Web Site
      2. 7.3.2 Low-Power RF Online Community
      3. 7.3.3 Texas Instruments Low-Power RF Developer Network
      4. 7.3.4 Low-Power RF eNewsletter
    4. 7.4 Trademarks
    5. 7.5 Electrostatic Discharge Caution
    6. 7.6 Export Control Notice
    7. 7.7 Glossary
  8. 8Mechanical Packaging and Orderable Information
    1. 8.1 Packaging Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6 Applications, Implementation, and Layout


Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

Few external components are required for the operation of the CC2538xFnn. Figure 6-1 is a typical application circuit. For a complete USB reference design, see the CC2538xFnn product page on www.ti.com. Table 6-1 lists typical values and descriptions of external components. The USB_P and USB_N pins require series resistors R21 and R31 for impedance matching, and the D+ line must have a pullup resistor, R32. The series resistors should match the 90-Ω ±15% characteristic impedance of the USB bus. Notice that the pullup resistor and DVDD_USB require connection to a voltage source between 3 V and 3.6 V (typically 3.3 V). To accomplish this, it is recommend to connect the D+ pull-up to a port/pin that does not have an internal pullup (that is, PC0..3), instead of connecting it directly to a 3.3 V supply (that is, software control of D+ pullup recommended).

CC2538 CC2538_Application_circuit_NEW.gif Figure 6-1 CC2538xFnn Application Circuit

Table 6-1 Overview of External Components (Excluding Supply Decoupling Capacitors)

Component Description Value
C21 USB D– decoupling 47 pF
C31 USB D+ decoupling 47 pF
C341 32-MHz xtal-loading capacitor 12 pF
C351 32-MHz xtal-loading capacitor 12 pF
C371 Part of the RF matching network 18 pF
C381 Part of the RF matching network 18 pF
C382 Part of the RF matching network 1 pF
C372 Part of the RF matching network 1 pF
C441 32-kHz xtal-loading capacitor 22 pF
C451 32-kHz xtal-loading capacitor 22 pF
C561 Decoupling capacitor for the internal digital regulator 1 µF
C321 Decoupling capacitor for the internal digital regulator 1 µF
C281 Filter capacitor for reset line 1 nF
L372 Part of the RF matching network 2 nH
L381 Part of the RF matching network 2 nH
R21 USB D– series resistor 33 Ω
R31 USB D+ series resistor 33 Ω
R32 USB D+ pullup resistor to signal full-speed device presence 1.5 kΩ
R281 Filter resistor for reset line 2.2 Ω
R421 Resistor used for internal biasing 56 kΩ

6.1 Input, Output Matching

When using an unbalanced antenna such as a monopole, use a balun to optimize performance. One can implement the balun using low-cost, discrete inductors and capacitors. The recommended balun shown in Figure 6-1 consists of L372, C372, C382 and L381.

If a balanced antenna such as a folded dipole is used, omit the balun.

6.2 Crystal

The 32-MHz crystal oscillator uses an external 32-MHz crystal, XTAL1, with two loading capacitors (C341 and C351). See the 32-MHz Crystal Oscillator section for details. Calculate the load capacitance across the 32-MHz crystal by Equation 1.

Equation 1. CC2538 E001_WRS096.gif

XTAL2 is an optional 32.768-kHz crystal, with two loading capacitors (C441 and C451) used for the 32.768-kHz crystal oscillator. Use the 32.768-kHz crystal oscillator in applications where both low sleep-current consumption and accurate wake-up times are needed. Calculate the load capacitance across the 32.768-kHz crystal by Equation 2.

Equation 2. CC2538 E002_WRS096.gif

Use a series resistor, if necessary, to comply with the ESR requirement.

6.3 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 decoupling capacitors (C561, C321) and an external connection between them for stable operation.

6.4 Power-Supply Decoupling and Filtering

Optimum performance requires proper power-supply decoupling. The placement and size of the decoupling capacitors and the power supply filtering are important to achieve the best performance in an application. TI provides a recommended compact reference design for the user to follow.

6.5 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)
  2. CC2538xFnn User's Guide
  3. Universal Serial Bus Revision 2.0 Specification http://www.usb.org/developers/docs/usb_20_052709.zip