BQ24072: Not reaching max charging current at 5V

Vladas

Part Number: BQ24072

Hi,

my BQ24072 it not reaching maximum charging current limits at 5V. I have it on a breadboard and connected to bench power supply with 2.5 A limit using the reference design, and these values:

CE -> low, TD -> low, TMR -> low, TS -> 10k, ILIM -> 1.3k, ISET -> 1.2k

And I try to charge LG 18650 cell with voltage around 3.5V.

When EN1 -> high, EN2 -> high, BA24072 operates without problem in suspend mode and des not consume more then 2 mA.

When EN1 -> low, EN2 -> low it draws at max 0.1 A as expected.

But when EN1 -> high, EN2 -> low with 5V at IN it charges the battery with only 0.3 mA if I rise the input voltage to around 6V then it reaches the limit of 0.5 A and charges the battery.

Same problem with configuration EN1 -> low, EN2 -> high.

Any suggestions how to debug this or it is a normal behavior?

Thanks

over 7 years ago

0 Bill Johns over 7 years ago

TI__Guru* 75976 points

Hello
This test is with no load on OUT, right?
Voltage at OUT looks OK?

Take a closer look at voltage on IN pin when the current is reduced, it could be IN to BAT ( battery voltage ) differential too low.

0 Vladas over 7 years ago in reply to Bill Johns

Prodigy 40 points

Hi,

yes it's without any load.

Volage on OUT is 3.8V so a bit low.

And the differential voltage between VBAT and IN is 1.2V, what is the minimum needed to get the full current limit?

Best,

Vladimir

0 Bill Johns over 7 years ago in reply to Vladas

TI__Guru* 75976 points

Hi Vladimir
Check the input voltage at Pin IN, is it 5V?
If voltage at OUT is low it may trigger reduce battery charge current (DPPM) even with no load.

The 1.2V IN to BAT is OK.
Is battery running about 3.6V for this test?

0 Vladas over 7 years ago in reply to Bill Johns

Prodigy 40 points

IN voltage is more around 4.5 V.

Yes, the battery is about 3.6 V.

If I understand the DPM correctly it reduce the charging current when IN gets below VIN_DPM so around 4.5V but this should be active only for modes USB100 and USB500 in the mode where ILIM is set by external resistance the current is drawn even if IN gets lower. Until the voltage IN to BAT gets to low, What is this IN to BAT limit?

Vladimir

0 Raheem over 7 years ago in reply to Vladas

TI__Mastermind 21590 points

Hello Vladimir,
Were you able to solve this issue?

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BQ24072: Not reaching max charging current at 5V