TPS22919: questions about temperatures.

Hi,

user5953335 said:

what's the relationship among these temperatures ? 

user5953335 said:

Ambient Temperature is from -40C to 105C, can i use it in 120C ambient temperature ? 

This is the recommended temperature of the ambient air for when the device is OPERATING. You can, but it is not recommended and the device performance is not guaranteed outside of the range Tj<-40C or Tj>125C conditions.

The relationship is that as the ambient temp is higher, the envelope for how much current the device can conduct before thermal limits is restricted.

user5953335 said:

storage temperature is from -65C to 150C.

This is the recommended temperature for storing the device or system which has hte device. For this temp, the device is NOT operating.

user5953335 said:

operating temperature range is from -40C to 125C

This is the recommended area for Tjmax. The actual Tjmax can be estimated by calculating based on board temp, and characterized temperature coefficients between the package and board. These parameters are all given in D/s.

user5953335 said:

operating temperature range is from -40C to 125C, does that mean the operating temperature can not exceed 125C ?

No. It the recommended range. If the system is not properly designed the Tj can exceed 125C, and the device will not stop until T_sd temperature of 180C.

user5953335 said:

what will happen if the operating temperature is 150C for example ?

The chip will continue to operate. The only time it will thermal shut-down is when 180C is reached. Please keep in mind this is INTERNAL to the IC. You can estimate it steady-state but you cant know exactly Tj of the IC. So important to design with headroom.

When TI gives the recommended max for operating conditions, it basically means that the performance and longevity is both characterized and guaranteed as sepcified in the datasheet. We can not recommend to go outside the abs. max operating conditions. When it comes to temperature, running at 170C constantly woudln't trip the TSD protection (overtemp), but it could decrease reliability, and we wouldn't guarantee stability of the parameters in the d/s. This is the case for virtually every IC. Usually, the Tjmax is listed at 125C for max recommended and 150C for absolute max.

The TSD feature of TPS22919 at 180C is basically a last-ditch effort to save the rest of the system before the IC meets its maker. The idea is there is this type of thermal runaway, theres going to be damage to the load switch or other things down the line, you better stop the current.

for instance where this could happen is if there is a dead short on VOUT or some other super large current draw. The temp is going to rise quickly, its not going to be hovering at 170C. If it does, the system is not designed right.

You shouldn't design the system such that the Tj of the load switch or any other ICs exceeds abs max, and reallly shouldkeep it within the recommended op. range.

If the system design is leading to frequent TSD tripping, its extremely likely the load switch will fail early. the dopant begin to move at such high temperatures and the transistors will no longer.

basically my recommendation is to design it to stay withing Recommended Operating Conditions.... Treat TSD=180C as the  last-ditch emergency brake.

let me know if you have any more questions. if this answered your question, can you let me know by pressing green button?

best

dimitri