TISP Terms and Letter Symbols Guide

TISP® Terms and Letter Symbols
Introduction
Thyristor-based overvoltage protectors for telecom systems were first introduced in the late 1970s. The characteristics of thyristor SPDs
(Surge Protective Devices) are very different than the normal SCR (Silicon Controlled Rectifier) and TRIAC (Triode for AC Control) type
thyristors. In many cases the standard thyristor terms, definitions and test circuits were inadequate for thyristor SPDs.
This situation led to many manufacturers and users “inventing” terms or using terms from other device types for the description of the thyristor
SPD parameters. Manufacturers of avalanche or zener breakdown diodes used for TVS (Transient Voltage Suppression) applications adopted
TVS terms. Manufacturers of SIDAC® (Silicon Diode for AC, in Japan a registered trademark of Shindengen) type thyristor devices which are
typically used for discharge lamp ignition, often used SIDAC® terms. Manufacturing testing was another problem area; standard thyristor
testers could not cope with thyristor SPD measurement and manufacturers had to either commission special test equipment or build it
themselves.
The lack of a common nomenclature and test conditions caused frustration for designers and users who wanted to compare and evaluate
products. The first comprehensive standard on thyristor SPD terms, letter symbols, definitions and test circuits was the result of the IEEE
Surge Protective Devices Committee (SPDC) authorizing the development of C62.37 - 1996 (IEEE Standard Test Specification for Thyristor
Diode Surge Protective Devices), which was published in August 1997. To further the understanding of how thyristor SPD parameters are used
in the design of protection systems, the IEEE SDPC has now released a companion publication called C62.37.1 (IEEE Guide for the Application
of Thyristor Surge Protective Devices).
The purpose of this review is to provide a cross-reference between some of the common non-standard parameter sets and the C62.37
parameters. This review is not intended to replace or summarize the IEEE C62.37 publications, and interested parties are encouraged to study
these comprehensive standards.
Letter Symbols
The letter symbol, read right to left, usually gives the parameter term. The first part of the symbol is the prime quantity. Some examples are:
V = voltage
I = current
P = power
C = capacitance
The first subscripted letter indicates the operating condition of the thyristor. Some examples are:
D = off state
(BR) = breakdown
T = on state
R = reverse
Note that the breakdown condition has parenthesis around the two letters, BR. This is to ensure that the two letters are read together rather
than separately. In addition, the first subscripted letter can also indicate a specific point. Some examples are:
(BO) = breakover
S = switching
H = holding
For ratings, the second subscript letter indicates the type of rating. These letters are:
R = repetitive
S = non-repetitive (surge)
The final subscript letter(s) may indicate a limit value, e.g. M = peak (maximum). In addition, there are some alternative subscript letters and
some subscript letters which have been established through historical use. Examples are:
o = off state as an alternative to “D” in capacitance symbols
PP = Peak (im) Pulse current
The above list is not comprehensive and readers are referred to C62.37. Only fixed voltage thyristor SPDs are covered here. Gated thyristor
SPDs are also available and the additional parameters needed for this type of protector are covered by C62.37.
OCTOBER 2000
Specifications are subject to change without notice.
TISP® Terms and Letter Symbols
Letter Symbols (continued)
To deduce a letter symbol term, the convention is to read the symbol from right to left as in the following examples:
VD = Off-state, D, voltage, V
ID = Off-state, D , current, I
VDRM = Peak, M, repetitive, R, off-state, D, voltage, V
V(BO) = Breakover, (BO) , voltage, V
IPPS = Non-repetitive, S, peak pulse, PP, current, I
ITSM = Peak, M, non-repetitive, S, on-state, T , current, I
IT = On-state, T, current, I
Electrical Characteristic Curves
Thyristor SPD current parameters cover a range from a few nanoamps to hundreds of amps. To represent this on a linear scale is impossible,
so the current scale used for the characteristic voltage-current curves is non-linear. The distorted scale is chosen to illustrate specific regions:
very low current parameters in the nanoamp to milliamp area for the off-state condition, hundreds of milliamps for breakover, switching and
holding points, amps for on-state voltage measurements, tens of amps for a.c. ratings and hundreds of amps for impulse ratings.
A similar situation exists for thyristor SPD voltages. This is a simpler situation with volts to tens of volts for the on-state region, a specific
region for any d.c. off-state current test and a specific voltage band for the breakdown region. Figure 1 shows the result for one voltagecurrent quadrant. There are four regions to the switching characteristic; off-state, breakdown, switching (from breakdown region, from on-state
region) and on-state. The breakdown region is often re-entrant (reduces in voltage with increasing current, then increases in voltage) as it is the
breakdown of an internal open-base transistor structure. Higher voltage Thyristor SPDs, e.g., 300 V breakdown, can show re-entrant levels of
20 V. The high current end of the breakdown region terminates at the switching point. The peak voltage point in the breakdown region will
always be higher in voltage than the switching point.
+i
Quadrant I
Impulse Rating
Switching
Characteristic
On-state
Region
AC Rating
Switching
Point
On-state Voltage
Measurement
Switching
Region
Holding
Measurement
Breakover
Point
Breakdown
Region
Off-state Current
Measurement
+v
-i
Off-state
Region
Figure 1. Thyristor SPD Switching Quadrant Regions
Several manufacturers approximate the characteristic curve by three straight lines, Figure 2. In working with this reduced form, there are
several points to be remembered. First, the variation of off-state current is not resistive as shown, but tends to be independent of off-state
voltage until the breakdown region is approached. Second, with a straight line for the breakdown region, the re-entrant voltage reduction is not
obvious. Third, at the high current termination of the breakdown region, there isn’t any differentiation between the breakover and switching
points. Fourth, the increase of on-state voltage as the holding point is approached is not shown.
OCTOBER 2000
Specifications are subject to change without notice.
TISP® Terms and Letter Symbols
Electrical Characteristic Curves (continued)
+i
Quadrant I
Impulse Rating
Switching
Characteristic
On-state
Region
AC Rating
Breakover
Point
On-state Voltage
Measurement
Switching
Region
Holding
Measurement
Breakdown
Region
Off-state Current
Measurement
+v
Off-state
Region
-i
Figure 2. Straight Line Approximation of Thyristor SPD Switching Quadrant Regions
Figure 3 shows the essential ratings and characteristic values for the voltage current characteristic from C62.37. One C62.37 rating, the peak
repetitive on-state current, ITRM, is not shown in Figure 3 as this would be normally covered by the long term, 1000 s, I TSM value. Most data
sheets will give two breakover voltage values (V(BO)); one for a.c. conditions and the other for impulse conditions. The impulse V(BO) test
conditions may be a specific waveshape of given peak current, IPP, or an equivalent di/dt ramp (See M. J. Maytum, K. Rutgers & D.
Unterweger “Lightning surge voltage limiting and survival properties of telecommunication thyristor-based protectors”, IEEE/ESD Association,
1994 Electrical Overstress/Electrostatic Discharge Symposium Proceedings., ISBN 1-878303-51-1, EOS-16, pp 4.6.1-4.6.11, Las Vegas,
Nevada).
+i
Quadrant I
IPPS
Switching
Characteristic
ITSM
V(BO) , I(BO)
IT
VT
IH
IDRM
ID
+v
VD
VDRM
-i
Figure 3. Thyristor SPD Switching Quadrant Regions with Letter Symbols
Comparison of TISP® and C62.37 Parameters
Bourns TISP® (Totally Integrated Surge Protector) thyristor SPDs are designed and manufactured at its Power Innovations facility. Production of
these devices started in 1982 and today, both fixed voltage and gated products are produced. The standard TISP® parameters align with
C62.37 apart from the impulse current rating parameter. The characteristic curves are shown in Figure 4 and the table below lists the single
parameter difference.
OCTOBER 2000
Specifications are subject to change without notice.
TISP® Terms and Letter Symbols
Comparison of TISP® and C62.37 Parameters (continued)
+i
+i
Quadrant I
ITSM
Quadrant I
IPPS
TISP®
C62.37
Switching
Characteristic
Switching
Characteristic
ITSM
ITSM
V(BO) , I(BO)
IT
VT
IH
V(BO) , I (BO)
IT
VT
IH
IDRM
IDRM
ID
+v
VD
ID
+v
VDRM
VD
-i
VDRM
-i
Figure 4. Comparison of TISP® and C62.37 Switching Quadrant Parameters
Differences between TISP® and C62.37 Terms and Letter Symbols
TISP®
C62.37
TERM
SYMBOL
Non-repetitive peak on-state pulse current
ITSP
TERM
SYMBOL
Non-repetitive peak pulse current IPPS
Comparison of Manufacturer A and C62.37 Parameters
The fixed voltage products from this manufacturer originally were negative breakdown slope devices, but now the majority are positive
breakdown slope devices like the Bourns TISP®. A straight line characteristic approximation is used and there are several term and symbol
differences from the C62.37 standard. The characteristic curves are shown in Figure 5 and the table below lists the parameter differences.
+i
+i
Quadrant I
IPP
Quadrant I
IPPS
Manufacturer A
Switching
Characteristic
ITSM
C62.37
Switching
Characteristic
ITSM
VS , IS
IT
VT
IH
V(BO) , I (BO)
IT
VT
IH
IDRM
IDRM
+v
+v
-i
VDRM
VDRM
-i
Figure 5. Comparison of Manufacturer A and C62.37 Switching Quadrant Parameters
.
OCTOBER 2000
Specifications are subject to change without notice.
TISP® Terms and Letter Symbols
Differences between Manufacturer A and C62.37 Terms and Letter Symbols
Manufacturer A
TERM
TISP®
C62.37
SYMBOL
Peak pulse current
IPP
TERM
SYMBOL
SYMBOL
Non-repetitive peak pulse current
IPPS
ITSP
Peak one cycle surge current
ITSM
Non-repetitive peak on-state current
ITSM
ITSM
Peak off-state voltage
VDRM
Repetitive peak off-state voltage
VDRM
VDRM
Leakage current
IDRM
Repetitive peak off-state current
IDRM
IDRM
Switching voltage
VS
Breakover voltage
V(BO)
V(BO)
Switching current
IS
Breakover current
I(BO)
I(BO)
Users are advised to carefully check parameter test conditions and measurement technique to confirm the equivalence of the above.
Comparison of Manufacturer B and C62.37 Parameters
The use of VR type letter symbols and terms like stand-off are a heritage from TVS diodes. Where a VBR value is quoted, in most cases the
TISP® V DRM value is equivalent. A combination of two straight lines and a curved line are used for the characteristic curve. There are several
term and symbol differences from the C62.37 standard. The characteristic curves are shown in Figure 6 and the table below lists the parameter
differences.
+i
+i
Quadrant I
IPP
Quadrant I
IPPS
Manufacturer B
Switching
Characteristic
ITSM
C62.37
Switching
Characteristic
ITSM
VBO , IBO
IT
VT
IH
V(BO) , I (BO)
IT
VT
IH
IRM
IR
IBR
+v
VRM
-i
VR
V(BR) , I (BR)
IDRM
VBR
ID
+v
VDRM
VD
-i
Figure 6. Comparison of Manufacturer B and C62.37 Switching Quadrant Parameters
Differences between Manufacturer B and C62.37 Terms and Letter Symbols
Manufacturer B
TERM
TISP®
C62.37
SYMBOL
TERM
SYMBOL
SYMBOL
Non-repetitive peak pulse current
IPPS
ITSP
ITSM
Non-repetitive peak on-state current
ITSM
ITSM
Leakage current at stand-off voltage
IRM
Off-state current
ID
ID
Stand-off voltage
VRM
Off-state voltage
VD
VD
Peak pulse current
Non repetitive surge peak on-state current
IPP
Continuous reverse current
IR
Repetitive peak off-state current
IDRM
IDRM
Continuous reverse voltage
VR
Repetitive peak off-state voltage
VDRM
VDRM
Breakdown current
IBR
Breakdown current
I(BR)
I(BR)
Breakdown voltage
VBR
Breakdown voltage
V(BR)
V(BR)
Breakover current
IBO
Breakover current
I(BO)
I(BO)
Breakover voltage
VBO
Breakover voltage
V(BO)
V(BO)
Users are advised to carefully check parameter test conditions and measurement technique to confirm the equivalence of the above .
OCTOBER 2000
Specifications are subject to change without notice.
TISP® Terms and Letter Symbols
Comparison of Manufacturer C and C62.37 Parameters
A combination of a straight line and a curved line are used for the characteristic curve. There are several term and symbol differences from the
C62.37 standard. The characteristic curves are shown in Figure 7 and the table below lists the parameter differences.
+i
+i
Quadrant I
IPP
Quadrant I
IPPS
Manufacturer C
Switching
Characteristic
ITSM
C62.37
Switching
Characteristic
ITSM
VBO, I BO
IT
VT
IH
V(BO) , I (BO)
IT
VT
IH
IDM
IDRM
+v
+v
VDRM
VDM
-i
-i
Figure 7. Comparison of Manufacturer C and C62.37 Switching Quadrant Parameters
Comparison of Manufacturer C and C62.37 Parameters
Manufacturer C
TERM
TISP®
C62.37
SYMBOL
TERM
SYMBOL
SYMBOL
Non-repetitive peak pulse current
IPPS
ITSP
ITSM
Non-repetitive peak on-state current
ITSM
ITSM
Off-state current
IDM
Repetitive peak off-state current
IDRM
IDRM
Maximum off-state voltage
VDM
Repetitive peak off-state voltage
VDRM
Breakover current
IBO
Breakover current
VDRM
I(BO)
Breakover voltage
VBO
Breakover voltage
V(BO)
V(BO)
IH
IH
Peak pulse current
Peak on-state surge current
Hold current
Ipp
IH
Holding current
I(BO)
Users are advised to carefully check parameter test conditions and measurement technique to confirm the equivalence of the above.
OCTOBER 2000
Specifications are subject to change without notice.