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ADS8528: Design of Daisy chain mode

Seungmo Kim
Prodigy 70 points
Part Number: ADS8528
Other Parts Discussed in Thread: ADS8568, TMS320F28335

ADS8528: in daisy chain mode

I have some question about ADS8528.

I am going to design of ADC board.
（conditions： Serial SPI Mode, daisy-chain mode using three ADS8568, using SDO_A, using software configuration,
   all eight channels are sampled simultaneously(all CONVST_x tied together)）

[1] Can I use only SDO_A channel each device in daisy-chain mode?
    (SDO_A of device 3 in the last stage is connected to McBSP channel of TMS320F28335)
[2] When ADC board is desinged, is it possible to designate separately?
    (device 1: hardware mode, device 2: hardware mode, device 3 in the last stage: software mode)

  • 0
    TI__Mastermind 46055 points

    Hello Seungmo,
    [1] No, all SDO's must be used, you cannot use only SDO_A. The last device in the chain would not know how many devices are 'downstream' so there is really no way to serialize all the data through a single SDO at the end of the chain.
    [2] It should work but a single (software) mode is suggested for all devices. If all devices are to be configured the same way, you can connect the three SDI and /CS pins together and send the configuration detail to all simultaneously. If they will have different configurations, these three devices can share the SDI line, but they would have to have independent chip selects.
    Please refer to other similar queries on E2E forum.
    e2e.ti.com/.../382747
    e2e.ti.com/.../620916

    Regards,
    Dale