AS5048B - magnetic encoder circuit questions

[konradIC13]

Hello,

Im going to use AS5048B (I2C version) sensor to control position of DC motorr (total 5 of sensors for 5 motors). Im starting with PCB project and im want to confirm something.

1. Have anyone used similar chip? Does this chip can store data written to it (for example Slave address, programmable 0 position) even if power is cut off? Because i want to power it from external 5v, but if I'll have to write data every time i power it up i will consider using 3.3v button battery

2. A1 and A2 inputs. From what i understand they are simply hardware pins to set last two bits of Slave address? By default its 10000XX so if i set A2 and A1 as low the slave address of sensor will be 10000(0)(0) and if i pull them up it will be 10000(1)(1)? If yes, can i just connect them to GND (or VCC) to make them permanently in low or high state? (ill use bits 5,4,3 to write different slave addresses for 5 sensors)

3. PWM output, can i just leave its pin floating since i wont be using it and i dont want to interfere with I2C signals

The sensors will be placed on motors, and will be connected to MCU that will be like 10-15 cm away from them so i want to minimise amount of wires going from sensors to MCU.

My schematic so far is in attachment (SCL and SDA will be connected to resistors on board where MCU will be).

Thank you kindly in advance for any help.

 

[ClydeCrashKop]

The AS5048 uses one time programmable (OTP) fuses for permanent programming of the user settings.
I like that chip. I'll keep that in mind for future reference.

 

[konradIC13]

Oh, does it mean that if ill write it once, i wont be able to change it later or correct anything?

I just made a little PCB small enough to fit into tiny enclosure to not out stand too much.

U1 is of course AS5048B
A1 and A2 are connected to GND for low state.
C1 - 100nF 1206 SMD capacitor
C2 - 10uF 1206 SMD capacitor (necessary when 5V is used)
PWM pin not used, left unconnected

Circuit powered from external 5V

 

[Joe G]

I agree w/ ClydeCrashKop , that seems like a usefull chip, I've thought of some projects w/ it already.......now where did that robot of mine go.........

 

[Joe G]

a quick read of the data sheet (page 10) otp=one time programmable if set to "permanent setting" , that I'm taking as not changable? also when setting the ZERO setting if set to permanent = not changable? All of the I2C chips I've used I just have the initial code run to "set the chip" on start up, usually I have a "ready" led turn off when starting the main code. Hope that helps abit.
'

 

[konradIC13]

I have last (i hope) question. In datasheet there is simple schematic about filtering the voltage. It doesnt say what kind of capacitor it has to be, but on image it looks like no polarised one. Do you think it can be electrolityc capacitor or it has to be ceramic/non polarised?

 

[ericgibbs]

hi,
The 100nF could be a ceramic type, the 10uF should be a electrolytic or tantalum type, 6Vdc rating minimum.

A 10uF type other than those suggested would be quite big physically.

E.
EDIT:
This pdf is a good reference