5.6

Maximum power dissipation

The maximum power supply voltage, as well as the usable output load current drive is limited by the maximum

power dissipation allowed by the device package. The absolute maximum junction temperature for the TSB951

and TSB952 is 150 °C. The junction temperature can be estimated as follows:

TJ=PD×RtℎJA+TA

(3)

TJ is the die junction temperature.

PD is the power dissipated in the package.

RthJA is the junction to ambient thermal resistance of the package.

TA is the ambient temperature.

The RthJA, given in table x for the available packages, is based on the JEDEC standard JESD51, for 2s2p (4

layers) board. This value has a large dependance on the board layout and is given as a guideline. Be aware that

the actual value can differ significantly and optimize the power dissipation on your board if this is critical for your

design. For thermally sensitive designs, prefer the SO8 version of the product for TSB951 and the DFN8 version

of the product for TSB952 that has a better thermal dissipation thanks to its exposed pad.

The power dissipated in the package PD is the sum of the quiescent power dissipated and the power dissipated

by the output stage transistor. It is calculated as follows:

PD= VCC×ICC + Vcc++VOUT ×ILoadwhentheopampissourcingthecurrent.

PD= VCC×ICC + VOUT+VCC− ×ILoadwhentheopampissinkingthecurrent.

Do not exceed the 150 °C maximum junction temperature for the device. Exceeding the junction temperature limit

can cause degradation in the parametric performance or even destroy the device.

For TSB951, the SOT23-5 package cannot be used at VCC = 36 V and at 125 °C ambient temperature. Due to the

Rth-ja value, the maximum junction temperature would be reached. The following figure shows the maximum VCC

for a given ambient temperature, considering only the device maximum ICC (output current should also be

considered).

Figure 46. Maximum VCC for safe operation using SOT23-5 package

There is no limitation to use TSB951 with SO8 package at VCC = 36 V and at 125 °C ambient temperature.

For TSB951, considering the ouput current limitation, the below figures give the maximum output current for a

given output voltage and temperature, at VCC = 36 V, for SOT23-5 and SO8 package.

TSB951, TSB952

Application information

DS14576 - Rev 3

page 20/38