Help reading data sheet

I'm using the H-bridge sn754410.
I want to power the logic of the H-bridge from an arduino pin (to turn on/off) the entire H-bridge.
the logic Vcc called Vcc_1, but I can't figure out how much current does he need (to make sure arduino pro mini pin can supply it).

Here is a link to the data sheet :

The only thing I found is : Icc1 = 70 which is quite large (and can't be true, because my whole circuit with arduino included takes 15mA)

I'm probably missing something.

I don't think it's worth it. Current will be very low when it's off and if you power any other pin while the printer is off that might damage it.

You probably safe more if you turn off Vcc2 when you don't use it.

It's probably not a good idea to turn off the logic in the chip while it's still connected to power. You really should leave that on. Just use the ENable lines to cut the outputs.

Icc1 is probably a maximum or peak current. It may draw that much for a few nanoseconds while switching. The datasheet doesn't explain it very well. Always decouple logic power inputs with 0.1uF capacitors.

It does not appear that you can safely power that chip from an Arduino I/O pin.

The Icc1=70 mA (max) specification is stated for the condition that all chip outputs are held low.

You will need to make sure that you create that condition by setting all the inputs properly, in order to verify the specification.

Just to clear things up:
When my arduino is sleeping he draws 3mA. The H-bridge draws 12mA (when not driving any motors).

I'm trying to run it for as long as possible on just batteries. So it is imperative to disable the H-bridge in some way.

I didn't understood why you said :
"It's probably not a good idea to turn off the logic in the chip while it's still connected to power"

12mA on the logic? With or without Vcc2?

septillion:
12mA on the logic? With or without Vcc2?

With Vcc2,
All the input pins set to low, no motors are connected.

Does it change when you disconnect Vcc2?

tautau123:
I didn't understood why you said :
"It's probably not a good idea to turn off the logic in the chip while it's still connected to power"

Vcc1 supplies power to the control circuitry. If it's unpowered but there's still (up to) 36V on Vcc2, then that 36V is not controlled. It could turn on an output or even "shoot through" and destroy the chip. It's like having your car rolling on the highway with the engine turned off.

However the datasheet does specifically say that there's no requirements for the power-up sequence, indicating that it is safe to have power on Vcc2 without power on Vcc1.

Why waste your time with this old, inefficient technology?

Pololu has some very nice, inexpensive motor drivers that have a proper sleep input.

I would worry more about the (in)efficiency of the ancient SN754410 (and L293 sister).
With a dropout voltage of ~2.5volt in H-bridge mode, most if your battery charge will end up in heat in the chip when the motor is running.
These 30+ year old chips, like the LM741, belong in a museum.
Leo..

The motors will run once a day for about 10seconds. they take about 50mA each.
so the 12mA for the rest of the day is the main power consumption

tautau123:
The motors will run once a day for about 10seconds...

One direction?
Then a single (mosfet) transistor would be better.
Less voltdrop, and zero current when off.
Leo..

tautau123:
The motors will run once a day for about 10seconds. they take about 50mA each.
so the 12mA for the rest of the day is the main power consumption

And that's why we're saying ditch the chip for a more modern one. A 754410 is a BJT based fossil, you will never get low current consumption out of it no matter what you try.

Wawa:
One direction?
Then a single (mosfet) transistor would be better.
Less voltdrop, and zero current when off.
Leo..

Unfortunately both directions.

Jiggy-Ninja:
And that's why we're saying ditch the chip for a more modern one. A 754410 is a BJT based fossil, you will never get low current consumption out of it no matter what you try.

Can you elaborate why ?
Where in the data sheet I can see how much current he uses while idle ?
Which H-bridge is better ? I need to drive 2 small 9v motors.

Which H-bridge is better ?

Depends on your motors. Shop and compare here.

Example

This driver has a 10nA sleep mode.
Study the datasheets.
Leo..

tautau123:
Can you elaborate why ?

Pages 8 and 9 show the equivalent output and input circuits, so you can see clearly there that the logic circuit is based around BJTs. BJT-based logic gates always drain current, even when the inputs are not changing. Their current draw will remain fairly constant no matter what the operating frequency is. Different states might produce different current draws, but the net current draw of BJT logic will depend on the combined duty cycle of the different states, not the switching frequency.

Contrast that with MOSFET based logic. FET logic only needs to draw current when changing state (to charge and discharge the gate capacitance). When the logic is static, the only current draw is leakage. High frequency operation directly correlates to higher current draw. This can be thought of as a downside, but the inverse is actually very critical to modern computing: lower frequency operation means drastically less current draw.

Why do computer reviewers need to "put a load on" the CPU or GPU when they're testing temperatures? Because with nothing to compute the scheduler will put the microprocessor to sleep.

Because of the direct dependence that power consumption has on frequency, a lot of modern microcontrollers (like this PIC16F18857 I just ordered to play around with) will quote their operating power consumption with the units uA / MHz (microamps per megahertz). This allows a more direct comparison of power efficiency for different chips by being able to directly estimate how much computation you can get for your energy input.

Where in the data sheet I can see how much current he uses while idle ?

Table 7.4 on page 9. It shows the difference in current consumption when the outputs are in different states. As I said in the previous section, frequency doesn't matter much for the current consumption of BJT logic, so it doesn't really matter whether it's working on DC or 1 MHz.