Power Supply Management ICs

Power supply management ICs perform power management functions for the power supplies employed in electronic systems. These functions include:

  • Power supply sequencer controllers
  • Power supply margining controllers
  • Power supply tracking controllers

Power Supply Sequencing Controllers
Usually, multi-voltage systems require one power supply to rise to the proper operating voltage before another supply is applied. When prime power is removed, the associated power supplies must also turn off in the proper sequence. Improper sequencing can lead to latchup, improper performance, or degraded reliability. Furthermore, supply loading can affect circuit turn-on and turn-off times.

To avoid these potential turn-on and turn-off problems, power sequencing ICs provide the proper local voltage sequencing in multi-supply systems. The sequencers use (internal or external) MOSFETs to switch power supplies on and off in the appropriate, safe sequence. Power sequencing ICs provide predictable and safe operation for locally-generated power, whereas power-on and power-off sequencing is difficult to control or predict when using externally generated power sources.

Among the systems that require reliable power sequencing are microprocessors and digital signal processors that employ two supply voltages.

A power supply sequencer IC for dual-voltage microprocessors (µPs) and multi-voltage systems. monitors a primary supply voltage and enables/disables an external N-channel MOSFET switch for a secondary supply voltage. The IC controls local component voltage sequencing when system power-on/power-off characteristics cannot be guaranteed. Therefore, these power supply sequencer ICs improve system reliability.

One of these sequencers includes an internal voltage reference/comparator with externally adjustable thresholds to monitor the primary power supply. When the primary supply is below the desired threshold, the IC disables an external secondary supply MOSFET switch.

When the primary supply exceeds the threshold, an internal charge pump is activated and the external MOSFET switch is enabled to connect the secondary supply to the load. The charge pump fully enhances the N-channel MOSFET switch to provide a very low on-resistance voltage drop. The devices can be connected to support various supply sequencing priorities such as VI/O before VCORE or VCORE before VI/O.

Power Supply Margining Controllers
One approach for determining the reliability of an electronic system is to test system functionality and performance at the specified upper and/or lower power supply voltage limits of a given design. This allows a system to test the correct operation of electrical components at the upper and/or lower power supply voltage limits specified for a given design. Known as "power supply margining," it improves the lifetime reliability of an electronic system. This function can be accomplished with a margining controller IC.

One margining controller IC allows power supplies and power supply module output voltages to be precisely adjusted both up and down for automated PCB testing. The power supply output voltage is changed by sourcing or sinking current into the feedback node or voltage adjust pin of the power supply. Among the margining controller applications are automated p.c. board production testing, automated preventative maintenance testing, and dc-dc converter module margining.

Any one margining channel requires only a single external resistor to symmetrically margin both above and below the nominal power supply voltage. A two-channel margining IC can be used to symmetrically margin two different power supplies. In cases where the design calls for margining one voltage above the nominal power supply voltage and a different voltage below the nominal, use the two-channel IC. Use one