P6KE6.8A Series

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4

APPLICATION NOTES

RESPONSE TIME

In most applications, the transient suppressor device is

placed in parallel with the equipment or component to be

protected. In this situation, there is a time delay associated with

the capacitance of the device and an overshoot condition

associated with the inductance of the device and the inductance

of the connection method. The capacitance effect is of minor

importance in the parallel protection scheme because it only

produces a time delay in the transition from the operating

voltage to the clamp voltage as shown in Figure 7.

The inductive effects in the device are due to actual turn-on

time (time required for the device to go from zero current to full

current) and lead inductance. This inductive effect produces an

overshoot in the voltage across the equipment or component

being protected as shown in Figure 8. Minimizing this

overshoot is very important in the application, since the main

purpose for adding a transient suppressor is to clamp voltage

spikes. The P6KE6.8A series has very good response time,

typically < 1 ns and negligible inductance. However, external

inductive effects could produce unacceptable overshoot.

Proper circuit layout, minimum lead lengths and placing the

suppressor device as close as possible to the equipment or

components to be protected will minimize this overshoot.

prevent overstress of the protection device. This impedance

should be as high as possible, without restricting the circuit

operation.

DUTY CYCLE DERATING

The data of Figure 1 applies for non-repetitive conditions

and at a lead temperature of 25

°C. If the duty cycle increases,

the peak power must be reduced as indicated by the curves of

Figure 6. Average power must be derated as the lead or ambient

temperature rises above 25

°C. The average power derating

curve normally given on data sheets may be normalized and

used for this purpose.

At first glance the derating curves of Figure 6 appear to be

in error as the 10 ms pulse has a higher derating factor than the

10

ms pulse. However, when the derating factor for a given

pulse of Figure 6 is multiplied by the peak power value of

Figure 1 for the same pulse, the results follow the expected

trend.

TYPICAL PROTECTION CIRCUIT

V

V

LOAD

OVERSHOOT DUE TO

INDUCTIVE EFFECTS

t

t

Figure 7.

Figure 8.

UL RECOGNITION*

The entire series including the bidirectional CA suffix has

Underwriters Laboratory Recognition for the classification of

protectors (QVGQ2) under the UL standard for safety 497B

and File #E210057. Many competitors only have one or two

devices recognized or have recognition in a non-protective

category. Some competitors have no recognition at all. With

the UL497B recognition, our parts successfully passed several

tests including Strike Voltage Breakdown test, Endurance

Conditioning, Temperature test, Dielectric Voltage-Withstand

test, Discharge test and several more.

Whereas, some competitors have only passed a flammability

test for the package material, we have been recognized for

much more to be included in their protector category.

*Applies to P6KE6.8A − P6KE200A.