The DE2-115 Altera FPGA development board uses "LM3150 Wide-VIN Synchronous Buck Controller" to generate two supply rails: 1) 1.2V/5A from a 12V rail 2) 3.3V/6A from a 12V rail

enter image description here

These switching regulators require quite a lot of external components to be used. Is this common with switching regulators? Why not use an "integrated version" of switching regulators which do not require such a large number of different types of external components.

  • 1
    \$\begingroup\$ It's pretty hard to push an inductor into a chip. \$\endgroup\$ – Eugene Sh. Mar 27 '18 at 21:03
  • \$\begingroup\$ The integrated versions are "bricks." Besides, that's not really a lot of components. Just buy a brick if you want still more simplicity. Inductors and large capacitors are hard to put on ICs, anyway. So are high current FETs (lots of space.) In any case, people have preferences for power devices they use, as well. \$\endgroup\$ – jonk Mar 27 '18 at 21:04
  • 2
    \$\begingroup\$ There are more highly-integrated regulators, but they tend to be more limited in their capabilities, especially with regard to low-voltage, high-current supplies like these. You choose the one that works best for your application. In high-volume manufacturing, you try to minimize the total BOM cost, not just the component count per se. \$\endgroup\$ – Dave Tweed Mar 27 '18 at 21:05
  • \$\begingroup\$ Actually, I am just surprised by the need of FET and strange combination of the R, L, C components. \$\endgroup\$ – quantum231 Mar 27 '18 at 21:07
  • 1
    \$\begingroup\$ no. the lm2596 requires the same external component count as the LM317 (4 BOM parts). \$\endgroup\$ – dandavis Mar 27 '18 at 21:57

Switching regulator components are sold in several configurations.

A switching regulator controller is an IC contains the control functions, and perhaps a gate-driver boost circuit. But it will require external inductors, external switching components (FETs), external capacitors, feedback resistors, etc.

A switching regulator IC often integrates the switching components (FETs) with the regulator controller. But it will still require an external inductor and capacitors.

A switching regulator module is typically a complete circuit with multiple components mounted on a small PCB. It usually includes an IC, inductor, some capacitors, etc. This can be a nearly complete solution in a single orderable part number.

Using a modular solution is a good idea when you do not want to devote resources to designing the regulator circuit, and when you can find a existing product that meets your needs.

A regulator IC is a good idea when you want more flexibility to tune the design to your requirements and can't find a modular solution that meets your needs. Cost might also be lower than for a modular solution.

A controller IC often allows handling higher load currents than an integrated regulator IC because the switches can be larger and not as much thermally coupled to each other and the rest of the circuit.

| improve this answer | |

To add the the existing answers:

  1. some components must be external to chip (and at some distance to other components) to keep ambient temperature as their characteristics may depend on the temp they operate in. If built into a single chip their operations features would suffer from heating;

  2. chips in your example assume varying output in terms of voltage, thus some components (like feedback resistors) must be external in order for you to adjust output voltage/amperage to needed level;

  3. some components are just too big to fit into the chip's casing.

If you would carefully look into the regulator's datasheet, you will most probably find the section explaining the best component layout on the PCB - and also how you should NOT lay them out. These recommendations focus on heat dissipation, EMI within regulator's circuit and crosstalk with other circuits, stability and reliability of the operation, and safety.

| improve this answer | |

Is this common with switching regulators?


Why not use an "integrated version" of switching regulators which do not require such a large number of different types of external components.

Not possible for this current and power range with dual outputs.

In order to improve cross load regulator noise, separate converters are used.

enter image description here Consider that every part has a design purpose that for better or worse was the most cost effective choice if the design is in high volume and has high quality specs. The design you show is one of the best buck regulators, a Half-Bridge feedback ratio variable voltage buck regulator with fixed parts.

In order to get the best bang for the buck, it is not feasible to combine all the parts into silicon.

The concepts start simple then get more complcated with low error and high power specs.

enter image description here

Small lithography analog and digital ASICs cannot do low RdsOn MOSFETs on the same wafer. Nor can they do large reactive parts or large current shunts.

Consider : high energy storage in LC reactive parts and high current in semiconductors, input transient OVP, output current limiting , output LC ripple filters.

Consider the specs for your DC-DC multiple output converter.

12Vin, Output 1.2V,3.3V, total 27W output <1% Voltage regulation <1% 50% load regulation error, < 2% ripple, crossload regulation error 0.5% , low EMI, etc etc.

Can you think of a better way? Look on your MOBO to see how little space it takes to supply all the internal voltages for RAM & CPU , all controlled by BIOS. Locate the coils near the CPU.

Then for AC to DC converters we have lightning transients and HIOT isolation requirements. Not every design is scaleable due to I^2R exponential demands.

But here is a simple AC-DC converter. enter image description here enter image description here

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.