Hi Yusuke,
The primary thermal protection for this device is to reduce the current as the input-to-output voltage increases in order to keep the power transistor in the safe operating region. It is possible under specific conditions to cause a latch; however, under most conditions this is not a latching thermal protection. Please read section 8.3.3 of the datasheet for more information.
Very Respectfully,
Ryan
Ryan-san,
Thank you for your response.
However, the following contents are described in the datasheet.
Please tell me the meaning of this thermal limit.
And Could you tell me the temperature threshold at which the thermal limit occurs.
Otherwise,
TL1963A has thermalshutdown protection (175℃),
https://e2e.ti.com/support/power_management/linear_regulators/f/321/t/521636?tisearch=e2e-quicksearch&keymatch=tl1963a
TPS7A45 has no thermalshutdown protection.
Is my understanding correct?
Customers make TPS7A45 the primary candidate.
Therefore, customers need this information.
Best Regards,
Yusuke/Japan Disty
Hi Yusuke-san,
The heat generated in an regulator is caused by the power dissipated in the regulator. Power dissipated is equal to the headroom (Vin - Vout) multiplied by the output current. TPS7A45 limits the thermal by reducing the output current as the headroom increases.
If this type of thermal limiting is not acceptable to the customer, then TPS7A45 is not a good candidate for their application.
Very Respectfully,
Ryan
Hi Tsukui,
this is just how the SOA protection is working:
In order to limit the heat dissipation, the SOA protection allows a higher output current at small input to output differential voltages and a smaller output current at high input to output differential voltages. This is very simple, no rocket science.
The idea of thermal shutdown is to decrease the output current even to zero, when a certain die temperature is reached and not even the least output current is allowed to flow anymore in order to prevent the die from damage. There's usually no precise temperature at which the shutdown will occur. The shutdown temperature depends on many factors like thermal gradient during over-temperature situation within the die, which depends on the actual cooling situation (heatsink or not), manufacturing tolerances and the dynamics of how fast the die temperature is rising. An exact shutdown temperature cannot be specified in the most cases, because it depends so much on the actual application. Also, die temperatures above 150...170°C are so stressful for the chip that you should never make use of these high die temperatures in a high reliability application. And under no circumstances the thermal shutdown must be missused as a replacement of proper cooling!
So, you should not ask: "What will the thermal shutdown exactly do at 175°C?", but you should ask: "What can I do to prevent the die from ever reaching 175°C?" :-)
Kai
