calculating resistor ohm and watts value

[harps]

hi
i wonder if anyone can help? i need to figure out how to create 0.44v for the REF signal input of this h bridge below

on my bread board is a 5v regulator.

i believe from looking at the pdf that the :

Reference Input Current IREF VREF = 0 V to 1 V — — ±5.0 μA

the h bridge pdf is here
A3953SB-T datasheet pdf datenblatt - Allegro MicroSystems - FULL-BRIDGE PWM MOTOR DRIVER ::: ALLDATASHEET :::

and below is a diagram of the IC.

i tried to calculate via a LED resistor calculator but the resistance field would not go low enough for the 5 micro amps. .005ma

thanks for your help : )

**broken link removed**

 

[ericgibbs]

hi,
The 5uA is the maximum current drawn by the REF pin.

You could use a resistive potential divider from 5Vreg supply or there are some some Schottky diodes that have a forward voltage drop about 0.44V

Do you follow OK.?

EDIT:
A simple resistive divider

 

[ronv]

The 5 ua is an error term. The chip can draw +/- 5 ua from the divider that produces the ref. voltage. So you want to keep the divider resistors fairly small like Eric shows not very large where the 5 ua can change the voltage.

 

[harps]

thanks for you replies : )

i think i understand the diagram , does the :

".tran.1" = ground?

Should the 6.2k and the 600 ohm resistor be o.k at around 1/4 watt value?

Thanks for your time on this. : )

 

[ericgibbs]

thanks for you replies : )

i think i understand the diagram , does the :

".tran.1" = ground?

Should the 6.2k and the 600 ohm resistor be o.k at around 1/4 watt value?

Thanks for your time on this. : )

hi h,
Ignore the .tran, thats only for a simulation program..
The 0V [ common lines/points ] are indicated by the downward point triangles.

The 6k2 and 600R can be 0.125W or you could use a 1k variable for the 600R, this will enable you to adjust the 0.44v more precisely.

 

[harps]

thanks again ericgibbs : )

so helpful , great idea, i shall hook up a variable resistor and see if i can get the the 0.44v.

have a great new year : P

 

[ben7]

Ohm's Law with Calculator