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  • Author Author: jw0752
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Decentralized Power Distribution Architecture

jw0752

About 6 months ago we had an Essential Post on Power Distribution:

 

Smart Power Distribution

 

Tonight as I studied a junk circuit board in my bin I came across a good example of the De-Centralized Architecture.

 

image

This is a board from an upscale Audio Video Sound System Receiver. The board has multiple micro processors which usually don't have much interest for me but in the lower right corner of the board I saw a parts layout that was repeated 4 times. The IC at the center of each repetition was an MP2363DN which turns out to be a 3A 365 kHz Step Down Converter.

 

Here is the Data Sheet if you are interested:

 

https://datasheet.octopart.com/MP2363DN-LF-Monolithic-Power-Systems-datasheet-13696477.pdf

 

The section of the Data Sheet that first caught my eye was the typical application circuit:

 

image

As I traced out and checked the circuits on the board it appeared that the designer had used the Typical Application for the configuration. The data Sheet also had information on using a resistor voltage divider to set the voltage output. I decided that it would be a fun exercise to figure out what resistors were used in each section and apply the formulas in the data sheet to predict the output voltage  of each section. I numbered the sections 1 to 4 left to right. Here are the formulas for setting output voltage:

 

image

 

This was extra fun as the designer had used parallel resistors to trim his required value for R-1 in each section. I tried to measure the R1 combination in circuit with my meter but it was obvious that other components were messing with my readings. Since the readings on the resistors were legible I was able to read and calculate them as #1 - 1.525k, #2 - 10k, #3 - 26k, #4 - 46k. Inserting these into the formulas yielded the following output voltages respectively:  1 volt, 1.84 volts, 3.3 volts, and 5.1 volts.

 

Now I wanted to test my calculations. I had no way to power the board like it was in the receiver but I could easily power the rails that fed these four circuits. I set up a couple of 10 volt power wires with Non-Slip Probe Tips and placed them so that I had 10 volts plus on pin 2 of chip #1 and ground on pin 4 of the same chip. Since this fed the rails for all four circuits no further movement was needed. I had already tied my multimeter negative probe to ground and while holding the power probes with one hand I probed the output of each of the 4 DC to DC converters. The result was 1.2 volts, 1.9 volts, 3.4 volts, and 5.2 volts respectively which matched very well with my calculations.

 

image

 

This is the first time I have encountered such an obvious example of the Distributed Power Architecture that was mentioned in the Essential Power Blog. It was fun to experiment with the circuit and who knows somewhere down the line I may even have an application for the MP2363 Step Down Converter Chip.

 

John

Parents

  • image

    Red 12+   Black Ground   White 1 V   Orange 1.7 V   Blue 3.3 V   Brown 5.3 V

     

    Tonight I decided to see if I could excise the 4 Step Down circuits from the larger board and still have an operational power section. I studied the layout and made my best guess as to where I could cut the board and not cut required circuitry. I used the SMD rework station to get a couple of larger ICs out of the way of the saw. When I first powered up the unit after cutting I had only the 5.5 volt section working. Trouble shooting and comparison of the sections showed that the enable pin 7 of the three down MP2363s was low. The data sheet indicates that pin 7 should be allowed to float for auto power up. The 5.5 volt section was already open but the other 3 sections were tied back to one of the chips I had removed to avoid the saw cut. Apparently the 1V, 1.7V, and 3.3V were designed to be powered on at the control of the chip I removed. With this insight I cut the trace to pin 7 on each of the non-functional MP2363s and tried once again to see if the unit was working. Once I had the unit working I also added a load to each channel. I did not try the three amps advertised in the data sheet as my jumper wires would have been stressed by this amount but I did subject each section individually to 2 Amps of load. To me it is simply amazing that these small DC converters can deliver 3 Amps with so little heat and such amazing voltage stability.

     

    image

     

    Simple experiments like this one always seem to net a little additional knowledge. Now I know that I can turn the chips on and off with the number 7 enable pin. This information was in plain sight in the data sheets but it always helps my learning process if I have to get physically involved with the process.

     

    Now I have to keep this circuit in mind so I can incorporate it into a future build somehow.

     

    John

Comment

  • image

    Red 12+   Black Ground   White 1 V   Orange 1.7 V   Blue 3.3 V   Brown 5.3 V

     

    Tonight I decided to see if I could excise the 4 Step Down circuits from the larger board and still have an operational power section. I studied the layout and made my best guess as to where I could cut the board and not cut required circuitry. I used the SMD rework station to get a couple of larger ICs out of the way of the saw. When I first powered up the unit after cutting I had only the 5.5 volt section working. Trouble shooting and comparison of the sections showed that the enable pin 7 of the three down MP2363s was low. The data sheet indicates that pin 7 should be allowed to float for auto power up. The 5.5 volt section was already open but the other 3 sections were tied back to one of the chips I had removed to avoid the saw cut. Apparently the 1V, 1.7V, and 3.3V were designed to be powered on at the control of the chip I removed. With this insight I cut the trace to pin 7 on each of the non-functional MP2363s and tried once again to see if the unit was working. Once I had the unit working I also added a load to each channel. I did not try the three amps advertised in the data sheet as my jumper wires would have been stressed by this amount but I did subject each section individually to 2 Amps of load. To me it is simply amazing that these small DC converters can deliver 3 Amps with so little heat and such amazing voltage stability.

     

    image

     

    Simple experiments like this one always seem to net a little additional knowledge. Now I know that I can turn the chips on and off with the number 7 enable pin. This information was in plain sight in the data sheets but it always helps my learning process if I have to get physically involved with the process.

     

    Now I have to keep this circuit in mind so I can incorporate it into a future build somehow.

     

    John

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