• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 641 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPL0401A initial V seen on RW pin 5?

Michelle Smekal
Prodigy 130 points

I am using TPL0401A in a design to connect to an op amp and use I2C signals as inputs to this DCP to ultimately generate VREFDQ on DDR3L DIMMs. Between this component and the op amp I have a voltage divider network connected to the DDR voltage (1.35V). The center of my voltage divider network is connected to RW (pin5) and the top of my voltage divider is connected to RH (pin6). If my divider network is something like 5.6K ohms on top and 12.1k on bottom, would the initial voltage at boot be 1.35 * 12.1/(12.1+5.6)? Does the DCP have any affect on the initial booting voltage or is this all based on the initial voltage generated at the voltage divider?

  • 0
    TI__Expert 5140 points

    Hi Michelle,

    Do you have a schematic of the circuit you are working on? This will make it easier for me to provide feedback.

    This is the application circuit that I've come up with for a DDR3 DIMM1 Voltage Reference.

    The reason that I put the DPOT before the DDR3 Memory is because the op amp is required to buffer the high-impedance output of the TPL0401A or else loading placed on the output of the voltage divider will affect the output voltage. 

    However, if you are using the DPOT instead of two resistors for the voltage divider creating the reference (which is what I assume you are doing), then there shouldn't be an effect on the initial booting voltage. It should be based on the initial voltage generated at the divider at that moment.

    Thanks,

    Siby

  • 0 in reply to Siby James
    Prodigy 130 points
    Yes, I am using a circuit similar to what you show. My pull-down resistor is much larger (100k). I have a resistor divider network between the DPOT and the op amp. I wanted to confirm that my starting voltage at boot will be set by however I configure my resistor divider network and the wiper mechanism will kick in after that (once there is traffic on I2C).
  • 0 in reply to Michelle Smekal
    TI__Expert 5140 points
    Hi Michelle,

    Unfortunately, the TPL0401A does not have non-volatile memory so when the device is not powered it will be in an unknown state. Once the device is powered on it will automatically go to mid-scale. I'm assuming that the resistor divider is used to have an acceptable voltage reference for you DDR3 Mem.

    Thanks,
    Siby
  • 0 in reply to Siby James
    Prodigy 130 points

    Yes, I have the resistor divider network so there is a good initial voltage going into the DIMMs. Thanks all!