H harps Member Jan 5, 2011 #1 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**
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 Well-Known Member Most Helpful Member Jan 5, 2011 #2 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 Attachments 000esp01.gif 19.4 KB · Views: 191 Last edited: Jan 5, 2011
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 Well-Known Member Most Helpful Member Jan 5, 2011 #3 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.
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.
H harps Member Jan 5, 2011 #4 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. : )
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 Well-Known Member Most Helpful Member Jan 6, 2011 #5 harps said: 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. : ) Click to expand... 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 said: 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. : ) Click to expand... 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.
H harps Member Jan 6, 2011 #6 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
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