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CM_ILIM of BQ51221

avraka
Intellectual 855 points
Other Parts Discussed in Thread: BQ51221

Dear TIer,

Datasheet of BQ51221 describe Pull High to enable CM_ILIM as below. But under the 5th line, Pin high to diable CM-ILIM.  What is the right operation of CM_ILIM?

"The communication current limit can be enabled by pulling CM_ILIM pin high (>1.4V) or disabled by pulling the
CM_ILIM pin low. There is an internal pull down that enables communication current limit when the CM_ILIM pin
is left floating. When the communication current limit is enabled, the amount of current that the load can draw is limited. If the charger in the system does not have a VIN-DPM feature, the output of the receiver will collapse if communication current limit is enabled. In order to disable Communication Current Limit, pull CM_ILIM pin high."

  • 0
    TI__Genius 14890 points

    Avraka,

    Section 9.3.7 helps describe the function of the CM_ILIM pin.  

    When it is enabled, the output current will be limited during communication (sending information from the RX to the TX).  On some systems, this will ensure more repeatable communication.  

    The benefit is increased accuracy of communication.  The drawback is that during communication packets, the current is limited as shown in Table 4.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Intellectual 855 points

    Thanks Dick..

    But what I confused is the logic status of CM_ILIM to enable the communication current limit.

    Pull high or low to enable this function?

  • 0 in reply to avraka
    TI__Genius 14890 points

    Avraka,

    Does this portion of section 9.3.7 help?  Please make sure to refresh your download to make sure you have the latest version of the datasheet.  The datasheet was updated for this section in  February 2014.

    The communication current limit is set according to Table 4. The communication current limit can be disabled by pulling CM_ILIM pin high (> 1.4 V) or enabled by pulling the CM_ILIM pin low. There is an internal pulldown that enables communication current limit when the CM_ILIM pin is left floating.

    Regards,

    Dick