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Old 5th April 2005, 01:03 AM   #1
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Default Ref, Ilim, and E/S pins

how do you connect the Ref, Ilim, and E/S pins on the OPA549?
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Old 5th April 2005, 02:41 AM   #2
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Ilim is explained on page 8. You use Equation 1 to determine the resistance value for a current limit you choose. Leaving Ilim floating sets output current to 0A, effectively disabling the IC. Connecting Ilim to Ref disables external current limiting, allowing the maximum 10A out before the hardwired protection circuits activate.

E/S allows 3 modes of operation. This is shown on page 9. By connecting the pin to Ref the output is disabled. Leaving E/S open or placing 2.4V above Ref to E/S enables the output. E/S also outputs the thermal status of the OPA549 for monitoring.

Ref is simply the reference point for the above 2 pins. I'd recommend connecting Ref to V-. This is the scheme I have used for other OPA54x ICs successfully.

By the way, the operation of these pins is explained well in the datasheet. It might be quicker to read the datasheet before posting. Then you could get the answer right away instead of waiting for a response
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Old 5th April 2005, 08:54 PM   #3
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thank you for helping me i built a single channel little amp to test out the opa549 and i am very surprised. i used low quality parts, but the sound was pretty good quality. it sounded like it had a good amount of power to it. How much power do one of these thingies put out?
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Old 5th April 2005, 09:11 PM   #4
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Default Re: Ref, Ilim, and E/S pins

Quote:
Originally posted by odysseybmx414
how do you connect the Ref...
To ground.

Quote:
Originally posted by odysseybmx414
...Ilim...
Shunt to Ref.

Quote:
Originally posted by odysseybmx414
...and E/S... pins on the OPA549?
Don't use.

Easy.
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Old 6th April 2005, 04:02 AM   #5
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Thanks carlos, I didn't realize anyone could interpret my scribblings It's almost easy to follow when you explain it

Well, take you supply voltage and subtract how close the OPA549 can get to the rails. This will be in the datasheet under the Output section. It should be a few volts from both rails. That will give you your maximum output voltage. Square that number and divide by the load and you will have the power. Of course, a real speaker has a varying load impedance over frequency but the above calculation will correspond to other amps' output power.
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