BQ25601: Pre-charge into fast-charge current question

Sam Shyu36

Part Number: BQ25601

Dear Sir,

Test the BQ25601's charging function. Found 2 stage in fast charging(in below) but it doesn't have any information about this in spec. Why fast charge have two stage charge current when pre-charge transfer to fast-charge?

Item	Expected value			Test point	Measured
Item	Min	Typ	Max	Test point	Measured
Pre-charge current	51	60mA	63	J201	54.3mA
Pre-charge voltage	3V	3.12V	3.24V	J201	3.027V
Fast charge current	216mA	240mA	264mA	J201	229.4mA@3.027~3.567V 239.8mA@3.567~4.049V

Best Regards,

Sam

over 6 years ago

0 Angelo Zhang87 over 6 years ago

TI__Genius 11850 points

Hi Sam,

The reason for this is that when the battery voltage is below the minimum system voltage Vsys_min (default value of 3.5 V, which is close to your 3.567 V measurement), the BATFET operates in LDO mode. When the battery voltage is above Vsys_min, the BATFET is fully on and the charger operates in CCM (see Section 8.3.7.8 in the datasheet for more details). These two different modes cause the slight difference in fast charge current that you noticed, but both currents (229.4 mA and 239.8 mA) are still within specs, so they won't cause any problems.

You may also have noticed that in the test conditions shown above, Vbat = 3.1 V or 3.8 V. Vbat = 3.1 V is below Vsys_min and corresponds to the BATFET operating in LDO mode, while Vbat = 3.8 V is above Vsys_min and corresponds to CCM. Since the charge currents are so similar in either case, they were both lumped together in the EC table.

Best Regards,

Angelo

0 Sam Shyu36 over 6 years ago in reply to Angelo Zhang87

Intellectual 735 points

Dear Angelo,

Thanks for your help~

Best Regards,
Sam

Power management

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BQ25601: Pre-charge into fast-charge current question