VNH2SP30 MOD3A: less power with 2 motors running together

Hi all,

Thanks to your generous help, I successfully tested my DC motor (12V 0.6A) with PWM speed control and direction change capability.
Everything works perfect with only one such type of motor connected to this dual board. But when I connected two of my DC motors on both sides, the motors ran stronger at about 28% duty cycle than they did at 100% duty cycle. (Actually at 100% duty cycle, the current is too small to power the motors.) I’m wondering how the two motors are actually connected. Are they in parallel? I saw this multi-motor configurations from the data sheet and it says [quote]The VNH2SP30-E can easily be designed in multi-motors driving applications such as seat positioning systems where only one motor must be driven at a time[/quote]. However, my design requires both motors run at its optimized voltage & current (12V, 0.6A) at the same time. Two ran at its max achievable speed at 28% duty cycle but they are still a lot weaker than each running individually. Should I assume a parallel connection and just double the current? Even for this solution, voltage from the power supply also increase, which would be too high for the board.

Any help would be greatly appreciated!!



Each motor is controlled by a separate VNH2SP30 IC; the channels are completely independent. It sounds like you are overtaxing your power supply. How are you powering your system? I assume the 0.6A rating you’re giving for your motors is their free-run current at 12V? What is their stall current at 12V?

- Ben

Thanks for that bullet-speed reply!

I’m using a single DC power supply (30V 1A).
The stall current of the motor is 40A at 12V; 26A at 6V. Here is the link: But I don’t think I will ever reach that situation. I’ve programmed some safety mechanism to keep it from being stalled.
Are you saying in order to let both motors run at its nominal standard(12V 0.6A), the power supply should provide at least 24V and 1.2A?


The power supply you are using is very, very underpowered for those motors! Even if you take care to never stall the motors, they will still try to draw close to the stall current whenever you first apply power to start them moving, and they can draw almost twice the stall current if you ever rapidly change from full-speed in one direction to full-speed in the other.

Both motors are being powered by the same 12V source, so each motors will have 12V across it when its H-bridge is delivering power. (The motors are connected in parallel to the same power source, but their individual H-bridges give you independent control of their speeds and directions.) However, each motor is drawing its own current. Using two 0.6A motors simutaneously from a single power source requries that power source to supply 1.2 A.

- Ben

Really appreciate it, Ben!

I tested with a rechargeable battery (13.8V 5.38A) and they worked perfectly.
I have another question, maybe it’s not quite related: do you know how to build a current-regulated circuit? Since we are using this type of battery to power multiple motors (12V 0.6A) and not all of them run at the same time, there would be the situation that 5A of current pumps into a single controller and fries it. Should I use a transistor or something similar to “filter” the current?

Thank you so much!!


I’m not sure I understand your problem. What controller are you worried about frying with 5A and under what conditions would this problem situation arise?

- Ben