In the A3901 Low Voltage Meter Driver datasheet Figure 8 on pg. 10 shown below indicates what the output "IOUT 2/3-4" will look like given input "IN1/3 or IN2/4".

enter image description here

But Figure 8 does not mention anything about how long it takes for the output to rise from 0amps to +Ireg nor is there any mention about how long it takes when it falls from +Ireg to -Ireg (when it switches from Foward / Fast Decay to Reverse / Fast Decay).

The same question applies for rise / fall times for Forward / Slow Decay and Reverse / Slow Decay.

Am I not reading this figure correctly or has Allegro not provided rise / fall times?

Is there any way I can discover the rise / fall times myself? How?


Scanning the datasheet, it appears that fast decay or slow decay are achieved by leaving the outputs off (high impedance) or on (low impedance) but at the same logic level.

So the rise and fall times are determined by the driver output impedances (which are given in the datasheet) and the inductance of your motor's windings (which the chip manufacturer obviously doesn't know). So they cannot give a reliable answer in the datasheet.

I think you have to do the rest of the work yourself; either using the motor's datasheet or your own measurements of its parameters.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.