Defining high performance for analog ICs

Electronic News, Feb 19, 1996 by Larry Sample

Micrel's PCMCIA power matrix switch designs enable full compliance with the complicated PCMCIA rise and fall time specification, but they also offer full protection for the user-available slot, with thermal shutdown, short circuit current limit and a balanced RDS(ON) guarantee, all of which allow nominal power supply tolerance. There are other approaches that may not be fully protected, may not meet the switching time specifications and may not have included pin resistance in their RDS(ON) calculations, all of which may mean that the system power supply will be prohibitively expensive to be made fully compliant. The Micrel devices' 1A output at Vcc ensures full PCMCIA compatibility and card interchangeability for PCMCIA card designers.

Rugged high speed high-side and low-side MOSFET drivers are further types of high-performance devices. The performance goals aren't just a few nanoseconds switching time, but to supply 12 amperes of drive current or to operate off of supply voltages over wide range. The new drivers may have to include internal charge pumps for generating the drive voltage. MOSFET drivers are used in applications ranging from handheld computer peripherals to motor controls, from lamp drivers to power bus switching. Analog IC manufacturers have to design in sophisticated electrostatic discharge protection and protection against latch-up. More advanced types incorporate zener clamps for gate protection, programmable over-current sensing, and dynamic current threshold setting to accommodate high in-rush currents. They also include fault output pins to flag fault conditions. Dual and quad devices have to guarantee matched rise and fall times. And manufacturers have to supply MOSFET drivers in multiple configurations for inverted, non-inverted and differential outputs for high side as well as low side driver applications.

Other high-performance analog ICs include flexible open-drain drivers for such things as motor controls, MOSFET bridges, squibs, isolated loads, pulsers and safety locks. The common element in all the new high-performance analog integrated circuits is that they more precisely meet the specialized needs of OEM designers. Rather than requiring greater ingenuity from the users, they insist on greater ingenuity from IC manufacturers to meet the users' needs. Today's high-performance analog IC is far more a market-driven product than in the past, when design engineering determined the direction analog circuits would take.

(Larry Sample, Design VP, Micrel Semiconductor)