TPS65988： TPS65988 control TPS55288

Hi Wei,

Please take the app note USB Type C Power Delivery Source with TPS65987 and TPS55288 as a reference.

Thanks

Bing

Hi Bing

If I want the following effect：

     1.PDO1 displays 5V, but it actually needs to output 5.25V
     2.PDO2 displays 9V, but it actually needs to output 9.25V

If the above effect can be achieved,how can I set it up?

thanks,

Wei

Hi Bing,

Can you tell me specifically how to do it，

Thanks 

Wei

Hi Wei,

You can start a new thread as this one, and in the header, you can type in the part number of "TPS55288", then the question will be submitted to the product line of TPS55288 and relevant expert will answer your question.

Thanks.

Bing

Hi Bing

I asked TPS55288, but they asked me to change the value of (2H) to 0xFF, how to configure it.

thanks.

Hi Bing

  TPS55288 Just tell me to set the value of IOUT_LIMIT Register (02h) to 0xFF, but how to set it through TPS65988,Need me to ask TPS65988.

Thanks,
wei

Hi Wei,

Can you describe your application scenario?

How many PDOs have been introduced on your board?

Which kind of feedback has been adopted by you for TPS55288, internal feedback or external feedback?

Thanks

Bing

Hi Bing,

The architecture I use is TPS 65988+TPS55288, and my product is DOCK.

A total of 4 PDOs

PDO1（5V/3A）     PDO2（9V/3A）      PDO3（15V/3A）       PDO4（20V/5A）

The following are the circuit diagrams of TPS65988 and TPS55288.

The I2C1 of my TPS65988 is connected to TPS55288.

thanks,

Wei

Hi Bing

Now I want to set the VREF of TPS55288 to 0011011110 (b) and IOUT_LIMIT of TPS55288 to 11110000 (b).

The I2C address of TPS55288 is 0x74, and it is connected to I2C1 of TPS65988.

How do I set it up, thank you.

4606.CSB_DOCK_V8_TRY_DRP_external_path_20V2_5A_DiscIden_Dell_VID.rar

thanks,

Wei

Hi Bing,

In addition，

This is the VEF register (00h, 01h)

This is the  IOUT_LIMIT  register (02h)

thanks,

Wei

Hi Wei,

OK, let me repeat your requirement and clarify it.

Now, although you set the PDO at 5V or 9V, you want to actually output the VBUS voltage at 5.25V or 9.25V, is that right? (For cable compensation?)

If that is the situation, below are the calculation formulas for corresponding reference voltage codes, and meanwhile you can take the TPS55288 datasheet as a reference. The formulas are as below:

PDO * Feedback = Vref                                (1)

Vref = dec_Codes * 1.129mV + 45mV                  (2)

Example:

If you want to get the output voltage @9V, and feedback divider has been set at 0.0564 (this value is based on internal feedback, you can take the datasheet or app note as a reference; if you want to use the external feedback divider, you can configure the divider as you want)

According to (1), you can get the Vref = 507.6mV;

According to (2), you can get the dec_Codes ≈ 410;

Then you can take TPS55288 datasheet as reference, and find the corresponding configuration of the register 0h & 1h. Actually here, the codes you need to write into TPS55288 is as 0x019A = 0b0000 0001 1001 1010, higher 6 bits are reserved by TI, and  lower 10 bits are used for configuration.

and here: 410 = 0*2^9 +1*2^8 +1*2^7 + 0*2^6 + 0*2^5 +1*2^4 + 1*2^3 +0*2^2 +1*2^1 + 0*2^0

As you can see, if you want to configure the output VBUS voltage @9.25, you can get the dec_Codes as 422 after calculate it, then you can transform the dec_Codes into binary code.

As for the method to write TPS55288, below are some principles you can use:

Take 0xd200 (data length 3) as an example (@5V);

1. Highest bits of 0 will be omitted, therefore, although the data length is 3, but you can see only two bytes in the code ==> 0x(00)d200;

2. Lowest byte is the start address for the register, which means that in 0xd200, the byte "00" is the first LSB register for REF register.

According to above two principles, writing 0xd200 (data length 3) to TPS55288 means that actually 0x00d2 is write into REF register. 

Here goes another example: 0x0304 (data length 2), means that write 0x03 into 0x04 register. This register is used for internal feedback divider value configuration, and 0x03 means that set the divider value as 0.0564 (You can find it in the datasheet for TPS55288)

Hope this will help you.

Thanks

Bing

Hi Bing,

According to your introduction, the PDO output problem has been solved.

However, I still have a problem that has not been solved. Modifying the OCP of 55288 is to change the value of 02h to 0xF0.

But I did not succeed, the configuration is as follows。

Please help to see if the configuration is wrong。

thanks,

Wei

Hi Wei,

Do you have any further question?

Hi Bing,

I have no problem。

thanks,
Wei