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Query regarding transistor chip

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Manchested

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Hi everyone,

I am trying to drive some identical loads with this chip.

https://www.google.co.nz/url?sa=t&rct=j&q=2981&source=web&cd=3&ved=0CFAQFjAC&url=http%3A%2F%2Fwww.allegromicro.com%2F~%2FMedia%2FFiles%2FDatasheets%2FA2981-2-Datasheet.ashx&ei=1BASUMyyJdOgiQforYHYAw&usg=AFQjCNEsQF8S6LTy5TZAJTLqqgmb-l1JGA

I would like to put resistor in series with the loads.
According page 3's schematic, I was wondering if I could just add one resistor at pin Vs instead of putting one resistor for each loads.
 

Why don't you use a resistor in the common ground connection of the loads
 

Because the load could be some leds which have common postive terminal.
 
Last edited:

So you intend to use a high side switch like the chip you mention which switches on/off the positive supply and you will drive with each output several leds that will also blink independently by using low side switches to their grounds?

I think a resistor to Vs would work (I assume you mean low values like 100 ohm) but you should do a test.
 

THis device is an 8 channel high-side switch with separate logic and load grounds (common collector) with Vc 50=Vmax and Ic -500mA an absolute max. and temp derating at 1 watt and assumes ambient is ventilated from self heat.

THe emitter output curves indicate an ESR of 1Ω of each transistor.

What p/n is your load? and V+ voltage?

- - - Updated - - -

Also Imax = 75mA when all 8 outputs are used Vs=15 100%d.f. at elevated temperatures. is recommended.

- - - Updated - - -

I assume you are power LED's with a current limiting resistor. What is the ESR of the LED's and what voltage are you applying.
YES you can use a common Anode power resistor to ground but why? It will be much bigger and more expensive.
 

I was wondering if I could just add one resistor at pin Vs instead of putting one resistor for each loads.
Click to expand...
Apart from other possible problems, the load current would change with the number of simultanouosly activated outputs. I don't believe that you want to achieve this.
 

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