When a protection circuit is unnecessary, it should be meaningless and cannot be loaded in to affect the operating circuit. Therefore, it should have a small parallel capacitance and a minimum series resistance required to be added to the signal line active circuit. In addition, a quick turn-on speed, which is essential for minimum capacitance loading, requires a simpler structure to express. A basic and simple protective structure of the switch arrangement is shown.
Each high-side and low-side protection structure is an embedded device, using the substrate and epitaxial materials for bipolar technology. Each unit of the fuse cap contains a thyristor and a series of step-down resistors, the voltage stimulus conditions and the traveling thyristor (fuse) are latched. Regarding the locking of resistance (fuse) is much lower than Ding. Moreover, depending on the polarity of the electrostatic voltage, the dump energy is grounded from the input signal line through a positive or negative switch. The return to ground or ESD polarity is not defined by the supply voltage, but may be positive or negative on the supply line, if this fits the application needs.
When the energy consumption and forward current are no longer in the fuse cap system, the SCR automatically opens. The figure shows the positive and negative cell protection circuit because it is suitable for progressive party and type transistors are used as equivalent thyristor structures. The structure of fuse protection allows forward opening to slightly higher than + power supply to turn on the high-voltage thyristor or slightly lower than-power supply to turn on the side thyristor. The active device of the signal line protects the signal input line in both directions and without series impedance. The shunt resistor is forward-biased to advance the conduction of the device and not directly connected to the signal line. As an on-chip protection cell, this structure may be an active circuit for the next keyboard input; this is the best position protection device. However, in many applications, the active chips of this technology may not be compatible with the structural formula.
