Based on the above calculation the proper PCB type and the necessary heat sink area can be determined with

reference to the specification in Table 4.

Example

Application conditions:

•

VIN = 13.5 V

•

VOUT = VADJ = 5 V

•

IOUT = 20 mA

•

Ta = 125°C

Calculation of RthJA,max:

PD= VIN−VOUT ×IOUT+VIN×Iq= 13.5V−5V ×20mA+13.5V×0.9mA=0.182W

Equation 3

RthJA,max=Tj,max−Ta

PD =150°C−125°C

0

.182W =137K/W

Equation 4

As a result, the PCB design must ensure a thermal resistance RthJA,max lower than 137 K/W.

According to Table 4, at least 300 mm2 heatsink area is required on the FR4 1s0p PCB, or the FR4 2s2p board can

be used.

OPTIREG™ linear voltage regulator TLS105B0MB

High-precision voltage tracker

5 Application information

Datasheet

21

Rev. 1.14

2023-07-25