Description/Features
TRANZAP’s are silicon PN junction diodes designed,
manufactured and specified as Transient Voltage Suppressors
having a non-linear current-voltage characteristic which
sustains an almost constant voltage over a wide range of
current. They are ideally suited to many transient voltage
protection applications and their high clamping efficiency and
low steady state power dissipation offer considerable circuit
advantages over most existing methods of protection.
During operation, the ZAP idles at a low current level at the
nominal voltage. When a transient voltage occurs, ZAP
current increases rapidly, its voltage remaining virtually con-
stant, and the transient energy content is thus absorbed.
Repetitive surge capability
Peak pulse power is fixed under non-repetitive conditions.
However, in practical use, there are cases when the surge is
often repeatedly applied.
In this case, even though the one pulse power remains
within the peak pulse power, the power is accumulative and
exceeds the peak pulse power in some cases.
Response time
Response time of psec order however, in its operating
response time, it depends largely on the influence of
capacitance, and the effect of the response time with respect
to the clamping voltages is negligible.
Capacitance
Capacitance is determined by the area of a silicon chip and
the breakdown voltage. The capacitance decreases as the
bias voltage increases as shown in Figure 8.
Taping
Standard taping is available upon request.
Forming
Standard forming is available upon request.
Features
■High surge current capability
■Excellent voltage clamping (1.2 @ 50% peak power)
■Symmetrical characteristic - use on AC or DC (bipolar)
■Instantaneous response (pico- second order)
■Low idling current (5
m
-Amps)
Applications
■Protection of all types of semiconductors
■Absorption of surges associated with lightning
■Suppression of switching surges
■Protection in inductive switching circuits
■Prolongation of contact life
■Voltage clipping
Construction
ZAP construction features
PN junctions on both faces
of a silicon chip and has
been sufficiently designed
for thermal dissipation of
high surge power in a short
period of time.
Lead wire
Epoxy resin
Header
Solder
Silicon chip
Surge suppression characteristics
Surge suppression is shown in Figure 2 when
standard surge is applied to test circuit of Figure 3.
Electrical characteristics
Figure 4 shows an almost symmetrical breakdown voltage
(V
B
) ratio between
forward (V
BF
) and
reverse breakdown
voltage (V
BR
).
Typically
0.9 1.10
V
BF
V
BR
<
=<
=
Stand-off voltage
TRANZAP’s are designed for transient voltage suppression, it
is not preferable to consume power at the operating voltage.
Stand-off voltage is fixed to be of a value 0.9 times the
minimum breakdown voltage.
Leakage current
The current when the stand-off voltage is applied is fixed as
the maximum leakage current. This leakage current is an
important factor when used in circuits with high impedance.
Breakdown voltage
The terminal voltage when a test current is passed, is fixed
to be the breakdown voltage. The breakdown voltage is
measured in air 25°C. The test current is normally 1 mA .
Continuous operating power
The PN junction temperature is determined by the
following equation:
Tj=(P
q)
+Ta
P: Applied power
Thermal resistance
Ta: Ambient temperature
Where,
q
is thermal resistance from the PN junction to
ambient space and is determined by following equation:
q
=(1/K)x(L/S)
K: Thermal conductivity
L: Length of lead wire
S: Sectional area of lead wire
In case of Ta=50°C, Tj = 150°C, the maximum
operating power is as follows:
Z1 type: 500m Watts
Z2 type: 1 Watt
Z6 type: 3 Watts
Surge capability
Surge capability (P) is determined by the following equation:
P=ƒi(t)(V(t)dt)
it : Pulse current wave
Vt : clamping voltage wave
Allowable surge capability (Pm) is determined by the
following equation:
Pm=IPx VC
IP: Peak current
VC: Maximum clamping voltage
The allowable surge capability (peak pulse power) is as
shown in Figure 5 and the surge capability derating
characteristic as shown in Figure 6.
Peak current
Test pulse wave form
Test pulse
ROZAP
R1
V(t)
105
104
103
102
10
100
80
60
40
20
Z6 Type
Z1 Type
Peak pulse power (w)
Power ratio (%)
Z2 Type
10-4 10-3 10-2 10-1 11010
2
Time (msec)
20 40 50 80 100 120 140
Ambient temperature (°C)
I(t)
VC
lp
Maximum clamping voltage
Clamping voltage waveform
Current
Voltage
Time
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
VC
VB
VB
VS
ILIT
VS: Stand-off voltage
VB: Break down voltage
VC: Maximum clamping voltage
IL: Maximum leakage current
IT: Test current
IP: Peak pulse current
ITIP
1 2 5 10 20 50 100 200 500 1000 2000 5000 10000
Repeating time (msec)
Pulse power ratio (%)
100
90
80
70
60
50
40
30
20
10
O Bias
1nF
100PF
10PF
O Bias
O Bias
70% Bias
Z6 Type
Capacitance
Z2 Type
Z1 Type
Break down voltage (V)
15 20 30 40 50 60 80 100 200
50% Bias
Figure 7
Figure 8