BQ25616: USB SDP Port detection and Input current limit clarification

Chandann27

Part Number: BQ25616

Hi,

We are planning to use BQ25616 charger IC in our wearable device. We have a Li ion battery of 650mAh.

Query:

When we connect the device to USB port for data transfer (SDP port), what should be the input current limitation of the device before configuration and if the configuration fails ?

As per USB specification, device shall draw only 100mA till the 500mA is configures during USB enumeration process. But BQ25616 IC limits the input current to 500mA (allowing device to take more than 100mA) as soon as it detects the SDP port.

Isn't it violation of USB spec ? Or am I missing some thing ?

Because many charger ICs limit the input current to 500mA for SDP port - except few linear charger ICs.

over 2 years ago

0 Ning T over 2 years ago

TI__Guru 50811 points

Hi,

500mA.

It does not violate the USB spec. Please refer to https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/528485/bq24295-pulls-500ma-before-enumeration-of-standard-downstream-port for the details.

Thanks,

Ning.

0 Chandann27 over 2 years ago in reply to Ning T

Prodigy 180 points

Hi Ning,

Thanks for the response.

Yes, Connect timing ECN allows to draw 500mA after attachment using dead battery or Weak Battery provision for a certain period of time.

After that time, we have to configure to 500mA.

If the configuration fails or if the host do not approve of drawing 500mA and If we draw 500mA (since the set input current limit is 500mA) will it not cause issues ?

Reference image from Connect timing ECN.

Thanks,

Chandan N

0 Ning T over 2 years ago in reply to Chandann27

TI__Guru 50811 points

Chandan,

After the D+/D- input current limit detection is complete, the host may modify the input current limit via I2C as needed.

Thanks,

Ning.

0 Chandann27 over 2 years ago in reply to Ning T

Prodigy 180 points

Hi Ning,

Thanks for the reply.

Sorry, I have raised question from a related query from BQ24295. So it might be confusing. We are using BQ25616, it is standalone IC and do not have I2C communication.

Any suggestions to comply with USB standard ?

0 Ning T over 2 years ago in reply to Chandann27

TI__Guru 50811 points

Hi,

The input current limit detection results supported by the BQ25616 is listed in Table 9-2. Input Current Limit Setting from D+/D– Detection on the d/s. If the desired input current limit setting is not available, please leave D+/D- pins open and use ILIM pin to set the input current limit.

Thanks,

Ning.

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BQ25616: USB SDP Port detection and Input current limit clarification