Greetings,

we are going to use a BQ24060 for Li-Ion battery charging. This chip has a mode called "Battery-Absent Detection". Can we charge a Li-Ion battery which is fully discharged? I mean that on battery`s output Vbat = 0 because of it`s internal protection. Does it mean that in that case we ought to use an additional button in our project for charging battery (at the TMR pin) ?

During the discharging of Li-Ion battery voltage on it`s output going down slowly. Inside the battery there is internal protector, which controls the critical voltage level on battery`s output while it is under load. For example, in Li-Ion battery CRAFTMANN PHILIPS XENIUM 9@9K the output voltage level near 2.4-2.5 V (only when battery is under load) forces the internal protection. The internal protection make the “+” output of the battery to disconnect from battery itself and short it to “-” output through 120K resistor. So when protection is on, potential of “+” output become equal to potential of “-” output, and the voltage between them will be 0 V. If we connect a battery in that state to BAT and GND pins of TPS65070, then after switching on the external power supply for battery charging TPS65070 will decide that there is no battery connected, and so the will be no charging.

But if we provide to such battery some external voltage it`s internal protection will cut a short between “+” output and “-” output, and connect “+” output to the battery itself. After that on output of the battery voltage will appear.

So our question was does the  BQ24060 chip checks the connection of the battery as it is done by  TPS65070?

If it is so, then BQ24060 won`t be able to charge batteries with forced internal protection (fully discharged).

In that case could we use for battery unlocking LDO mode of BQ24060? For example it can be done by turning it on (temporary) by placing the button in the break of the net TMR – Rtmr (Figure 16 datasheet)?  

bq24060 doesn't have same short circuit detection as TPS65070. It will put 25mA on the out when Vbat is lower than 1.4V. Please check datasheet page 4th.

?

In our case we haven`t a short, we have a break with a 120K resistance.

I can`t find anything about 25 mA on 5th page of datasheet.

My datasheet is called SLUS689A–JUNE 2006–REVISED OCTOBER 2006.

It is a typo.  Please check the page 4th of datasheet: PRECHARGE AND OUTPUT SHORT-CIRCUIT CURRENT REGULATION,.

I have similar problem with BQ24060. It reduce the current down to 20 mA and it also reduce voltage output to 1,8V. When I have a LiPo battery with protection circuitry it will not take any current before voltage rise to 3V. Is there any trick to get BQ24060 to continue to drive 20 mA current as long voltage rise to 3V. I read from your documents that current drive for different input voltages should be so that from 0-1,4V it is 20 mA from 1,4-2,9 it is about 100 mA and the 2,9-4,1 fast charge current (max 1A) and then reduce to constant 4,2V. See page 23 bq24060 Short Circuit Behaviour.