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BQ24253: Fast charging current different to ISET

Groupe-HW
Prodigy 50 points
Part Number: BQ24253

Tool/software:

Hello,

The fast charging current is set to about 1A using the RSET resistor set to 237 ohm.

We measured the maximum charge current to 500/600mA.

ILIM is set to 2A by connecting ILIM to ground.

EN1 and EN2 are set in order to configure ISET and VDPM externally.

Below the schematic of the charger, do you have an idea why the fast charging current is different from the setting ?

  • 0
    TI__Mastermind 25645 points

    Hello, 

    Thank you for reaching out via E2E. 

    Can you please help to provide VIN and VBAT measurements as close to the IC pins as possible when charge current is 500/600mA? 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 50 points

    Hello,

    I resolved my issue by connecting D+ and D- as mentionned in several forum issues...

  • 0 in reply to Groupe-HW
    TI__Mastermind 25645 points

    Hello, 

    Thank you for the update and confirming your issue is resolved. My mistake for initially glossing over D+/D- pins being left open in your design.

    Even though shorting ILIM pin sets input current limit to 2A open D+/D- pins result in in detection of "non-standard' adapter type and input current limit is set to 500mA. 

    Shorting D+/D- pins together results in DCP detection and input current limit will be 2A set by external connection at ILIM pin. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 50 points

    Hello,

    The charger is now charging the battery with a current of 1A.

    But regarding the SW signal from the charger, I saw a switching frequency to 3MHz (BLUE trace below) when starting the charge and few minutes after a switching frequency to about 1.5MHz (RED trace below).

    I don't see this behaviour in the datasheet. Is it a normal operation of the charger ?

    Best regards.

  • 0 in reply to Groupe-HW
    TI__Mastermind 25645 points

    Hello, 

    When you observe 1.5MHz switching what is the battery voltage and charge current? 

    As the device is approaching full charge and current draw decreases it is expected for there to be some pulse skipping. Based on your provided waveforms that does appear to be what is occurring and it is normal operation. 

    Best Regards,

    Garrett