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I am reading the schematic of a microcontroller (SODAQ ONE V3 which is based on Arduino Zero) in order to design my own PCB with my components embedded in a chip. I would like to know what this notation means (eg. 1*2 in a symbol pin/terminal):

MCP73831 symbol (this is the battery charging module that the microcontroller uses to charge if battery is connected, the manufacturer is microchip.

MCP73831 symbol (this is the battery charging module that the microcontroller uses to charge if battery is connected, the manufacturer is microchip.

I have been reading how to read electronics schematics in different blogs and posts like this but I did not find the answer. (How to read schematics).

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4 Answers 4

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The notation 1*2 means "two pins, including pin 1." The additional pin(s) can't be determined from the schematic, which is a reason some people avoid this notation style in schematic symbols. (Others prefer it to explicitly drawing each duplicated pin on the symbol.)

You'll have to look in the datasheet for the part, or the symbol properties in your CAD software, to see what the additional pins are.

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Looking at the datasheet, it appears that the symbol is referencing the DFN package that has pins 1 and 2 as VDD and pins 3 and 4 as Vbat (for higher current handling capability). The footprint should match and have 2 pin 1s and 2 pin 3s. The more common way to do this is to keep the pins separate on the symbol and leave it up to the designer to connect them correctly like so: enter image description here

Screencap from Mouser.com/SamacSYS

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The portion of your schematic with that notation is for the Microchip MCP73831. Its datasheet shows (pg 11):

MCP73831 Pin Description

VDD is being labeled as VIN on your schematic. Note that there are two pins (1 and 2 for the DFN package).

VBAT is labeled as VBAT on your schematic. It also has two pins (3 and 4 for the DFN package).

The notation in your schematic I think is unusual and confusing (hence your question!). 1*2 should be interpreted as "pin 1, two pins" but it does not specify what other pin besides 1 is used.

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It means that there are two pins starting at pin 1 (1*2) for Vin and two pins starting at pin 3 (3*2) for VBAT.

The data sheet indicates which pins.

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