TISP3xxxF3 (HV) Overvoltage Protector Series
APPLICATIONS INFORMATION
Protection Voltage
The protection voltage, (V
(BO)
), increases under lightning surge conditions due to thyristor regeneration. This increase is dependent on
the rate of current rise, di/dt, when the TISP
®
device is clamping the voltage in its breakdown region. The V
(BO)
value under surge
conditions can be estimated by multiplying the 50 Hz rate V
(BO)
(250 V/ms) value by the normalized increase at the surge’s di/dt (Figure
7 ). An estimate of the di/dt can be made from the surge generator voltage rate of rise, dv/dt, and the circuit resistance.
As an example, the ITU-T K.21 1.5 kV, 10/700 µs surge has an average dv/dt of 150 V/µs, but, as the rise is exponential, the initial dv/dt
is higher, being in the region of 450 V/µs. The instantaneous generator output resistance is 25
Ω.
If the equipment has an additional
series resistance of 20
Ω,
the total series resistance becomes 45
Ω.
The maximum di/dt then can be estimated as 450/45 = 10 A/µs. In
practice, the measured di/dt and protection voltage increase will be lower due to inductive effects and the finite slope resistance of the
TISP
®
breakdown region.
Capacitance
Off-state Capacitance
The off-state capacitance of a TISP
®
device is sensitive to junction temperature, T
J
, and the bias voltage, comprising of the d.c. voltage,
V
D
, and the a.c. voltage, V
d
. All the capacitance values in this data sheet are measured with an a.c. voltage of 100 mV. The typical 25 °C
variation of capacitance value with a.c. bias is shown in Figure 17. When V
D
>> V
d
, the capacitance value is independent on the value of
V
d
. The capacitance is essentially constant over the range of normal telecommunication frequencies.
NORMALIZED CAPACITANCE
vs
RMS AC TEST VOLTAGE
1.05
AIXXAA
1.00
Normalized Capacitance
0.95
0.90
0.85
0.80
Normalized to V
d
= 100 mV
DC Bias, V
D
= 0
0.70
1
10
100
1000
V
d
- RMS AC Test Voltage - mV
0.75
Figure 17.
MARCH 1994 - REVISED MARCH 2006
Specifications are subject to change without notice.
Customers should verify actual device performance in their specific applications.
BOURNS [ BOURNS ELECTRONIC SOLUTIONS ]
