BQ25895: Using 5.3V/0.85A solar power input

JeffYC Yang

Part Number: BQ25895

Hi Sir,

If BQ25895 using 5.3V/0.85A solar power input, this source only have power and ground, I just need connect D+/D- together, let it always recognize to 5V/1A input, right?

Thanks!

Jeff

over 8 years ago

0 Fernando Lopez over 8 years ago

TI__Expert 8230 points

Hello Jeff,

If D+/D- are shorted, the D+/D- detection on the bq25895 will detect the connection as DCP and set the input current limit to 3.25A. This will allow the device to use the full 0.85A from your input.

Having said that, if you want to limit the input current limit to 1A, there are two options you can also follow:

After D+/D- detection, you can change the input current limit using your host to 1A.
Set the ILIM resistor to fix the input current limit to 1A. A 360 Ohms resistor results the input current limit to 1A. Please note, this is assuming the input current limit was set to 3.25A initially after the D+/D- detection, since the actual input current limit is the lowest value between ILIM setting and the register setting.

0 Jeff F over 8 years ago

TI__Guru**** 167136 points

Jeff,

The bq2895 has the ICO feature which can be used to implement Maximum Power Point Tracking. When an ICO event occurs, VBUS is pulled down to VINDPM and actual input current = IDPM_LIM instead of IIN_LIM (assuming ILIM resistor is higher than either). You could write a simple loop similar to find the maximum power point voltage (optimal VINDPM most likely between 0.75-0.85 of VINDPM instead of fixed VINDPM) for the panel (i.e. the voltage at which it provides the most current). Keep in mind that when the battery voltage is low, ICO needs at least 500mA input current to function correctly.

0 JeffYC Yang over 8 years ago in reply to Jeff F

Expert 1290 points

Hi Jeff,

Got it, thanks for your reply.

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BQ25895: Using 5.3V/0.85A solar power input