TCM1030 Datasheet, PDF (4/8 Pages) Texas Instruments – DUAL TRANSIENT-VOLTAGE SUPPRESSORS

TCM1030, TCM1050
DUAL TRANSIENT-VOLTAGE SUPPRESSORS
SCTS040B – JUNE 1989 – REVISED JUNE 1997
TYPICAL CHARACTERISTICS
TIP OR RING CURRENT
vs
TIP OR RING TO GND VOLTAGE
0.5
VS = – 48 V
0.4 TA = 25°C
0.3
0.2
0.1
0
– 0.1
– 0.2
– 0.3
– 0.4
– 0.5
– 50 – 40 – 30 – 20 – 10 0 10 20 30 40 50
Tip or Ring to GND Voltage – V
Figure 1
APPLICATION INFORMATION
The trip voltage represents the most negative level of stress applied to the system. Positive transients are
clamped by diodes D1 and D2. When a negative transient is applied, current flows from V_S to TIP or RING where
the transient voltage is applied. When the current through TIP or RING reaches the pulse-trip current, the SCR
turns on and shorts TIP or RING to GND. The majority of the transient energy is dissipated in the external resistor
(nominally 100 Ω for the TCM1030 and 70 Ω for the TCM1050). Current into V_S ceases when the SCR turns
on. When the energy of the transient has been dissipated so that the current into TIP or RING due to the transient
plus the battery feed supply is less than the holding current, the SCR turns off.
To help ensure reliability and consistency in the firing voltage, it is recommended that two capacitors be
connected between V_S and GND, as close to the device terminals as possible. One capacitor should be a 0.1-µF,
100-V ceramic unit and the other, a 0.47-µF, 100-V stacked-film (not wound) metalized plastic capacitor. If
inductance is present in the line to V_S, these capacitors help prevent overshoot in the firing voltage during fast
rise-time transients.
To avoid dc latchup after the SCR has fired, the current must be less than the holding current, I_H. To prevent
dc latchup, the line feed current must be limited to the following conditions:
* VTP
) ^t Rline
VRP
2Rp
IH
where V_TP and V_RP are the voltages on TIP and RING, respectively, of the TCM1030 or TCM1050. Induced ac
currents into TIP or RING (e.g., power-line inductive coupling) must be less than the trip current to prevent the
SCR from firing.
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