INTEGRATED CIRCUITS APPLICATION NOTE AN10156 Sorting through the low voltage logic maze Authors: Ramin Kowssari, Mike Magdaluyo 2002 June 06 Philips SemiconductorsPhilips Semiconductors Application note Sorting through the low voltage logic maze AN10156 Authors: Ramin Kowssari, Mike Magdaluyo Introduction Digital systems are running at faster speeds, operating at lower voltages, and they are becoming more highly integrated. Many functions can be integrated into FPGAs or ASICs, however, this does not mean that generic standard logic has gone away. Designers may choose to design with standard logic for the following reasons: The need for cheap, simple fixed functions with high speed and lower power consumption Space constraints requiring small packaging Bus driving capability Interfacing between mixed voltage systems Need for hot insertion capability Need for bus switching. Today designers are challenged with the task of choosing among many low voltage logic families. This paper provides information on the various families, their key features and how to choose among them, based on the criteria listed above. Standard Logic vs. ASICs or FPGAs There are situations in which standard logic is more cost effective and suitable than FPGAs or ASICs. This becomes more evident when to you realize the crucial role that standard logic plays in many systems. For example, the design engineer may need to add a single function to an ASIC or FPGA in the final stage of the design due to a last minute change in the systems protocol. Rather than re-spin an ASIC or reprogram the FPGA and reinvest the engineering time, effortlessly adding a logic device thats close to the source of the problem at the critical peak of the design cycle will get the system to market on time. Furthermore, speed, high output drive, lower power consumption, space constraints, distinctive features, and a collection of standard functions can also compel designers to utilize high-speed low voltage logic ICs. (See Tables 1 and 2). LV/LVX LVC/LCX ALVC LVT 9 ns typical t 4 ns typical t 2 ns typical t 2 ns typical t PD PD PD PD 6-8 mA I /I 24 mA I /I 24 mA I /I 32/64 mA I /I OH OL OH OL OH OL OH OL 130 ohm line drive 50 ohm line drive 50 ohm line drive 35 ohm line drive 20 A standby current 10 A standby current 40 A standby current 190 A standby current V : 1 - 3.6 V V : 1.2 - 3.6 V V : 1.2 - 3.6 V V : 2.7 - 3.6 V CC CC CC CC Gates, MSI, bus interface Gates, MSI, 8/16/32 bit bus Gates, MSI, 8/16/32 bit bus Gates, MSI, 8/16/32 bit bus functions interface functions interface functions interface functions 1 Termination resistor option Termination resistor option Termination resistor option 5 V tolerant inputs 2 5 V tolerant I/O 5 V tolerant I/O 5 V tolerant inputs Supports hot swap Bus hold feature Supports hot swap Bus hold feature Bus hold feature Notes: 1. Vendor dependent 2. Vendor dependent Propagation delays are approximate typicals for a 245 function Table 1. Low voltage standard logic families and features 2002 June 06 1