The birth and evolution of the switching voltage regulator—The SG1524
The birth and evolution of the switching voltage regulator—The SG1524

 “All I did was being an enabler to help others apply switching technology to power supplies easier”, humbly spoken by the man who is called the “Father” of the switching regulator controller. Bob Mammano’s biggest battle was to convince the marketing team at Silicon General (Founded by Mammano) that it would be a good idea for him to spend time on this project.

The SG1524 came out of this effort and was unique in the industry among 1975 power solutions because it put all of the blocks a switching power supply needed together in one chip. As a matter of fact, it can be arguably classified as the first mixed-signal IC design.

In 1975 there were a series of technical challenges in fitting all the pulse-width modulation (PWM) control circuitry into a single IC. At that time IC’s were either analog or digital and both had to be integrated into this design. To compound the problem, analog circuits were designed on a bipolar process to get the voltage and current needs of a power management solution. How would one build a digital circuit on the same process?

Mammano went back to an even older technology for digital logic circuitry, a basic bipolar technology. This would also now work for the analog portion of the circuit.  This design was unique in that it was also the first design to implement protection as well as control on an IC and became the mainstay of all future power controllers. Another innovative idea was to limit the output current on a pulse-by-pulse basis, a key requirement for switching regulators.

Mammano had the unique experience of founding the Unitrode IC division in 1981 and his team developed the first PWM controllers with current-mode control, the UC1843 and UC1846. Later at Texas Instruments he was on the first digital power committee, when digital power was just a “name”.

Modern digital power architectures have PWM’s integrated into the microcontroller with time granularities of 150 ps, unheard of and unachievable in the past.  The Texas Instruments Piccolo processor is a good example of this capability.

Higher integration technology also now enables integration of MOSFET switches right into the PWM IC.

Mammano says, “Power supply solutions are determined by the needs of the system it’s going to power. The challenge is to optimize the supply and make it more cost-effective, smaller and more efficient. The problem has always been that a different system needs a different power supply which is optimized to that particular system needs.”

In the past any technique that could give an analog supply more versatility increased the price and size, but with the advent of digital power, software now is the enabler for power supply versatility, at equal or lower ultimate system cost.

The DSP or microcontroller now gives better control management, sequencing, monitoring and margining for adaptive capability that is most evident in being capable of maximizing efficiency in near real-time as loads quickly change.