AN130 - Using CC2592 Front End With CC2538

AN130 - Using CC2592 Front End With CC2538
Application Report
SWRA447 – February 2014
AN130 - Using CC2592 Front End With CC2538
James Elliott
ABSTRACT
This application report describes how to implement the CC2538 and the CC2592 in the same design. It
further describes the expected performance from this combination as well as important factors to consider
with respect to the layout and regulatory requirements. The combined CC2538 and CC2592 solution is
suitable for systems targeting compliance with FCC CFR47 Part 15.
Contents
1
Introduction ................................................................................................................... 2
2
Absolute Maximum Ratings ................................................................................................ 2
3
Electrical Specifications .................................................................................................... 2
4
Application Circuit ............................................................................................................ 9
5
PCB Layout Considerations............................................................................................... 11
6
Regulatory Requirements ................................................................................................. 12
7
Controlling the CC2592 .................................................................................................... 15
8
References .................................................................................................................. 16
Appendix A
Marker - Delta Method ............................................................................................ 17
List of Figures
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
..................................... 5
Output Power vs. Temperature ............................................................................................ 5
Sensitivity vs. Frequency and Power Supply Voltage................................................................... 6
Sensitivity vs. Temperature and Power Supply Voltage ................................................................ 6
Selectivity Operating at Channel 18 (2440 MHz) ........................................................................ 7
RSSI Readout vs. Input Power ............................................................................................ 7
CC2592 Maximum Input Power and CC2538 Output Power vs Temperature ...................................... 8
Conducted Power Spectral Density, TXPOWER = 0xC5, RBW = 100 KHz ......................................... 9
Application Circuit for the CC2538 With CC2592 ...................................................................... 10
Spur DC to Fundamental at 25°C ....................................................................................... 11
Spur DC to Fundamental at -40°C ....................................................................................... 11
Spur Fundamental to 2nd at 25°C ....................................................................................... 11
Spur Fundamental to 2nd at -40°C ...................................................................................... 11
Spur 2nd to 3rd Harmonic at 25°C ....................................................................................... 11
Spur 2nd to 3rd Harmonic at -40°C ...................................................................................... 11
Output Power vs. Frequency and Power Supply Voltage, TXPOWER = 0xC5
16
Conducted Spurious Emission vs. FCC Part 15.247 Limit (TXPOWER = 0xC5, RBW = 1 MHz, VBW = 10
kHz) .......................................................................................................................... 14
17
Conducted Spurious Emission, Lower Band Edge (TXPOWER = 0xC5, RBW = 1 MHz, VBW = 10 KHz) .... 14
18
Conducted Spurious Emission, Upper Band Edge (TXPOWER = 0xC5, RBW = 1 MHz, VBW = 10 KHz) .... 15
19
CC2538-CC2592 Interconnect
20
...........................................................................................
Band Edge Setup ..........................................................................................................
16
17
List of Tables
1
Operating Conditions ........................................................................................................ 2
SmartRF is a trademark of Texas Instruments.
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2014 trademarks of ARM Limited.
AN130 - Using CC2592 Front End With CC2538
ARM, Cortex
are registered
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Copyrightowners.
© 2014, Texas Instruments Incorporated
All other trademarks are the property of their respective
1
Introduction
1
www.ti.com
2
Current Consumption........................................................................................................ 3
3
Receive Parameters ......................................................................................................... 3
4
RSSI Compensation ......................................................................................................... 3
5
Transmit Parameters ........................................................................................................ 4
6
Power Table .................................................................................................................. 4
7
Transmit PSD Limits......................................................................................................... 9
8
Summarized FCC 15.247 Regulations for the 2.4 GHz Band ........................................................ 13
9
Back-Off Requirement for FCC Part 15.247 Compliance Under Typical Conditions .............................. 13
10
Control Logic for Connecting the CC2592 to a CC2538 Device ..................................................... 15
11
CC2538 Registers for CC2592 Control
.................................................................................
16
Introduction
The CC2538 is TI's ARM® Cortex®-M3 ZigBee®/IEEE 802.15.4 RF System-on-Chip (SoC) for the 2.4 GHz
unlicensed ISM band. This chip enables industrial grade applications by offering state-of-the-art
selectivity/co-existence, excellent link budget, and low voltage operation.
CC2592 is a range extender for 2.4 GHz RF transceivers, transmitters and SoC products from Texas
Instruments. CC2592 increases the link budget by providing a Power Amplifier (PA) for higher output
power and a Low Noise Amplifier (LNA) for improved receiver sensitivity. CC2592 contains further RF
switches, RF matching, and an on-chip balun for a seamless interface with the CC2538. This allows for
simple design of high performance wireless applications.
Texas Instruments ZigBee SW solution, Z-Stack (www.ti.com/z-stack), includes the necessary SW
changes for using the CC2592. For details, see the “PA/LNA Service” section in the “HAL Driver API.pdf”
in the Z-Stack documents folder, which is located in the Z-stack installation.
2
Absolute Maximum Ratings
The absolute maximum ratings and operating conditions listed in [1] and [2] must be followed at all times.
Stress exceeding one or more of these limiting values can cause permanent damage to any of the
devices.
3
Electrical Specifications
Note that these characteristics are only valid when using the recommended register settings presented in
Section 3.6. For further recommendations, see Section 7.
3.1
CC2538 - Operating Conditions
Table 1. Operating Conditions
Parameter
Min
Max
Unit
Operating Frequency
MHz
2405
2483.5
Operating Supply Voltage
2.0
3.6
V
Operating Temperature
-40
125
°C
CC2538 absolute maximum rating is 3.9 V, CC2592 absolute maximum rating is 3.8 V. The CC2538CC2592EM has been characterized at a maximum 3.7 V to keep continuity with the CC2592 standalone
characterization.
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3.2
Current Consumption
TC = 25°C, VDD = 3.0 V, f = 2440 MHz if nothing else is stated. All parameters are measured on [3] with a
50 Ω load.
Table 2. Current Consumption
3.3
Parameter
Condition
Typical
Unit
Receive Current
Wait for sync, -90 dBm input level
Wait for sync, -50 dBm input level
30
26
mA
Transmit Current
TXPOWER = 0xFF
TXPOWER = 0xED
TXPOWER = 0xD5
TXPOWER = 0xC5
TXPOWER = 0xB6
TXPOWER = 0xB0
TXPOWER = 0xA1
TXPOWER = 0x91
TXPOWER = 0x88
TXPOWER = 0x72
TXPOWER = 0x62
TXPOWER = 0x58
TXPOWER = 0x42
191
168
156
142
135
128
116
104
96
88
82
79
77
mA
Power Down Current
CC2538 PM2 – CC2592
1.4
µA
Power Down Current
CC2538 PM3 – CC2592
0.5
µA
Power Down Current
CC2592 Standalone
0.1
µA
Receive Parameters
TC = 25°C, VDD = 3.0 V, f = 2440 MHz if nothing else is stated. All parameters are measured on [3] with a
50 Ω load.
Table 3. Receive Parameters
3.4
Parameter
Condition
Typical
Unit
Receive Sensitivity HGM
Receive Sensitivity LGM
1 % PER, IEEE 802.15.4 [4] requires -85 dBm
-101
dBm
1 % PER, IEEE 802.15.4 [4] requires -85 dBm
-99
dBm
Saturation HGM
IEEE 802.15.4 [4] requires -20 dBm
-3
dBm
Saturation LGM
IEEE 802.15.4 [4] requires -20 dBm
-2
dBm
Interferer Rejection
Wanted signal 3 dB above the sensitivity level,
IEEE 802.15.4 modulated interferer at IEEE 802.15.4 channels
±5 MHz from wanted signal, IEEE 802.15.4 [4] requires 0 dB
43.5
dB
±10 MHz from wanted signal, IEEE 802.15.4 [4] requires 30 dB
46.4
dB
±20 MHz from wanted signal. Wanted signal at -82dBm
46.5
dB
Received Signal Strength Indicator (RSSI)
Due to the external LNA and the offset in the CC2538, the RSSI readouts from the CC2538 - CC2592 are
different from RSSI offset values for a standalone CC2538 design. The offset values are shown in Table 4.
Table 4. RSSI Compensation
CC2530-CC2591EM LNA Mode
(1)
RSSI Offset
High Gain Mode
85
Low Gain Mode
81
(1)
Real RSSI = Register value – RSSI offset.
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Electrical Specifications
3.5
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Transmit Parameters
TC = 25°C, VDD = 3.0 V, f = 2440 MHz if nothing else is stated. All parameters are measured on [3] with a
50 Ω load. Radiated measurements are done using the PCB antenna.
Table 5. Transmit Parameters
3.6
Parameter
Condition
Radiated Emission with
TXPOWER = 0xC5
Complies with FCC 15.247.
See Chapter 7 for more
details about regulatory
requirements and compliance
Conducted 2•RF (FCC restricted band)
Conducted 3•RF (FCC restricted band)
Radiated 2•RF (FCC restricted band)
Radiated 3•RF (FCC restricted band)
Typical
Unit
-44.3
-63.9
-47.5
-42
dBm
Max Error Vector Magnitude
(EVM)
IEEE 802.15.4 [4] requires maximum 35%
Measured as defined by IEEE 802.15.4 [4] ls
TXPOWER = 0xFF, f = IEEE 802.15.4 channels
21
%
TXPOWER = 0xED, f = IEEE 802.15.4 channels
13.8
%
TXPOWER = 0xD5, f = IEEE 802.15.4 channels
5
%
TXPOWER = 0xC5 f = IEEE 802.15.4 channels
2.5
%
TXPOWER = 0xB6 f = IEEE 802.15.4 channels
1.8
%
TXPOWER = 0xB0, f = IEEE 802.15.4 channels
1.7
%
Output Power Programming
The RF output power of the CC2538 - CC2592EM is controlled by the 8-bit value in the CC2538
TXPOWER register. Table 6 shows the typical output power and current consumption for the
recommended power settings. The results are given for TC = 25°C, VDD = 3.0 V and f = 2440 MHz, and are
measured on [3] with a 50 Ω load. For recommendations for the remaining CC2538 registers, see
Section 7 or use the settings given by SmartRF™ Studio.
Table 6. Power Table
TXPOWER
Power [dBm]
Current [mA]
0xFF
22
191
0xED
21.5
168
0xD5
20.9
156
0xC5
20.1
142
0xB6
19.6
135
0xB0
19
128
0xA1
17.8
115
0x91
16.4
105
0x88
14.9
96
0x72
13
88
0x62
11
82.5
0x58
9.5
79
0x42
7.5
77
Note that the recommended power settings given in Table 6 are a subset of all the possible TXPOWER
register settings. However, using other settings than those recommended might result in sub-optimal
performance in areas like current consumption, EVM, and spurious emission. The CC2538 – CC2592 EM
has been certified at 0xC5 and for any application requiring 20dBm output power this is recommended.
For applications targeting operation across the full temperature range, Figure 7 indicates that the
recommended supply voltage with the 0xC5 power setting is 3 V or higher.
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3.7
Typical Performance Curves
TC = 25°C, VDD = 3.0 V, f = 2440 MHz if nothing else is stated. All parameters are measured on [3] with a
50 Ω load.
Figure 1. Output Power vs. Frequency and Power Supply Voltage, TXPOWER = 0xC5
Figure 2. Output Power vs. Temperature
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Figure 3. Sensitivity vs. Frequency and Power Supply Voltage
Figure 4. Sensitivity vs. Temperature and Power Supply Voltage
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Figure 5. Selectivity Operating at Channel 18 (2440 MHz)
Figure 6. RSSI Readout vs. Input Power
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10
9
8
Input Power [dBm]
7
6
2.0 V
2.5 V
3.0 V
CC2538
0xC5 3.0V
5
4
3
2
1
0
−40
−30
−20
−10
0
Temperature [C]
10
20
30
Figure 7. CC2592 Maximum Input Power and CC2538 Output Power vs Temperature
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3.8
IEEE - Transmit Power Spectral Density (PSD) Mask
The IEEE standard 802.15.4 [7] requires the transmitted spectral power to be less than the limits specified
in Table 7.
Table 7. Transmit PSD Limits
Frequency
|f – fc| > 3.5 MHz
Relative Limit
Absolute Limit
-20 dB
-30 dBm
The results are given for TC = 25°C, VDD = 3.0 V and f = 2440 MHz, and are measured on [3] with a 50 Ω
load.
Figure 8. Conducted Power Spectral Density, TXPOWER = 0xC5, RBW = 100 KHz
4
Application Circuit
Only a few external components are required for [3]. A typical application circuit is shown in Section 4.1.
Note that the application circuit figure does not show the complete layout of the CC2538 - CC2592EM.
The board layout greatly influences the RF performance of the CC2538 - CC2592EM.
When using the CC2538 - CC2592EM at high power levels, a shield is required to be complaint with FCC
harmonic emission regulations. TI provides a compact CC2538 - CC2592EM reference design
incorporating shielding footprints that it is highly recommended to follow. The layout, stack-up and
schematic for the CC2592 need to be copied exactly to obtain optimum performance.
Note that the reference design also includes the bill of materials with manufacturers and part numbers.
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Application Circuit
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VDD
C107
L101
VDD_PA
C106
VDD_BIAS
VDD_LNA
VDD
CC2538
RF_P
RF_P
RF_N
RF
_N
RF_N
C110
L104
L102
CC2592
ANT
C103
PA_EN
PC3
LNA_EN
PC2
HGM
PD2
C101
BIAS
C105
R81
Alternatively to
VDD/GND/MCU
Figure 9. Application Circuit for the CC2538 With CC2592
4.1
Power Decoupling
Proper power supply decoupling must be used for optimum performance. Figure 9 is a simplified
schematic only showing the output matching and a reduced number of VDD decoupling components for the
CC2592.
The placement and size of the decoupling components, the power supply filtering and the PCB lines are
very important to achieve the best performance. Details about the importance of copying [3] exactly and
potential consequences of changes are explained in Section 5.
4.2
Input/Output Matching and Filtering
The CC2592 includes a balun and a matching network in addition to the PA, LNA and RF switches, which
makes the interface to the CC2538 seamless.
Note that the PCB lines that connect the two devices also are part of the RF matching. Therefore, it is
important to copy the distance between the devices, the transmission lines and the stack-up of the PCB
according to the reference design to ensure optimum performance.
The network between the CC2592 and the antenna (C101, L101, C106, L102, C103, L104, C105 and
C110) matches the CC2592 to a 50 Ω load and provides filtering to pass regulatory demands. C110 also
works as a DC-block.
4.3
Bias Resistor
R81 is a bias resistor. The bias resistor is used to set an accurate bias current for internal use in the
CC2592.
4.4
Antenna Considerations
The TI reference design contains two antenna options. As default, the PCB antenna, which is a planar
inverted F antenna (PIFA), is connected to the output of CC2592 through C110. This capacitor can be
soldered off and rotated 90° clockwise in order to connect to the SMA connector. Note that all testing and
characterization has been completed using the SMA connector. The PCB antenna has been used to
obtain radiated results and FCC certification. The FCC certification will be void if the PCB antenna is not
used. For further details on the antenna solutions, see [4] and [5].
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PCB Layout Considerations
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5
PCB Layout Considerations
The Texas Instruments reference design uses a 1.6 mm (0.062”) 4-layer PCB solution. Note that the
different layers have different thickness; it is important to follow the recommendations given in [3] to
ensure optimum performance. The top layer is used for components and signal routing, and the open
areas are filled with metallization connected to ground using several vias. The areas under the two chips
are used for grounding and must be well connected to the ground plane with multiple vias. Footprint
recommendation for the CC2592 is given in [2].
Layer two is a complete ground plane and is not used for any routing. This is done to ensure short return
current paths. The low impedance of the ground plane prevents any unwanted signal coupling between
any of the nodes that are decoupled to it. A dedicated ground plane is also needed to improve stability
(see Section 5.1). Layer three is a power and signal routing plane. The power plane ensures lowimpedance traces at radio frequencies and prevents unwanted radiation from power traces. Layer four is
used for routing, and as for layer one, open areas are filled with metallization connected to ground using
several vias.
5.1
CC2538 – CC2592 Stability
The figures located on the next page illustrate the stability of the CC2538-CC2592. Figure 10, Figure 11
and Figure 12 depict the stability of the CC2538-CC2592 at 2480 MHz, 3.6 V and 25°C. Alternatively,
Figure 13, Figure 14 and Figure 15 again depict the stability of the CC2538-CC2592, however, this time at
2480 MHz, 3.6 V and -40°C. Note the device stays stable at extreme temperatures and at the maximum
recommended voltage level. Furthermore, note that the scaling on each figure may vary.
Figure 10. Spur DC to Fundamental at 25°C
Figure 11. Spur DC to Fundamental at -40°C
Figure 12. Spur Fundamental to 2nd at 25°C
Figure 13. Spur Fundamental to 2nd at -40°C
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Figure 14. Spur 2nd to 3rd Harmonic at 25°C
5.2
Figure 15. Spur 2nd to 3rd Harmonic at -40°C
The Gain of the CC2592
Changing the layout or the stack-up of [3] affects the RF performance of the CC2592. Due to all the
contributors to the CC2592 performance, several observations can be made on how changing layout and
PCB stack-up affects the amplifier:
• Bad soldering of the ground paddle can reduce the gain significantly
• Too few or too long vias will reduce the gain significantly. This is why a checkered pattern of vias and
solder paste and a 4-layer PCB with the ground plane close to the top layer has been chosen for [3].
6
Regulatory Requirements
In the United States, the Federal Communications Commission (FCC) is responsible for the regulation of
all RF devices. CFR 47, Part 15, regulates RF products intended for unlicensed operation. A product
intended for unlicensed operation has to be subject to compliance testing. If the product is approved, the
FCC will issue an identification number.
The specific frequency bands used for unlicensed radio equipment for the 2.4 GHz band are regulated by
section 15.247 and 15.249. General rules for certification measurements are found in section 15.35.
Restricted bands and general limits for spurious emissions are found in sections 15.205 and 15.209.
[3] has been tested for compliance with FCC Part 15.247. The FCC Part 15.247 compliance is generally a
tougher requirement than ETSI compliance (EN 300 328) due to the restricted bands of operation.
However, there are requirements with regards to ETSI compliance (EN 300 328) that prevents operation
at maximum output power. The clause 4.3.2.2 Maximum Power Spectral Density requirement of EN 300
328 requires maximum +10 dBm/1 MHz. The output power must, therefore, be reduced to approximately
+12 dBm in order to get CE approval. The final output power level depends on the antenna used.
FCC Part 15.247 limits the output power to 1W or +30 dBm when Direct Sequence Spread Spectrum
(DSSS) modulation or Frequency Hopping Spread Spectrum (FHSS) with at least 75 hop channels is
used. The spectral density of digital modulation systems (not including FHSS) shall not exceed 8 dBm/3
kHz. The minimum 6 dB bandwidth of such systems is 500 kHz. Since the CC2538 is an IEEE 802.15.4
compliant transceiver, it uses DSSS modulation. The +30 dBm limit, therefore, apply for the CC2538 with
the CC2592 combination.
When complying with Part 15.247, in any 100 kHz bandwidth outside the operating band, the power level
shall be at least 20 dB below the level in the 100 kHz bandwidth with the highest power level in the
operating band. Attenuation below limits given in 15.209 is not required. Emission that fall within restricted
bands (15.205) must meet general limits given in 15.209. This is summarized in Table 8. More details
about the 2.4 GHz FCC regulations are found in [8].
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Table 8. Summarized FCC 15.247 Regulations for the 2.4 GHz Band
Standard
Relevant Frequency
FCC 15.247
2400 – 2483.5 MHz
Radiated Power (EIRP)
Conducted Power
+30 dBm
Restricted bands defined by
15.205, including the 2nd, 3rd and
5th harmonics
Comment
Maximum
6 dBi antenna gain
-41.2 dBm
All frequencies not covered in
above cells
-20 dBc
When using CC2592 with the CC2538, back-off is required for the highest IEEE 802.15.4 channel
(channel 26) to comply with FCC. Table 9 shows the back-off needed to comply with the FCC Part 15.247
limits at typical conditions. Note that the numbers in Table 9 are based on conducted emission
measurements from [3]. The real required back-off may be different for applications with different
antennas, plastic covers, or other factors that amplify/ attenuate the radiated power.
Figure 16 depicts the level of the conducted spurious emission and margins to the FCC Part 15.247 limits
for the IEEE 802.15.4 channels under typical conditions (TC = 25°C, VDD = 3.0 V) when transmitting at
maximum recommended power (TXPOWER = 0xC5) using [3]. Figure 17 and Figure 18 show the margins
versus the FCC 15.247 for the lowest frequency channels at the lower band edge and for the upper
frequency channels at the upper band edge, respectively. At the band edge, the FCC allows for a Markerdelta method measurement [9] to determine the amount of back-off or duty cycle required to comply with
the FCC Part 15.247. This is necessary when conducting radiated band-edge measurements, because
there can be an issue obtaining meaningful data since a measurement instrument that is tuned to a bandedge frequency may also capture some of the in-band signal when using the resolution bandwidth (RBW)
required by the measurement procedure ANSI C63.4-1992. Appendix A provides a step-by-step example
of using the marker-delta method to calculate the required back-off required.
Table 9. Back-Off Requirement for FCC Part 15.247 Compliance Under Typical Conditions
Frequency [MHz]
Back-Off [dB]
2405
0
2410
0
2415
0
2420
0
2425
0
2430
0
2435
0
2440
0
2445
0
2450
0
2455
0
2460
0
2465
0
2470
0
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2475
0
2480
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Figure 16. Conducted Spurious Emission vs. FCC Part 15.247 Limit (TXPOWER = 0xC5, RBW = 1 MHz,
VBW = 10 kHz)
Figure 17. Conducted Spurious Emission, Lower Band Edge (TXPOWER = 0xC5, RBW = 1 MHz, VBW = 10
KHz)
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Figure 18. Conducted Spurious Emission, Upper Band Edge (TXPOWER = 0xC5, RBW = 1 MHz, VBW = 10
KHz)
7
Controlling the CC2592
There are three digital control pins on the CC2592 that control the state the chip is in: PA_EN, LNA_EN,
and HGM. Table 10 shows the control logic when connecting the CC2592 to a CC2538 device.
Table 10. Control Logic for Connecting the CC2592 to a CC2538 Device
PA_EN
LNA_EN
HGM
Mode of Operation
0
0
X
Power Down
X
1
0
RX Low Gain Mode
X
1
1
RX High Gain Mode
1
0
X
TX
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References
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The CC2538 – CC2592EM reference design from TI [3] uses three of the CC2538 GPIO pins on the
CC2538 to control the CC2592. The I/O pins used is shown in Table 10. PA_EN and LNA_EN must be
controlled by RF observation signals as illustrated in Figure 19, whereas, the HGM pin can be controlled
by any GPIO or alternatively tied to VDD or GND.
CC2592
CC2538
PC3
PA_EN
PC2
LNA_EN
PD2
HGM
Figure 19. CC2538-CC2592 Interconnect
When using the CC2592 with the CC2538, the RF observation registers must be set according to
Table 11. This enables the CC2538 to automatically control the CC2592 through PC2 and PC3. If
required, any other PC pin can be used. For details, see [6].
It is not required to change any of the CC2538 radio settings from the recommend configuration when
used with the CC2592.
Table 11. CC2538 Registers for CC2592 Control
8
CC2538 Register
Reccommened Value
CCTEST_OBSSEL2
0x80
CCTEST_OBSSEL3
0x81
RFC_OBS_CTRL0
0x6A
RFC_OBS_CTRL1
0x68
References
1. CC2538 A Powerful System-On-Chip for 2.4-GHz IEEE 802.15.4, 6LoWPAN and ZigBee Applications
Data Sheet (SWRS096)
2. CC2592 CC2592 2.4-GHz Range Extender Data Manual (SWRS159)
3. CC2538-CC2592 Reference Design (www.ti.com/tool/cc2538-cc2592em-rd)
4. AN058 - Antenna Selection Guide (SWRA161)
5. DN007 - 2.4 GHz Inverted F Antenna Design Note (SWRU120)
6. CC2538 System-on-Chip Solution for 2.4-GHz IEEE 802.15.4 and ZigBee®/ZigBee IP® Applications
User's Guide (SWRU319)
7. IEEE std. 802.15.4 – 2006: Wireless Medium Access Control (MAC) and Physical Layer (PHY)
specification for Low Rate Wireless Personal Area Networks (LR-WPANs)
(http://standards.ieee.org/getieee802/download/802.15.4-2011.pdf)
8. AN032 - SRD regulations for license-free transceiver operation in the 2.4 GHz band (SWRA060)
9. DA 00-705 (http://www.fcc.gov/Bureaus/Engineering_Technology/Public_Notices/2000/da000705.doc)
16
AN130 - Using CC2592 Front End With CC2538
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Appendix A Marker - Delta Method
•
•
•
•
Power Setting: 0xC5
Set the DUT in Modulated TX
Center Frequency: 2480 MHz
Span: 10 MHz
RBW
VBW
1 MHz
1 MHz
Max Peak + Max Hold
1 MHz
10 Hz
Average + Max Hold
•
Meas.
Name
Power
PEAK
19.57
AVERAGE
17.31
Detector
Comments
The power will be lower for
AVERAGE than for PEAK
Choose a spectrum analyzer that encompasses both the peak of the fundamental emission and the
band-edge emission under investigation (2483.5 MHz, edge in Figure 20).
Figure 20. Band Edge Setup
RBW
VBW
Detector
Meas.
Name
Power
Comments
1%
of total span
>= RBW (100
KHz)
Max Peak + Max Hold
TOP PEAK
13.9
RBW - never less than 30 kHz. several
sweeps in peak hold mode
1%
of total span
>= RBW (100
KHz)
Max Peak + Max Hold
Band-Edge PEAK
-33
RBW - never less than 30 kHz. several
sweeps in peak hold mode
DELTA
46.9
Delta will normally be > 40dB
TOP PEAK - Band Edge PEAK ->
•
•
Record the peak levels of the fundamental emission and the relevant band edge emission. The band
edge peak is measured at the highest point to the right of the 2483.5 MHz line, which is typically on
this line. However, in some cases there may be a higher peak nearby. Observe the stored trace and
measure the amplitude delta between the top peak of the fundamental and the peak of the band-edge
emission.
Note a lower RBW, even as low as 30 KHz may be required to see the band-edge peak.
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17
Appendix A
•
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When the DELTA value is calculated, this can be used to check how the PEAK and Average Values
are compared to their respective limits.
MATH
Power (dBm)
Limits and Comments
PEAK - DELTA =
-27.33
-21.2 dBm (74 dBuV/m)
AVERAGE - DELTA =
-29.59
-41.2 dBm (54 dBuV/m)
BACK OFF =
18
(-29.59)-(-41.2) = 11.61
Required back-off on channel 26
AN130 - Using CC2592 Front End With CC2538
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SWRA447 – February 2014
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