ADA4625-1ARDZ-R7 datasheet(29/30 Pages) AD

29 / 30 page

Data Sheet

ADA4625-1

Rev. 0 | Page 29 of 30

THERMAL MANAGEMENT

The ADA4625-1 can operate with up to a 36 V supply voltage

with a typical 4 mA quiescent current. Heavy loads increase

power dissipation and raise the chip junction temperature.

The maximum safe power dissipation for the ADA4625-1 is

limited by the associated rise in junction temperature (TJ) on

the die. Two conditions affect TJ: power dissipation (PD) of the

device and ambient temperature (TA) surrounding the package.

This relationship is shown in Equation 11.

TJ = PD × θJA + TA

(11)

where θJA is the thermal resistance between the die and the

ambient environment. The total power dissipation in the

amplifier is the sum of the power dissipated in the output stage

plus the quiescent power. Power dissipation for the sourcing

current is shown in Equation 12, where VSY is the total supply

voltage (V+) – (V−).

PD = VSY × ISY + ((V+) − VOUT)IOUT

(12)

Replace ((V+) − VOUT) in Equation 12 with ((V−) − VOUT) when

sinking current.

For symmetrical supplies with a ground referenced load, use the

following equation to calculate the average power for the amplifier

processing sine signal.











































PEAK

)

SINE

AVG,

(13)

where VPEAK is the peak value of a sine wave output voltage.

The specified thermal resistance θJA of the ADA4625-1 is 52.8°C/W.

A good PCB layout and an external heat sink can improve thermal

performance by reducing junction to ambient temperature.

The ADA4625-1 features an exposed pad that floats internally

to provide the maximum flexibility and ease of use. Solder the

exposed pad to the PCB board GND, or the V+ or V− plane for

best thermal transfer. Where thermal heating is not an issue, the

exposed pad can be left floating.

Incorporate the use of thermal vias or heat pipes into the design

of the mounting pad for the exposed pad to lower the overall θJA.

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