Fast Level Shifter Converting Ecl-To-Ttl Levels
Original Publication Date: 1988-Nov-01
Included in the Prior Art Database: 2005-Feb-15
An ECL (Emitter Coupled Logic) or CCSL (Cascode Current Switch Logic) logic circuit is fast, but when it has to drive an off-chip driver delivering TTL or VTL levels (which are referenced to ground), a level- shifter circuit has to be put at the interface between the logic circuit and the output driver. This level shifter circuit brings out some penalties, especially in terms of delay. The present circuit, while (Image Omitted) giving a low delay penalty, allows very well-controlled down levels, allowing an emitter follower as output device. This emitter follower has the possibility of being part of a push-pull output stage. The KVBE reference voltage source, illustrated in Fig. 1, is designed to provide a voltage that is independent of the Vcc power supply voltage.