What is the ITIC curve?

The ITIC curve, from the Information Technology Industry Council, is a voltage-tolerance envelope: for each duration of a disturbance it gives the range of voltage that typical information-technology equipment is expected to ride through. It was written for 120 V, 60 Hz single-phase equipment and is widely used as a general yardstick.

What is the difference between the CBEMA curve and the ITIC curve?

CBEMA is the older curve from the Computer and Business Equipment Manufacturers Association. The ITIC curve replaced it in the 1990s with a stepped envelope that is easier to apply to measured events. People still say CBEMA when they mean ITIC.

Does a point outside the ITIC curve mean equipment tripped?

No. A point outside the envelope says the disturbance was more severe than typical IT equipment is designed for. Whether a particular drive, PLC or computer dropped out depends on that equipment, and a point inside does not say that everything rode through.

What does SEMI F47 require?

SEMI F47 asks semiconductor processing equipment to ride through sags to 50% of nominal for 200 ms, to 70% for 0.5 s and to 80% for 1 s. It says nothing below 50 ms or beyond 1 s.

The ITIC (CBEMA) curve and SEMI F47, point by point

The voltage-tolerance envelopes of the ITIC (CBEMA) curve and SEMI F47 with every corner point, how an event is placed on them, and what a point outside the envelope does and does not mean.

Updated 25 September 2026 · SagSwell

The ITIC curve, published by the Information Technology Industry Council and descended from the older CBEMA curve, draws the voltage disturbances that typical single-phase information-technology equipment is expected to tolerate. It plots voltage as a percentage of nominal against the duration of the disturbance on a logarithmic time axis. Between its upper and lower edges is the no-interruption region; above the upper edge is the prohibited region, where damage is possible; below the lower edge is the no-damage region, where the equipment may stop working but should not be harmed.

The ITIC envelope, corner by corner

Edge	Duration	Voltage (% of nominal)
Lower	up to 20 ms	0 (a complete dropout is tolerated)
Lower	20 ms – 0.5 s	70
Lower	0.5 s – 10 s	80
Lower	beyond 10 s (steady state)	90
Upper	up to 1 ms	200
Upper	1 ms – 3 ms	140
Upper	3 ms – 0.5 s	120
Upper	beyond 0.5 s (steady state)	110

The curve was drawn for 120 V, 60 Hz equipment. It is widely used at 50 Hz and at other voltages as a reference envelope, and read that way it is a useful common yardstick, but it is not a specification of any particular piece of equipment.

SEMI F47

SEMI F47 is the voltage-sag ride-through requirement for semiconductor manufacturing equipment. It only has a lower edge: the equipment should ride through a sag to 50% for up to 200 ms, to 70% for up to 0.5 s and to 80% for up to 1 s. Between 50 and 200 ms it asks equipment to ride through a deeper sag than ITIC does (50% against ITIC’s 70%), and it is often used as a ride-through target for industrial process equipment beyond semiconductors.

Placing an event on the curve

Each disturbance becomes one point:

Duration on the horizontal axis: how long the voltage stayed outside the 90 – 110% band.
Voltage on the vertical axis: the retained voltage of the worst phase for a sag, the highest RMS for a swell.

A point is compared with the envelope edge at its own duration. A sag to 65% for 100 ms is below the 70% edge and sits outside ITIC; the same sag for 15 ms is inside, because a full dropout is tolerated for up to 20 ms. SagSwell reports, for each event, whether it is inside or outside and by how many percentage points, measured against the nearer edge.

Duration comes from a one-cycle RMS, so an event shorter than about a cycle is placed less precisely than a long one. Read points near the left of the curve with that in mind.

What a point outside the envelope means

A point outside ITIC says the disturbance was more severe than the envelope typical IT equipment is designed for. It does not say that any piece of equipment tripped or was damaged, and a point inside does not say that everything rode through: real equipment has its own tolerance, and motor contactors and drives often drop out well inside the ITIC envelope. Use the curve to rank and communicate events, and the equipment’s own data to decide what happened to it.

The ITIC tab in SagSwell plots every event in a record on the ITIC curve, with SEMI F47 as an overlay and each phase separately if you choose. The events come from the same detection described in the IEEE 1159 guide.

Questions people ask

What is the ITIC curve?: The ITIC curve, from the Information Technology Industry Council, is a voltage-tolerance envelope: for each duration of a disturbance it gives the range of voltage that typical information-technology equipment is expected to ride through. It was written for 120 V, 60 Hz single-phase equipment and is widely used as a general yardstick.
What is the difference between the CBEMA curve and the ITIC curve?: CBEMA is the older curve from the Computer and Business Equipment Manufacturers Association. The ITIC curve replaced it in the 1990s with a stepped envelope that is easier to apply to measured events. People still say CBEMA when they mean ITIC.
Does a point outside the ITIC curve mean equipment tripped?: No. A point outside the envelope says the disturbance was more severe than typical IT equipment is designed for. Whether a particular drive, PLC or computer dropped out depends on that equipment, and a point inside does not say that everything rode through.
What does SEMI F47 require?: SEMI F47 asks semiconductor processing equipment to ride through sags to 50% of nominal for 200 ms, to 70% for 0.5 s and to 80% for 1 s. It says nothing below 50 ms or beyond 1 s.

References

Information Technology Industry Council, ITI (CBEMA) Curve Application Note
SEMI F47, Specification for Semiconductor Processing Equipment Voltage Sag Immunity
IEEE Std 1159-2019, IEEE Recommended Practice for Monitoring Electric Power Quality