BQ24195 -- queries for Battery power bank

Hello Pradhan,

The bq24195 supports input voltages up to 17V, but it's mainly designed for USB inputs since it implements a D+/D- detection scheme to auto-detect and set the input current limit of the device based on what type of USB host is connected. You can operate the bq24195 without host involvement by making use of the device's default values, please refer to the datasheet for the details regarding the registers' default values.

The OTG pin serves 2 functions: as part of the input current limit detection scheme and to enable/disable the OTG functionality. OTG on the bq24195 is a bit different than the rest of the 19x family: the output of the OTG is on the PMID pin instead of the VBUS pin. I recommend you verify the application example on the datasheet that shows an example of an implementation where the OTG pin is controlled by plugging in the adapter/USB host to control the OTG pin, to ensure you don't try to charge/OTG at the same time.

Regarding charging time, it will depend on your fast charge current setting as well as your termination current settings. The adapter you use will limit the fast charging current. You mentioned 3 different adapter ratings in your post, assuming an adapter of 5V/3A, you can fast charge up to ~2.7A before hitting input current limit. Something to consider in this example is that if you want to use a 3A input current limit, this limit would need to be modified via I2C, since the highest value the limit can be as the result of the D+/D- detection scheme is 1.5A.

Hope this helps.

HI

Thanks for the quick response.

I will revert back if any issues.

Thanks and regards

Pradhan

Dear Sir/Madam

We want to use DC voltage supply only for our design. USB and I2C is not required. so in that case what shall we do with USB and I2C pins. Is it ok to keep it open?

Below are more specs.

We are design the schematics as per below consideration

(1) Input voltage 5V/3A or 12V/2A DC
(2) battery capacity is 3.7V/7500mAh ( 3 cell of 3.7V/2500mAh in parallel)
(3) battery charging current is 2.7A
(4) Output Voltage/current is 5V/3A
(5) When input power is present & Battery is full, Load directly drive from input power.

As per above my design requirement, following are the quires
(1) is it required to configure BQ24195 via I2C or not
(2) what will happen if D+/D- pin is left open or Ground
(3) If not required I2C then SDA, SCL left open
(4) OTG pin left open or connected as per page 34 of data sheet ( 9.2 Typical Application on Page 34 of data sheet)

Thanks and regards

Pradhan

Hello Pradhan,

Since your adapter options are rated to 2A or 3A, the bq24195 in standalone mode wouldn't be the best option to ensure you get the most out of your adapters. This is because, in standalone mode, the charger will use the D+/D- pins to set the input current limit; in the 195 the highest current limit value in standalone mode  is 1.5A.

The bq25895 is another charger device tailored for power bank options, and similar to the 195 can operate in standalone using default values, but this part can be configured to set the input current limit to 3.25A in standalone mode by configuring the D+/D- pins so that the charger detects a USB DCP host which sets the input current limit to 3.25A. Shorting D+/D- with a 20 Ohms resistor should allow the device to detect a DCP host and set the input current limit to 3.25A. Leaving D+/D- pins open/shorting may cause the charger to detect an incorrect host and set the incorrect input current limit, so proper configuration in standalone mode is important.

If not using the I2C pins, these can be terminated by using a 10k pull-up resistor. 

Regarding the OTG pin on the application example, this example shows how to control the OTG pin by means of the presence of the adapter. If the adapter is connected, the OTG pin is pulled down and the OTG functionality is disabled. When the adapter is absence, the OTG pin is pulled high, enabling the OTG functionality.

Thanks. 

Dear Fernando Lopez

As per our last conversion, We final to used BQ25895 in our design.

(1) D+ and D- is short with 20 ohm register.
(2) If my input source is 12V/2A DC then no need to used i2C configuration?
(3) If I2C line is not used then SCl, SDA & INT line pull up with sys pin or battery positive line?
(4) If not used reset switch at QON pin then QON pis left open?
(5) DSEL pin not used then left open?
(6) BQ 25895 is support simultaneously battery charging and supply current to load?

Awaiting for your kind confirmation.

Thanks and regards

Pradhan

Dear Fernando Lopez

As per our last conversion, We final to used BQ25895 in our design.

Attached is the schematic.PB_VER 1.0.pdf
(1) D+ and D- is short with 20 ohm register.
(2) If my input source is 12V/2A DC then no need to used i2C configuration?
(3) If I2C line is not used then SCl, SDA & INT line pull up with sys pin or battery positive line?
(4) If not used reset switch at QON pin then QON pis left open?
(5) DSEL pin not used then left open?
(6) BQ 25895 is support simultaneously battery charging and supply current to load?

Awaiting for your kind confirmation.

Thanks and regards

Pradhan

Hello Pradhan,

Your schematic looks good. Regarding your questions:

• If using a 12V/2A adapter, input detection should identify the host as USB DCP, setting the input current limit to 3.25A. Ensure also that the ILIM resistor value can let the charger draw at least 2A to ensure you use the most out of your adapter.
• You can tie the pull-up to battery or system. You can tie it to battery since it's always present.
• If not using the QON functionality, you can leave it floating since it has an internal pull-up.
• Pull up DSEL using a 10k resistor.
• The bq25895 supports simultaneous charging and providing current to SYSTEM load. It does not support simultaneous charging and OTG.
• OTG pin can be pulled high to ensure that OTG can be enabled assuming the other conditions are met. You can also add an external FET to pull low the OTG pin based on the adapter presence if you like and leave it pulled high when the adapter is disconnected.
• You might want to consider using capacitors in parallel on the PMID pin instead of a one big 60uF to help reduce the ESR.

Hope this helps.

Dear Fernando Lopez

Please find the final schematic for the review. I have done required changes suggested by you.

Please review and let me know if any thing is missing.

Thanks and regards

Pradhan

Hello Pradhan,

I don't see the schematic attached. Can you please re-attach it?

Dear Lopez

Sorry for the inconvenience.

Attached is the schematic.

thanks and regards

PradhanMSIPL PB V1.0.pdf

Hello Pradhan,

The schematic looks good.

Dear Fernando Lopez

Greeting from India.

PFA schematics of my design, we have made the PCB board and test it, but we having following query

(1)we can used default condition of BQ25895, We can not getting more then 2A output cirrent

(3) When i am give the input voltage 9V/12V, then my output voltage change from 5V to input voltage (9V/12V).

We required 5V/3A output, when input voltage is 9V/12V.

Please resolve it and reply ASAP.

Thanks in advance and awaiting for your kind inputs on the same.

Pradhan

MSIPL PB V1.0_.pdf

Dear Fernando Lopez

Awaiting for your feedback on this.

PFA schematics of my design, we have made the PCB board and test it, but we having following query

(1)we can used default condition of BQ25895, We can not getting more then 2A output cirrent

(2) When i am give the input voltage 9V/12V, then my output voltage change from 5V to input voltage (9V/12V).

We required 5V/3A output, when input voltage is 9V/12V.

Attached is the schematic.

Regards

Pradhan6786.MSIPL PB V1.0_.pdf

Hello Pradhan,

The bq25895's current limit for the boost converter is limited by the integrated FET cycle by cycle current limit. Assuming the device is operating at peak efficiency, it can provide an OTG output with 3.1A. Having said that, I didn't find anything obviously wrong with your schematic. Do you have enough thermal vias on the PowerPad of the devices (typically a 3x3 grid of vias) as well as thermal vias across the PCB?

Is the device warming up significantly?

Regarding item #2, if you plug in VBUS, OTG is disabled automatically and the PMID voltage should be VBUS minus the drop across Q1. You cannot boost from the adapter; only from the battery.