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ADS1299: Needed hardware configuration for Daisy-Chain Mode standard using two ADS1299

Jabrane Chakroun1
Intellectual 260 points
Part Number: ADS1299

Hi all,

I need your help to explain me if I made a mistake with my Hardware configuration to use two ADS1299

- Did the second CLKSEL should be low to force the ADS to use the external clock give it by the first chip 

Please see the follow schematic 

  • 0
    TI__Genius 11550 points

    Hi Jabrane,

    As mentioned, Figure 70(b) in the datasheet shows how to configure the device in a daisy-chain configuration. From your schematic, you are not connecting both the ADS1299 devices in a daisy-chain configuration. Referring to Figure 70(b), the DAISY_IN signal of Device2 is grounded and the DOUT signal is routed to the DAISY_IN pin of Device 1. The daisy-chain data for both devices can then be retrieved from the DOUT pin of Device 1. 

    If you are not driving both devices with the same CLK externally as shown in Figure 70(b), then it is recommended to use a separate RESET signal for each device for a more robust power-up initialization sequence. If you are using the internal CLK of device 1 to drive the second ADC, then you need to set the CLKSEL pin of device 2 to low (external clock). Table 6 on the DS shows how to set the clock for the device. You will also need to set the CLK_EN bit to 1 in the CONFIG1 register to enable the clock to be output in the CLK pin for device 1 (CLKSEL pin set to 1). 

    Please refer to the same diagram for the remaining signals that can be shared in a daisy-chain configuration. 

    Thanks.

    -TC

  • 0 in reply to TCT
    Intellectual 260 points

    I am referring to figure 70(a).

    Did the second ADS1299 chip need to be externally CLK driven from the First ADS1299 chip ?  

  • 0 in reply to Jabrane Chakroun1
    TI__Genius 11550 points

    Hi Jabrane,

    Figure 70(a) is a standard configuration and not a daisy-chain configuration. You can use device 1 to clock device 2 in this standard configuration as well. The setup I described previously is still valid for this configuration. 

    Thanks.

    -TC

  • 0 in reply to TCT
    Intellectual 260 points

    My question is so easy . I can or I should (must) use external clock for the second chip

    Thanks,

  • 0 in reply to Jabrane Chakroun1
    TI__Genius 11550 points

    The device can accommodate either per your design requirement. 

    Thanks.

    -TC

  • 0 in reply to TCT
    Intellectual 260 points

    thanks for your help.

    but I didn't get a clear respond