SWRZ072B May   2017  – December 2020 AWR1642

 

  1. 1Introduction
  2. 2Device Nomenclature
  3. 3Device Markings
  4. 4Usage Notes
    1. 4.1 MSS: SPI Speed in 3-Wire Mode Usage Note
  5. 5Advisory to Silicon Variant / Revision Map
  6. 6Known Design Exceptions to Functional Specifications
    1.     MSS#10
    2.     MSS#11
    3.     MSS#12
    4.     MSS#14
    5.     MSS#16
    6.     MSS#17
    7.     MSS#18
    8.     MSS#19
    9.     MSS#20
    10.     MSS#22
    11.     MSS#37B
    12.     MSS#38A
    13.     MSS#39
    14.     MSS#40
    15.     MSS#42
    16.     MSS#43
    17.     MSS#44
    18.     MSS#45
    19.     ANA#06
    20.     ANA#08A
    21.     ANA#09A
    22.     ANA#10A
    23.     ANA#11A
    24.     ANA#12A
    25.     ANA#15
    26.     ANA#16
    27.     ANA#17A
    28.     ANA#18B
    29.     ANA#20
    30.     ANA#21A
    31.     ANA#22A
    32.     ANA#24A
    33.     ANA#27
    34.     DSS#01
    35.     DSS#02
    36.     DSS#03
    37.     DSS#04
    38.     DSS#05
    39.     DSS#06
    40.     DSS#07
  7. 7Trademarks
  8. 8Revision History

ANA#18B

Spurs Caused due to Digital Activity Coupling to XTAL

Revision(s) Affected:

AWR1642 ES1.0 and AWR1642 ES2.0

Description:

Digital filtering activity can potentially couple to XTAL pins and lead to spurs in the LO, which would also be seen in the Rx data. The spur in the Rx data would be seen at the spur frequency offset around a strong object. For example if the spur frequency is 500Khz and there is a strong object at 2Mhz , the Rx ADC spectrum could have a spike at 1.5Mhz or 2.5Mhz. Note that the Tx – Rx antenna coupling would also form a strong object close to DC. The spur frequency depends on the sampling rate (Fs). The strongest of these spurs have been observed when Fs is close to 10, 12.5, 18, 18.75,20, 25, Msps. In these ranges, an IF spur can appear at Fs-10 Mhz, 2Fs-40MHz, 4Fs-40 MHz, 4Fs-100 MHz, 8Fs-100 MHz , 2Fs-37.5 MHz, 2Fs-36 MHz. The spur is observable when the spur frequency falls within 1.5 MHz, beyond that it gets heavily filtered out. Please refer the device datasheet for max usable sampling rate.

Workaround(s):

Workaround #1:

Avoid sampling rates close to these numbers (10, 12.5, 18, 18.75, 20, 25 Msps) or use exactly these numbers (spur is at 0 Hz in the latter case).

Workaround #2:

Using external TCXO, instead of XTAL, with voltage swing between 1.4-1.8 Vpp can avoid these spurs.