BQ25713: efficiency data

Hey Toshiro-san,

Please refer to Figures 4, 5, 6, and 7 in the datasheet for the system efficiency. Specifically, refer to the VOUT = 3.7V curves for the 1S configuration. 

The data for charge efficiency can be directly derived from the system converter efficiency (in the figures above) by adding the I2R conduction loss of your customer's particular PMOS BATFET. Thus the efficiency of the charger is the system efficiency @ charging current minus I2R loss at charging current due to the external BATFET RDSON. 

As an example, with 5VIN, 3.7VOUT, 1A Output Current, System Efficiency is ~92%. Let's assume the charging current is 1A, and the BATFET RDSON is 20mOhm. 

The new efficiency can be calculated by the following:

(1/eff_new) = (1/eff_prev + Ploss_new/Pout). 

In our example, the new loss = ICHG^2 x Rdson = 0.02W. New efficiency = 91.54%.

Regards,

Joel H