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Does Stepper driver IC have clamp diodes on its inputs?

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eem2am

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Hello

Do you think that the NJM2673 bipolar, switch-mode stepper driver IC has clamp diodes on its signal input pins?
(pins: I01, I11, I02, I12, PHASE1, PHASE2)





NJM2673 DATASHEET (njr.com):-
2shared - download NJM2673.pdf

Or find datasheet here:
**broken link removed**





(i.e. protection diodes with anode to pin, and cathode to VCC?)

..by signal pins, I mean that the current magnitude and direction inputs (I01, I11, I02, I12, PHASE1, PHASE2)



Its just that we I have connected the microcontroller outputs directly to the signal pins of NJM2673 with no series resistors.

-Also, there is a switch so that we can switch off the VCC supply to NJM2673 when we are not driving the stepper motors (this saves some power)

-in this state, VCC = 0V, and for a short time, the microcontroller will be putting logic highs into the current magnitude pins (I01, I11, I02, I12)………

……..if such clamp diodes exist, then the microcontroller pins will end up basically driving into short circuits.
 

I don't think that anyone can give a valid answer, we can only assume but i want to go back one step and ask you what is the point of saving 30ma on a 5v power supply (0.15W)
when you risk having an uncontrolled output stage?

Alex
 
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    eem2am

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Do you have the chip at your fingers? Use a multimeter to know the answer.

The datasheet's maximum ratings suggest diodes of both polarities, but you can't be sure. So why not simply shutting down the input signals before the power supply?
 
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    eem2am

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FvM: ...unfortunately the high level input signal (I01 = 5V & I11 = 5V) turns off the current....so this would be the state just before switching off the 5V.....also, the software guy may make a mistake while practising and take the pin high anyway, so i want to protect against this.

I am ordering some chips but need to lay out the board now.

alexan_e: Do you think there is reason to believe it (NJM2673) will be unstable with 36V on the VMM pin and 0V on the VCC pin.?


(saving 150mW is a big deal for us becasue we have strict standby requirement, and also there are two of these ICs)
 
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The only part i see in the datasheet about that is
"VCC , VMM
The supply voltages, VCC and VMM, can be turned on or off in any order. Normal dv/dt values are assumed.
Before a driver circuit board is removed from its system, all supply voltages must be turned off to avoid destructive
transients being generated by the motor. "

This seems to indicate that you can remove the Vcc without problem but i don't know what it means by Normal dv/dt values,
does it mean the increase/decrease rate of Vcc or VMM voltage (one of them)
or does it mean the time difference between applying the same voltage in the first and the second supply (turn the first on/off and then follow with the other one).

Alex
 
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    eem2am

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I am ordering some chips but need to lay out the board now.
In other words, you are still able to place current limiting resistors between processor and SM driver. Then it's no reason to discuss this any longer, I think.
 
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