TISP61089A
DUAL FORWARD-CONDUCTING P-GATE THYRISTORS
PROGRAMMABLE OVERVOLTAGE PROTECTORS
JUNE 1999
THERMAL INFORMATION
NON-REPETITIVE PEAK ON-STATE CURRENT
vs
CURRENT DURATION
TI6HAC
I
TSM(t)
- Non-Repetitive Peak On-State Current - A
10
9
8
7
6
5
4
3
V
GEN
= 600 Vrms, 50/60 Hz
R
GEN
= 1.4*V
GEN
/I
TSM(t)
EIA/JESD51-2 ENVIRONMENT
EIA/JESD51-3 PCB
T
A
= 25 °C
GROUND RETURN = 2xI
TSM(t)
2
1.5
1
0.9
0.8
0.7
0·1
1
10
100
t - Current Duration - s
1000
Figure 2. NON-REPETITIVE PEAK ON-STATE CURRENT AGAINST DURATION
APPLICATIONS INFORMATION
gated protectors
This section covers three topics. Firstly, it is explained why gated protectors are needed. Second, the voltage
limiting action of the protector is described. Third, an example application circuit is described.
purpose of gated protectors
Fixed voltage thyristor overvoltage protectors have been used since the early 1980s to protect monolithic
SLICs (Subscriber Line Interface Circuits) against overvoltages on the telephone line caused by lightning, a.c.
power contact and induction. As the SLIC was usually powered from a fixed voltage negative supply rail, the
limiting voltage of the protector could also be a fixed value. The TISP1072F3 is a typical example of a fixed
voltage SLIC protector.
SLICs have become more sophisticated. To minimise power consumption, some designs automatically adjust
the supply voltage, V
BAT
, to a value that is just sufficient to drive the required line current. For short lines the
supply voltage would be set low, but for long lines, a higher supply voltage would be generated to drive
sufficient line current. The optimum protection for this type of SLIC would be given by a protection voltage
which tracks the SLIC supply voltage. This can be achieved by connecting the protection thyristor gate to the
SLIC supply, Figure 3. This gated (programmable) protection arrangement minimises the voltage stress on
the SLIC, no matter what value of supply voltage.
PRODUCT
INFORMATION
5
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