Question about H-Bridge voltage drops.

I am using a SN754410NE Quad Half H-Bridge to control 2 motors. It works great, except for one thing. When I supply a voltage to pin 8 for the motor power (separate from the chip's logic power), the voltage that comes out of the motor output pins is about 2 volts lower that what I put in. Is this supposed to happen? Can I fix this?

datasheet: http://www.ti.com/lit/ds/symlink/sn754410.pdf

On the fifth page, there is something that might be related. It says that for the test condition "IOH = –1 A" that "VCC2 – 2 V" Is this related? What does this mean?

Thanks!

You shouldn't be driving a motor if the motor supply isn't present and isn't >= than the logic supply, otherwise you are abusing the chip and could fry it.

the voltage that comes out of the motor output pins is about 2 volts lower that what I put in. Is this supposed to happen?

Yes

Can I fix this?

1) By applying 2V more to the motor supply of the chip.

2) By using a H bridge that uses FETs and not transistor. Transistors drop at least 0.7V often more when switching large currents. With a H bridge you have two in series so you are always going to loose 1.4V and so loosing 2V is not unreasonable.