BQ24072T: No output voltage if no battery - empty battery not charging

Hello,

Can you check for proper solder connection on all pins. This is what i've seen a cause in the past.

Hi,

Unsolder and solder again : The Vout is now Vbat + approx 200mV : OK.

But if no battery / Vin 5V OK : Vout only 600mV approx.  and If battery is empty : no charging. (Charging are OK if battery are not totaly empty)

Do you think it a solder issue again ? What I can check to debug it ?

Hello,

Can you check if you see a square wave on the BAT pin similar to figure 25 in the datasheet when battery is absent.

Also check for shorts on both the output and the bat pins.

Hi,

No square wave on Vbat pin. If I put battery and remove battery, OK, I had square wave on Vbat.

No short circuit on In, Out or bat

It's seem like the BQ doesn't start if no battery is present.

I just tested with no one cheap : same result.

Try also with labo power supply : same.

Try with 10uF cap on the IN pin : same.

Some time, I don't know why, the cheap start and can I see the square wave on the bat pin ! (I put an cut power supply, each 2 or 3 seconds, and sometimes it works).

I think I have an issue with inrush current, it is possible ?

Because when I plus power, my MCU are not started yet and some power supply are ON. When MCU is UP, with power supply goes off (with enable PIN). But during this amount of time, I think the inrush current is > Ilim (1.45A).

I tested this :

No batt, Vin 5V : in this case, output voltage of 600mV, no square wave.

I power up my MCU with external 3.3V (This supply is only for the MCU), after a few millisecons/seconds, BQ start ! I see square wave.

So I think it start because my powers supplies are off so less current draw.

It is possible ? If Yes, can I do something to let the BQ start ?

Hello,

The BQ24072T has inrush current protection built in. The device starts with a 100mA input current limit at startup. Have you tried disconnecting the MCU from OUT pin and just see if the charger works without any load?

So without battery, load must not consume over 100mA if not the BQ won't start ?

The current limit at startup is active for a brief moment to prevent inrush current. At this point, the charger also checks for shorts. Were you able to run the test?

Hello Benjamin,

Any updates on this?