Error
If the "7.4V" is from a 2S lipo then it's perhaps worth noting that these provide 8.4V when fully charged and are almost empty by the time they reach 7.4V. 80% of 8.4V is 6.72V.
But despite that it's the current the motor is drawing that you need to keep an eye on. It's current that burns out motors not voltage as I'm pretty sure I already told you in one of your many other threads on this same subject.
Steve
L293's are so inefficient at low voltages that you should be running PWM at 100% to get
6V on the motor.
GEFORCE:
VOH( High-level output voltage) = VCC2 (7,4 V) – 1.4V .What it means? The voltage on the motor is (7.4-1.4) = 6V ?
Worse if you use the chip in H-bridge configuration.
Then you "loose" about 1.4volt@600mA motor current in the top half of the bridge,
and about 1.2volt@600mA in the lower half of the bridge.
So the motor gets 2.6volt less than battery voltage.
Leo..
GEFORCE:
I use two Li-ion batteries of 3.7 V and 400mAh. The stall current of the motor is 700 mA. Any problems ?
You're confusing capacity (mAh) with current (mA).
What is the C rating of the LiPo pack? A 10C 400mAh pack would produce upto 10 x 400mA,
a 30C 2.2Ah pack upto 30 x 2.2A, etc.
LiPos are generally powerful enough to handle a L293D, the issue is whether the L293D can
handle the stall current of the motor.
GEFORCE:
Sorry MarkT but i don't understand the first part! These are my batteries [Lithium Ion Battery - 400mAh - PRT-13851 - SparkFun Electronics].
The datasheet from that page clearly says the maximum discharge current is 1C or 400mA. So some other battery would probably be a lot more useful.
Steve