ADP5065ACBZ-1-R7 datasheet(36/40 Pages) AD

36 / 40 page

ADP5065

Data Sheet

Rev. D | Page 36 of 40

JUNCTION TEMPERATURE

In cases where the ambient temperature, TA, is known, the

thermal resistance parameter, θJA, can be used to estimate the

junction temperature rise. TJ is calculated from TA and PD using

the formula

TJ = TA + (PD × θJA)

(9)

The typical θJA value for the 20-bump WLCSP is 46.8°C/W (see

Table 5). A very important factor to consider is that θJA is based

on a 4-layer, 4 in × 3 in, 2.5 oz copper board as per JEDEC

standard, and real applications may use different sizes and

layers. It is important to maximize the copper to remove the heat

from the device. Copper exposed to air dissipates heat better

than copper used in the inner layers.

When designing an application for a particular ambient

temperature range, calculate the expected ADP5065 power

dissipation (PD). From this power calculation, the junction

temperature, TJ, can be estimated using Equation 9.

Maximum junction temperature (TJ) can also be calculated

from the board temperature (TB) and power dissipation (PD)

using the formula

TJ = TA + (PD × θJB)

(10)

where θJB is the junction-to-board thermal resistance.

The typical value for the 20-bump WLCSP is 9.2°C/W (see

Table 5). θJB is based on a 4-layer, 4 in × 3 in, 2.5 oz copper

board, as per the JEDEC standard.

For a WLCSP device, where possible, remove heat from every

current carrying bump (PGNDx, VINx, SWx, ISO_Sx, and

ISO_Bx). For example, thermal vias to the board power planes

can be placed close to these pins, where available.

The reliable operation of the charger can be achieved only if the

estimated die junction temperature of the ADP5065 (Equation 9)

is less than 125°C. Reliability and mean time between failures

(MTBF) are highly affected by increasing the junction temper-

ature. Additional information about product reliability is

available in the ADI Reliability Handbook at the following URL:

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