# beginner h bridge questions

i have some questions regarding the L298 h bridge.

1. what are the current sensing pins, and how do i use them?

2. why is there a supply voltage and a logic supply voltage?

3. what do the 2 inputs do? what will happen if they are both high?

• It seems to me that you have not really read the datasheet properly. – MrGerber Jan 4 '18 at 16:10
• This antiquated and very lossy chip is probably not what you want to use anyway. For at least a decade now, FET based solutions have made more sense. – Chris Stratton Jan 4 '18 at 16:35
• A perfect case of a question that could easily be solved if the OP would simply RTFM! – DerStrom8 Jan 4 '18 at 17:46

1) The sense pin allows you have a sense resistor so you can monitor and limit current

2) They are separate so you can drive the logic from one voltage (up to 7 V), and the thing the H Bridge is driving from a different voltage (up to 50 V)

3) The two inputs are to change the 'direction' of drive current. With an h bridge usually to choose which way a motor turns.

• would enabling both of the inputs brake the motor? – parzival Jan 4 '18 at 16:19
• See Figure 6 in the data sheet, both high is fast motor stop. – Colin Jan 4 '18 at 16:20
1. The current sense outputs are as the name suggests current-sensing ouputs, they allow you to measure the current in the two bridges. it works like this; All the current that flows into either bridge will come out its corrosponding current-sense-output, If you put a small-value power resistor from either current sense output to ground then the current flowing into the corresponding bridge is going to produce a voltage across the resistor which can be measured and used to calculate the current.

2. That is because you need a low "logic-level" supply voltage for the control logic and you need typically a higher voltage to be sourced through the bridge. So considder this; you might want to supply 30v from the bridge (that is when the bridge output is high it is at 30v) but you need to control the bridge from an mcu (or an arduino for instance) that has 5v logic, then you need the logic supply voltage of the bridge to be 5v too otherwise they want be able to talk together.

3. In1 controls the left side of the first bridge, In2 controls the right side of the first bridge. if they are both high AND YOUR LOAD IS CONNECTED BETWEEN THE TWO SIDES OF THE BRIDGE then all that will happen is that the output on both sides of the bridge is going to be either high or low, and no current will run in your load.