TD230 Просмотр технического описания (PDF) - STMicroelectronics

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TD230

ELECTRONIC CIRCUIT BREAKER

STMicroelectronics 

TD230

Figure 10 : Visual Alarm-Shutdown

Vcc +

TD230

S hutdown

which, in most cases are, are not worrying. But in

some very demanding applications, it is necessary

to remove this noise.

A good way to eliminate such peaks is to add a

resistor connected in series with the inductance

and an electrolytic capacitor between the common

point of resistor and inductance, and ground of the

Step-Up Converter as shown on figure 11.

Figure 11 : Step Up Noise Reduction

Rse nse

where CISS1/2 , CSS1/2, VTH1/2 , IP/N1 are respectively

the input capacitance, the soft start capacitor, the

threshold voltage and the internal gate current

sources of NMOS1/2 ; and where VSP1/2 , CTRIP1/2 ,

IP/N2 are respectively the voltage source, current

source and external capacitor of the protection

mode pins PM1/2. Considering the typical values of

VSP1/2, IP/N2, IP/N1, and the fact that classical power

MOSFETs have a threshold voltage around 5V, this

condition can be translated to inequation (vi) :

• CTRIP1/2 > 0.8 x (CSS1/2 + CISS ) (vi)

If CISS = 1nF and CSS1/2 = 4.7nF, CTRIP1/2 should

be superior to 4.56nF.

Table (b) summerizes Protection Mode Time Con-

stants corresponding to different CTRIP1/2 values.

Table (b) : Protection Mode Time Constants

CTRIP1/2

22nF

220nF

2.2µF

22µF

Time Constant Range

for Protection Mode

- Shutdown -

#10ms

#100ms

#1s

#10s

5. ENHANCEMENTS

The performances of TD230 are well adapted to

most of the circuit breaking applications in many

differents industry segments (Telecom, Automo-

tive, Industrial, Computer etc...), but in the case of

very demanding environment, or outstanding fea-

tures, the few following advices may be helpful.

5.1. Step-Up Noise Reduction

The inductive step-up converter inevitably gener-

ates current peaks in the output of the power switch

12/15

R

C

TD2 3 0

The resistor’s voltage drop will be due to the prod-

uct of the average consumption current with the

resistor’s value and the inductive current peaks will

be totally absorbed by the capacitor. With a 100Ω

resistor, the voltage drop is negligible and the

attenuationgood with a 4.7µF as shown on

figure 12.

Figure 12 : Step Up Noise Reduction

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