TCM1050 datasheet(4/8 Pages) TI

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TCM1030, TCM1050

DUAL TRANSIENT-VOLTAGE SUPPRESSORS

SCTS040B – JUNE 1989 – REVISED JUNE 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

– 0.1

– 0.3

– 0.4

– 0.5

0.4

– 0.2

– 50 – 40 – 30 – 20 – 10

0.2

0.1

0.3

Tip or Ring to GND Voltage – V

0.5

VS = – 48 V

TA = 25°C

TIP OR RING CURRENT

TIP OR RING TO GND VOLTAGE

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 VS 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 VS 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 VS 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 VS, 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, IH. To prevent

dc latchup, the line feed current must be limited to the following conditions:

TP *

line )

2Rp

t I

where VTP and VRP 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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