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ADS8168EVM-PDK: crossetalk between different channels at the auto sequence mode

Part Number: ADS8168EVM-PDK
Other Parts Discussed in Thread: ADS8168

Based on ADS8168EVM-PDK, when a unipolar signal (1V PEAK TO PEAK, 2.5 V BIAS, 1kHz) was sampled at 100kHz through the channal 1 as a single-ended input, there are obvious output curves on the channel 2 and 3. 

The register is configured as following:

USER REGISTERS_REG_ACCESS_REG AA
USER REGISTERS_PD_CNTL_REG 1C
USER REGISTERS_SDI_CTL_REG 00
USER REGISTERS_SDO_CTL1_REG 03
USER REGISTERS_SDO_CTL2_REG 00
USER REGISTERS_SDO_CTL4_REG 00
USER REGISTERS_DATA_CNTL_REG 00
USER REGISTERS_PARITY_CNTL_REG 00
USER REGISTERS_OFST_CAL_REG 00
USER REGISTERS_REF_MRG1_REG 00
USER REGISTERS_REF_MRG2_REG 00
USER REGISTERS_REFby2_MRG_REG 00
USER REGISTERS_DEVICE_CFG_REG 02
USER REGISTERS_CHANNEL_ID_REG 00
USER REGISTERS_SEQ_START_REG 01
USER REGISTERS_SEQ_ABORT_REG 01
USER REGISTERS_AIN_CFG_REG 00
USER REGISTERS_COM_CFG_REG 00
USER REGISTERS_ON_THE_FLY_CFG_REG 00
USER REGISTERS_ALERT_CFG_REG 00
USER REGISTERS_HI_TRIG_LSB_AIN7_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN7_REG FF
USER REGISTERS_HYSTERESIS_AIN7_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN6_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN6_REG FF
USER REGISTERS_HYSTERESIS_AIN6_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN5_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN5_REG FF
USER REGISTERS_HYSTERESIS_AIN5_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN4_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN4_REG FF
USER REGISTERS_HYSTERESIS_AIN4_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN3_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN3_REG FF
USER REGISTERS_HYSTERESIS_AIN3_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN2_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN2_REG FF
USER REGISTERS_HYSTERESIS_AIN2_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN1_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN1_REG FF
USER REGISTERS_HYSTERESIS_AIN1_REG FC
USER REGISTERS_HI_TRIG_LSB_AIN0_REG FF
USER REGISTERS_HI_TRIG_MSB_AIN0_REG FF
USER REGISTERS_HYSTERESIS_AIN0_REG FC
USER REGISTERS_LO_TRIG_LSB_AIN7_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN7_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN6_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN6_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN5_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN5_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN4_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN4_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN3_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN3_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN2_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN2_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN1_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN1_REG 00
USER REGISTERS_LO_TRIG_LSB_AIN0_REG 00
USER REGISTERS_LO_TRIG_MSB_AIN0_REG 00
USER REGISTERS_ALERT_LO_STATUS_REG 00
USER REGISTERS_ALERT_HI_STATUS_REG 00
USER REGISTERS_ALERT_STATUS_REG 00
USER REGISTERS_CURR_ALERT_LO_STATUS_REG 00
USER REGISTERS_CURR_ALERT_HI_STATUS_REG 00
USER REGISTERS_CURR_ALERT_STATUS_REG 00
USER REGISTERS_AUTO_SEQ_CFG1_REG FF
USER REGISTERS_AUTO_SEQ_CFG2_REG 01
USER REGISTERS_CCS_START_INDEX_REG 00
USER REGISTERS_CCS_END_INDEX_REG 0F
USER REGISTERS_CCS_SEQ_LOOP_REG 00
USER REGISTERS_CCS_CHID_INDEX_0_REG 00
USER REGISTERS_REPEAT_INDEX_0_REG FF
USER REGISTERS_CCS_CHID_INDEX_1_REG 00
USER REGISTERS_REPEAT_INDEX_1_REG FF
USER REGISTERS_CCS_CHID_INDEX_2_REG 00
USER REGISTERS_REPEAT_INDEX_2_REG FF
USER REGISTERS_CCS_CHID_INDEX_3_REG 00
USER REGISTERS_REPEAT_INDEX_3_REG FF
USER REGISTERS_CCS_CHID_INDEX_4_REG 00
USER REGISTERS_REPEAT_INDEX_4_REG FF
USER REGISTERS_CCS_CHID_INDEX_5_REG 00
USER REGISTERS_REPEAT_INDEX_5_REG FF
USER REGISTERS_CCS_CHID_INDEX_6_REG 00
USER REGISTERS_REPEAT_INDEX_6_REG FF
USER REGISTERS_CCS_CHID_INDEX_7_REG 00
USER REGISTERS_REPEAT_INDEX_7_REG FF
USER REGISTERS_CCS_CHID_INDEX_8_REG 00
USER REGISTERS_REPEAT_INDEX_8_REG FF
USER REGISTERS_CCS_CHID_INDEX_9_REG 00
USER REGISTERS_REPEAT_INDEX_9_REG FF
USER REGISTERS_CCS_CHID_INDEX_10_REG 00
USER REGISTERS_REPEAT_INDEX_10_REG FF
USER REGISTERS_CCS_CHID_INDEX_11_REG 00
USER REGISTERS_REPEAT_INDEX_11_REG FF
USER REGISTERS_CCS_CHID_INDEX_12_REG 00
USER REGISTERS_REPEAT_INDEX_12_REG FF
USER REGISTERS_CCS_CHID_INDEX_13_REG 00
USER REGISTERS_REPEAT_INDEX_13_REG FF
USER REGISTERS_CCS_CHID_INDEX_14_REG 00
USER REGISTERS_REPEAT_INDEX_14_REG FF
USER REGISTERS_CCS_CHID_INDEX_15_REG 00
USER REGISTERS_REPEAT_INDEX_15_REG FF

  • Hello,

    The ADS8168EVM-PDK will show crosstalk if the unused channels are floating.  This is due to the capacitance on the output of the multiplexor.  If the unused inputs are connected to GND, then you will not see this crosstalk.

    Below, an input sine wave with 2.5V offset, 1Vpp, is applied to Channel 0 (labeled Ain1 on the EVM).  Channel 1 (Ain2) is floating, so that you can see the crosstalk.  Channels 2,3,4,5,6,7 are all connected to ground.  (On the EVM header P2, Ain3, Ain4, Ain5, Ain6, Ain7, and Ain8 are connected to ground)

    Also, please note that Channel 1 (Ain2) is always floating on the ADS8168EVM due to an error in the build of the board.  If you want to use Channel 1, solder a 0ohm resistor into R26.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • Thanks for your help. The crosstalk between two adjacent channels has been suppressed to appr. -80dB with your suggested configurations, however, in datasheet of ADS8168, this index is about -115dB. There seems to be a gap between them.

    Here is another question, when I try to export the sampled data (sampling frequency: 800kHz, samples: 4M), the option "export to excel" can not be selected, that is, the options box is grayed out. I try it again on another laptop, it seems  to work, but a while later, another window pops up, it says there is no enough memory. Could you please tell me what is wrong with my laptop and how to solve the tissue about the other laptop, thank you.

  • Thanks for your help. The crosstalk between two adjacent channels has been suppressed to appr. -80dB with your suggested configurations, however, in datasheet of ADS8168, this index is about -115dB. There seems to be a gap between them.

    Here is another question, when I try to export the sampled data (sampling frequency: 800kHz, samples: 4M), the option "export to excel" can not be selected, that is, the options box is grayed out. I try it again on another laptop, it seems  to work, but a while later, another window pops up, it says there is no enough memory. Could you please tell me what is wrong with my laptop and how to solve the tissue about the other laptop, thank you.

  • Hello,

    Excel has a maximum row limit of 2^20, or 1048576.  Exporting 4M samples is not an option with the ADS8168 GUI software.

    I just tried exporting 1M samples, and this worked well.

    Regards,
    Keith