TUSB551: TUSB551RWBR, operating temperature

Afthab Hussain

Prodigy 10 points

Part Number: TUSB551

I wanted to know whether TUSB551RWBR can survive +85C Ambient temperature in active mode.

According to datasheet Device operating temperature is -40C to +85C

but according to my calculation at +85C the junction temperature crosses above recommended junction temp of +105C

Calculation

Amb = +85C

junction to ambient resistance Rja = 175.2 C/W

Vcc= 1.8V

Icc- active = 82.35 mA

PD= Vcc* Icc= 0.1485W

junction temp = (Rja * PD) + 85C

= +111 C

so, the junction crosses recommended junction temp of device (+105C)

over 2 years ago

0 David (ASIC) Liu over 2 years ago

TI__Guru**** 176721 points

Hi,

Please refer to this app note for the junction temperature, https://www.ti.com/lit/an/spra953c/spra953c.pdf.

The formula you are using, junction temp = (Rja * PD) + 85C, mis-apply the RθJA thermal parameter because RθJA is a variable function of not just the package, but of many other system level characteristics such as the design and layout of the printed circuit board (PCB) on which the part is mounted.

Thanks

David

0 Afthab Hussain over 2 years ago in reply to David (ASIC) Liu

Prodigy 10 points

So can you confirm that device can operate at +85C ambient temp. If yes on what condition and setup.

+1 David (ASIC) Liu over 2 years ago in reply to Afthab Hussain

TI__Guru**** 176721 points

Hi,

The device will operate at 85C.

Thanks

David

0 Afthab Hussain over 2 years ago in reply to David (ASIC) Liu

Prodigy 10 points

Thanks

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TUSB551: TUSB551RWBR, operating temperature