MTL7707+ for switch inputs and switched outputs

MTL7707+ for switch inputs and switched outputs

The MTL7707+ is a 2-channel shunt-diode safety barrier similar to the MTL7787+ but with built-in electronic overvolt protection. It is intended primarily for safeguarding a hazardous-area switch controlling a relay, opto-coupler or other safe-area load from an unregulated dc supply in the safe area.

The outgoing channel accepts supply voltages up to +35V and is protected against reverse voltages: the return channel is unaffected by voltages up to +250V.

In normal operation the protection circuit introduces only a small voltage drop and shunts less than 1mA to earth, so its overall effect is minimal.

If the supply voltage exceeds about 27V, however, causing the Zener diodes to conduct-or if the safe-area load has a very low resistance-the supply current is limited automatically to 50mA, protecting the fuse and power supply and enabling the loop to continue working.