AN2456 datasheet(13/15 Pages) STMICROELECTRONICS

13 / 15 page

AN2456

SLIC protection

13/15

Figure 15.

120 Vrms - 25 Arms - 15 min. - metallic on tip - ANP mode

Figure 16.

120 Vrms - 25 Arms - 15min. - longitudinal - ringing mode

Figure 15 and Figure 16 show the protection behavior in ANP mode and Ringing mode

when the power cross is applied in metallic configuration on TIP and in Longitudinal

configuration respectively. The current is 11.3 Apk (120 Vrms / (4.8 Ω+10 Ω) ~ 8.1 Arms ~

11.3 Apk). It is seen that the power is engaged on the wire for 1.5 to 2 cycles before the fuse

opens. During this time it is noted that the voltage is clamped to GND by the diode inside

LCP1521S for the positive half cycles. During the negative half cycles, the thyristor structure

inside LCP1521S fires when the voltage exceeds –Vbat. We see some disturbance in –Vbat

voltages but it returns to initial condition after the test. In Figure 15 the protection on Ring

doesn’t react because the power cross is only applied on TIP. But however there is a small

disturbance on VRing during the surge due to the disturbance on -Vbat.

VTip (20 V/div)

VRing (20 V/div)

-Vbat (20 V/div)

ISurge (20 A/div)

VTip (20 V/div)

VRing (20 V/div)

-Vbat (20 V/div)

ISurge (20 A/div)

AN2456 Datasheet(PDF) 13 Page - STMicroelectronics