Reviewing an eFuse Blanking Timer Against Repeated Load Pulses

A pulsed load can exceed a protection device’s nominal current threshold without representing a fault. An adjustable blanking timer can accommodate that behavior, but its setting must also leave the wiring, connector and protected circuit adequately protected during a real overload.

Identify the protection variant

The TPS25947 data sheet distinguishes circuit-breaker and active-current-limit variants. Its timer permits certain temporary overloads, while a separate fast-trip response addresses more severe events. The document also explains that closely repeated overloads can encounter a shorter interval when the timer capacitor has not fully recharged.

Record the complete ordering code, current threshold resistor, timer capacitor and fault-recovery behavior. A family name alone does not establish whether the output turns off, limits current, retries automatically or remains latched after an event.

Describe a pulse train

Measure the load current at the protection device, including the shortest interval between bursts. Record baseline current, peak current, rise time, pulse width and repetition period. Include startup activity and overlapping functions, such as a transmitter operating while a motor or heater control also changes state.

For an illustrative product, a brief radio burst every second and a cluster of the same bursts separated by milliseconds are different protection cases. Both may have identical individual pulse widths. Their timer recovery and temperature histories need separate review.

Set the timer within a fault budget

Calculate the permitted interval using the selected part’s specified timer parameters and capacitor tolerance. Compare the shortest expected blanking interval with legitimate load pulses. Compare the longest interval with the time the rest of the power path can tolerate the overload.

Do not lengthen the timer solely until a demonstration stops resetting. Investigate whether the measured current is a real functional demand, unexpected capacitor charging or a fault in the load. A larger capacitor can hide the symptom while increasing stress elsewhere.

Verify both sides of the boundary

Use a controlled load to reproduce valid pulses and deliberate sustained overloads within the test setup’s ratings. Capture input voltage, output voltage, current and fault indication together. Repeat at relevant input voltages and temperatures, including burst clusters that exercise incomplete recovery.

Keep the accepted pulse envelope and fault response with the resistor and capacitor values. State which production options change the load profile. When firmware changes the burst schedule, revisit this record even if average power consumption appears unchanged. A useful protection setting recognizes the product’s actual transient demand while retaining an explicit response to excessive current.