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BQ25792EVM: Charging current was correct?

Nakka Malesh
Prodigy 130 points
Part Number: BQ25792EVM

Hi,

   I am using BQ25792EVM board in 4S configuration. I am following your BQ25792EVM document for testing purpose. Used power supply at battery

Characteristics:

ILIM =1.23v--> means 250ma input current limit.

i have removed the Thermister (means TS= 85% of Vx(5V))

initially  i am disable the WatchDOG, TS fault, and enable the ADC.

i am reading the data from all registers.

my charger status registers are (0x1B-0x0x1F)=0x0d,0x0a,0x01,0x40,0x00

all are working perfectly as you mention,

BUT the charging current was not correct it was too low, ranging from 100ma to 30ma only for all pre, fast, termination stages.  why this was happen?

Voltages:

VAC2=5V/2A(input)

VBUS=5V(output)

VSYS=12.4V(output)---> no LOAD connected

VBat=5V to 16.8V(pre, fast, termination limits ( you suggested to use a power supply at battery in the document ( it was 16V/2A source)) (input)

Please answer my doubt?

Is there anything i have missed?

Best Regards,

Malesh Nakka

  • 0
    TI__Guru**** 165886 points

    HI Malesh,

    Since V(SYS)=12.4V, it appears you have the charger configured for 4S.  Your input power is 5V*250mA = 1.25W.  So the max output current available is approximately 1.25W/V(BAT)*efficiency.  You can use the datasheet efficiency curves for the efficiency value.

    Regards,

    Jeff