TPS2549: Questions about TPS2549

Hello,

Please see my responses in red below.

(question 1)
Set "001" in the DCP mode setting.
The Current Limit Setting will be "Hi", but I will not use "Lo".
In this case, do I need to connect a resistor between ILIM_LO and GND? Or is it okay if the resistor is not connected?

R(ILIM_LO) is optional and the ILIM_LO pin may be left unconnected if the following conditions are met:
• The TPS2549 device is configured as DCP(001) or CDP(111).
• Load detection is not used.

(Question 2)
The following is described in the description of the STATUS item of the Pin function.
Is there a specific value for the load detection threshold value?
"Active-low open-drain output, asserted when the load exceeds the load-detection threshold"

STATUS asserts in a charging port when the load current is above ILIM_LO + 40 mA for 210 ms (typical).
STATUS de-asserts in a charging-port when the load current is below ILIM_LO – 10 mA for 3 seconds (typical).

(Question 3)
I think that setting CTL1, CTL2, CTL3 to "001" sets DCP mode and Divider3 mode.
Then, when power is supplied from the DCDC converter, DC5V should be output to the VBUS pin, and 2.7V each should be output to the DP and DM pins.
At this time, I understand that the above voltage is maintained unless a portable device is connected from the outside, but is it correct?

In 001, the mode will be DCP which includes divider 3, 1.2-V mode, and BC1.2 mode. The auto-detect state machine starts in the Divider3 scheme. I will follow up tomorrow with a scope capture of what the VBUS, DP, and DM pins look like before/after connection. 

(Question 4)
If a portable device is connected from the outside and the portable device is in Divider3 mode, will the DP and DM pins continue to output 2.7V until the connection is disconnected?

Yes. 

(Question 5)
If a portable device is connected from the outside and the portable device is in Divider1 mode or Divider2 mode, how will the device behave?

The TPS2549 does not offer Divider1 or Divider2 mode. The TPS2546 offers these modes. 

(Question 6)
When an external portable device is connected from the unconnected state and the portable device is BC1.2 and YD/T 1594-2009, the DP and DM pins are short-circuited at 200Ω max, but What happens to the 2.7V that was initially output between the DP and DM pins?

I am not sure what you mean by "the portable device is BC1.2 and YD/T 1594-2009" as the TPS2549 cannot be in two modes at once. Please take a look at Figure 8-11 in the datasheet, which displays the different switches for the different modes. I would also recommend getting a TPS2549Q1EVM to further test functionality. 

(Question 7)
When an external portable device is connected from the unconnected state and the portable device is in 1.2V / 1.2 mode, the DP and DM are short-circuited at 200Ω max and 1.2V is applied, but What happens to the 2.7V that was initially output between the DP and DM pins?

I would again recommend looking at Figure 8-11 to see the switches for the different DCP modes. 

(Question 8)
Will this device revert to the default Divider 3 mode when the external portable device is disconnected?

Yes, the auto-detect state machine starts in the Divider3 scheme.

(Question 9)
I understand that there is no temporary interruption of VBUS when switching modes within DCP mode, but is that correct?

Yes that is correct. Below is a good description of DCP auto mode from the datasheet: 

The auto-detect state machine starts in the Divider3 scheme. However, if a BC1.2 or YD/T 1591-2009 compliant device is attached, the TPS2549-Q1 device responds by turning the power switch back on without output discharge and operating in 1.2-V mode briefly before entering BC1.2 DCP mode. Then the auto-detect state machine stays in that mode until the device releases the data line, in which case the autodetect state machine goes back to the Divider3 scheme.

 (Question 10)

I only use DCP mode. Therefore, DP-OUT and DM_OUT are not used.
In this case, can the DP-OUT and DM-OUT pins be open?

Yes you can leave these pins floating if you do not plan to use them.

Thanks,

Emma