TPS25947: Active current limit vs. Circuit Breaker

Hi Hayashi-san,

Hideki Hayashi1 said:

1. What is the key factor to choose which part?

In some system requirement, customer want hard limit on the current and want the device to cut-off the circuit when the limit is crossed. In those cases, circuit breaker is required. In other system use case, when the load is demanding higher and higher current, they want to limit the current so current-limiter is useful. Please note that Current limit eFuse will not maintain output voltage when in current limiting and the Vout = ILIM*R_load. Also due to higher power dissipation, they will turn of after some time due to thermal shutdown. 

Hideki Hayashi1 said:

2. 8.3.5.4 Short-Circuit Protection is unsure for me. In a steady state, when input current exceeds ISC, the device detect it as output short, and ISC should be smaller than IFT. What is the reason does IFT exist?

Scalable fast trip (SFT) provides you configurable short circuit protection limit whereas Fixed Fast trip (FFT) provides you fixed limit. There mechanism also slightly differ. FFT works on basis of voltage drop at main FET and a comparator to measure it. SFT is based on current monitoring and a faster cut-off mechanism then regular current limiting mechanism.

Hideki Hayashi1 said:

3. Adjustable threshold (ILIM) is ranged from 0.5 A–6 A. Can customer set <0.5A in a specific use-case? What will be happen to do that? 

The device won't provide reliable current limiting functionality. The device is not designed for <0.5A current limiting so process corners will also cause lots of device to device variation. If lower current limiting is required, I would recommend TPS2596 or TPS25961.

Best Regards,
Arush