TPS61288: Boost converter from Lithium battery

Hi Khoi,

TPS61288 is ok but it is not the only option.

The device is not true disconnection. That means even the device is disabled, the output voltage will be same as input voltage.

I will recommend other devices If you need other features just like true disconnection.

For your questions,

1. yes. the device can output up to 5A in this condition.

Please see attached calculation tool.

2514.TPS61288 Calculation tool.xlsx

The max output power depends upon its inductor peak current.

2. It's saying that the input source should be a stable voltage.

A voltage source with long connecting wires will fluctuate when drawing current, which is not a good choice.

Usually, it is required to add a ceramic bypass capacitor at input side.

For a battery, it will be a good source when input wire is short, input side capacitor is also welcomed.

Regards

Fergus

Hi Gergus,

Thank you for your reply. Do you have a suggestion for a true disconnect converter? It would be very helpful for me since we would like not to draw power when it is not needed.

Thank you for your point 2. I did see that in the EVM you have a 150 uF capacitor to smooth out the input fluctuation. I think I can do the same.

Khoi Ly

Hi Khoi,

In your application, the average input current will be about 6A.

TPS61178 data sheet, product information and support | TI.com can be used, it needs an external P-MOS to disconnect. 

Best Regards

Fergus

Hi Fergus,

I looked into TPS61178 and it's EVM and it seems to me that the Vin range is not within 2.7 to 4.2V, even though the datasheet summary says so. can I use exactly the EVM, except that I will adjust the resistors for Vout to meet my need, and expect the circuit to work with my application?

Thank you very much,

Khoi Ly

Hi Khoi,

The device's input range is 2.7to 20V.

For the EVM, you can just change the feedback resistors and used it in your application.

The TPS61178's switching frequency and current limit can both be adjusted.

Please be noted that the efficiency of TPS61178 will be lower than TPS61288 due to the inner MOS difference and output N-MOS.

Regards,

Fergus

Hi Fergus,

Thank you for your suggestion. Regarding selecting the Vout based on the Rup and Rdown values. I have a question.

From the datasheet, it seems to me that Vfb is 1.3V, but based on the equation 4, Vout (16V) = Vfb x (1 + Rup/Rdown), with Rup = 1M, and Rdown = 80.6k, Vfb is 1.192V, so I am curious what is the value of Vfb in the EVM module?

Thank you,

Khoi Ly