issues with the L298N and its power-supply :: how robust is this ic!?

dear community,

I have been trying to connect 5v supply to a L298N motor driver-IC at it’s 12V-35V input pin. Note L298N motor driver-IC is very well known to be very very robust. Findings: If I’m connecting to 7.2V supply it’s working. Is there any way to connect 5v supply? What is aimed - the goal is to have a fairly constant 5v at output pins for motors that i have connected.

I have tried to find out some things that might be of interest: I assume that the “12V-35V input pin” is the V_S pin, despite that label. Afaik there are only two supply pins on the L298-IC with the following electrical characteristics:

V_S, Supply Voltage, on pin 4, Operative Condition V_IH + 2.546V (max.: 46V)
V_SS, Logic Supply Voltage, on pin 9, typical 5V (minimal voltage.: 4.5V, max.: 7V)

with the following specs:

V_IH, Input High Voltage, ranging from 2.3V to V_SS

conclusion: the circuit works at 7.2V under the assumption that the logic inputs (if we have enabled the ports A and B as well as inputs 1 through 4) are at very close to 5V high levels. Note: here’s we have a trick that might be very important to get all to work: as noted V_S (the supply voltage) needs to be at a level of V_IH + 2.546V while V_IH could be as low as 2.3V and 2.3V + 2.546V < 5V. So if we are driving the L298’s logic inputs with a lower voltage for logic 1, i.e. closer to 2.3V high levels. What do you suggest or recommend.

Some friends allready told me to look for a more robust solution while

use even a higher supply voltage
forget the L298 and its high voltage that is needed here; drop Darlingtons and use a MOSFET H-bridge motor driver,
forget the L298 and use some nice single bipolar transistors-solutions, depending on the output current

Hi,
L298 IC are basically a dinosaur, it uses BJT output transistors and is not very efficient.

You would be better to go looking for a MOSFET based motor controller.
For example;

Tom... :slight_smile:

good day dear TomGeorge

first of all many many thanks for the quick reply i am very glad to hear from you!!

TomGeorge:
Hi, L298 IC are basically a dinosaur, it uses BJT output transistors and is not very efficient.
You would be better to go looking for a MOSFET based motor controller.
For example;
Pololu - Brushed DC Motor Drivers

Tom... :slight_smile:

many thanks for the idea-exchange and the recomendation. I am glad to here about all the ideas that help to replace the old horse called L298 N IC

Glad - and i will take all your recomendations into account.
you literally saved my day

greetings

the goal is to have a fairly constant 5v at output pins for motors that i have connected.

You can’t get a constant output voltage, since the voltage drop depends on the current.

At higher currents, the L298 drops almost 5V, so you need 10V in for 5V out. But then when the current drops and the voltage drop decreases to 2V, your output goes to 8V.

298 volt drop.GIF

That’s why the L298 even in its day, was never a great choice for low voltage duty, where the drop is proportionally more evident than at higher voltages. (In the 35V area you mention, say, you would get 30V at high current (5V drop) and 33V at lower current (2V drop), not so drastic relatively speaking.)

You realize this is a 20 year old part, I believe one of there first BCD type parts. To answer your question it is a very robust part. sayHovis explained what the part is doing, and it is behaving like it is specified. It was not designed to control voltage but motors. They build other devices called voltage regulators. You can get the data sheet here: https://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf The data sheets will tell you how much voltage drop to expect on whatever power device you choose to use. A non-inductive 100nF capacitor must be connected between this pin and ground, if not you will get a lot of high frequency noise and heating.
Good Luck & Have Fun!
Gil

gilshultz:
You realize this is a 20 year old part

You can double that according to this thread.
Leo..