BQ24780S: About Register Settings

Hi Tomoya,

1. Independent comparator is a build-in comparator, it is a "bonus" for some customers. You can use it for input under-voltage lockout, or battery overvoltage protection. If unused, tie CMPIN to GND, let CMPOUT float.

2. To prepare the battery for shipping mode, the output cap on the battery terminal needs to be discharged. The charger implements this function by sinking a small current 5mA for a short period 140ms on the SRN pin. You can follow our BQ24780SEVM user guide for test setup. 

3. Yes, if enabled, the discharge current is regulated to 0x39H discharge current level. 

Regards,

Tiger

Hi Tiger,

1. Is the explanation of the Independent comparator included in the data sheet?
    If CMPIN is float, will it stop working?

4. Should I pull up /BATPRESS to 3.3 V if I don't use the LEARN function or hybrid power boost mode?
    If /BATPRESS is float, will it stop working?

Tomoya Yoshino

Hi Tomoya,

1. Yes, it is in the datasheet. The charger is believed to continue working even if CMPIN is floated. 

2. /BATPRESS low means battery present. Suggest tying to LOW. TI does not suggest float /BATPRESS. Undefined /BATPRESS voltage probably affects the converter operation. 

Regards,

Tiger

Hi Tiger,

1. Where can I find the explanation of the Independent comparator in the datasheet? Could you tell me?

2. Do I need a pull-down resistor to tie it to LOW?

Tomoya Yoshino

Hi Tomoya,

1. The Independent comparator is in the pin description.

2. You can directly tie the CMPIN to ground . 

Regards,

Tiger

Hi Tiger,

2. /BATPRESS, not CMPIN

Can I directly tie the /BATPRESS to ground?　Or do I need a pull-down resistance?

Tomoya Yoshino

Hi Tomoya,

BATPRESZ is a logic input. It can tie to ground directly. 

Regards,

Tiger