Multiple Output Controller and Regulator ICs

Multiple output controller ICs consist of two or more of switchmode dc-dc converters in a single package or combinations of LDOs and dc-dc converters. They can be controllers that employs external power switches or regulators with an internal power switch. One possibility is a 5V output and a 3.3V output for processor and logic applications.

These devices are used in ac powerline and battery-powered applications. Some of the more sophisticated ICs include supervisory and power sequencing capability.

Among the features found in multiple output controller ICs are:

  • Fixed or adjustable outputs
  • Soft-start
  • Fixed or variable switching frequency
  • Undervoltage lockout (UVLO)
  • Thermal protection
  • Power Good output
  • Current limit
  • Overvoltage protection
  • Enable/disable
  • Independently regulated outputs
  • Power sequencing control

Following are typical examples of combined LDO/switchmode converters.

1. This IC combines a dual synchronous buck controller and a linear regulator controller, providing a cost-effective, high performance and flexible solution for multi-output applications. You can configure the dual synchronous controller as two-independent or two-phase controller. In two-phase configuration, the IC provides a programmable current sharing that is ideal when the output power exceeds any single input power budget. It drives its two output stages 180°out of phase. In two-phase configuration, the two inductor ripple currents cancel each other, reducing the output current ripple and allowing a smaller output capacitor for the same ripple voltage requirement.

The IC provides a separate adjustable outputs by driving a switch as a linear regulator. This device features programmable switching frequency of 200 to 400kHz per phase, undervoltage lockout for all input supplies as well as output undervoltage detection that latches off the device when it detects an output short.

It has a programmable soft start to control the output voltage rise and limit the current surge at the start-up. The soft-start function operates by sourcing an internal current to charge an external capacitor to about 3V. As the charging voltage of the external capacitor ramps up, the PWM signals increase from zero to the point the feedback loop takes control.

The IC?s two independent outputs can be either common or different input voltages. The output voltage of the individual channel is set and controlled by the output of the error amplifier, this is the amplified error signal from the sensed output voltage and the reference voltage. This voltage is compared to the ramp signal and generates fixed frequency pulses of variable duty-cycle, which drives the two N-channel external MOSFETs.

In the current sharing mode, the two converter's outputs tie together and provide one single output. In this mode, one control loop acts as a master and sets the output voltage as a regular voltage mode buck controller and the other control loop acts as a slave and monitors the current information for current sharing. The current sharing is programmable and sets by using two external resistors in output currents' path. The slave's error amplifier, error amplifier 2, measures the voltage drops across the current sense resistors, the differential of these signals is amplified and compared with the ramp signal and generates the fixed frequency pulses of variable duty cycle to match the output currents.

2. This IC is a dc-to-dc switching power supply controller that combines the functions of three PWM and PSM converter ICs in a single device. It is aimed at power conversion applications in consumer appliances such as set-top boxes, DVD players, notebook computers, and telecom and broadband networks.

It is a current