TPS2549: About TPS2549 apple 2.4A charging mode

Hi Adam,

Wow, thanks for you reply so quickly :)

1.  a. So that means I can replace TPS2546 with TPS2549 directly, even if DESCRIPTION of pin4 is different ?

     b. The divider 3 mode maximum current is 2.4A (12W/5V=2.4A), right ?

2.  a. "There are multiple charging currents for Apple charging."  I'm confused, TPS2549 only supply Apple divider 3 mode,what it the other mode for Apple charging? 

     b. If I setup DCP mode (000 or 001), the initial mode is DCP Auto Mode (8.4.6), and the will auto-detect the other scheme (divider/short/1.2-V), right ?  

     c. What is different between DCP (000) and DCP1 (001)? 

Jimmy

Hi Jimmy,

I apologize, I forgot about that difference. Yes the TPS2549 offers cable compensation for the voltage drop in long cables and keep the remote USB port output voltage constant. TheTPS2546 does not have this feature. Pin 4 on the TPS2549 is connection you put through the feedback divider to utilize this feature.

To answer your question, you cannot replace the TPS2546 and TPS2549 directly with one another due to this feature difference.

2. The other charging modes are divider 1 and divider 2. Divider 1 offers 1A of continuous current while Divider 2 offers 2.1A.

2b. Yes

2c. It changes what current limit setting you are using. There are two external resistors connected to ILIM_LO and ILIM_HI. You can connect different resistor values to each of these so that they have different current settings for if you want the TPS254x to supply a lower/higher amount of current depending on a specific scenario.

Hi Adam,

thanks for your clearly reply~

One last question about CS pin want to confirm with you. 

1a. According to 9.2.1 ~ 9.2.2, can I just following the example rds(on) = 420m ohm to design in ?

      Cause our product is the docking station and doesn't include the cable

1b. If I don't want this features (CS), does it need to pull down or just let this pin empty?

thanks~

Jimmy

Hello Jimmy,

I would say to tie the CS pin to a 5V source based on this graph. However, it would also make sense to not have it connected sense you will not be applying a load to the pin. I have not seen the TPS2549 used without implementing the cable compensation feature, so I am unsure how it will operate without having that connection.

What I would recommend doing is having resistor tied to 5V and resistors tied to GND, so that if one does not work, you can depopulate/populate the resistors to change the design.

Let me know if this helps answer your question.