TPS61288:

Hi Gabriel,

Thank you for reaching out.

1. It is ok to connect EN to Vin when Vin is lower than 6V.

2. The EN High-level input voltage is 1.2V.

The VCC voltage is from Vin(or Vout, the higher one) through LDO, and will be about 2.3V when Vin is 2.3V,

that is when Vin is above its UVLO voltage, the EN is already higher than its high level.

Regard,

Fergus

Thanks so much.

The 10k current limiting resistor is okay?

Hi Gabriel,

Do you mean to connect 10k directly to the EN pin without a resistor to GND?

There is an inner pull-down resistor 850k.

The connect resistor just need to ensure the voltage higher than its high level voltage.

Best Regards,

Fergus

Yes. For current limiting. To avoid loading the battery. Is it necessary?

Could you also suggest a buck-boost converter with at least the same current capabilities with the TPS61288, has a wide input range (minimum - around 2 V and maximum - 30 V or more), and can supply an output of 5.5 V? I tried looking for one using the filters and couldn't find.

Hi Gabriel,

For the EN resistor, it can be used.

For the Buck-boost, please see if TPS55289 is fit for your application.

 Its current limit is a little smaller than TPS61288.

Best Regards,

Fergus

Thanks. 

Is the external compensation network (conected to COMP pin) sensitive or is it okay to use the one used in the datasheet for any application?

Hello Brigitte,

I was talking about the TPS61288.

Hi Gabriel,

For the TPS61288, the comp network is sensitive and cannot use one for any application.

please adjust the comp parameters due to the working condition and output capacitance.

Please refer to TPS61288's calculation tool or give us the schematic for check.

Best Regards,

Fergus

Hi Fergus,

Here is the schematic:

The circuit is designed to provide a 5.5 V output and a current of upto 5 A. I used the typical values provided in the TPS61288 datasheet for the compensation circuit. Could you suggest better values of the components of the compensation circuit for this setup? 

The input voltage range is:

1. Min. voltage - 2.8 V

2. Nominal voltage - 3.7 V

3. Max. voltage - 4.2 V

Hi Gabriel,

Our engineer is currently out of office, please expect a reply by next week Tuesday. Thank you for your patience.

Best regards

Yezi

Okay. Thanks Yezi.

Hello Brigitte,

Thanks for the response. I have used the tool but the parameter for the compensation circuit are for the user to input as shown below:

I used the Webench tool. Is it a reliable tool?

Hello Gabriel,

When you enter the values in the tool it calculates for you the bode diagram, so you can take e.g. the values from the EVM and if you do not like the result in the picture below, vary them until it fits to your needs.

Webench can be used as well.

Nevertheless, no calculation tool takes parasitic effects of your system into account, so it is necessary to check stability in the lab, e.g. with load transients or a bode plot.

In general the crossover frequency shall be just good enough for your system as mostly a lower crossover frequency means a more stable system.

Best regards,
Brigitte

Thanks so much Brigitte.