ESD protection devices have low dynamic resistance

The CM1242 is said to be an ideal solution for space-constrained applications in multimedia smartphones, netbooks and mobile internet devices, e-book readers and personal media players.

The device provides a single channel of bidirectional +/- 30kV contact ESD protection in a compact outline of 0.6 x 0.3mm.

With multiple ESD ingress points, such as side function keys and individual keys in a keypad array, designers of smart phones need to pay particular attention to ESD design criteria.

The robustness of the ESD protection, physical size and price are all important design considerations.

Varistors, popular for their small size and low cost, also have high clamping voltages, slower response times than semiconductor-based diode solutions and ESD performance that degrades after each ESD event - as a result, they are not very effective.

When compared with other semiconductor-based solutions, the CM1242-33CP is said to offer performance and form-factor advantages.

With low dynamic resistance specification of 0.4ohm, the CM1242 features low clamping voltage and robust ESD protection.

An ESD protection device is only effective if it can shunt the majority of an ESD strike's energy to ground.

This ability is a function of the protection device's dynamic resistance, which should be as low as possible.

If the ESD protection device has a high dynamic resistance, energy that normally would be channelled through the ESD protection device will instead be allowed to reach the device under protection (DUP), resulting in a higher probability of damage.