BQ25185: Temperature Rise based on my application based Power Dissipation Calculation Required

Hi Ahmed,

The die junction temperature of the charger can be estimated using:

T_J = T_A + θ_JA * P_DISS

From the BQ25185 datasheet, θ_JA = 68.3°C/W and ambient temperature (T_A) is typically assumed to be 25°C.

That said, θ_JA is highly dependent on board layout, so this is only a rough estimate. The following application note provides more detail:

Semiconductor and IC Package Thermal Metrics

1.21W does seem like a lot of power for the BQ25185 to dissipate. Could you share your calculations for PDISS?

Best regards,

Alec

The following calculations are based on the worst-case scenario in my application:

PSYS = (VIN - VSYS)*Iin = (5-4.5)*1.1 = 0.55W
PBAT = (VSYS - VBAT)*IBAT = (4.5-3.4)*0.6 = 0.66W
PDISS = PSYS + PBAT = 0.55 + 0.66 = 1.21W

Although my load current is 350mA in the worst case, I want to ask how to incorporate it into my calculations.

I am looking forward to hearing back.

Regards,
Ahmed Ali

Thank you, Alec. Please help me on my other thread regarding BQ25185 as well.