Common Items

Q-1

NEC Electronics' photocoupler and optical MOS FET products meet many overseas safety standards, but why is this necessary?

A-1

There are regulations applying to the isolation of the primary circuit and secondary circuit in sets incorporating photocouplers (power supplies, FA devices, etc.). The photocoupler accomplishes this isolation function. Therefore, if the photocouplers meet these regulations, the sets themselves may be exempted from the relevant qualification tests. This is why NEC Electronics has developed photocouplers to meet these overseas safety regulations.

The status of each of NEC Electronics' photocoupler and optical MOS FET product in terms of meeting overseas safety regulations can be checked at the following URLs.
[Photocouplers]
   http://www.necel.com/opto/en/safety.html
[Optical MOS FETs]
   http://www.necel.com/opto/en/safetyocmos.html

(2007/11)

Q-1

Is it possible to obtain a copy of the document that certifies that a product has met a certain overseas safety standard?

A-1

Certification documents cannot be downloaded from NEC's Website, but it is possible to obtain a copy from an authorized NEC dealer.

(2009/04)

Q-1

What are the meanings of the terms isolation voltage, creepage distance, isolation thickness, and clearance?

A-1

These terms are defined as follows.

- Isolation voltage
It indicates the maximum value of the AC voltage that can be applied between the input pin and the output pin, expressed as a root mean square (r.m.s) value.
The measurement conditions are normally Ta = 25°C, RH = 60%, with application of the rated AC voltage between all input-side pins and all output-side pins for 1 minute.

- Creepage distance
It indicates the minimum distance between the two conductors (input pin, output pin) along the insulating material.

- Isolation thickness
It indicates the minimum thickness of the insulating material between the two conductors (input, output).

- Clearance
It indicates the minimum distance between the two conductors (input pin, output pin) in the atmosphere.

For details about the above three terms, go to the following URL.

http://www.necel.com/opto/en/parameter_p/index.html

(2007/10)

Q-1

The maximum junction temperature is not stated on the data sheets of photocouplers and optical MOSFETs. How can the maximum junction temperature be calculated?

A-1

The maximum junction temperature of photocouplers and optical MOS FETs differs when power is applied and when it is not applied.
When power is not applied, the maximum junction temperature is the upper limit of the maximum rating of the storage temperature, as in general semiconductor devices.
When power is applied, the maximum junction temperature is lower than when power is not applied due to a high-temperature degradation phenomenon unique to optoelectronic devices. The characteristics curve of the power dissipation vs. the ambient temperature below shows the value.
Extending the sloping line of the characteristics curve, the power dissipation would be 0 mW at about 125°C.
If internal dissipation occurs near the sloping line within the allowable range of the operating ambient temperature, the junction temperature is assumed to be around 125°C. 125°C is therefore the maximum junction temperature when power is applied.



See the explanation provided at the following link for details of the maximum junction temperature.
http://www.necel.com/opto/en/technology/standard_p/index.html

(2009/01)

Q-1

What is the thermal resistance of photocouplers such as the PS2501? (It is not stated on the date sheets.)

A-1

For photocouplers and optical MOS FETs, the power dissipation derating value (mW/°C) might be specified in the maximum ratings.
In this case, the reciprocal of the power dissipation derating value can be used as the junction-ambient thermal resistance R_th (j-a).
If the power dissipation derating value is not specified, the gradient of the sloping line of the characteristics curve, power dissipation vs. ambient temperature, is the junction-ambient thermal resistance R_th (j-a), as in general signal devices.

(2009/01)