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TMS320VC5510A: Resistor value for internal pulls

Koichiro Tashiro
Mastermind 21150 points
Part Number: TMS320VC5510A

Hi,

What are internal pullup and pulldown resistor values for IO pins?
[min., typ., max.]

Customer wants to know for HPIENA and /HAS pins.

Data sheet (SPRS139I) Table 2-2 just says there are internal pulls, but no value is specified.

Thanks and regards,
Koichiro Tashiro

  • 0
    TI__Guru**** 393215 points
    Hi,

    Please see parameter "Ii Input current" for input pins with internal pulldown and input pins with internal pullup. Pullup/pulldown resistor value is calculated from DVdd divided by Ii.
  • 0 in reply to Biser Gatchev-XID
    TI__Mastermind 21150 points

    Hi Biser,

    Thanks for your quick reply!

    I understood for 400uA (or -400uA), we can calculate the internal resistor value like this;
    3.6V (max. DVdd) / 400uA = 9k Ohm
    I guess this is the minimum resistor value.

    But how to calculate for 10uA (or -10uA)?
    Data sheet section 5.3 says VI=DVss to DVdd for Ii. This means 0V to 3.6V.
    If so, no inverse current is expected.

    Thanks and regards,
    Koichiro Tashiro

  • 0 in reply to Koichiro Tashiro
    TI__Guru**** 393215 points
    Resistor value will be in the range from 3.6V/300uA (or 12k) to 3.6V/5uA (or 720kOhm). These are not physical resistors, rather they are biased FET channels, therefore their resistance is not precise.
  • 0 in reply to Biser Gatchev-XID
    TI__Mastermind 21150 points

    Hi Biser,

    I understood these are min. and max.
    Do we have typ. value ? 12k to 720k is really wide range (x60).

    Thanks and regards,
    Koichiro Tashiro

  • 0 in reply to Koichiro Tashiro
    TI__Mastermind 29270 points
    Hi Tashiro-san,

    The internal pull-up (IPU) and internal pull down (IPD) resistors are not the only factors that are sinking or sourcing current. The CMOS input consumes small amount of current. And there are leakage paths through the CMOS input as well as the transistors used for IPU/IPD resistors.

    Process voltage and temperature affect the strength of the internal resistors significantly and in non-linear ways.
    * You do not need typical values for the IPU/IPD - you only need the worst case
    * You need to solve for the size of the external resistor so that it is small/strong enough to pull Vi > VIH or Vi < VIL (with margin to account for resistor tolerance)

    External pull-up and pull-down resistors both need to be sized about 2.5k (or smaller/stronger) to meet VIH/VIL with the internal pulls enabled in the opposite direction.

    Regards,
    Mark
  • 0 in reply to Mark Mckeown
    TI__Mastermind 21150 points
    Hi Mark,

    Sorry my late reply. I close this item.

    Thanks and regards,
    Koichiro Tashiro