Diode

Q-1

Only backward direction characteristics are listed for Zener diodes. What about the forward direction characteristics?

A-1

The same characteristics as for general diodes are indicated.
In the case of silicon, the rise characteristics are approximately 0.6 V.
However, in the case of Zener diodes, the forward direction characteristics are not measured, and they are therefore not guaranteed.

Q-1

Do you have Zener diode of 2.5 V at 1 mA?

A-1

Yes, we do. However, in the case of low-voltage (5 V or lower) Zener diodes, it is difficult to obtain a stable voltage in the low-current range. (As the current changes, so does the voltage.) How about the uPC1093? (shunt regulator)
In the case of this IC, a stable voltage can be obtained at 1 mA. However, the uPC1093 is an active element.
Unlike a Zener diode, an oscillation stopping capacitor is required.
For details, refer to Data Sheet , etc.

Q-1

Is it all right to measure the Zener voltage via a resistor, as shown in the following diagram?

A-1

When the Zener voltage is measured via a resistor, the Zener diode may be damaged by an overcurrent that is generated if the resistance is too low or if the supply voltage fluctuates.
Use of the following constant current source is recommended.
Note that the measured value may differ from the rated voltage if the temperature rises depending on the time of measurement.

(2008/02)

Q-1

I am considering inserting a Zener diode in my reference voltage circuit.
What Zener current (I_Z) value should I use to enable the voltage to be output stably?

A-1

Use the Zener current value (I_Z) described under the Zener voltage (V_Z) measurement conditions in the data sheet as a guide.
If the current increases, the amount of heat generated increases, increasing the Zener voltage variation.
If the current decreases, however, the amount of noise generated from the diode itself increases.

Q-1

How high can the Zener current go?

A-1

The permissible value of the Zener current varies according to the Zener voltage, the current application conditions (usage conditions), and the mounting conditions.
Concretely, calculate the junction temperature for the actual usage conditions and verify that the absolute maximum rating for the junction temperature (Tj) is not exceeded.
For the concept and junction temperature calculation method, refer to the following document provided on this website.
Precautions Regarding Use of NNCD Series and RD Series

Q-2

How high a voltage can be applied?

A-2

The applicable voltage differs for the following two possible cases.
(1) Case of voltage application through static electricity

If the static electricity withstand amount is an issue, use of the NNCD Series, which guarantees the static electricity withstand amount, is recommended.

(2) Case of repeated application of pulse voltage and DC

This is the most common case, involving the application of the L load breakup surge absorption.
In this case as well, calculate the junction temperature under the actual usage conditions similarly to Q1, and check that the absolute maximum rating for the junction temperature (T_j) is not exceeded.

For the concept and junction temperature calculation method, refer to the following document provided on this website.
Precautions Regarding Use of NNCD Series and RD Series

Q-1

How should the responsiveness of Zener diodes be considered?

A-1

The responsiveness depends on the inter-pin capacitance.
For the relationship between the inter-pin capacitance and responsiveness, refer to the NNCD Series of noise clipping diode on this website.

•NNCD Series

Q-1

What is the capacitance between pins in an RD series diode?

A-1

The RD series has been developed for reference voltage, voltage detection, level shift and other such applications, so the capacitance between pins is not prescribed.
We advise you to use a product with a prescribed pin-to-pin capacitance, such as the NNCD series or NSAD series, which has been developed for high-speed signal line ESD protection and surge absorption applications.

(2006/09)

Q-1

I would like to connect several Zener diodes in parallel to achieve loss dispersion, but can this be done without problems?

A-1

Do not connect Zener diodes in parallel.
If several Zener diodes are connected in parallel and a voltage that exceeds the Zener voltage is applied, the Zener current becomes extremely unbalanced if there are even slight fluctuations in the Zener voltage, causing topical load concentrations In the case of combinations with large fluctuations in Zener voltage, sometimes only one of the Zener diodes switches on.

Q-1

The characteristics of Zener diodes in the data sheet include a characteristic called dynamic impedance Zz. What kind of impedance is this?

A-1

Dynamic impedance Zz is the differential impedance of the area surrounded by the circle in the following figure.
To measure it, a small AC signal is superposed on a Zener current and measured as the differential impedance.
The dynamic impedance of a Zener diode with Vz within the range of about 6 V to 7 V is lowest. It becomes higher for Zener diodes with either lower or higher Vz.

(2007/09)

Q-2

Is the on-resistance of the forward direction constant in a switching diode?

A-2

No, the larger the forward current, the smaller the on-resistance. If the resistance were constant, the V-I characteristic would be a straight line, but in a diode, I increases exponentially as V increases. Since the resistance is V/I, the fact that the tangent (I/V) of the V-I characteristic curve forms a steep slope means that the resistance becomes lower.

(2007/11)

Q-1

I heard that the 1SZ series voltage reference diodes with a guaranteed temperature coefficient will soon be discontinued.
Are substitute products available for which temperature coefficients are guaranteed?

A-1

No other Zener diodes for which temperature coefficients are guaranteed are available, but the high-precision variable shunt regulator uPC1093 is recommended.

(2008/02)

Q-1

Do you have ESD protection diodes for data lines?

A-1

Yes, we have the NNCD Series and NSAD Series.
The NSAD Series in particular consists of diodes that have developed for high-speed data lines such as USB2.0, IEE1394a, DVI, and 100B.
For details on these series, visit the following links.

•NSAD Series Features
•NNCD Series Features

Q-2

I plan to use the NNCD Series for noise cutting of a 5 V power supply.
Regarding the NNCD breakdown voltage, what voltage product should I select?

A-2

What is the upper limit voltage of the power supply line you want to protect?
To determine the breakdown voltage, select an NNCD diode with a lower limit voltage that is higher than the higher limit of the power supply line.
In the case of a 5 V power supply, the NNCD 6.8V should be suitable.

Q-3

When using NNCDs to protect signal lines such as RS-232C from ESD, should two NNCDs, each facing the other, be used?

A-3

Both positive and negative ESD may be superimposed on signal lines.
Therefore, connect the cathodes of the two and the anode of one to the line and the anode of the other to ground, respectively.

Q-1

I want to burn off a Zener diode like a fuse in the case of an overcurrent, but what are the conditions for ensuring breakage resulting in complete insulation?

A-1

Since Zener diodes are elements that assure a constant voltage with a reverse bias, they are not designed for such destruction applications.
Therefore, do not use Zener diodes for such an application. Characteristics data for such an application are not available.

The destruction mode of semiconductor products can be either open, short, or ohmic contact, so specification of a particular mode is not possible.

Q-1

Is there a recommended mount pad for surface mount diodes?

A-1

The pads differ depending on the package, so please go to the following Web site and click the mount pad for the relevant package.

http://www.necel.com/discrete/en/package/smd.html

Q-1

"1" is marked on RD6.2S B1. What is the marking of the B-class product?

A-1

The request for a B-class product is responded by standard B1, B2, or B3. Therefore, there is no such marking as "B", but only "1", "2", or "3" is marked.

Q-2

The NNCD[ ]J does not appear in the above technical documents; what are its marking specifications?

A-2

The marking specifications for the NNCD[ ]J are as follows.

(2008/05)

Q-3

The RD27S rank is only indicated as "B" in the data sheet, but the marking on the actual product shows "B1". Is there actually any difference between B1, B2, and B3 ranks?

A-3

No, it has no difference. The RD27S rank is only "B".
The "1" in the "B1" is marked only for convenience.

(2006/04)

Q-4

The same diode comes both in a gray color and as transparent glass. Are the characteristics different?
The color bands are the same though.

A-4

The characteristics are the same.
In April 2002, the gray substrate was discontinued.

Q-1

If a static electricity of 8 kV is applied to surge protection diode NNCD5.6LH, to what extent (volts) is the surge suppressed?

A-1

According to the result of a test with the IEC61000-4-2, the diode clips at around 2.5 kV when 8 kV is applied.

Q-1

What is the L rank model of RD[ ]E?
To replace the L rank model with a B rank model, what B rank model should be used?

A-1

The L rank model guarantees the Zener voltage V_Z at I_Z = 1 mA, but this L rank product has been discontinued.
The RD[ ]E series itself is close to being phased out, so you would be advised to replace your product with another RD series product.
Also, please note that the RD[ ]E series cannot simply be replaced with a product of the same voltage because I_Z, which determines the voltage, differs.
In Japan, for details, consult the NEC Electronics-related distributor where you purchased the product.

(2006/10)

Q-1

What is the production status of the 1S953 (glass-sealed through-hole type product) and 1SS220 (resin-sealed surface mounting type product) switching diodes.

A-1

Glass-sealed through-hole type products such as the 1S953 are being phased out and will be discontinued. (The data sheet is no longer available.)
Resin-sealed surface mounting type switching diodes such as the 1SS220 are also being phased out. New orders will no longer be accepted and no alternative products will be provided. (You can find the data sheet on the website.)
The specifications of major switching diode products are summarized below.

[Summarized specifications of glass-sealed through-hole type products]

Parameter	1S953	1S954	1S955	Unit
Peak reverse voltage	35	75	100	[V]
Surge current (1 µs)	2000	4000	4000	[mA]
Average rectified current	100	200	200	[mA]
Power dissipation	500	500	500	[mW]
Reverse recovery time	MAX.3.0	MAX.3.0	MAX.3.0	[ns]

[Summarized specifications of resin-sealed surface mounting type products]

Parameter	1SS220	1SS221	1S2835	1S2836	Unit
Peak reverse voltage	70	100	35	75	[V]
Surge current (1 µs)	2000	2000	4000	4000	[mA]
Average rectified current	100	100	100	100	[mA]
Thermal resistance Rth (j-a)	670	670	670	670	[°C/W]
Reverse recovery time	MAX.3.0	MAX.3.0	MAX.4.0	MAX.4.0	[ns]

(2009/01)

Q-1

As shown in the equivalent circuit in the figure, the RD[ ]MW Series features two Zener diodes in the anode common, and the total power dissipation for both diodes is listed as 200 mW in the ratings.
Must this be interpreted as 100 mW per diode?
Or does it mean that if the loss for one of the diodes is 0 mW, up to 200 mW can be used for the remaining diode?

A-1

The total power dissipation is the rating per package.
Therefore, when using only one diode in an RD[ ]MW Series product with two diodes, the total power dissipation is 200 mW for the one diode.

(2007/02)

Q-1

What is the meaning of power dissipation maximum rating, P = 1 W, for RD2.0FM to RD120FM?

A-1

The power dissipation, P = 1 W, for RD2.0FM to RD120FM is the maximum consumption power allowable during DC-type operation. When this power dissipation is exceeded, the junction temperature exceeds the rated temperature of 150°C, and it can cause destruction. The dissipation of a zener diode is obtained by multiplying zener voltage V_Z and zener current I_Z.
Regarding the power rating for the surge, a surge reverse power rating is described in the data sheet, listing non-repetition as a condition.
Also refer to User's Manual "Precautions Regarding Use of NNCD Series and RD Series" (D14724E) .

(2007/03)

Q-1

What do the red, blue and yellow of the N413 color codes indicate?

A-1

They indicate different breakover voltage ranges.
The voltage ranges are as follows. Red: 26 to 32 V, Blue: 29 to 37 V, Yellow: 34 to 40 V.

(2007/03)

Q-1

The 1SS220, 1SS221, and the 1SS222, 1SS223, seem to have exactly the same package and electrical characteristics. What makes them different?

A-1

The difference between the 1SS220, 1SS221, and the 1SS222, 1SS223 is the pin assignment.
The anode and cathode placement in the 1SS220, 1SS221 and in the 1SS222, 1SS223 are opposite.
The 1SS220, 1SS221, 1SS222, and 1SS223 all have one element, but the 1S2835, 1S2836, 1S2837, 1S2838, and 1SS123, among other products, have two elements.

(2007/10)