The MAX366 and MAX367 are multiple, two-terminal circuit protectors. Placed in series with signal lines, each two-terminal device guards sensitive circuit components against voltages near and beyond the normal supply voltages. These devices are used at interfaces where sensitive circuits are connected to the external world and could encounter damaging voltages (up to 35V beyond the supply rails) during power-up, power-down, or fault conditions.

The MAX366 contains three independent protectors and the MAX367 contains eight. They can protect analog signals using either unipolar (4.5V to 36V) or bipolar (±2.25V to ±18V) power supplies. Each protector is symmetrical. Input and output terminals may be freely interchanged.

These devices are voltage-sensitive MOSFET transistor arrays that are normally on when power is applied and normally open circuit when power is off. With ±10V supplies, on-resistance is 100Ω max and leakage is less than 1nA at +25°C.

When signal voltages exceed or are within approximately 1.5V of either power-supply voltage (including when power is off), the two-terminal resistance increases dramatically, limiting fault current as well as output voltage to sensitive circuits. The protected side of the switch maintains the correct polarity and clamps approximately 1.5V below the supply rail. There are no "glitches" or polarity reversals going into or coming out of a fault condition.