AD9251 output_adjust

Hello,

I copied and pasted part of register map from AD9251 datasheet.

Could you explain more about drive strength and stripe?

How does an output congiured witn bigger stripes work?

Best Regards,

Mack

  • 0
    •  Analog Employees 
    on Dec 16, 2014 11:54 PM over 6 years ago

    Hi Mack,

    Thank you for your interest in the AD9251. “Stripes” refers to the quantity of transistor stacks or "stripes" that are invoked for a given drive strength setting. More “stripes” means that more drivers are driving in parallel and thus result in a greater drive strength.

    The Output Mode (Register 0x14) and Output_Adjust (Register 0x15) registers are used to select the output drive strength, i.e.  how many “stripes” are invoked.

    When Register 0x14 Bits[7:6] = 00, Register 0x15 Bits[7:6,3:2] "3.3V" fields are enabled. Register 0x15 Bits[7:6] controls the drive strength of DCO; Register 0x15 Bits[3:2] controls the drive strength of the data drivers.

    Similarly, when  Register 0x14 Bits[7:6] = 10, Register 0x15 Bits[5:4,1:0] "1.8V" fields are enabled. In this case, Register 0x15 Bits[5:4] controls the drive strength of DCO; Register 0x15 Bits[1:0] controls the drive strength of the data drivers.

    EXAMPLES

    In the default condition we have the following:

    Register 0x14 Bits[7:6] = 00 --> "3.3V" fields in Register 0x15 are enabled

    Register 0x15 Bits[7:6] = 00 --> DCO drive strength is 1 "stripe"

    Register 0x15 Bits[3:2] = 00 --> data drive strength is 1 "stripe"

    The exact same drive strength can be realized by doing the following:

    Register 0x14 Bits[7:6] = 10 --> "1.8V" fields in Register 0x15 are enabled

    Register 0x15 Bits[5:4] = 00 --> DCO drive strength is 1 "stripe"

    Register 0x15 Bits[1:0] = 00 --> data drive strength is 1 "stripe"

    If you wanted to have 3 "stripe" 3X drive strength, you could do either of the following:

    Register 0x14 Bits[7:6] = 00 --> "3.3V" fields in Register 0x15 are enabled

    Register 0x15 Bits[7:6] = 10 --> DCO drive strength is 3 "stripes"

    Register 0x15 Bits[3:2] = 10 --> data drive strength is 3 "stripes"

    OR

    Register 0x14 Bits[7:6] = 10 --> "1.8V" fields in Register 0x15 are enabled

    Register 0x15 Bits[5:4] = 10 --> DCO drive strength is 3 "stripes"

    Register 0x15 Bits[1:0] = 10 --> data drive strength is 3 "stripes"

    The same set of output drivers is used for Register0x14 Bits[7:6] = 00 or Register0x14 Bits[7:6] = 10.

    Please let me know if you have any other questions. Thanks again.

    Doug