TDE1798

[Nithin_Jack996]

We are using the TDE1798 (500 mA power switch) as a digital output (DO) driver on our controller board. The connected load is a 24 V DC valve rated at 16 W, which corresponds to a nominal current of approximately 667 mA. However, the measured steady-state (holding) current is around 550 mA, and the inrush current data is currently not available.

Despite the load current exceeding the specified 500 mA rating of the IC, we have not observed any failures in the DO driver.

According to the datasheet, the output is protected against short circuits to both the positive supply and ground, and the device includes thermal shutdown protection to prevent overheating. When internal power dissipation becomes excessive, the driver is expected to shut down. Additionally, the output behavior under overload conditions depends on the reset input state.

Given this, I would like to understand:

• What specific current threshold is considered a “short circuit” condition for this device?
• How long must an overcurrent condition persist before the protection (thermal shutdown or current limiting) is activated?

[AScha.3]

You want to use an about 20Y old design chip, close/over its limit - really ?

(no good idea, i think)

I would use something like 

TPS1H000AQDGNRQ1   , 40V , 1A ; Ti ;

or

TDE1747FPT  , 45V , 1A ; STM ;

[Nithin_Jack996]

We are not adding this chip to any new design, trying to understand how it is working. It is working without any failure in the field even though the conditions are very worse. 
How was it working so far??
I have calculated the approx. Tj (Iout= 550mA, Ta= 25 degC). It is 80 Deg C

Then what is the max limit?? Is the current or Temp which makes the IC shutdown @ what point??

[AScha.3]

ok.

>How was it working so far??

Close to its thermal limits, but still within.

>Then what is the max limit?? Is the current or Temp which makes the IC shutdown @ what point??

from ds:

1. current limit , about 1A max.

2. then thermal limit, at long time (over) load, 150° .

So it limits output at about 1A , or : if chip reaching 150° , until cool down, then switch on again...

Based on your 550mA load, about 90°/W mounted on board, at 1.1V dropout : about 605mW -> 55° temp.rise above ambient; at 40° ambient, it will reach about 95° on chip, which is still ok. (But not "nice" , for years..)

[MasterT]

Max current of the IC is not limited by temperature rising/ power dissipation. It may be applied to diodes or transistors. For IC, where thin film wiring widely in use, local temperature stress becomes more important. And other things is atom migration in case of high current density, that leads to failure rate increasing over time. Do math, assuming 500 mA for guaranteed 10 years of service, and divide this time by /2 for each 10% overcurrent condition, (hypothetically, I don't know exact numbers, but you've got an idea).