4 BA6209 motor controllers

I intend to make a 4 motor controller using 4 BA 6209

(datasheet **broken link removed**).

You will find an application circuit in there.
I just wanted to know if I could use just one zener diode for all 4 BA6209's.

Also I couldnt understand why the 10ohm resistor is going from Vcc to Pin 8 and not to Pin 7. I ask because Pin 8 is supposed to be set to output supply voltage and pin 7 to control logic supply voltage. wouldnt the 10ohm lower the supply voltage for the motors ?

pkshima said:

I intend to make a 4 motor controller using 4 BA 6209

(datasheet **broken link removed**).

You will find an application circuit in there.
I just wanted to know if I could use just one zener diode for all 4 BA6209's.

Also I couldnt understand why the 10ohm resistor is going from Vcc to Pin 8 and not to Pin 7. I ask because Pin 8 is supposed to be set to output supply voltage and pin 7 to control logic supply voltage. wouldnt the 10ohm lower the supply voltage for the motors ?

Click to expand...

Yes, you could use 1 zener for the reference for all 4 parts. Each reference draws ~800uA according to datasheet. So assuming you need at least 2mA to bias the zener (deep into knee), be sure then your circuit biases the zener to 2ma+4*(0.8mA) = 5.2mA (say 5mA)

With a 12V supply and the zener diode limiting the output voltage to near 7V then the power dissipation if the motor's current is high would melt the BA6209 if the 10 ohm resistor is not there to share the heat.
See Operation Note #1 on page 6.

Thanks optikon and audioguru !!!
Could I then also use just 1 10ohm resistor for all 4 chips. Something like a 1 W resitor ?

Calculate the value of the resistor:
1) 12V supply, 7.4V zener causing a voltage of 5V across the resistor.
2) If the total max current is 500mA then the resistor value is 5V/0.5A= 10 ohms.
3) Then the 10 ohm resistor will dissipate 2.5W.

Meaning I need to put in 4 2.5W resistors !!!
wow. Can I connect the power supply pin of all 4 chips together and connect that point to the powersupply via these 4 bulky resistors put in parallel ?

You could use a single resistor if you calculate its value and its power rating correctly.

You need to calculate the value of the resistors and their power rating.
My example used a 12V supply, a 7.4V zener diode and motors that have a max current of only 500mA. If your circuit has anything different then the value of the resistors must be different.

Have you ever measured the temperature of a 2.5W resistor that is dissipating 2.5W? It is extremely hot, enough to burn you or something near it. A 3W or 4W resistor will be cooler.