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ADS7870: Design Verification

M SANDEEP
Prodigy 160 points
Part Number: ADS7870

Hai Sir,

My End application is - Controlling & Analog outputs driving.

As per the customer suggestion we are going to use the ADS7870 for receiving the Analog Inputs.

As per the attached image pls verify the design and let me know if any modifications to be done.ADS7870

1) Is there any Series Resistance Required for SPI Signals (Pin no.20,21,22&23) ? 

2) Is there any protection or filter circuit required for Analog inputs(Pin.no.1 to 8) from outside signals ? like RC filter ?

  • 0
    TI__Mastermind 25020 points

    Hello,

    Looking at the schematic provided, the OSC_ENABLE is pulled low, which means that the device would need an external CCLK provided. Since this pin is floating, I am assuming that you are setting the register content, OSCE to enable the internal oscillator. One of these is necessary

    1. A series resistance is not required, but can be proven helpful to reduce reflections across the lines. In long transmission lines in particular a series resistance near each source of the signal would be best

    2. A RC circuit can prove to be beneficial, though not always necessary, can you provide the input source circuit for review?

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Prodigy 160 points

    Thank you for your reply

    Cynthia said:
    Looking at the schematic provided, the OSC_ENABLE is pulled low, which means that the device would need an external CCLK provided. Since this pin is floating, I am assuming that you are setting the register content, OSCE to enable the internal oscillator. One of these is necessary

    Yes... we are not providing any external clock to this Pin, so can we proceed like this design with enabling the OSCE register for internal clock?

    I'm, taking reference from these designs as per the datasheet Fig 40 i Page no.36.

    Cynthia said:
    A series resistance is not required, but can be proven helpful to reduce reflections across the lines. In long transmission lines in particular a series resistance near each source of the signal would be best

    ok sir...but presently i'm planning to place the 22ohm standard series resistor, based on practical verification we will change the value...

  • +1 in reply to M SANDEEP
    TI__Mastermind 25020 points

    1. Correct, you can move forward with using internal clock 

    2. This is a good plan 

    Looks like you have a good plan moving forward. Best of luck -Cynthia

  • 0 in reply to Cynthia
    Prodigy 160 points

    Hi sir,

    If I am not using the Digital I/O port (Pins 11 to 14), Can i put NC to those pins....

  • +1 in reply to M SANDEEP
    TI__Mastermind 25020 points

    yes, you can leave the digital I/O  not connected if not used