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CC1110 + CC1190 FCC PSD Test Failures

Other Parts Discussed in Thread: CC1190, TEST2, CC1101

I'm doing FCC testing for Part 15.247.  Device is a CC1110 with CC1190 PA.  Setting are 2FSK, 38.4K, 178KHz deviation.  PSD measurements are reading about 1dB below peak power.  This means I have to set my output power to less than 9dBm out to pass teh SPD limit of 8dBm.  Are there any setting I can change to try and bring the PSD down?  This design is supposed to be FCC compliant at about 17dB out.

<rfparameters>
<Property name="Xtal frequency" role="46">27.000000</Property>
</rfparameters>
<Register>
<Name>PKTCTRL0</Name>
<Value>0x22</Value>
</Register>
<Register>
<Name>FSCTRL1</Name>
<Value>0x06</Value>
</Register>
<Register>
<Name>FREQ2</Name>
<Value>0x21</Value>
</Register>
<Register>
<Name>FREQ1</Name>
<Value>0xB4</Value>
</Register>
<Register>
<Name>FREQ0</Name>
<Value>0x25</Value>
</Register>
<Register>
<Name>MDMCFG4</Name>
<Value>0xCA</Value>
</Register>
<Register>
<Name>MDMCFG3</Name>
<Value>0x75</Value>
</Register>
<Register>
<Name>MDMCFG2</Name>
<Value>0x00</Value>
</Register>
<Register>
<Name>CHANNR</Name>
<Value>0x00</Value>
</Register>
<Register>
<Name>DEVIATN</Name>
<Value>0x65</Value>
</Register>
<Register>
<Name>MCSM0</Name>
<Value>0x18</Value>
</Register>
<Register>
<Name>FOCCFG</Name>
<Value>0x16</Value>
</Register>
<Register>
<Name>AGCCTRL2</Name>
<Value>0x43</Value>
</Register>
<Register>
<Name>FREND0</Name>
<Value>0x10</Value>
</Register>
<Register>
<Name>FSCAL3</Name>
<Value>0xE9</Value>
</Register>
<Register>
<Name>FSCAL2</Name>
<Value>0x2A</Value>
</Register>
<Register>
<Name>FSCAL1</Name>
<Value>0x00</Value>
</Register>
<Register>
<Name>FSCAL0</Name>
<Value>0x1F</Value>
</Register>
<Register>
<Name>TEST2</Name>
<Value>0x88</Value>
</Register>
<Register>
<Name>TEST1</Name>
<Value>0x31</Value>
</Register>
<Register>
<Name>TEST0</Name>
<Value>0x09</Value>
</Register>
<Register>
<Name>PA_TABLE0</Name>
<Value>0x8f</Value>
</Register>

  • Refer to design note www.ti.com/lit/SWRA123, table 2. From this table you see that approx 8 dBm is the maximum output power @38.4 kbps, 177 kHz deviation due to the 8 dBm/3 kHz PSD requirement. Thus, no benefit in using CC1190 for this data rate. For higher data rates the output power can be increased and you will still meet PSD requirement. Since the sensitivity will be degraded with increased data rate you need to look at the link budget (TX output power - Sensitivity) to check if there is a benefit in increasing the data rate.

    There are no hidden bits that can be set to improve PSD for the 38.4 kbps case. 

  • Thanks for the info Sverre.  Is there a table for finer power control than what is available in SmartRf Studio?  I can only select output power in 5dB steps but would like to get at least 1dB control or finer.

  • See design note "DN013 Programming Output Power on CC1101"; www.ti.com/lit/swra151