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Application Schematics of BCI in DM

Antony Lin
Genius 13480 points

Hi,

In TPS65950DM, there are 4 Application schematics of BCI in Firgure 8-1 A~D.

I have some questions about them.

1. Some of them supports "current nonlimited chargers", and some only support "current limited chargers."  What exactly do  "current limited chargers" & "current nonlimited chargers"  mean?  Does it mean the charger device CAN/CANNOT limit the maximum current it can supply?

2. What's the relation between "current limited chargers" & "constant voltage mode"?  It seems "constant voltage mode" is supported only for "current limited chargers" application, but not for "current nonlimited chargers" application?

3. For Figure 8-1D, it mentions "current nonlimited chargers are supported".  Does it imply "current limited chargers" are also supported in Figure 8-1D?

4. Is there any relation between "current limited chargers" and "pulsed charging"?  Since "pulsed charge" requires an "ac charger device that can limit the charge
current," can it be supported only with Figure 8-1A&B or also Figure 8-1D?

5. Can typical CC & CV charging be supported for all of them (Figure 8-1A~D)?  (Since "current limited chargers" imply to some people that the charging current is limited by the charging device itself instead of ICTLxx1)

Thanks,

Antony

  • 0
    TI__Genius 15100 points

    Hi Antony,

    It may be a little difficult to explain all the questions. Let me try. My answers may not have every fine detail, however, it will help in understanding why the specs are such.

    In the diagrams you will notice that the RC compensation circuits are connected to either VAC or to VCCS. When the RC is connected to VCCS it is - Miller compensation, which is more stable than regular, that’s why we use it in CV mode where we need a very accurate voltage, but it is less secure (at charger plug PFET is totally ON and must use an in-rush circuit limitation). Regular compensation is more secure at charger plug because PFET is OFF.

    Based of the above you can see why we need current limited chargers for circuits with Miller compensation, current limitation is needed with this circuit.

    Pulsed charging is possible with AC charger only and these should be current limited chargers. It would be supported only in 8-1 (A and B).

    CC and CV can be supported by all figures. This depends on the charging current an dthe battery voltage, it is independent of the charger.

    I hope the above helps.

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    TI__Genius 13480 points

    Hi Gandhar,

    Thanks for the answers, and now I have a better understanding.

    Some furher questions as below,

    For "Figure 8-2 Typical Application Schematic (In-Rush Current Limitation)", it's mentioned that it can enhance to support in-rush current at the charging device plug to maximum 850 mA.  What does it mean?

                    a. It can support current limited charger which limit current <850mA?

                    b. For current limited charger with current limit >850mA (e.g. 1.5A), Figure 8-2 can ensure the (in-rush) charging current through PFET <850mA?

    Which one is true? 

    If a is true, what will happen if a current limit charger with limit current>850mA is plugged in?

    If b is true, does it mean Figure 8-2 can support current nonlimited charger?

    Thanks,

    Antony