BQ25616: how to achieve lowers QUIESCENT CURRENT when the load is in sleep mode

Sachira Withanage

Prodigy 90 points

Part Number: BQ25616

According the the BQ25616 datasheet Quiescent battery current could be as low as 9.5uA.

I have followed the datasheet and the datasheet of the BQ25616EVM EVALUATION BOARDS and made a prototype.

the current reading on the battery line fluctuates a lot between 22uA and 178uA wen measured using DMM.

On the scope it looks as the attached picture. (using 10R resistor in series)

The settings and the setup of BQ25616 as below
1) OTG Function is disabled
2) VSET = 4.2V (Float Pin)
3) ILIM = 478/200R = 2.39A (Detection as Unknown adapter)
4) ICHG (Max battery charging current) = 1.2A
5) Measured with a battery pack with 4.1V
6) 3.9M ohm load connected as a load. (or considered as lo load)
7) The PCB layout guidance and component selection closely followed as in the datasheet

My question is why is the current reading has the spikes as in the picture?
How can I lower the QUIESCENT CURRENT to minimum level as in the datasheet?

Thanks.

over 5 years ago

0 Hong Mao over 5 years ago

TI__Expert 5590 points

Hi, Sachira:

Our datasheet shows average BAT current. The pulsing current you saw is true. If you average the current, the DC current should be within the spec.

Regards,

Hong

0 Sachira Withanage over 5 years ago in reply to Hong Mao

Prodigy 90 points

Hi Hong,

I have measured the average QUIESCENT CURRENT and it is between 31.13uA to 33.47uA

But it also goes down to 11.23uA to 13.08uA after about 3 minutes. This figure is more closure to the datasheet figure.
Could you please tell me why I'm seeing 2 QUIESCENT CURRENT stages?

The scope capture of the 2nd stage is as below,

Regards,

0 Sachira Withanage over 5 years ago in reply to Sachira Withanage

Prodigy 90 points

Scope capture of the 2nd stage again

0 Hong Mao over 5 years ago in reply to Sachira Withanage

TI__Expert 5590 points

Hi Sachira:

I cannot see your attachment. Could you explain what is the pulse magnitude, pulse width and frequency? From the waveform, we can estimate average current. The measurement result may depend on meter. Besides, have you take off any external circuits on SYS, BAT and PMID?

0 Sachira Withanage over 5 years ago in reply to Hong Mao

Prodigy 90 points

Hi Hong,

The magnitude of the current spike is 1300uA.

The average Pulse width is 322us. The frequency is between 0.54 Hz to 0.53 Hz (roughly every 2 seconds)
Please see the attached 2 captures for the 2 stages.
I have a resistor divider (going in to opamp) connected across the BAT and GND. Nothing other than the 10uF cap on PMID.

measurements done on a pico-scope.

Please see the attached picture of the current spike (does not allow to attach the scope log)